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FLUENT 6.3 UDF Manual

1. Fluent Inc September 11 2006 5 7 Compiling UDFs As the build process progresses the results of the build will be displayed on the console window You can also view the compilation history in the log file that is saved in your working directory Console messages for a successful compile build for a source file named udfexample c and a UDF library named libudf for a Windows architecture are shown below Deleted old libudf ntx86 2d libudf d1ll 1 file s copied system copy C Fluent Inc fluent6 3 23 src makefile_nt udf libudf ntx86 2d makefile 1 file s copied chdir libudf chdir ntx86 2d udfexample c Generating udf_names c because of makefile udfexample obj udf_names c Linking libudf dll because of makefile user_nt udf udf_names obj udfexample obj Microsoft R Incremental Linker Version 7 10 3077 Copyright C Microsoft Corporation All rights reserved Creating library libudf lib and object libudf exp Done In the Compiled UDFs panel Figure 5 2 3 load the shared library that was just built into FLUENT by clicking Load A message will be displayed on the console window providing a status of the load process For example C Fluent Inc ntbin ntx86 Opening library libudf Library libudf ntx86 2d libudf d1l1l opened inlet_x_velocity Done indicates that the shared library named libudf was successfully loaded on a Win dows machine and it contains one function nam
2. Fluent Inc September 11 2006 6 79 Hooking UDFs to FLUENT 6 80 UDS Diffusion Coefficients User Defined Scalar Diffusion uds 0 Coefficient luser defined anisotropic Edit plane cancet Help Figure 6 6 2 The UDS Diffusion Coefficients Panel In the UDS Diffusion Coefficients panel select a scalar equation e g uds 0 and choose user defined anisotropic from the drop down list under Coefficient This will open the User Defined Functions panel and allow you to select the UDF you wish to hook Note that you will get an error if you have neglected to previously interpret or compile a DEFINE_ANISOTROPIC_DIFFUSIVITY UDF Note that you can hook a unique diffusion coefficient UDF for each scalar tranpsport equation you have defined in your model See Section 2 7 2 DEFINE_ANISOTROPIC_DIFFUSIVITY for details about defining DEFINE_ANISOTROPIC_DIFFUSIVITY UDFs and the User s Guide for general information about UDS anisotropic diffusivity Fluent Inc September 11 2006 6 6 Hooking User Defined Scalar UDS Transport Equation UDFs 6 6 2 Hooking DEFINE_UDS_FLUX UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_UDS_FLUX UDF the name of the argument that you supplied as the first DEFINE macro argument e g my_uds_flux will become visible and selectable in the User Defined Scalars panel Figure 6 6 3 in FLUENT De
3. c0 F_CO f t tO THREAD_TO t num_in_data F_UDMI f t NUM_OF_HITS Average diameter of particles that hit the particular wall face F_UDMI f t AVG_DIAMETER P_DIAM p num_in_data F_UDMI f t AVG_DIAMETER num_in_data 1 C_UDMI c0 t0 AVG_DIAMETER F_UDMI f t AVG_DIAMETER Average velocity normal to wall of particles hitting the wall F_UDMI f t AVG_RADI_VELO vel_ortho num_in_data F_UDMI f t AVG_RADI_VELO num_in_data 1 C_UDMI c0 t0 AVG_RADI_VELO F_UDMI f t AVG_RADI_VELO F_UDMI f t NUM_OF_HITS C_UDMI cO t0 NUM_OF_HITS num_in_data 1 num_in_data 1 Fluent Inc September 11 2006 2 1 57 DEFINE Macros F_AREA A f t area NV_MAG A F_STORAGE_R f t SV_DPMS_ACCRETION Mdot area copied from source P_USER_REAL p 0 1 Evaporate DEFINE_DPM_LAW stop_dpm_law p if_cpld if 0 lt P_USER_REAL p 0 P_MASS p 0 Evaporate DEF INE_ON_DEMAND reset_UDM assign domain pointer with global domain domain Get_Domain 1 reset_UDM_s Hooking an Erosion Accretion UDF to FLUENT After the UDF that you have defined using DEFINE DPM EROSION is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible in the Discrete Phase Model panel in FLUENT See Section 6 4 4 Hooking DEFINE
4. Fluent Inc September 11 2006 8 19 Examples 4 46e 01 4 05e 01 3 64e 01 3 23e 01 2 83e 01 2 42e 01 2 01e 01 1 60e 01 1 19e 01 7 78e 00 3 68e 00 Turbine Vane 1551 cells 2405 faces 893 nodes Contours of Velocity Magnitude m s Figure 8 2 5 Velocity Magnitude Contours for a Parabolic Inlet x Velocity 4 56e 01 4 13e 01 3 70e 01 3 26e 01 2 83e 01 2 40e 01 1 97e 01 1 53e 01 1 10e 01 6 68e 00 2 35e 00 Turbine Vane 1551 cells 2405 faces 893 nodes Velocity Vectors Colored By Velocity Magnitude m s Figure 8 2 6 Velocity Vectors for a Parabolic Inlet x Velocity 8 20 Fluent Inc September 11 2006 8 2 Detailed UDF Examples Transient Velocity Inlet Profile for Flow in a Tube In this example a temporally periodic velocity boundary condition will be applied to the inlet of a tube using a UDF The velocity has the form Uz Vo Asin wt The tube is 1 m long with a radius of 0 2 m It is assumed to be filled with air with a density of 1 kg m and a viscosity of 2x10 kg m s The velocity of the air fluctuates about an equilibrium value vo of 20 m s with an amplitude of 5 m s and at a frequency of 10 rad s The source file listing for the UDF that describes the transient inlet profile is shown below The function named unsteady_velocity
5. My Recent Documents My Network UDF Source File Judfexample c S Places Files of type UDF Source Files X Cancel Figure 8 1 5 The Select File Panel 3 In the Select File panel highlight the directory path under Directories e g nfs homeserver home clb mywork and the desired file e g udfexample c under Files and click OK This will close the Select File panel and display the path to the selected source file in the Interpreted UDFs panel 4 In the Interpreted UDFs panel specify the C preprocessor to be used in the CPP Command Name field You can keep the default cpp or you can select Use Con tributed CPP to use the preprocessor supplied by Fluent Inc If you installed the contrib component from the PrePost CD then by default the cpp preprocessor will appear in the panel For Windows NT users the standard Windows NT installation of the FLUENT product includes the cpp preprocessor For Windows NT systems if you are using the Microsoft compiler then use the command cl E FA Note that the default CPP Command Name is different for 2d and 3d cases The default preprocessor is cpp and cc E for a 2d and 3d case respec tively 8 8 Fluent Inc September 11 2006 8 1 Step By Step UDF Example 5 Keep the default Stack Size setting of 10000 unless the number of local variables in your function will cause the stack to overflow In this case set the Stack Size to a number that is greater t
6. O we switch Pollut_Par gt pollut_io_pdf case IN_PDF Source terms other than those from char must be included here if POLLUT_EQN Pollut_Par EQ_NO Prompt NOx if NOx gt prompt_nox amp amp NOx gt prompt_udf_replace int j real f rf real xc_fuel 0 0 Rate_Const K_PM 6 4e6 0 0 36483 49436 Kh Il 4 75 0 0819 NOx gt c_number 23 2 NOx gt equiv_ratio 32 0 pow NOx gt equiv_ratio 2 12 2 pow NOx gt equiv_ratio 3 for j FUEL j lt FUEL NOx gt nfspe j 2 50 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros xc_fuel MOLECON Pollut j rf ARRH Pollut K_PM rf pow Pollut_Par gt uni_R Pollut gt temp_m Pollut gt press 1 Pollut gt oxy_order rf pow MOLECON Pollut 02 Pollut gt oxy_order rf MOLECON Pollut N2 xc_fuel Pollut gt fluct fwdrate fxrf case OUT_PDF Char Contributions that do not go into pdf loop must be included here break default 3 Hooking a NO Rate UDF to FLUENT After the UDF that you have defined using DEFINE_NOX_RATE is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user_nox will be come visible and selectable in the NOx Model panel in FLUENT See Section 6 2 10 Hooking DEFINE_NOX_RATE UDFs for details Fluent Inc September
7. real ash_mass P_INIT_MASS p 1 DPM_CHAR_FRACTION p DPM_VOLATILE_FRACTION p real one_minus_conv MAX O P_MASS p ash_mass P_INIT_MASS p DPM_CHAR_FRACTION p real rate A1 exp E1 UNIVERSAL_GAS_CONSTANT P_T p rr rate P_DIAM p P_DIAM p M_PIxsf 0 one_minus_conv 2 54 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros Example 2 The following compiled UDF named user_rate specifies a particle reaction rate given by Equation 14 3 4 to Equation 14 3 7 in the User s Guide The reaction order on the kinetic rate is 0 9 and the effectiveness factor 7 is defined as ee where x is the fractional conversion of the particle char mass In this case it is necessary to obtain a numerical solution for the overall surface reaction rate This UDF is called only for reaction 2 which means that the default FLUENT solution will be used for the rest of the particle surface reactions defined UDF of specifying the surface reaction rate of a particle using a numerical solution include udf h define ci 5e 12 define A1 0 002 define E1 7 9e7 define tolerance 1e 4 define order 0 9 real reaction_rate real rate real ruser int iuser cxboolean buser char cuser return ruser 2 pow MAX 0 ruser 0 rate ruser 1 order rate DEFINE_PR_RATE user_rate c t r mw pp p sf dif_i cat_i rr if strcmp r gt name reaction 2 cxboolean if
8. Fill the UDM with magnitude of gradient thread_loop_c t domain begin_c_loop c t C_UDMI c t 0 NV_MAG C_UDSI_G c t 0 end_c_loop c t 3 44 Fluent Inc September 11 2006 3 2 Data Access Macros Reserving UDM Variables Using Reserve User Memory Vars The new capability of loading more than one UDF library into FLUENT raises the possi bility of user defined memory UDM clashes If for example you want to use one UDF library that has a fixed 2D magnetic field stored in User Memory 0 and User Memory 1 and you want to use another UDF library that models the mass exchange between phases using User Memory O for the exchange rates and these two libraries are loaded at the same time then the two models are going to interfere with each other s data in User Memory 0 To avoid data contention problems a new macro has been added that will allow a UDF library to reserve UDM locations prior to usage Note that there are other methods you can use within UDFs to hardcode the offset for UDMs to prevent contention that are not discussed here int Reserve_User_Memory_Vars int num The integer given as an argument to the macro num specifies the number of UDMs needed by the library The integer returned by the function is the starting point or offset from which the library may use the UDMs It should be saved as a global integer such as offset in the UDF and it should be initialized to the special variable UD
9. Open the User Defined Function Hooks panel Figure 6 1 11 Define S User Defined Function Hooks User Defined Function Hooks Initialization mone Adjust none Execute at End none Edit Read Case none Edit Write Case none Edit Read Data none Edit Write Data none Edit Execute at Exit Edit Figure 6 1 11 The User Defined Function Hooks Panel You have the choice of hooking a UDF to read and write a case and data file Below is a description of what each function does e Read Case is called when you read a case file into FLUENT It will specify the customized section that is to be read from the case file e Write Case is called when you write a case file from FLUENT It will specify the customized section that is to be written to the case file e Read Data is called when you read a data file into FLUENT It will specify the customized section that is to be read from the data file e Write Data is called when you write a data file from FLUENT It will specify the customized section that is to be written to the data file 6 12 Fluent Inc September 11 2006 6 1 Hooking General Purpose UDFs To hook a read case file UDF for example click on the Edit button next to Read Case This will open the Read Case Functions panel Figure 6 1 12 Read Case Functions Available Read Case Functions Selected Read Case Functions luser_readl lib
10. Zones Fluent Inc September 11 2006 6 5 Hooking Dynamic Mesh UDFs Dynamic Mesh Zones Zone Names Dynamic Zones axis Type C Stationary Rigid Body C Deforming C User Defined Motion Attributes Geometry Definition Meshing Options Six DOF UDF Six DOF Solver Options stage libudf M On Passive Center of Gravity Location Center of Gravity Orientation x in o Theta_Z deg fo Y fin o T of Gravity Yelocity Center of Gravity Angular Velocity _X mis o Omega_Z rad s o _Y m s f Draw Delete Update Close Help Figure 6 5 4 The Dynamic Mesh Zones Panel Select Rigid Body under Type in the Dynamic Mesh Zones panel Figure 6 5 4 and click on the Motion Attributes tab Choose the function name e g stage from the Six DOF UDF drop down list Click Create then Close See Section 2 6 4 DEFINE_SDOF_PROPERTIES for details about DEFINE SDOF PROPERTIES functions Fluent Inc September 11 2006 6 77 Hooking UDFs to FLUENT 6 6 Hooking User Defined Scalar UDS Transport Equation UDFs This section contains methods for hooking anisotropic diffusion coeffient fluex and un steady UDFs for scalar equations that have been defined using DEFINE macros described in Section 2 7 User Defined Scalar UDS Transport Equation DEFINE Macros and in terpreted or compiled using methods described in Chapters 4 or 5 respectively See Secti
11. declares a pointer named ip that points to an integer variable Now suppose you want to assign an address to pointer ip To do this you can use the amp notation For example ip amp a assigns the address of variable a to pointer ip You can retrieve the value of variable a that pointer ip is pointing to by ip Fluent Inc September 11 2006 A 9 C Programming Basics Alternatively you can set the value of the variable that pointer ip points For example xip 4 assigns a value of 4 to the variable that pointer ip is pointing The use of pointers is demonstrated by the following int a 1 int ip ip amp a amp a returns the address of variable a printf content of address pointed to by ip d n ip xip 4 ea 4 printf now a d n a Here an integer variable a is initialized to 1 Next ip is declared as a pointer to an integer variable The address of variable a is then assigned to pointer ip Next the integer value of the address pointed to by ip is printed using ip This value is 1 The value of variable a is then indirectly set to 4 using ip The new value of a is then printed Pointers can also point to the beginning of an array and are strongly connected to arrays in C Pointers as Function Arguments C functions can access and modify their arguments through pointers In FLUENT thread and domain pointers are common arguments to UDFs When you specify these argu
12. 2 3 14 DEFINE PROPERTY UDFs Description You can use DEFINE PROPERTY to specify a custom material property in FLUENT for single phase and multiphase flows When you are writing a user defined mixing law UDF for a mixture material you will need to use special utilities to access species material properties These are described below If you want to define a custom mass diffusivity property when modeling species transport you must use DEFINE_DIFFUSIVITY instead of DEFINE PROPERTY See Section 2 3 3 DEFINE DIFFUSIVITY for details on DEFINE_DIFFUSIVITY UDFs For an overview of the FLUENT solution process which shows when a DEFINE_PROPERTY UDF is called refer to Figures 1 9 1 1 9 2 and 1 9 3 Some of the properties you can customize using DEFINE_PROPERTY are e density as a function of temperature e viscosity e thermal conductivity e absorption and scattering coefficients e laminar flow speed e rate of strain e user defined mixing laws for density viscosity and thermal conductivity of mixture materials il UDFs cannot be used to define specific heat properties specific heat data can be accessed only and not modified in FLUENT FA Note that when you specify a user defined density function for a com pressible liquid flow application you must also include a speed of sound function in your model Compressible liquid density UDFs can be used in the pressure based solver and for single phase multiphase mixture and cavitation mod
13. Argument Type Description symbol name UDF name cell_t c Index of cell on which the Prandtl number function is to be applied Thread t Pointer to cell thread Function returns real There are three arguments to DEFINE_PRANDTL_D name c and t You supply name the name of the UDF c and t are variables that are passed by the FLUENT solver to your UDF Your UDF will need to return the real value for the turbulent dissipation Prandtl number to the solver Example An example of a Prandtl_D UDF is provided below in the source listing for DEFINE_PRANDTL_K Hooking a Prandtl Number UDF to FLUENT After the UDF that you have defined using DEFINE_PRANDTL_D is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user_pr_d will become visible and selectable in the Viscous Model panel in FLUENT See Sec tion 6 2 12 Hooking DEFINE PRANDTL UDFs for details 2 58 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros DEF INE_PRANDTL_K Description You can use DEFINE PRANDTL K to specify Prandtl numbers for turbulence kinetic energy k Usage DEFINE_PRANDTL_K name c t Argument Type Description symbol name UDF name cell_t c Index that identifies the cell on which the Prandtl number function is to be applied Thread t Pointer to cell thread Function returns real There are thre
14. Click Load to load the shared library into FLUENT The console will report that the library has been opened and the function e g x velocity loaded Opening library libudf Library libudf 1nx86 2d libudf so opened x_velocity Done See Chapter 5 Compiling UDF for more information on the compile build process Fluent Inc September 11 2006 8 1 Step By Step UDF Example 8 1 6 Step 5 Hook the UDF to FLUENT Now that you have interpreted or compiled your UDF following the methods outlined in Step 4 you are ready to hook the profile UDF in this sample problem to the Velocity Inlet boundary condition panel see Chapter 6 Hooking UDFSs to FLUENT for details on how to hook UDFs First click on the Momentum tab in the Velocity Inlet panel Figure 8 1 8 and then choose the name of the UDF that was given in our sample problem with udf preceeding it udf x_velocity from the X Velocity drop down list Once selected the default value will become grayed out in the X Velocity field Click OK to accept the new boundary condition and close the panel The user profile will be used in the subsequent solution calculation 1 Open the Velocity Inlet panel Define Boundary Conditions Velocity Inlet Zone Name velocity inlet Momentum Thermal Radiation Species DPM Multiphase UDS Velocity Specification Method Components Reference Frame Absolute Coordinate System Cartesian K Y Z
15. Execute at Exit none Edit Wall Heat Flux none Net Reaction Rate none Chemistry Step Mixing Model Constant Cphi none Figure 6 2 1 The User Defined Function Hooks Panel FH EDC or PDF Transport models must be enabled to hook chemistry step UDFs To hook the UDF to FLUENT choose the function name e g user_chem_step in the Chemistry Step drop down list in the User Defined Function Hooks panel and click OK See Section 2 3 1 DEFINE_CHEM_STEP for details about defining DEFINE_CHEM_STEP func tions Fluent Inc September 11 2006 6 15 Hooking UDFs to FLUENT 6 2 2 Hooking DEFINE_CPHI UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_CPHI UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Function Hooks panel Figure 6 2 2 in FLUENT Define User Defined Function Hooks User Defined Function Hooks Initialization none Edit Adjust none ui Execute at End none Edit Read Case none Edit Write Case none Edit Read Data none Edit Write Data none Edit Execute at Exit none Edit Wall Heat Flux none y Net Reaction Rate none Chemistry Step none Mixing Model Constant Cphi Figure 6 2 2 The User Defined Function Hooks Panel EDC or PDF Transport models must be enabled to hook the mixin
16. The following UDF named xmom_source is used to add source terms in FLUENT The source code can be interpreted or compiled The function generates an z momentum source term that varies with y position as source 0 5C2py vz Vx Suppose source Alv vz where A 0 5C2py Then dS d S All Aver loal The source term returned is 2 94 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros source Al v vz and the derivative of the source term with respect to v true for both positive and negative values of vy is ds 22 A dux POR oo o oo o kkk kkk kkk kkk UDF for specifying an x momentum source term in a spatially dependent porous media ARR Tete CTC e TT etererorerere terror roreTrr rere rrrr rrr rrr creer rT sy include udf h define C2 100 0 DEFINE_SOURCE xmom_source c t dS eqn real x ND_ND real con source C_CENTROID x c t con C2 0 5 C_R c t x 1 source con fabs C_U c t C_U c t dS eqn 2 con fabs C_U c t return source Hooking a Source UDF to FLUENT After the UDF that you have defined using DEFINE_SOURCE is interpreted Chapter 4 In terpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g xmom source will become visible and selectable in the Fluid or Solid boundary condition panel in FLUENT See Section 6 2 17 Hooking DEFINE_SOURC
17. else set dens to cell value NV_DS psi_vec F_U f t F_V f t F_W f t dens flux NV_DOT psi_vec A flux through Face else ci F_C1 f t Get cell on other side of face ti F_C1_THREAD f t NV_DS psi_vec C_U c0 t0 C_V c0 t0 C_W c0 t0 C_R c0 t0 NV_DS psi_vec C_U c1 t1 C_V c1 t1 C_W c1 t1 C_R c1 t1 flux NV_DOT psi_vec A 2 0 Average flux through face Fluent will multiply the returned value by phi_f the scalar s value at the face to get the complete advective term return flux Hooking a UDS Flux Function to FLUENT After the UDF that you have defined using DEFINE UDS FLUX is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g my_uds_flux will become visible and selectable in the User Defined Scalars panel in FLUENT See Sec tion 6 6 2 Hooking DEFINE_UDS_FLUX UDFs for details 2 218 Fluent Inc September 11 2006 2 7 User Defined Scalar UDS Transport Equation DEFINE Macros 2 7 4 DEFINE_UDS_UNSTEADY Description You can use DEFINE_UDS_UNSTEADY to customize unsteady terms in your user defined scalar UDS transport equations See Section 9 3 User Defined Scalar UDS Trans port Equations in the User s Guide for details on setting up and solving UDS transport equations Usage DEFINE UD
18. linear Evaporating Species Devolatilizing Species Product Species v v v Point Properties Turbulent Dispersion Wet Combustion Components UDF Multiple Reactions User Defined Functions _ Initialization none Heat Mass Transfer init_bubbles File Cancel Help Figure 6 4 5 The Injections Panel Fluent Inc September 11 2006 6 4 Hooking Discrete Phase Model DPM UDFs Click Create in the Injections panel to open the Set Injection Properties panel and set up your particle injections Next select the UDF tab in the Set Injection Properties panel Figure 6 4 5 and choose the function name e g init bubbles from the Heat Mass Transfer drop down list under User Defined Functions Click OK See Section 2 5 6 DEFINE_DPM_INJECTION_INIT for details about DEFINE_DPM_INJECTION_INIT functions 6 4 6 Hooking DEFINE_DPM_INJECTION_INIT UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_INJECTION_INIT UDF the name of the function you sup plied as a DEFINE macro argument will become visible and selectable in the Set Injection Properties panel Figure 6 4 6 in FLUENT Before you hook the UDF you ll need to create your particle injections in the Injections panel Define Injections Click Create in the Injections panel to open the Set Injection Properties panel and set up your particle injections Next select the UDF tab i
19. EEEE ooo ooo o DH D D ED kkk kk kkk kkk real NV_VEC psi NV_VEC A declaring vectors psi and A defining psi in terms of velocity field NV_D psi F_U f t F_V f t F_W f t NV_S psi F_R f t multiplying density to get psi vector F_AREA A f t face normal vector returned from F_AREA return NV_DOT psi A dot product of the two returned Additionally since most quantities in FLUENT are not allocated in memory for interior faces only for boundary faces e g wall zones your UDF will also need to calculate interior face values from the cell values of adjacent cells This is most easily done using the arithmetic mean method Vector arithmetic can be coded in C using the NV_ and ND_ macros see Chapter 3 Additional Macros for Writing UDFs Note that if you had to implement the default advection term in a UDF without the fluid density in the definition of 4 see above you could simply put the following line in your DEFINE_UDS_FLUX UDF 2 216 Fluent Inc September 11 2006 2 7 User Defined Scalar UDS Transport Equation DEFINE Macros return F_FLUX f t rho where the denominator p can be determined by averaging the adjacent cell s density values C_R F_CO f t THREAD_TO t and C_R F_C1 f t THREAD_T1 t Example The following UDF named my_uds_flux returns the mass flow rate through a given face The flux is usually available through the Fluent supplied macro F_FL
20. Index 7 Index fclose function A 16 grid fclose 7 44 components FILE 3 28 domains threads cells faces 1 8 file inclusion A 18 topology 1 8 file inclusion directive 1 2 zones 1 8 file sharing on Windows machines in paral grid motion UDFs 2 202 lel 4 3 File XY Plot panel 8 25 header files 1 5 Fill Face_Part_With_Different 7 31 udf h 4 2 5 3 Fill_Face Part With Same 7 31 heat flux function 8 48 fixed value boundary condition UDFs heat flux UDFs 2 44 Fit heterogeneous reaction rate UDFs 2 127 flow variable macros 3 9 3 20 hooking UDFs to FLUENT FLUENT data types 1 10 about 6 1 FLUENT solution process 1 12 DPM 6 53 FLUENT variables accessing 3 1 dynamic mesh 6 71 Fluid panel 6 39 8 28 errors 6 83 fluid thread checking 3 75 general purpose 6 1 FLUID_THREAD P 2 6 2 9 2 154 2 185 model specific 6 14 3 75 8 38 multiphase 6 46 flux UDFs 2 210 UDS 6 78 fopen function A 15 user defined scalars 6 78 fopen 7 44 host_to_node 7 16 for loops A 12 FORTRAN A 19 I O functions A 15 fprintf function A 16 LAM NODE HOST P 7 18 fprintf 2 24 3 28 AM_NODE_LAST P 7 18 fscanf function A 17 AM NODE LESS P 7 18 fscanf 2 24 AM_NODE_MORE_P 7 18 functions A 8 A 14 LAM NODE ONE P 7 18 reader 2 24 AM_NODE_SAME_P 7 18 writer 004 AM_NODE_ZERO_P 7 18 7 44 identifying processes parallel 7 39 general purpose UDFs if statement A 11 hooking to FLUENT 6 1 if else statement A 11 general so
21. User Scalar 2 none Figure 6 2 15 The Fluid Panel with Fixed Value Inputs for User Defined Scalars 6 30 Fluent Inc September 11 2006 6 2 Hooking Model Specific UDFs 2 If you are using your UDF to define a specific value or flux for a scalar equation you will need to first select the UDS tab in the wall inflow or outflow boundary panel Figure 6 2 16 Zone Name wall Adjacent Cell Zone fluid Momentum Thermal Radiation Species DPM Multiphase UDS User Defined Scalar Boundary Condition User Defined Scalar Boundary Yalue User Scalar 0 Specified Flux X User Scalar 0 udf pressure_profile User Scalar 1 Specified Flux User Scalar 1 g constant User Scalar 2 Specified Flux m User Scalar 2 jo constat E zi Cancel Help Figure 6 2 16 The Wall Panel with Inputs for User Defined Scalars Next for each UDS User Scalar 0 User Scalar 1 etc specify the boundary con dition value as a constant value or a UDF e g pressure_profile If you select Specified Flux then your input will be the value of the flux at the boundary i e the negative of the term in parentheses on the left hand side of Equation 9 3 2 in the User s Guide dot fas in the dot product of n as in the vector n where n is the normal into the domain If you select Specified Value then your input will be the value of the scalar itself at the boundary In the sample panel shown above for example the S
22. exp ACTIVE UNIVERSAL_GAS_CONSTANT temp Y Species numbers Must match order in Fluent panel define HF O Reaction Exponents define HF_EXP 2 0 Reaction Rate Routine used in UDF real reaction_rate cell_t c Thread cthread real mw real yil Note that all arguments in the reaction_rate function call in your c source file MUST be on the same line or a compilation error will occur real concenHF C_R c cthread yi HF mw HF return arrhenius_rate C_T c cthread pow concenHF HF_EXP J Fluent Inc September 11 2006 2 1 63 DEFINE Macros real contact_area cell_t c Thread t int s_id int n DEFINE_DPM_INJECTION_INIT init_bubbles I int count i real area mw MAX_SPE_EQNS yi MAX_SPE_EQNS MAX_SPE_EQNS is a Fluent constant in materials h Particle p cell_t cell Thread cthread Material mix sp Message Initializing Injection s n I gt name loop p I gt p Standard Fluent Looping Macro to get particle streams in an Injection cell P_CELL p Get the cell and thread that the particle is currently in cthread P_CELL_THREAD p Set up molecular weight amp mass fraction arrays mix THREAD_MATERIAL cthread mixture_species_loop mix sp i mw i yili MATERIAL_PROP sp PROP_mwi C_YI cell cthread i area contact_area cell cthread REACTING_SURFACE_ID amp count Function that gets
23. ment that you supplied as the first DEFINE macro argument e g writer will become visible and selectable in the User Defined Function Hooks panel in FLUENT Note that you can hook multiple read write functions to your model See Section 6 1 7 Hooking DEFINE_RW_FILE UDFs for details Fluent Inc September 11 2006 2 25 DEFINE Macros 2 3 Model Specific DEFINE Macros The DEFINE macros presented in this section are used to set parameters for a particular model in FLUENT Table 2 3 provides a quick reference guide to the DEFINE macros the functions they are used to define and the panels where they are activated in FLUENT Definitions of each DEFINE macro are listed in udf h For your convenience they are listed in Appendix B 2 26 Section 2 3 1 Section 2 3 2 Section 2 3 3 Section 2 3 4 Section 2 3 5 Section 2 3 6 Section 2 3 7 Section 2 3 8 Section 2 3 9 Section 2 3 10 Section 2 3 11 Section 2 3 12 Section 2 3 13 Section 2 3 14 Section 2 3 15 Section 2 3 16 Section 2 3 17 Section 2 3 18 Section 2 3 19 Section 2 3 20 Section 2 3 21 Section 2 3 22 Section 2 3 23 DEFINE CHEM STEP DEFINE CPHI DEFINE DIFFUSIVITY DEFINE DOM DIFFUSE REFLECTIVITY DEFINE DOM SOURCE DEFINE DOM SPECULAR REFLECTIVITY DEFINE GRAY BAND ABS COEFF DEFINE HEAT_ FLUX DEFINE NET REACTION RATE DEFINE NOX RATE DEFINE PR RATE DEFINE PRANDTL UDF s DEFINE PROFILE DEFINE PROPERTY UDF s DEFINE SCAT PHASE F
24. ments in your UDF the FLUENT solver automatically passes data that the pointers are referencing to your UDF so that your function can access solver data You do not have to declare pointers that are passed as arguments to your UDF from the solver For example one of the arguments passed to a UDF that specifies a custom profile defined by the DEFINE PROFILE macro is the pointer to the thread applied to by the boundary condition The DEFINE_PROFILE function accesses the data pointed to by the thread pointer A 10 Fluent Inc September 11 2006 A 11 Control Statements A1 Control Statements You can control the order in which statements are executed in your C program using control statements like if if else and for loops Control statements make decisions about what is to be executed next in the program sequence A 11 1 if Statement An if statement is a type of conditional control statement The format of an if statement is if logical expression statements where logical expression is the condition to be tested and statements are the lines of code that are to be executed if the condition is met Example if q 1 a 0 b 1 A 11 2 if else Statement if else statements are another type of conditional control statement The format of an if else statement is if logical expression statements else statements where logical expression is the condition to be tested and the first set of statement
25. s ID c and thread pointer t and returns the real value of the cell temperature to the FLUENT solver Fluent Inc September 11 2006 3 3 Additional Macros for Writing UDFs Example peaa kkk kkk kk kkk kkk kkk k k kk kk kkk k k k k k k kk k k EL k k kk k k k k k k k K kkk k 2k 2K k UDF for initializing flow field variables Example of C_T and C_CENTROID usage EEEE ooo ooo A A A 1 21 1 21 21 21 kk kkk kkk kk kkk kk include udf h DEFINE_INIT my_init_func d cell_t c Thread t real xc ND_ND loop over all cell threads in the domain thread_loop_c t d loop over all cells begin_c_loop_all c t C_CENTROID xc c t if sqrt ND_SUM pow xc 0 0 5 2 pow xc 1 0 5 2 pow xc 2 0 5 2 lt 0 25 C_T c t 400 else C_T c t 300 5 end_c_loop_all c t 3 4 Fluent Inc September 11 2006 3 2 Data Access Macros 3 2 Data Access Macros 3 2 1 Introduction The macros presented in this section access FLUENT data that you can utilize in your UDF Unless indicated these macros can be used in UDFs for single phase and multiphase applications e Section 3 2 1 Introduction e Section 3 2 2 Node Macros e Section 3 2 3 Cell Macros e Section 3 2 4 Face Macros e Section 3 2 5 Connectivity Macros e Section 3 2 6 Special Macros e Section 3 2 7 Model Specific Macros e Section 3 2 8 User Defined Scalar UDS Transport Equation Macros e Section 3 2 9 User Defin
26. 0 0 J end_c_loop c t Fluent Inc September 11 2006 2 13 DEFINE Macros 2 14 Hooking an Execute From GUI UDF to FLUENT After the UDF that you have defined using DEFINE_EXECUTE_FROM_GUI is compiled Chap ter 5 Compiling UDFs the function will not need to be hooked to FLUENT through any graphics panels Instead the function will be searched automatically by the FLU ENT solver when the execution of the UDF is requested e when a call is made from a user defined Scheme program to execute a C function Fluent Inc September 11 2006 2 2 General Purpose DEF INE Macros 2 2 6 DEFINE_EXECUTE_ON_LOADING Description DEFINE_EXECUTE_ON_LOADING is a general purpose macro that can be used to specify a function that executes as soon as a compiled UDF library is loaded in FLUENT This is useful when you want to initialize or setup UDF models when a UDF library is loaded Alternatively if you save your case file when a shared library is loaded then the UDF will execute whenever the case file is subsequently read Compiled UDF libraries are loaded using either the Compiled UDFs or the UDF Library Manager panel see Section 5 5 Load and Unload Libraries Using the UDF Library Manager Panel An EXECUTE_ON_LOADING UDF is the best place to reserve user defined scalar UDS and user defined memory UDM for a particular library Sections 3 2 8 and 3 2 9 as well as set UDS and UDM names Sections 3 2 8 and 3 2 9
27. 1 x 0 0 endif dmatrix is computed as xT diff x dmatrix 0 0 diff 0 x 0 0 x 0 0 diff 1 x 1 0 x 1 0 if RP_3D diff 2 x 2 0 x 2 0 endif dmatrix 1 1 diff 0 x 0 1 x 0 1 diff 1 x 1 1 x 1 1 if RP_3D diff 2 x 2 1 x 2 1 endif dmatrix 1 0 diff 0 x 0 1 x 0 0 diff 1 x 1 1 x 1 0 if RP_3D diff 2 x 2 1 x 2 0 endif oo Ole if RP_3D dmatrix 2 2 diff 0 x 0 2 x 0 2 diff 1 x 1 2 x 1 2 diff 2 x 2 2 x 2 2 dmatrix 0 2 diff 0 x 0 0 x 0 2 diff 1 x 1 0 x 1 2 diff 2 x 2 0 x 2 2 dnar iloi e aol dmatrix 11 2 diff 0 x 0 11 x 0 2 diff 1 x 1 1 x 1 2 diff 2 x 2 1 x 2 2 Mat Sansa IE Hendif Fluent Inc September 11 2006 2 213 DEFINE Macros Hooking an Anisotropic Diffusivity UDF to FLUENT After the UDF that you have defined using DEFINE_ANISOTROPIC_DIFFUSIVITY is in terpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g cyl ortho diff will become visible and selectable in the User Defined Functions panel You ll first need to select defined per uds for UDS Diffusivity in the Materials panel then select the user defined anisotropic option for Diffusivity from the UDS Diffusio
28. 1 m user defined Edi E o it gb_abs_coeff Scattering Coefficient 1 m feonstant ean 8 Scattering Phase Function isotopic Edit Thermal Expansion Coefficient 17k o nstant vl Edit 1e 65 E Change Create Delete Close Help Figure 6 2 8 The Materials Panel To hook the UDF to FLUENT first select user defined gray band from the Absorption Co efficient drop down list in the Materials panel This will open the User Defined Functions panel Then choose the name of the function e g gb_abs_coeff from the list of choices in the panel and click OK See Section 2 8 1 DEFINE GRAY BAND ABS COEFF for details about DEFINE GRAY BAND ABS COEFF functions 6 22 Fluent Inc September 11 2006 6 2 Hooking Model Specific UDFs 6 2 8 Hooking DEFINE_HEAT_FLUX UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_HEAT_FLUX UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Function Hooks panel Figure 6 2 9 in FLUENT Define User Defined Function Hooks User Defined Function Hooks Initialization none Edit Adjust none Edit Execute at End none Edit Read Case none Edit Write Case none Edit Read Data none Edit Write Data none Edit Execute at Exit none Edit Wall Heat Flux user_heat_flux li
29. 3 32 DPM property UDFs 2 172 DPM UDFs body force 2 149 boundary condition 2 141 drag coefficient 2 151 errosion and accretion rates 2 153 heat and mass transfer 2 159 particle initialization 2 162 particle laws 2 166 property 2 172 scalar update 2 176 source term 2 180 spray collide 2 182 switching custom laws 2 185 DPM variable macros 3 31 dpm h file 3 31 DPM_BOILING_TEMPERATURE 3 32 DPM_CHAR_FRACTION 3 32 DPM_EMISSIVITY 3 32 DPM_EVAPORATION_TEMPERATURE 3 32 DPM_HEAT_OF_PYROLYSIS 3 32 DPM_HEAT_OF_REACTION 3 32 DPM_LIQUID_SPECIFIC_HEAT 3 32 DPM_OUTPUT 2 177 DPM_SCAT_FACTOR 3 32 DPM_SPECIFIC_HEAT 3 32 DPM_SWELLING COEFF 3 32 DPM_VOLATILE FRACTION 3 32 drag law default 2 123 DT_THREAD 2 197 2 203 duct flow 8 26 Fluent Inc September 11 2006 Index dynamic loading 1 6 5 2 dynamic mesh DEFINE macros quick reference guide 2 196 dynamic mesh macros 3 37 dynamic mesh UDFs center of gravity motion 2 197 deforming zone geometry 2 200 grid motion 2 202 Dynamic Mesh Zones panel 6 71 6 73 6 75 6 76 edge 1 10 emission term 2 39 emulator 1 6 erosion rate UDFs 2 153 Error 3 74 error messages 4 6 errors compiling source files 5 26 hooking UDFs 6 83 interpreting source files 4 6 parallel 4 7 5 28 Eulerian model DEFINE macro usage C 7 laminar flow C 11 C 14 C 18 examples porosity function 2 75 examples porous resistance direction vec tor 2 77 examples UDF
30. 5 5 x 10 kg m s while the viscosity for the cooler region T lt 286 K has a much larger value 1 0 kg m s In the intermediate temperature range 286 K lt T lt 288 K the viscosity follows a linear profile that extends between the two values given above u 143 2135 0 497257 2 3 6 This model is based on the assumption that as the liquid cools and rapidly becomes more viscous its velocity will decrease thereby simulating solidification Here no correction is made for the energy field to include the latent heat of freezing The source code can be interpreted or compiled in FLUENT J EK K K K K 2k 2k 3k ak ak 3k ak 3K ak aK a 2K 2 aK aK aK K K K aK K K K 2K 3K 2K 3K 3K 3K 3K 3K 3K 2K 3K 2K 2k 2 2K 2K 2K aK 2K K 2K aK i x K 4 4 4 K K UDF that simulates solidification by specifying a temperature dependent viscosity property FER ak HAE EE EEE DEEE I I I K A A A KE K K Ik kk FK KK KKK include udf h DEFINE_PROPERTY cell_viscosity c t real mu_lam real temp C_T c t if temp gt 288 mu_lam 5 5e 3 else if temp gt 286 mu_lam 143 2135 0 49725 temp else mu_lam 1 return mu_lam The function cell viscosity is defined on a cell Two real variables are introduced temp the value of C_T c t and mu lam the laminar viscosity computed by the function The value of the temperature is checked and based upon the range into which it falls the appropriate value of mu_lam is computed At th
31. 8 1 compiled only 2 55 2 60 2 101 2 103 2 105 2 112 2 142 2 144 2 149 2 151 2 154 2 162 2173 9 177 2 185 2 197 2 200 2 202 2 203 2 217 8 43 interpreted or compiled 2 5 2 9 2 19 2 21 2 24 2 35 2 68 2 69 2 75 2 77 2 88 2 94 2 108 2 115 2 167 2 220 examples viscous resistance profile 2 75 exchange macros parallel 7 36 exchange property UDFs 2 122 EXCHANGE_SVAR_FACE_MESSAGE 7 36 EXCHANGE_SVAR_MESSAGE 7 36 execute from GUI UDFs 2 12 Fluent Inc September 11 2006 Execute On Demand panel 6 11 execute on loading UDFs 2 15 execute at end UDFs 2 9 execute at exit UDFs 2 11 exterior cell looping macro parallel 7 25 F AREA 2 101 2 103 2 154 2 162 2 197 9517310 75 T FCO 2 101 2 103 2 154 2 217 3 22 pCi 017 39 F_CENTROID 2 68 2 69 2 73 2 142 3 18 3 26 3 28 3 29 8 18 F_D 3 20 F_FLUX 2 216 3 20 F_H 3 20 F_K 3 20 F_NNODES 3 6 F_NODE 2 203 3 54 f_node_loop 2 203 3 53 F_P 3 20 F_PART 7 31 F_PROFILE 2 67 2 69 2 73 3 29 8 18 F_R 3 20 F_STORAGE R 2 153 FT 2 103 3 20 FU 2 216 3 20 F_UDMI 2 154 3 42 6 14 FV 2 216 3 20 FEW 2 216 3 20 FYI 3 20 face 1 10 face area vector macro 3 19 face centroid macro 3 18 face ID 1 11 face identifier 3 3 face looping macros examples of 2 66 general purpose 7 28 face normal gradient 3 21 face partition IDs parallel 7 31 face variables macros 3 18 setting 3 29 face_t data type 1 10
32. An example of the usage of the DEFINE_HEAT_FLUX macro is included in that implementation Hooking a Heat Flux UDF to FLUENT After the UDF that you have defined using DEFINE_HEAT_FLUX is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g heat flux will become visible and selectable in the User Defined Function Hooks panel in FLUENT See Section 6 2 8 Hooking DEFINE_HEAT_FLUX UDFs for details Fluent Inc September 11 2006 2 45 DEFINE Macros 2 3 9 DEFINE_NET_REACTION_RATE Description You can use DEFINE NET REACTION RATE to compute the homogeneous net molar reaction rates of all species The net reaction rate of a species is the sum over all reactions of the volumetric reaction rates where R is the net reaction rate of species i and R is the Arrhenius molar rate of creation destruction of species in reaction r A DEFINE_NET_REACTION_RATE UDF may be used for the Laminar finite rate EDC and PDF Transport models as well as for the surface chemistry model In contrast the volumetric UDF function DEFINE_VR_RATE and surface UDF function DEFINE_SR_RATE A return the molar rate per reaction R Usage DEFINE_NET_REACTION_RATE name c t particle pressure temp yi rr jac Argument Type Description symbol name UDF name cellt c Cell index of current particle Thread t Pointer to cell thread for
33. B 2 Model Specific DEFINE Macro Definitions The following definitions for model specific DEFINE macros see Section 2 3 Model Specific DEFINE Macros are taken from the udf h header file define DEFINE_CHEM_STEP name c t p num_p n_spe dt pres temp yk void name int cell_t c Thread t Particle p int num_p int n_spe double dt double pres double temp double yk define DEFINE_CPHI name c t real name cell_t c Thread t define DEFINE_DIFFUSIVITY name c t i real name cell_t c Thread t int i define DEFINE_DOM_DIFFUSE_REFLECTIVITY name t nb n_a n_b diff_ ref_a diff_tran_a diff_ref_b diff_tran_b void name Thread t int nb real n_a real n_b real diff_ref_a real diff_tran_a real diff_ref_b real diff_tran_b define DEFINE_DOM_SPECULAR_REFLECTIVITY name f t nb n_a n_b ray_direction e_n total_internal_reflection specular_reflectivity specular_transmissivity void name face_t f Thread t int nb real n_a real n_b real ray_direction real e_n int total_internal_reflection real specular_reflectivity real specular_transmissivity define DEFINE_DOM_SOURCE name c t ni nb emission in_scattering abs_coeff scat_coeff void name cell_t c Thread t int ni int nb real emission real in_scattering real abs_coeff real scat_coeff define DEFINE_GRAY_BAND_ABS_COEFF name c t nb real name cell_t c Thread t int nb de
34. DEFINE DPM INJECTION INIT DEFINE DPM LAW DEFINE DPM OUTPUT DEFINE DPM PROPERTY DEFINE DPM SCALAR UPDATE DEFINE DPM SOURCE DEFINE DPM SPRAY COLLIDE DEFINE DPM SWITCH DEFINE DPM TIMESTEP DEFINE DPM VP EQUILIB Fluent Inc September 11 2006 2 1 39 DEFINE Macros Table 2 5 1 Quick Reference Guide for DPM Specific DEFINE Macros Function DEFINE Macro Panel Activated In particle state at boundaries body forces on particles drag coefficients between particles and fluid erosion and accretion rates heat and mass transfer of multicomponent particles to the gas phase initializes injections custom laws for particles modifies what is written to the sampling plane output material properties updates scalar every time a particle position is updated particle source terms particle collisions algorithm changes the criteria for switching between laws time step control for DPM simulation equilibrium vapor pressure of vaporizing components of multicomponent particles DEFINE_DPM_BC DEFINE DPM BODY FORCE DEFINE DPM DRAG DEFINE DPM EROSION DEFINE_DPM_HEAT_MASS DEF INE_DPM_INJECTION_INIT DEFINE DPM LAW DEFINE DPM OUTPUT DEFINE DPM PROPERTY DEFINE DPM SCALAR UPDATE DEFINE DPM SOURCE DEFINE DPM SPRAY_COLLIDE DEFINE DPM SWITCH DEFINE DPM TIMESTEP DEFINE DPM VP EQUILIB boundary condition e g Velocity Inlet Discrete Phase Model Discrete Phase Model Discrete Phase Model Set Inj
35. DEFINE WALL_FUNCTIONS boundary condition e g Velocity Inlet boundary condition boundary condition boundary condition Pressure Outlet boundary condition boundary condition boundary condition boundary condition boundary condition boundary condition boundary condition boundary condition boundary condition boundary condition boundary condition boundary condition boundary condition boundary condition boundary condition Wall Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros Table 2 3 3 Quick Reference Guide for Model Specific DEFINE Functions Continued Function DEFINE Macro Panel Activated In density as function of DEFINE PROPERTY Materials temperature density as function of pressure for compressible liquids viscosity mass diffusivity thermal conductivity thermal diffusion coefficient absorption coefficient scattering coefficient laminar flow speed rate of strain speed of sound function user defined mixing law for mixture materials density viscosity thermal conductivity scattering phase function solar intensity mass source momentum source energy source turbulence kinetic energy source turbulence dissipation rate source species mass fraction source user defined scalar source P1 radiation model source surface reaction rate SO formation rate turbulent premixed source turbulent viscosity UDS flux function UDS unsteady function
36. DPM_SWELLING_COEFF p DPM_SURFTEN p DPM_VAPOR_PRESSURE p m DPM_VAPOR_TEMP p m DPM_VOLATILE_FRACTION p Tracked Particle p Tracked Particle xp Material m Tracked Particle p Tracked_ Particle xp particle temperature t Tracked Particle p Material m Tracked Particle xp Material m Tracked Particle p Tracked Particle p Tracked Particle p Tracked Particle xp particle temperatire t Note particle temp typically determined by P_T p Tracked_Particle p Tracked_Particle p Material m Tracked_Particle p particle temperature t Note particle tem perature is typically determined by P_T p Tracked_Particle p Tracked Particle p Tracked Particle p Material m Tracked Particle p Material m Tracked Particle p material pointer boiling temperature char fraction diffusion coefficient to be used the gaseous boundary layer around particle emissivity for the radiation model evaporation temperature heat of pyrolysis heat of reaction latent heat specific heat of material used for liquid associated with particle dynamic viscosity of droplets scattering factor for radiation model specific heat at temperature t swelling coefficient for devolatilization surface tension of droplets vapor pressure of liquid part of particle vaporization temperature used to switch to vaporization law volatile fraction 3 34 Fluent Inc September 11 2006 3
37. Dynamic_Thread dt real position define DEFINE_GRID_MOTION name d dt time dtime void name Domain d Dynamic_Thread dt real time real dtime define DEFINE_SDOF_PROPERTIES name properties dt time dtime void name real properties Dynamic_Thread dt real time real dtime Fluent Inc September 11 2006 B 5 DEFINE Macro Definitions B 5 Discrete Phase Model DEFINE Macros The following definitions for DPM DEFINE macros see Section 2 5 Discrete Phase Model DPM DEFINE Macros are taken from the dpm h header file Note that dpm h is included in the udf h header file define DEFINE_DPM_BC name p t f normal dim int name Tracked_Particle p Thread t face_t f real normal int dim define DEFINE_DPM_BODY_FORCE name p i real name Tracked_Particle p int i define DEFINE_DPM_DRAG name Re p real name real Re Tracked_Particle p define DEFINE_DPM_EROSION name p t f normal alpha Vmag mdot void name Tracked_Particle p Thread t face_t f real normal real alpha real Vmag real mdot define DEFINE_DPM_HEAT_MASS name p Cp hgas hvap cvap_surf dydt dzdt void name Tracked_Particle p real Cp real hgas real hvap real cvap_surf real dydt dpms_t dzdt define DEFINE_DPM_INJECTION_INIT name I void name Injection I define DEFINE_DPM_LAW name p ci void name Tracked_Particle p int ci define DEFINE_DPM_OUTPUT name header fp p
38. Fluent Inc September 11 2006 3 73 Additional Macros for Writing UDFs Error You can use Error when you want to stop execution of a UDF and print an error message to the console window Example if table_file NULL Error error reading file i Error is not supported by the interpreter and can be used only in compiled UDFs 3 8 Miscellaneous Macros N_UDS You can use N_UDS to access the number of user defined scalar UDS transport equations that have been specified in FLUENT The macro takes no arguments and returns the integer number of equations It is defined in models h N_UDM You can use N_UDM to access the number of user defined memory UDM locations that have been used in FLUENT The macro takes no arguments and returns the integer number of memory locations used It is defined in models h Data_Valid_P You can check that the cell values of the variables that appear in your UDF are accessible before you use them in a computation by using the Data_Valid_P macro cxboolean Data_Valid_P Data Valid P is defined in the id h header file and is included in udf h The function returns 1 true if the data that is passed as an argument is valid and 0 false if it is not Example if Data_Valid_P return 3 74 Fluent Inc September 11 2006 3 8 Miscellaneous Macros Suppose you read a case file and in the process load a UDF If the UDF performs a calculation using variables that
39. For example C_T_M2 c t returns the value of the cell temperature at the time step before the previous one re ferred to as second previous time step Two previous time step macros are shown in Table 3 2 12 i Note that data from C T M2 is available only if user defined scalars are defined It can also be used with adaptive time stepping Derivative Macros The macros listed in Table 3 2 13 can be used to return real velocity derivative variables in SI units The variables are available in both the pressure based and the density based solver Definitions for these macros can be found in the mem h header file Fluent Inc September 11 2006 3 13 Additional Macros for Writing UDFs Table 3 2 12 Macros for Cell Time Level 2 Defined in mem h Macro Argument Types Returns CRM2 c t cell_t c Thread t density second previous time step CPM2 c t cell t c Thread t pressure second previous time step CU_M2 c t cell t c Thread t velocity second previous time step CVM2 c t cell_t c Thread t velocity second previous time step C_W_M2 c t cell_t c Thread t velocity second previous time step C_TM2 c t cell_t c Thread t temperature second previous time step C YI M2 c t i cell_t c Thread t int i species mass fraction second previous time step 3 14 Table 3 2 13 Macros for Cell Velocity Derivatives Defined in mem h Macro Argument Types Returns C_STRAIN RATE MAG c t
40. Microsoft R 32 bit C C Standard Compiler Version 13 10 3077 for 80x86 Copyright C Microsoft Corporation 1984 2002 All rights reserved udf_names c Linking libudf dll because of makefile user_nt udf udf_names obj udfexample obj link Libpath c fluent inc fluent6 3 23 ntx86 2d d1l out libudf dl 1 udf_names obj udfexample obj 16323s 1ib Microsoft R Incremental Linker Version 7 10 3077 Fluent Inc September 11 2006 5 3 Compile a UDF Using the TUI Copyright C Microsoft Corporation All rights reserved Creating library libudf lib and object libudf exp C Fluent Inc ntbin ntx86 libudf ntx86 2d gt Note that if there are problems with the build you can do a complete rebuild by typing nmake clean and then nmake again UNIX and Linux Systems 1 Using a text editor edit the file makefile in your src directory to set the following two parameters SOURCES and FLUENT_INC SOURCES the name of your source file s e g udfexample c Multiple sources can be specified by using a space delimiter e g udfexamplei c udfexample2 c FLUENT_INC the path to your release directory 2 If your architecture is irix6 5 make the following additional change to the makefile a Find the following line in the makefile CFLAGS_IRIX6R10 KPIC ansi fullwarn 0 n32 b Change ansi to xansi CFLAGS_IRIX6R10 KPIC xansi fullwarn 0 n32 For all other architectures do not make any further changes to the ma
41. Resetting is typically done at the beginning of a FLUENT session by the use of DEFINE_ON_DEMAND in order to avoid the use of uninitialized data fields Resetting prevents the addition of sampled data being read from a file e average diameter of particles hitting the wall e average radial velocity of particles Before tracing the particles you will have to reset the UDMLs and assign the global domain pointer by executing the DEFINE_ON_DEMAND function BRR OFC OI K 3K 2K K K 2K 2K K OK 2 A K 2K FK 2K K 2K 2K K FK FK K FK 2k kA 2K 2 K FK 2k K FK FK 2k LL FK 2 K 2k 2k 2K K UDF for extending post processing of wall impacts EEEE ooo oo kkk k kkk kkk kkk k include udf h define MIN_IMPACT_VELO 1000 Minimum particle velocity normal to wall m s to allow Accretion Domain domain Get the domain pointer and assign it later to domain enum Enumeration of used User Defined Memory Locations NUM_OF_HITS Number of particle hits into wall face considered AVG_DIAMETER Average diameter of particles that hit the wall AVG_RADI_VELO Average radial velocity of NUM_OF_USED_UDM int UDM_checked 0 Availability of UDMLs checked void reset_UDM_s void Function to follow below 2 1 54 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros int check_for_UDM void Check for UDMLs availability Thread t if
42. The Adjust Functions Panel Select the function s you wish to hook to your model from the Available Adjust Functions list Click Add and then OK to close the panel Click OK in the User Defined Function Hooks panel to apply the settings Once added the name of the function you selected will be displayed in the User Defined Function Hooks panel If you select more than one function the number will be indicated e g 2 selected See Section 2 2 1 DEFINE ADJUST for details about defining adjust functions using the DEFINE_ADJUST macro Fluent Inc September 11 2006 6 3 Hooking UDFs to FLUENT 6 1 2 Hooking DEFINE_DELTAT UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DELTAT UDF the name of the function you supplied as a DE FINE macro argument will become visible and selectable in the lterate panel Figure 6 1 3 in FLUENT Solve _ Iterate Iterate Time Adaptive Time Step Parameters Time Step Size s 2e 66 fruncation Error Tolerance Number of Time Steps z Ending Time s Time Stepping Method Minimum Time Step Size s C Fixed Adaptive fS Variable Maximum lime Step i Animum tep Change Fa Options imum Step Char l Data Sampling for Time Statistics Number of Fixed Time Step keraton User Defined Time Step mydeltat libudf Max Iterations per Time Step 40 4 Reporting Interval 4 4 UDF Profile Update In
43. UDM_checked return UDM_checked if rp_axi Internal_Error UDF Error only valid for 2d axisymmetric cases n thread_loop_c t domain We require all cell threads to provide space in memory for UDML if FLUID_THREAD_P t if NULLP THREAD_STORAGE t SV_UDM_I return 0 UDM_checked 1 To make the following work properly reset_UDM_s This line will be executed only once return UDM_checked because check_for_UDM checks for UDM_checked first void reset_UDM_s void Thread t cell_t c face_t fj int 1 if check_for_UDM Don t do it if memory is not available return Message Resetting User Defined Memory n thread_loop_f t domain if NNULLP THREAD_STORAGE t SV_UDM_I begin_f_loop f t for i 0 i lt NUM_OF_USED_UDM i F_UDMI f t i 0 Fluent Inc September 11 2006 2 1 55 DEFINE Macros end_f_loop f t Message Skipping FACE thread no d n THREAD_ID t thread_loop_c t domain if CNNULLP THREAD_STORAGE t SV_UDM_I begin_c_loop c t for i 0 i lt NUM_OF_USED_UDM i C_UDMI c t i 0 end_c_loop c t Message Skipping CELL thread no d n THREAD_ID t Skipping Cell Threads can happen if the user uses reset_UDM prior to initializing Message Done n DEFINE_DPM_SCALAR_UPDATE dpm_scalup c t if_init p if G init P
44. and mu t ke 2 for multiphase will become visible and selectable in the Viscous Model panel in FLUENT See Section 6 2 21 Hooking DEFINE_TURBULENT_VISCOSITY UDFs for details 2 1 10 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros 2 3 22 DEFINE_VR_RATE Description You can use DEFINE_VR_RATE to specify a custom volumetric reaction rate for a single reaction or for multiple reactions During FLUENT execution DEFINE VR RATE is called for every reaction in every single cell Usage DEFINE VR RATE name c t r mw yi rr rrt Argument Type Description symbol name UDF name cellt c Cell index Thread t Pointer to cell thread on which the volumetric reaction rate is to be applied Reaction r Pointer to data structure that represents the current reaction real mw Pointer to array of species molecular weights real yi Pointer to array of the species mass fractions real rr Pointer to laminar reaction rate real rr_t Pointer to turbulent reaction rate Function returns void There are eight arguments to DEFINE VR RATE name c t r mw yi rr and rr_t You supply name the name of the UDF c t r mw yi rr and rr_t are variables that are passed by the FLUENT solver to your UDF Your UDF will need to set the values referenced by the real pointers rr and rr_t to the laminar and turbulent reaction rates respectively rr and rr_t defined by the UDF are computed and the lower of the two values is
45. for the resulting objects and loading the compiled UDF library into FLUENT using the graphical user interface GUI is as follows A Note that if you are running serial or parallel FLUENT on a Windows system then you must have Microsoft Visual Studio installed on your ma chine and have launched FLUENT from the Visual Studio console window to compile a UDF 1 Make sure that the UDF source file you want to compile is in the same directory that contains your case and data files FH Note that if you wish to compile a UDF while running FLUENT on a Windows parallel network then you must share the directory where the UDF is located so that all computers on the cluster can see this directory To share the directory that the case data and compiled UDF reside in using the Windows Explorer right click on the directory choose Sharing from the menu click Share this folder and then click OK If you forget to enable the sharing option for the directory using the Win dows Explorer then FLUENT will hang when you try to load the library in the Compiled UDFs panel 5 4 Fluent Inc September 11 2006 5 2 Compile a UDF Using the GUI 2 Start FLUENT from your working directory 3 Read or set up your case file 4 Open the Compiled UDFs panel Figure 5 2 1 Define User Defined Functions gt Compiled Compiled UDFs Source Files Header Files Add Delete A
46. hooking to FLUENT 6 46 DEF INE_CG_MOTION UDFs defining 2 197 hooking to FLUENT 6 71 DEFINE_CHEM_STEP UDFs defining 2 31 hooking to FLUENT 6 15 DEFINE_CPHI UDFs defining 2 33 hooking to FLUENT 6 16 DEFINE_DELTAT UDFs defining 2 7 hooking to FLUENT 6 4 DEFINE DIFFUSIVITY UDFs defining 2 34 example 8 48 hooking to FLUENT 6 17 DEFINE_DOM_DIFFUSE_REFLECTIVITY UDFs defining 2 36 hooking to FLUENT 6 19 DEFINE_DOM_ SOURCE UDF s defining 2 38 hooking to FLUENT 6 20 Index 3 Index DEF INE_DOM_SPECULAR_REFLECTIVITY UDFs defining 2 40 hooking to FLUENT 6 21 DEFINE_DPM_BC UDFs defining 2 141 hooking to FLUENT 6 53 DEF INE_DPM_BODY_FORCE UDF s defining 2 149 hooking to FLUENT 6 55 DEFINE_DPM_DRAG UDFs defining 2 151 hooking to FLUENT 6 56 DEF INE_DPM_EROSION UDFs defining 2 153 hooking to FLUENT 6 57 DEFINE_DPM_HEAT MASS UDFs defining 2 159 hooking to FLUENT 6 58 DEF INE_DPM_INJECTION_INIT UDFs defining 2 162 hooking to FLUENT 6 59 DEFINE_DPM_LAW UDFs defining 2 166 hooking to FLUENT 6 61 DEFINE_DPM_OUTPUT UDFs defining 2 168 hooking to FLUENT 6 62 DEFINE_DPM_PROPERTY UDFs defining 2 172 hooking to FLUENT 6 63 DEFINE DPM SCALAR UPDATE UDF s defining 2 176 hooking to FLUENT 6 65 DEFINE DPM SOURCE UDFs defining 2 180 hooking to FLUENT 6 66 DEFINE DPM SPRAY COLLIDE UDF s defining 2 182 hooking to FLUENT 6 67 DEFINE DPM SWITCH UDFs defining 2 185 h
47. mixture mixture Fluid mass source momentum source energy source DEFINE SOURCE DEFINE SOURCE DEFINE SOURCE primary and secondary phase s mixture mixture Fluent Inc September 11 2006 C 1 VOF Model Table C 1 2 DEFINE Macro Usage for the VOF Model Variable Macro Phase Specified On Fluid continued turbulence kinetic energy source turbulence dissipation rate source user defined scalar source species source velocity temperature user defined scalar turbulence kinetic energy turbulence dissipation rate species mass fraction porosity DEFINE SOURCE DEFINE SOURCE DEFINE SOURCE DEFINE SOURCE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE mixture mixture mixture phase dependent mixture mixture mixture mixture mixture phase dependent mixture Boundary Conditions Wall species boundary condition internal emissivity irradiation roughness height roughness constant shear stress components swirl components moving velocity components heat flux heat generation rate heat transfer coefficient external emissivity external radiation temperature free stream temperature user scalar boundary value discrete phase boundary value DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DE
48. once for each Injection before the particles are injected into the domain at each subsequent DPM iteration Function returns void There are two arguments to DEFINE DPM_INJECTION_INIT name and I You supply name the name of the UDF I is a variable that is passed by the FLUENT solver to your UDF Example The following UDF named init_bubbles initializes particles on a surface injection due to a surface reaction This function must be executed as a compiled UDF and can be used only on UNIX and Linux systems Note that if you are going to use this UDF in a transient simulation to compute transient particles you will need to replace loop p I gt p with loop p I gt p_init Transient particle initialization cannot be performed with a loop over I gt p 2 1 62 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros POCO COC kk kk kkk kkk kk kkk kk k kk kkk kk kk k k kk I I A A kk kk k kkk 4 4 k UDF that initializes particles on a surface injection due to a surface reaction kkk OO OR FK 2K 2K K FK 2K 2K K FK IR I FKK FK FK 2K K FK 2K KFK 2K K LS 2K K 2k 2K 2k K 2k 2k 24 LC 2k 6 2k 2k 2k ak include udf h include surf h RP_CELL and RP_THREAD are defined in surf h define REACTING_SURFACE_ID 2 define MW_H2 2 define STOIC_H2 1 ARRHENIUS CONSTANTS define PRE_EXP 1e 15 define ACTIVE 1e 08 define BETA 0 0 real arrhenius_rate real temp return PRE_EXP pow temp BETA
49. parallelized if it performs an operation that is dependent on sending or receiving data from another compute node or the host UDFs that involve global reductions such as global sums minimums or maximums or ones that perform computations on data residing in adjacent compute nodes for example will need to be modified in order to run in parallel Some other types of operations that require parallelization of serial source code include the following e Reading and Writing Files e Global Reductions e Global Sums e Global Minimums and Maximums e Global Logicals e Certain Loops over Cells and Faces e Displaying Messages on a Console e Printing to a Host or Node Process Once the source code for your parallelized UDF has been written it can be compiled using the same methods for serial UDFs Instructions for compiling UDFs can be found in Chapter 5 Compiling UDFs Fluent Inc September 11 2006 7 11 Parallel Considerations 7 4 Parallelization of Discrete Phase Model DPM UDFs The DPM model can be used for the following parallel options e Shared Memory e Message Passing When you are using a DPM specific UDF see Section 2 5 Discrete Phase Model DPM DEFINE Macros it will be executed on the machine that is in charge of the considered particle based on the above mentioned parallel options Since all fluid variables needed for DPM models are held in data structures of the tracked particles no special care
50. piling UDFs your DEFINE_MASS_TRANSFER UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable from the Mass tab in the Phase Interaction panel Figure 6 3 5 Define Phases Interaction Phase Interaction Drag Lift Collisions Slip Heat Mass Reactions Surface Tension F Cavitation Number of Mass Transfer Mechanisms 3 Mass Transfer From To Phase Species Phase Species Mechanism 1 phase 1 z phase 1 s user defined Edit liq_gas_source IA Cancel Help Figure 6 3 5 The Phase Interaction Panel To hook the UDF to FLUENT click the Mass tab and then specify the Number of Mass Transfer Mechanisms greater than 0 The Mechanism drop down list will appear Next choose user defined from the Mechanism drop down list to open the User Defined Functions panel Select the function name e g liq_gas_source from the UDF list and click OK The UDF name will appear in the text entry box below the Mechanism drop down list in the Phase Interaction panel See Section 2 4 4 DEFINE_MASS_TRANSFER for details about writing DEFINE_MASS_TRANSFER functions Fluent Inc September 11 2006 6 51 Hooking UDFs to FLUENT 6 3 5 Hooking DEFINE_VECTOR_EXCHANGE_PROPERTY UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_VECTOR_EXCHANGE_ RATE UDF the name of the f
51. see Chapter 22 Modeling Discrete Phase in the User s Guide for details Usage DEFINE DPM OUTPUT name header fp p t plane Argument Type symbol name int header FILE fp Tracked_Particle p Thread t Plane plane Function returns void Description UDF name Variable that is equal to 1 at the first call of the function before particles are tracked and set to 0 for subsequent calls Pointer to the file to or from which you are writing or reading Pointer to the Tracked_Particle data structure which contains data related to the particle being tracked Pointer to the thread that the particle is passing through if the sampler is represented by a grid surface If the sampler is not defined as a grid surface then the value of t is NULL Pointer to the Plane structure see dpm h if the sampling device is defined as a planar slice line in 2d If a grid surface is used by the sampler then plane is NULL There are six arguments to DEFINE_DPM_OUTPUT name header fp p t and plane You supply name the name of the UDF header fp p t and plane are variables that are passed by the FLUENT solver to your UDF The output of your UDF will be written to the file indicated by fp Pointer p can be used as an argument to the macros defined in Sec tion 3 2 7 DPM Macros to obtain information about particle properties e g injection properties 2 168 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM D
52. sign can be replaced by or and the sign can be replaced by Fluent Inc September 11 2006 3 65 Additional Macros for Writing UDFs NV_VS_VS The utility NV_VS_VS adds a vector to another vector which are each multiplied by a scalar NV_VS_VS a x 2 0 y 0 5 2D a 0 x 0 2 0 y 0 0 5 alt x 1 2 0 y 1 0 5 Note that the sign can be used in place of or and the sign can be replaced by 3 4 4 Vector Operation Macros There are macros that you can use in your UDFs that will allow you to perform oper ations such as computing the vector magnitude dot product and cross product For example you can use the real function NV MAG V to compute the magnitude of vector V Alternatively you can use the real function NV_MAG2 V to obtain the square of the magnitude of vector V Vector Magnitude Using NV_MAG and NV_MAG2 The utility NV_MAG computes the magnitude of a vector This is taken as the square root of the sum of the squares of the vector components NV_MAG x 2D sqrt x 0 x 0 x 1 x 1 3D sqrt x 0 x 0 x 1 x 1 x 2 x 2 The utility NV_MAG2 computes the sum of squares of vector components NV_MAG2 x 2D x 0 x 0 x 1 x 1 3D x 0 x 0 x 1 x 1 x 2 x 2 See Section 2 5 1 DEFINE DPM BC for an example UDF that utilizes NV MAG 3 66 Fluent Inc September 11 2006 3 4 Vector and Dimension Macros Dot Product Th
53. skipped over when the Replace by UDF Rate option is selected See Section 2 3 10 DEFINE_NOX_RATE for details about defining DEFINE_NOX_RATE func tions 6 26 Fluent Inc September 11 2006 6 2 Hooking Model Specific UDFs 6 2 11 Hooking DEFINE_PR_RATE UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_PR_RATE UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Function Hooks panel Figure 6 2 12 in FLUENT Define User Defined Function Hooks User Defined Function Hooks Initialization none Edit Adjust none Edit Execute at End none Read Case none Et Write Case none Read Data none i Write Data none Execute at Exit none Edit Wall Heat Flux none Volume Reaction Rate none Particle Reaction Rate Figure 6 2 12 The User Defined Function Hooks Panel il You must enable the particle surface reactions option before you can hook the UDF by selecting Volumetric and Particle Surface under Reactions in the Species Model panel To hook the UDF to FLUENT choose the function name e g user pr rate in the Particle Reaction Rate Function drop down list in the User Defined Function Hooks panel and click OK See Section 2 3 11 DEFINE PR RATE for details about defining DEFINE PR RATE functions Fluent Inc September 11 2006 6 27 Hooki
54. 01 7 02e 01 6 02e 01 5 03e 01 4 03e 01 3 04e 01 2 04e 01 1 05e 01 5 50e 03 Contours of Molecular Viscosity kg m s Physical Property Application Figure 8 2 13 Laminar Viscosity Generated by a User Defined Function Fluent Inc September 11 2006 8 35 Examples 1 73e 03 1 55e 03 1 38e 03 1 21e 03 1 04e 03 8 63e 04 6 91e 04 5 18e 04 3 45e 04 1 73e 04 0 00e 00 Contours of Velocity Magnitude m s Physical Property Application Figure 8 2 14 Contours of Velocity Magnitude Resulting from a User Defined Viscosity 8 00e 00 7 20e 00 6 40e 00 5 60e 00 4 80e 00 4 00e 00 3 20e 00 2 40e 00 1 60e 00 8 00e 01 0 00e 00 Contours of Stream Function kg s Physical Property Application Figure 8 2 15 Stream Function Contours Suggesting Solidification 8 36 Fluent Inc September 11 2006 8 2 Detailed UDF Examples 8 2 4 Reaction Rates This section contains an example of a custom reaction rate UDF It is executed as a compiled UDF in FLUENT Volume Reaction Rate A custom volume reaction rate for a simple system of two gaseous species is considered The species are named species a and species b The reaction rate is one that converts species a into species b at a rate given by the following expression KX Se 8 2 4 R at
55. 1 2 DEFINE_ANISOTROPIC_DIFFUSIVITY lt o 4 4 4 4 4 4 4 mu ens 2 207 2m3 DERINE OS FLUX sise re ses sea See 2 211 2 144 DEFINE DS UNSTEADY gt o 2 ae be deb an tbe du 2 215 3 Additional Macros for Writing UDFs 3 1 al L o 2 ARS DURS BER Pe AL Pe RAY RS EES 3 2 3 2 Data Access Macros sceno dan ee ee eR eb a 4 ES 3 5 G20 Tntroduction scs Le ees Mise Eee Ras beG oe OSS 3 5 322 Node Macross OL ur He ERE arte 3 6 Genet Noell MaCs 40 eb ee eee be eee mime ee Se des 3 7 piece Face Macros ars s taiea 8 ed OR ee BO Sd eH 3 19 3 2 5 Connectivity Macros 4 2464 eh dS eh EGA GERM 3 22 320 Special Marts 2 s si ta miss des sense er issued 3 26 3 2 7 Model Specific Macros 3 32 3 2 8 User Defined Scalar UDS Transport Equation Macros 3 39 3 2 9 User Defined Memory UDM Macros 3 42 x3 Looping Macrob Li 42h lt a ew ee ee ee eS oe ee a Soe ee oS 3 51 3 3 1 Multiphase Looping Macros 3 55 3 3 2 Advanced Multiphase Macros 3 59 a4 Vector and Dimension Macros 2 s 02208 26Gb 8 a SN e Ee 3 64 3 4 1 Macros for Dealing with Two and Three Dimensions 3 64 34 2 TheND Magee ss Los LR sa 6 eae RSD DESY OES 3 64 sA The NV ISO etsa oe ca ee oe Ge ee en ee Se 3 66 344 Vector Operation Macrae p scoe e w a ao de ed ew Ge Gee 3 67 3 5 Time Dependent Macros e sar ierasti eae ae wo Ree 3 69 IV Fl
56. 11 2006 2 51 DEFINE Macros 2 3 11 DEFINE PR RATE Description You can use DEFINE PR RATE to specify a custom particle surface reaction for the multiple surface reactions particle model During FLUENT execution the same UDF is called sequentially for all particle surface reactions so D FINE PR RATE can be used to define custom reaction rates for a single reaction or for multiple reactions The volumetric and wall surface reactions are not affected by the definition of this macro and will follow the designated rates Note that a DEFINE PR RATE UDF is not called with the coupled solution option so you will need to disable the Coupled Heat Mass Solution option in the Discrete Phase Model panel when using it The auxiliary function zbrent_pr_rate which is provided below can be used when there is no analytical solution for the overall particle reaction rate Usage DEFINE_PR_RATE name c t r mw ci p sf dif_index cat_index rr Argument Type symbol name cell tc Thread t Reaction r real mw real ci Tracked_Particle p real sf int dif_index int cat_index real rr Function returns void 2 52 Description UDF name Cell index of current particle Pointer to cell thread for particle Pointer to data structure that represents the current reaction Pointer to array containing gaseous and surface species molecular weights Pointer to array containing gas partial pressures Pointer to Tracked_Particle da
57. 2 Data Access Macros NO Macros The following macros can be used in NO model UDFs in the calculation of pollutant rates These macros are defined in the header file sg_nox h which is included in udf h They can be used to return real NO variables in SI units and are available in both the pressure based and the density based solver See Section 2 3 10 DEFINE_NOX_RATE for an example of a DEFINE_NOX_RATE UDF that utilize these macros Table 3 2 32 Macros for NO UDFs Defined in sg nox h Macro Returns POLLUT_EQN Pollut Par index of pollutant equation being solved see below MOLECON Pollut SPE molar concentration of species specified by SPE see below NULLIDX Pollut_Par SPE TRUE if the species specified by SPE doesn t exist in FLUENT case i e in the Species panel ARRH Pollut K Arrhenius rate calculated from the constants specified by K see below POLLUT_FRATE Pollut production rate of the pollutant species being solved POLLUT_RRATE Pollut reduction rate of the pollutant species being solved Pollut Par is a pointer to the Pollut_Parameter data structure that con tains auxilliary data common to all pollutant species and NOx is a pointer to the NOx_Parameter data structure that contains data specific to the NO model e POLLUT_EQN Pollut Par returns the index of the pollutant equation currently being solved The indices are EQ_NO for NO EQ_HCN for HCN EQ_N20 for N2O and EQ_NH3
58. 3 66 NV_S 2 197 2 203 2 216 NV_V 2 105 2 203 3 65 NV_V_VS 3 65 NV_VEC 2 125 2 142 2 197 2 203 2 216 NV_VS 2 154 NV_VS_VS 3 66 NV VV 2 203 3 65 object code 1 6 on demand UDFs 2 21 ONE_COMPUTE_NODE_P 7 18 P 1 radiation model UDF 8 46 P_CELL 2 162 2 185 3 32 P_CELL_THREAD 2 162 3 32 P_CURRENT_LAW 2 185 3 32 P_DEVOL_SPECIES_INDEX 3 32 P_DIAM 2 53 2 55 2 144 2 162 2 167 3 31 P_DT 2 177 2 185 3 31 P_EVAP_SPECIES_INDEX 3 32 P_FLOW_RATE 2 162 3 31 P_INIT_DIAM 2 167 2 183 P_INIT_MASS 2 53 2 55 2 173 P_LATENT_HEAT 3 32 P_LF 3 31 P_MASS 2 55 2 149 2 154 2 162 2 167 2 173 2 185 3 31 P_MATERIAL 2 185 3 32 P_NEXT_LAW 3 32 P_OXID_SPECIES_INDEX 3 32 P_POS 3 31 P_PROD_SPECIES_INDEX 3 32 PRHO 2 144 2 162 2 167 3 31 P_T 2 185 3 31 P_THREAD 2 185 P_TIME 2 149 3 31 P_USER_REAL 2 154 3 32 P VEL 2 144 2 149 3 31 P_VELO 2 144 P_VFF 3 31 parabolic velocity UDF example 8 16 Index 11 Index PARALLEL 7 13 7 44 parallel macros 7 13 global logicals 7 23 global maximums and minimums 7 22 global sums 7 21 global synchronization 7 23 parallel UDF example 7 41 parallel UDFs about 7 1 communication macros 7 16 global reduction macros 7 19 macros 7 13 overview 7 1 predicates 7 18 writing files 7 44 parallelizing your serial UDF 7 13 particle boundary condition UDF 2 141 custom law UDFs 2 166 diameter 2 162 dr
59. 7 41 Wriitme Files in Parallel sss mos Se moa ee whe hawker eae dae 7 44 8 Examples 8 1 8 1 Step By Step UDF Example 4 con nad dd us RY eee ee RS 8 1 eld Process Overvi w 12 4 eda eee dau we dig we hes eo 8 1 8 1 2 Step 1 Define Your Problem 4244 54 64564543 8 3 8 1 3 Step Create a U Source Pile 4 so sosu ee sue ook 8 5 8 1 4 Step 3 Start FLUENT and Read or Set Up the Case File 86 8 1 5 Step 4 Interpret or Compile the Source File 8 6 8 1 6 Step 5 Hook the UDF to FLUENT 4 4 sur uses 8 13 SLT Step 6 Run the Calculation o t ec osos aep ee eos a eus 8 14 8 1 8 Step 7 Analyze the Numerical Solution and Compare to Expected Results e isir duos dax EE we Ew 8 14 8 2 Detailed UDF Examples gt s oe c Sew eR drug Degree de dura 8 15 BEL Boundary Conditions 24442648248 dee eb dud oe ods 8 15 8 2 2 S urce Terms es os wee Se Rae Dec eR be 8 26 O25 Physical Properti s mis sr his ad ee Od ee we eS HS 8 33 O28 Reaction Rates s sorei ea 844 6o444 29444 oo Rw a 8 38 8 2 5 User Defined Scalars 2 52444 4464 446d EGR DR Ra 8 44 A C Programming Basics A 1 A1 Intr du ction 4 bod ee PES OE et Dee eee di we ee A 1 A2 Commenting Your C Code 444444464 Re 6 4 OR RES A 2 A3 C Data Types in FLUENT 4 a sata ee ee we a e a A 2 AM CO eS a ee Se oe ne He ee E ri ou A 3 AD Variables su san RS RE ROR na RS LO ee Ed a a Mere A 3 A 5 1 Declaring Variables A 4 A52 Externa
60. B 1 ff 0 045 pow ufree del VISC 0 25 utau sqrt ff pow ufree 2 2 0 knw pow utau 2 sqrt CMU kinf 0 002 pow ufree 2 begin_f_loop f t F_CENTROID x f t y x 1 if y lt del kay knwt y del kinf knw else kay knw h y del kinf knw if VKC y lt 0 085 del mix VKC y else mix 0 085 del F_PROFILE f t i pow CMU 0 75 pow kay 1 5 mix end_f_loop f t Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros Example 3 Fixed Velocity UDF In the following example DEFINE PROFILE is used to fix flow variables that are held con stant during computation in a cell zone Three separate UDFs named fixed_u fixed_v and fixed_ke are defined in a single C source file They specify fixed velocities that simulate the transient startup of an impeller in an impeller driven mixing tank The physical impeller is simulated by fixing the velocities and turbulence quantities using the fix option in FLUENT Click Section 7 27 Fixing the Values of Variables to go to the User s Guide for more information on fixing variables DORR CC A 2k 2K A 2K 2K K K K K 2K 2K 2K FK 2K 2K 2K A 2K 2K A K 2K 2K 2K 2K 2K A 2K 2k aK K 2K aK FK FK LES 2K K K K K K k ok K K K K Concatenated UDFs for simulating an impeller using fixed velocity BO ooo oo oo kkk k KK kkk include define define define define define define define define define define define define define
61. C_D c t C_VOLUME c t end_c_loop c t printf Volume integral of turbulent dissipation g n sum_diss Fluent Inc September 11 2006 2 5 DEFINE Macros Example 2 The following UDF named adjust_fcn specifies a user defined scalar as a function of the gradient of another user defined scalar using DEFINE_ADJUST The function is called once every iteration It is executed as a compiled UDF in FLUENT DOC OO OC 2k 2K K FK 2K 2K RO RK 2K 2K a LL LL LS SELS K K 2k 2K 2k UDF for defining user defined scalars and their gradients BOAR DH DH DEEE I I A A A 21 1 21 21 21 21 2 kk kkk DH A A kkk kk kkk kkk include udf h DEFINE_ADJUST adjust_fcn d Thread t cell_t c real K_EL 1 0 Do nothing if gradient isn t allocated yet if Data_Valid_P return thread_loop_c t d if FLUID_THREAD_P t begin_c_loop_all c t i C_UDSI c t 1 K_EL NV_MAG2 C_UDSI_G c t 0 C_VOLUME c t end_c_loop_all c t Hooking an Adjust UDF to FLUENT After the UDF that you have defined using DEFINE_ADJUST is interpreted Chapter 4 In terpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g adjust_fcn will become visi ble and selectable in the User Defined Function Hooks panel in FLUENT Note that you can hook multiple adjust functions to your model See Section 6 1 1 Hooking DEFINE_ADJUST UDFs f
62. DEFINE_TURBULENT_VISCOSITY name c t Fluent Inc September 11 2006 2 1 07 DEFINE Macros Argument Type Description symbol name UDF name cellt c Cell index Thread t Pointer to cell thread on which the turbulent viscosity is to be applied Function returns real There are three arguments to DEFINE_TURBULENT_VISCOSITY name c and t You supply name the name of the UDF c and t are variables that are passed by the FLUENT solver to your UDF Your UDF will need to return the real value of the turbulent viscosity to the solver Example 1 Single Phase Turbulent Viscosity UDF The following UDF named user_mu_t defines a custom turbulent viscosity for the stan dard k e turbulence model Note that the value of M keCmu in the example is defined through the graphical user interface but made accessible to all UDFs The source code can be interpreted or compiled in FLUENT DOERR A AAR kkk k A I A IK KK kk A ACA A A A kkk k kkk UDF that specifies a custom turbulent viscosity for standard k epsilon formulation BEAR RR I EE DO OK ACA A A 1 1 1 21 21 21 21 D A ED DH A kkk kk kkk kkk include udf h DEF INE_TURBULENT_VISCOSITY user_mu_t c t real mu_t real rho C_R c t real k C_K c t real d C_D c t mu_t M_keCmu rho SQR k d return mu_t 2 1 08 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros Example 2 Multiphase Turbulent Viscosity UDF pLa o o o kkk k kkk kkk kkk k
63. DPM Drag Coefficient UDF to FLUENT After the UDF that you have defined using DEFINE DPM DRAG is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible in the Discrete Phase Model panel in FLUENT See Section 6 4 3 Hooking DEFINE_DPM_DRAG UDFs for details on how to hook your DEFINE_DPM_DRAG UDF to FLUENT 2 1 52 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros 2 5 4 DEFINE_DPM_EROSION Description You can use DEFINE_DPM_EROSION to specify the erosion and accretion rates calculated as the particle stream strikes a wall surface The function is called when the particle encounters a reflecting surface Usage DEFINE DPM EROSION name p t f normal alpha Vmag mdot Argument Type Description symbol name UDF name Tracked Particle p Pointer to the Tracked Particle data structure which contains data related to the particle being tracked Thread t Pointer to the face thread the particle is currently hitting face_t f Index of the face that the particle is hitting real normal Array that contains the unit vector that is normal to the face real alpha Variable that represents the impact angle between the particle path and the face in radians real Vmag Variable that represents the magnitude of the particle velocity in m s real mdot Flow rate of the particle stream as
64. EEEE ooo oo DH DD DH DH DH ED HO kkk include udf h define K1 2 0e 2 define K2 5 DEFINE_VR_RATE user_rate c t r mole_weight species_mf rate rr_t if FLUID_THREAD_P t amp amp THREAD_VAR t fluid porous rate Ki s1 pow 1 K2 s1 2 0 mw1 real s1 species_mf 0 real mw1 mole_weight 0 else rate 0 rr_t rate H This UDF is executed as a compiled UDF in FLUENT Follow the procedure for compiling source files using the Compiled UDFs panel that is described in Section 5 2 Compile a UDF Using the GUI Once the function vol_reac_rate is compiled and loaded you can hook the reaction rate UDF to FLUENT by selecting the function s name in the Volume Reaction Rate Function drop down list in the User Defined Function Hooks panel Figure 6 2 28 Define User Defined 8 40 gt Function Hooks Fluent Inc September 11 2006 8 2 Detailed UDF Examples User Defined Function Hooks Initialization none Edit Adjust none Edit Execute at End one Edit Read Case none Edit Write Case none Edit Read Data none Edit Write Data none Edit Execute at Exit one Edit Wall Heat Flux jones Volume Reaction Rate user vr rate Initialize and run the calculation The converged solution for the mass fraction of species a is shown in Figure 8 2 19 The gas that moves through the porous region is gradually converted to s
65. Example The following UDF named user_chem_step assumes that the net volumetric reaction rate is the expression dy on NN 2 3 2 where Nspe is the number of species An analytic solution exists for the integral of this ODE as YA YL 1 Nepe exp At 1 Nope 2 3 3 paaa kkk k k kkk kk kk kkk kk kkk kk kkk kk k Example UDF that demonstrates DEFINE_CHEM_STEP EEEE o ooo o kkk aR A A include udf h DEFINE_CHEM_STEP user_chem_step cell thread particle nump nspe dt pres temp yk int i double c 1 double nspe double decay exp dt for i 0 i lt n_spe i yk i yklil c xdecay c Hooking a Chemistry Step UDF to FLUENT After the UDF that you have defined using DEFINE_CHEM_STEP is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user_chem_step will become visible and selectable in the User Defined Function Hooks panel in FLUENT See Section 6 2 1 Hooking DEFINE_CHEM_STEP UDF for details 2 32 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros 2 3 2 DEFINE_CPHI Description You can use DEFINE_CPHI to set the value of the mixing constant Cy see Equation 18 2 6 and Equation 18 2 8 in the the User s Guide for details It is useful for modeling flows where Cy departs substantially from its default value of 2 which occurs at low Reynolds and or high Sc
66. FA DEFINE EXECUTE ON LOADING UDFs can be executed only as compiled UDFs Usage DEFINE EXECUTE ON LOADING name libname Argument Type Description symbol name UDF name char libname compiled UDF library name Function returns void There are two arguments to DEFINE_ EXECUTE_ON_LOADING name and libname You supply a name for the UDF which will be used by FLUENT when reporting that the EXECUTE_ON_LOADING UDF is being run The libname is set by FLUENT to be the name of the library e g libudf that you have specified by entering a name or keeping the default libudf libname is passed so that you can use it in messages within your UDF Fluent Inc September 11 2006 2 15 DEFINE Macros Example 1 The following simple UDF named report_version prints a message on the console that contains the version and release number of the library being loaded include udf h static int version ibe static int release 2 DEF INE_EXECUTE_ON_LOADING report_version libname Message nLoading s version 7 d d n libname version release Example 2 The following source code contains two UDFs The first UDF is an EXECUTE_ON_LOADING function that is used to reserve three UDMs using Reserve User Memory Vars for a library and set unique names for the UDM locations using Set User Memory Name The second UDF is an ON_DEMAND function that is used to set the values of the UDM locations after the solution has been initialized T
67. FLUENT After the UDF that you have defined using DEFINE_CG_MOTION is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible in the Dynamic Zones panel in FLUENT See Section 6 5 1 Hooking DEFINE CG MOTION UDFs for details on how to hook your DEFINE_CG_MOTION UDF to FLUENT Fluent Inc September 11 2006 2 1 99 DEFINE Macros 2 6 2 DEFINE_GEOM Description You can use DEFINE GEOM to specify the geometry of a deforming zone By default FLUENT provides a mechanism for defining node motion along a planar or cylindrical surface When FLUENT updates a node on a deforming zone e g through spring based smoothing or after local face re meshing the node is repositioned by calling the DEFINE_GEOM UDF Note that UDFs that are defined using DEFINE_GEOM can only be executed as compiled UDFs Usage DEFINE_GEOM name d dt position Argument Type Description symbol name UDF name Domain d Pointer to domain Dynamic_Thread dt Pointer to structure that stores the dynamic mesh attributes that you have specified or that are calculated by FLUENT real position Pointer to array that stores the position Function returns void There are four arguments to DEFINE GEOM name d dt and position You supply name the name of the UDF d dt and position are variables that are passed by the FLUENT solv
68. FLUENT is doing it outside of the function call Fluent Inc September 11 2006 2 211 DEFINE Macros Example The following UDF named cyl_ortho_diff computes the anisotropic diffusivity matrix for a cylindrical shell which has different diffusivities in radial tangential and axial directions This function can be executed as a compiled UDF POCO CAO k k kk kkk kkk kk k k k kk kk k kkk Ik k 4 K k k Example UDF that demonstrates DEFINE_ANISOTROPIC_DIFFUSIVITY BOO KDE kkk kkk kkk kkk kkk include udf h Computation of anisotropic diffusivity matrix for cylindrical orthotropic diffusivity axis definition for cylindrical diffusivity static const real origin 3 0 0 0 0 0 0 static const real axis 3 0 0 0 0 1 0 diffusivities in radial tangential and axial directions static const real diff 3 1 0 0 01 0 01 DEFINE_ANISOTROPIC_DIFFUSIVITY cyl_ortho_diff c t i dmatrix real x 3 3 principal direction matrix for cell in cartesion coords real xcent ND_ND real R C_CENTROID xcent c t NV_VV x 0 xcent origin if RP_3D NV_V x 2 axis endif if RP_3D R NV_DOT x 0 x 2 NV_VS x 0 x 2 R endif R NV_MAG x 0 if R gt 0 0 NV_S x 0 R if RP_3D N3V_CROSS x 1 x 2 x 0 Helse 2 212 Fluent Inc September 11 2006 2 7 User Defined Scalar UDS Transport Equation DEFINE Macros x 1 0 x 0 1 x 1
69. Generation Rate Profile The following UDF named wallheatgenerate generates a heat generation rate profile for a planar conduction wall Once interpreted or compiled you can activate this UDF in the Wall boundary condition panel in FLUENT Wall Heat Generation Rate Profile UDF include udf h DEFINE_PROFILE wallheatgenerate thread i real source 0 001 face_t f begin_f_loop f thread F_PROFILE f thread i source end_f_loop f thread Example 5 Viscous Resistance Profile in a Porous Zone You can either use F_PROFILE or C_PROFILE to define a viscous resistance profile in a porous zone Below are two sample UDFs that demonstrate the usage of F_PROFILE and C_PROFILE respectively Note that porosity functions are hooked to FLUENT in the Porous Zone tab in the appropriate Fluid boundary conditions panel The following UDF named vis_res generates a viscous resistance profile in a porous zone Once interpreted or compiled and loaded you can activate this UDF in the Fluid boundary condition panel in FLUENT Fluent Inc September 11 2006 2 75 DEFINE Macros Viscous Resistance Profile UDF in a Porous Zone that utilizes F_PROFILE include udf h DEFINE_PROFILE vis_res t i real x ND_ND real a cell_t c begin_c_loop c t C_CENTROID x c t if x 1 lt x 0 0 01 a 1e9 else a 1 0 F_PROFILE c t i a end_c_loop c t Viscous Resistance Profile UDF in a Porous Zo
70. Interpreting a UDF Source File Using the Interpreted UDFs Panel 4 2 Interpreting a UDF Source File Using the Interpreted UDFs Panel This section presents the steps for interpreting a source file in FLUENT Once interpreted the names of UDFs contained within the source file will appear in drop down lists in graphics panels in FLUENT The general procedure for interpreting a source file is as follows 1 Make sure that the UDF source file is in the same directory that contains your case and data files eal If you are running the parallel version of FLUENT on a network of Windows machines you must share the working directory that contains your UDF source case and data files so that all of the compute nodes in the cluster can see it To do this a Open the Windows Explorer application right click on the folder for the work ing directory e g mywork select the Sharing option and specify a Share Name e g mywork 2 Start FLUENT from your working directory 3 Read or set up your case file 4 Open the Interpreted UDFs panel Figure 4 2 1 Define gt User Defined Functions Interpreted Interpreted UDFs Source File Name f mywork udfexample c Browse CPP Command Name cpp Stack Size M Display Assembly Listing Use Contributed CPP Interpret Close Help Figure 4 2 1 The Interpreted UDFs Panel 5 In the Interpreted UDFs panel se
71. OK Curves Axes Cancel Help In this example Velocity and Velocity Magnitude are chosen in the drop down lists under Report of The location of the report is pressure outlet 5 which is selected in the Surfaces list A simple Area Weighted Average is chosen in the Report Type drop down list with the Flow Time chosen in the X Axis drop down list Once the first time step has been completed the monitor should appear in the chosen plot window Alternatively you can read the file by opening the File XY Plot panel Plot File File XY Plot Plot Title Legend Title Convergence history of Velocity average Velocity Magn Files Legend Entries ZATUTORIALS Updated 6 3 introduction Delete 63 introduction uelocity xy Convergence history 0 Change Legend Entry Axes Curves Close Help You can read the output file by typing its name in the text entry box under Files and clicking on Add By selecting this file and clicking on Plot you can obtain the plot shown in Figure 8 2 7 Fluent Inc September 11 2006 8 25 Examples 2 50e 01 4 2 40e 01 2 30e 01 2 20e 01 4 3 2 10e 01 4 Average 2 00e 01 4 Velocity Magnitude 190e 01 7 pascal 1 80e 01 4 1 70e 01 1 60e 01 4 1 50e 01 0 0 2 0 4 0 6 0 8 1 12 1 4 1 6 1 8 2 Flow Time 1 D Unsteady Flow in a Tube Convergence history of Velocity Magnitude on pressure outlet 5 in SI units
72. Refractive index of medium a real n_b Refractive index of medium b real diff ref a Diffuse reflectivity at the interface facing medium a real diff_tran_a Diffuse transmissivity at the interface facing medium a real diff_ref_b Diffuse reflectivity at the interface facing medium b real diff_tran_b Diffuse transmissivity at the interface facing medium b Function returns void There are nine arguments to DEFINE_DOM_DIFFUSE_REFLECTIVITY name t nb n a n_b diff ref a diff tran a diff ref b and diff tran b You supply name the name of the UDF t nb n a n_b diff ref_a diff _tran_a diff ref _b and diff tran_b are variables that are passed by the FLUENT solver to your UDF 2 36 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros Example The following UDF named user_dom_diff_ref1 modifies diffuse reflectivity and trans missivity values on both the sides of the interface separating medium a and b The UDF is called for all the semi transparent walls and prints the value of the diffuse reflectivity and transmissivity values for side a and b UDF to print the diffuse reflectivity and transmissivity at semi transparent walls include udf h DEFINE_DOM_DIFFUSE_REFLECTIVITY user_dom_diff_refl t nband n_a n_b diff_ref_a diff_tran_a diff_ref_b diff_tran_b printf diff_ref_a f diff_tran_a f n diff_ref_a diff_tran_a printf diff_ref_b f diff_tran_b f n diff_ref_b diff_tra
73. Thread t int number of nodes in a face 3 6 Fluent Inc September 11 2006 3 2 Data Access Macros 3 2 3 Cell Macros The macros listed in Table 3 2 3 3 2 19 can be used to return real cell variables in SI units They are identified by the C_ prefix These variables are available in the pressure based and the density based solver The quantities that are returned are available only if the corresponding physical model is active For example species mass fraction is available only if species transport has been enabled in the Species Model panel in FLUENT Definitions for these macros can be found in the referenced header file e g mem h Cell Centroid C_CENTROID The macro listed in Table 3 2 3 can be used to obtain the real centroid of a cell C_CENTROID finds the coordinate position of the centroid of the cell c and stores the co ordinates in the x array Note that the array x can be a one two or three dimensional array Table 3 2 3 Macro for Cell Centroids Defined in metric h Macro Argument Types Outputs C_CENTROID x c t real x ND ND cell_t c Thread t x cell centroid See Section 2 2 7 DEFINE_INIT for an example UDF that utilizes C_CENTROID Cell Volume C_VOLUME The macro listed in Table 3 2 4 can be used to obtain the real cell volume for 2D 3D and axisymmetric simulations Table 3 2 4 Macro for Cell Volume Defined in mem h Macro Argument Types Retu
74. UDS or UDM prior to usage See Sections 3 2 8 and 3 2 9 respectively for details e Section 5 1 Introduction e Section 5 2 Compile a UDF Using the GUI e Section 5 3 Compile a UDF Using the TUI e Section 5 4 Link Precompiled Object Files From Non FLUENT Sources e Section 5 5 Load and Unload Libraries Using the UDF Library Manager Panel e Section 5 6 Common Errors When Building and Loading a UDF Library e Section 5 7 Special Considerations for Parallel FLUENT Fluent Inc September 11 2006 5 1 Compiling UDFs 5 1 Introduction Compiled UDFs are built in the same way that the FLUENT executable itself is built Internally a script called Makefile is used to invoke the system C compiler to build an object code library that contains the native machine language translation of your higher level C source code The object library is specific to the computer architecture being used during the FLUENT session as well as to the particular version of the FLUENT executable being run Therefore UDF object libraries must be rebuilt any time FLUENT is upgraded when the computer s operating system level changes or when the job is run on a different type of computer architecture The generic process for compiling a UDF involves two steps compile build and load The compile build step takes one or more source files e g myudf c containing at least one UDF and compiles them into object files e g myudf o or myudf obj and then
75. Wall species boundary condition shear stress components moving velocity components temperature heat flux heat generation rate heat transfer coefficient external emissivity external radiation temperature free stream temperature granular flux granular temperature discrete phase boundary condition user defined scalar boundary value DEFINE_PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE DPM BC DEFINE PROFILE phase dependent primary and secondary phase s mixture mixture mixture mixture mixture mixture mixture mixture secondary phase s secondary phase s secondary phase s secondary phase s Material Properties granular diameter granular viscosity granular bulk viscosity granular frictional viscosity granular conductivity granular solids pressure granular radial distribution granular elasticity modulus turbulent viscosity DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE _TURBULENT_ VISCOSITY secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s mixture primary and secondary phase s Fluent Inc September 11 2006 C 4 Eulerian M
76. Write Data none Edit Execute at Exit none Edit Wall Heat Flux mone Net Reaction Rate mone Volume Reaction Rate mone Surface Reaction Rate jusersrrate Figure 6 2 25 The User Defined Function Hooks Panel Fluent Inc September 11 2006 6 41 Hooking UDFs to FLUENT A You must enable the wall surface reactions option before you can hook the UDF by selecting Volumetric and Wall Surface under Reactions in the Species Model panel To hook the UDF to FLUENT choose the function name e g user sr rate in the Surface Reaction Rate Function drop down list in the User Defined Function Hooks panel and click OK See Section 2 3 19 DEFINE_SR_RATE for details about DEFINE_SR_RATE functions 6 2 20 Hooking DEFINE_TURB_PREMIX_SOURCE UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE TURB PREMIX SOURCE UDF the name of the function you sup plied as a DEFINE macro argument will become visible and selectable in the User Defined Function Hooks panel Figure 6 2 26 in FLUENT Define gt User Defined 6 42 Function Hooks User Defined Function Hooks Initialization none Edit Adjust none SCE Execute at End none Edit Read Case none Edit Write Case none Edit Turbulent Premixed Source user turb_pre_src Read Data none Edit Write Data none Edit Execute at Exit none Edit
77. a Linux machine will result in the following message reported to the console and log file for a Linux machine Opening library libudf Library libudf 1nx86 3d libudf so opened superfluid_density speed_sound Done If instead no function names are listed then it is likely that your source file did not successfully compile In this case you ll need to consult the log to view the compilation history and debug your function s Note that you ll need to unload the UDF library using the UDF Library Manager panel before you reload the debugged version of your library Another common error occurs when you try to read a case file that was saved with a shared library and that shared library has subsequently been moved to another location In this case the following error will be reported to the console and log file on a Linux machine Opening library libudf Error open_udf_library couldn t open library libudf 1n86 2d libudf so 5 26 Fluent Inc September 11 2006 5 6 Common Errors When Building and Loading a UDF Library Similarly you will get an error message when you try to load a shared library before it has been built Opening library libudf Error open_udf_library No such file or directory Windows Parallel If you are trying to load a compiled UDF while running FLUENT in network parallel you may receive this error Error open_udf_library The system cannot find the path specified This
78. a b c computes the sum of the first two arguments 2D or all three arguments 3D It is useful for writing functions involving vector operations so that the same function can be used for 2D and 3D For a 2D case the third argument is ignored See Chapter 3 Additional Macros for Writing UDFs for a description of predefined macros such as C_CENTROID and ND_SUM Hooking an Initialization UDF to FLUENT After the UDF that you have defined using DEFINE_INIT is interpreted Chapter 4 In terpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g my init func will become visible and selectable in the User Defined Function Hooks panel in FLUENT Note that you can hook multiple init functions to your model See Section 6 1 5 Hooking DEFINE_INIT UDFs for details 2 20 Fluent Inc September 11 2006 2 2 General Purpose DEF INE Macros 2 2 8 DEFINE_ON_DEMAND Description DEFINE ON DEMAND is a general purpose macro that you can use to specify a UDF that is executed on demand in FLUENT rather than having FLUENT call it automatically during the calculation Your UDF will be executed immediately once it is activated but it is not accessible while the solver is iterating Note that the domain pointer d is not explicitly passed as an argument to DEFINE_ON_DEMAND Therefore if you want to use the domain variable in your on demand function you will need t
79. a partitioned grid Fig ure 7 5 1 and is identified by the suffix int This macro pair can also be used by the serial version of FLUENT to loop over all cells in the given thread It contains a begin and end statement and between these statements operations can be performed on each of the thread s interior cells in turn The macro is passed a cell index c and a cell thread pointer tc begin_c_loop_int c tc end_c_loop_int c tc 7 24 Fluent Inc September 11 2006 7 5 Macros for Parallel UDFs Example real total_volume 0 0 begin_c_loop_int c tc C_VOLUME gets the cell volume and accumulates it The end result will be the total volume of each compute node s respective grid total_volume C_VOLUME c tc end_c_loop_int c tc Exterior Cell Looping Macro The macro begin end_c_loop_ext loops over exterior cells in a partitioned grid Fig ure 7 5 2 and is identified by the suffix ext It contains a begin and end statement and between these statements operations can be performed on each of the thread s exterior cells in turn The macro is passed a cell index c and cell thread pointer tc In most situations there is no need to use the exterior cell loop macros They are only provided for convenience if you come across a special need in your UDF begin_c_loop_ext c tc end_c_loop_ext c tc Fluent Inc September 11 2006 7 25 Parallel Considerations Figure 7 5 2 Loopi
80. an overview of user defined functions UDFs and their usage in FLUENT Details about UDF functionality are described in the following sections e Section 1 1 What is a User Defined Function UDF e Section 1 2 Why Use UDFs e Section 1 3 Limitations e Section 1 4 Defining Your UDF Using DEFINE Macros e Section 1 5 Interpreting and Compiling UDF s e Section 1 6 Hooking UDFs to Your FLUENT Model e Section 1 7 Grid Terminology e Section 1 8 Data Types in FLUENT e Section 1 9 UDF Calling Sequence in the Solution Process e Section 1 10 Special Considerations for Multiphase UDFs 1 1 What is a User Defined Function UDF A user defined function or UDF is a function that you program that can be dynamically loaded with the FLUENT solver to enhance the standard features of the code For ex ample you can use a UDF to define your own boundary conditions material properties and source terms for your flow regime as well as specify customized model parameters e g DPM multiphase models initialize a solution or enhance post processing See Section 1 2 Why Use UDFs for more examples UDFs are written in the C programming language using any text editor and the source code file is saved with a c extension e g myudf c One source file can contain a single UDF or multiple UDFs and you can define multiple source files See Appendix A for some basic information on C programming Fluent Inc September 11 2006 1 1 Ove
81. and the velocity vector Debut pv 2 z 7 2 To define the advection term in Equation 2 7 1 using DEFINE_UDS_FLUX your UDF needs to return the scalar value A to FLUENT where w is the same as defined in Equa tion 2 7 1 and A is the face normal vector of the face Fluent Inc September 11 2006 2 215 DEFINE Macros Note that the advective flux field that is supplied by your UDF should be divergence free i e it satisfies the continuity equation In discrete terms this means that the sum of fluxes over all the faces of each cell should be zero If the advective field is not divergence free then is not conserved and will result in overshoots undershoots in the cell value of You will need to compute mn in your UDF using for example predefined macros for velocity vector and scalar density that Fluent has provided see Chapter 3 Additional Macros for Writing UDFs or using your own prescription The first case is illustrated in the sample C source code shown below FA Note that if more than one scalar is being solved you can use a conditional if statement in your UDF to define a different flux function for each i i 0 is associated with scalar 0 the first scalar equation being solved FH Note also that d must have units of mass flow rate in SI i e kg s paaa oo oo oo o kkk kk kkk kk kkk kk kkk sample C source code that computes dot product of psi and A Note that this is not a complete C function
82. are listed below assignment addition subtraction multiplication division modulo reduction increment decrement Note that multiplication division and modulo reduction operations will be performed before addition and subtraction in any expression When division is performed on two integers the result is an integer with the remainder discarded Modulo reduction is the remainder from integer division The operator is a shorthand notation for the increment operation A 12 2 Logical Operators Some common logical operators are listed below lt less than lt less than or equal to gt greater than gt greater than or equal to equal to not equal to Fluent Inc September 11 2006 A 13 C Programming Basics A 13 C Library Functions C compilers include a library of standard mathematical and I O functions that you can use when you write your UDF code Lists of standard C library functions are presented in the following sections Definitions for standard C library functions can be found in various header files e g global h These header files are all included in the udf h file A 13 1 Trigonometric Functions The trigonometric functions shown below are computed with one exception for the variable x Both the function and the argument are double precision real variables The function acos x is the arccosine of the argument x cos z The function atan2 x y is the arctan
83. are three arguments to DEFINE_DPM_TIMESTEP name p and ts You supply the name of your user defined function p and ts are variables that are passed by the FLUENT solver to your UDF Your function will return the real value of the DPM particle timestep to the solver Example 1 The following compiled UDF named limit_to_e minus_ four sets the time step to a maximum value of le 4 If the time step computed by FLUENT and passed as an argument is smaller than le 4 then FLUENT s time step is returned Time step control UDF for DPM include udf h include dpm h DEF INE_DPM_TIMESTEP limit_to_e_minus_four p dt if dt gt 1 e 4 p gt next_time_step 1 e 4 2 1 90 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros return 1 e 4 return dt Example 2 The following compiled UDF named limit to fifty of prt computes the particle re laxation time based on the formula where 24 d18u 2 5 2 mer Re 2 5 2 d Re olat 2 5 3 H The particle time step is limited to a fifth of the particle relaxation time If the particle time step computed by FLUENT and passed as an argument is smaller than this value then FLUENT s time step is returned Particle time step control UDF for DPM include udf h include dpm h DEFINE_DPM_TIMESTEP limit_to_fifth_of_prt p dt real drag_factor 0 real p_relax_time cphase_state_t c amp
84. bulence Flow Variable Macro Phase Specified On Other drag coefficient lift coefficient heat transfer coefficient mass transfer coefficient heterogeneous reaction rate DEF INE_EXCHANGE DEFINE EXCHANGE DEFINE PROPERTY DEFINE MASS TRANSFER DEFINE HET RXN RATE phase interaction phase interaction phase interaction phase interaction phase interaction Fluent Inc September 11 2006 C 21 Quick Reference Guide for Multiphase DEFINE Macros C 22 Fluent Inc September 11 2006 Bibliography 1 S Jendoubi H S Lee and T K Kim Discrete Ordinates Solutions for Radia tively Participating Media in a Cylindrical Enclosure J Thermophys Heat Transfer 7 2 213 219 1993 2 B Kernighan and D Ritchie The C Programming Language Prentice Hall second edition 1988 3 S Oualline Practical C Programming O Reilly Press 1997 Fluent Inc September 11 2006 Bib 1 BIBLIOGRAPHY Bib 2 Fluent Inc September 11 2006 Index A ND_ND 3 23 accessing domain pointer not passed as ar gument 3 27 accretion rate UDFs 2 153 adjacent cell index macros 3 22 adjacent cell thread macros 3 23 adjust UDFs 2 4 advection term 2 215 advective flux field 2 215 anisotropic diffusivity UDFs 2 211 area normal vector macro 3 23 arithmetic operators A 13 arrays A 9 ARRH 3 35 3 36 Arrhenius constants 2 101 axisymmetric considerations for macros 3 5 begin
85. called Makefile is used to invoke the system C compiler to build an object code library You initiate this action in the Compiled UDFs panel by clicking on the Build pushbutton The object code library contains the native machine language translation of your higher level C source code The shared library must then loaded into FLUENT at runtime by a process called dynamic loading You initiate this action in the Compiled UDFs panel by clicking on the Load pushbutton The object libraries are specific to the computer architecture being used as well as to the particular version of the FLUENT executable being run The libraries must therefore be rebuilt any time FLUENT is upgraded when the computer s operating system level changes or when the job is run on a different type of computer In summary compiled UDFs are compiled from source files using the graphical user interface in a two step process The process involves a visit to the Compiled UDFs panel where you first Build shared library object file s from a source file and then Load the shared library that was just built into FLUENT Interpreted UDFs Interpreted UDFs are interpreted from source files using the graphical user interface but in a single step process The process which occurs at runtime involves a visit to the Interpreted UDFs panel where you Interpret a source file Inside FLUENT the source code is compiled into an intermediate architecture independent machine code
86. called several times in each cell Different values are assigned to the pointer r depending on which reaction the UDF is being called for Therefore you will need to determine which reaction is being called and return the correct rates for that reaction Reactions can be identified by their name through the r gt name statement To test whether a given reaction has the name reaction 1 for example you can use the following C construct if strcmp r gt name reaction 1 r gt name is identical to reaction 1 il Note that strcmp r gt name reaction 1 returns 0 which is equal to FALSE when the two strings are identical It should be noted that DEFINE_VR_RATE defines only the reaction rate for a predefined stoichiometric equation set in the Reactions panel thus providing an alternative to the Arrhenius rate model DEFINE_VR_RATE does not directly address the particular rate of species creation or depletion this is done by the FLUENT solver using the reaction rate supplied by your UDF The following is a source code template that shows how to use DEFINE_VR_RATE in con nection with more than one user specified reaction Note that FLUENT always calculates the rr and rr_t reaction rates before the UDF is called Consequently the values that are calculated are available only in the given variables when the UDF is called Fluent Inc September 11 2006 2 1 13 DEFINE Macros POR oo o o k kkk KEK A ACA A A A
87. cell_t c Thread t strain rate magnitude C_DUDX c t cell_t c Thread t velocity derivative C DUDY c t cell t c Thread t velocity derivative C_DUDZ c t cell_t c Thread t velocity derivative C_DVDX c t cell_t c Thread t velocity derivative C_DVDY c t cell_t c Thread t velocity derivative C_DVDZ c t cell_t c Thread t velocity derivative C_DWDX c t cell t c Thread t velocity derivative C_DWDY c t cell_t c Thread t velocity derivative C_DWDZ c t cell_t c Thread t velocity derivative Fluent Inc September 11 2006 3 2 Data Access Macros Material Property Macros The macros listed in Tables 3 2 14 3 2 16 can be used to return real material property variables in SI units The variables are available in both the pressure based and the density based solver Argument real prt is the turbulent Prandtl number Definitions for material property macros can be found in the referenced header file e g mem h Table 3 2 14 Macros for Diffusion Coefficients Defined in mem h Macro Argument Types Returns CMUL c t cell t c Thread t laminar viscosity C_MU_T c t cell_t c Thread t turbulent viscosity C_MU_EFF c t cell_t c Thread t effective viscosity CKL c t cell_t c Thread t thermal conductivity CKT c t prt cell t c Thread t real prt turbulent thermal conductivity CK EFF C t prt cell_t c Thread t real prt effective thermal conductivity CDIFFL c t i j cell_t c Thre
88. compute node ID and the partition ID are different For example in a parallel system with two compute nodes 0 and 1 the exterior cells of compute node 0 have a partition ID of 1 and the exterior cells of compute node 1 have a partition ID of 0 Figure 7 5 4 7 30 Fluent Inc September 11 2006 7 5 Macros for Parallel UDFs Face Partition IDs For interior faces and boundary zone faces the partition ID is the same as the compute node ID The partition ID of a partition boundary face however can be either the same as the compute node or it can be the ID of the adjacent node depending on what values F_PART is filled with Figure 7 5 4 Recall that an exterior cell of a compute node has only partition boundary faces the other faces of the cell belong to the adjacent compute node Therefore depending on the computation you want to do with your UDF you may want to fill the partition boundary face with the same partition ID as the compute node using Fill_Face_Part_With_Same or with different IDs using Fill Face Part With Different Face partition IDs will need to be filled before you can access them with the F_PART macro There is rarely a need for face partition IDs in parallel UDFs 7 5 7 Message Displaying Macros You can direct FLUENT to display messages on a host node or serial process using the Message utility To do this simply use a conditional if statement and the appropriate compiler directive e g if RP_NODE to
89. define define define define define define define define define define Fluent Inc udf h FLUID_ID 1 ual 7 1357e 2 ua2 54 304 ua3 3 1345e3 ua4 4 5578e4 ua5 1 9664e5 val 3 1131e 2 va2 10 313 va3 9 5558e2 va4 2 0051e4 va5 1 1856e5 kal 2 2723e 2 ka2 6 7989 ka3 424 18 ka4 9 4615e3 ka5 7 7251e4 ka6 1 8410e5 dal 6 5819e 2 da2 88 845 da3 5 3731e3 da4 1 1643e5 da5 9 1202e5 da6 1 9567e6 September 11 2006 2 73 DEFINE Macros DEFINE_PROFILE fixed_u t i cell_t c real x ND_ND real r begin_c_loop c t se centroid is defined to specify position dependent profiles C_CENTROID x c t r x 1 F_PROFILE c t i ual ua2 r ua3 r r ua4 r r r ua5 r r r r end_c_loop c t DEFINE_PROFILE fixed_v t i cell_t c real x ND_ND real r begin_c_loop c t centroid is defined to specify position dependent profiles C_CENTROID x c t r x 1 F_PROFILE c t i val va2 r va3xr r va4xr r r va5 r r r r end_c_loop c t DEFINE_PROFILE fixed_ke t i cell_t c real x ND_ND 2 74 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros real r begin_c_loop c t centroid is defined to specify position dependent profiles C_CENTROID x c t r x 1 F_PROFILE c t i ka1 ka2 r ka3 r r ka4 r r r ka5 r xr r r ka6 r xr xr r r end_c_loop c t Example 4 Wall Heat
90. define ACTIVE 1e 08 define BETA 0 0 real arrhenius_rate real temp return PRE_EXP pow temp BETA exp ACTIVE UNIVERSAL_GAS_CONSTANT temp Species numbers Must match order in Fluent panel define HF O define WF6 1 define H20 2 define NUM_SPECS 3 Reaction Exponents define HF_EXP 2 0 define WF6_EXP 0 0 define H20_EXP 0 0 define MW_H2 2 0 define STOIC_H2 3 0 Reaction Rate Routine real reaction_rate cell_t c Thread cthread real mw real yi Note that all arguments in the reaction_rate function call in your c source file MUST be on the same line or a compilation error will occur real concenHF C_R c cthread yi HF mw HF return arrhenius_rate C_T c cthread pow concenHF HF_EXP J DEFINE_SR_RATE arrhenius f fthread r mw yi rr 2 1 02 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros rr reaction_rate F_CO f fthread THREAD_TO fthread mw yi Example 2 Surface Reaction Rate Using Site Species The following compiled UDF named my rate defines a custom surface reaction rate that takes into account site species VEEEEEEEEEEEEEEEEEEEE EEEE ER RER ER RE ER RE ER RER ER EEE ER EEK Custom surface reaction rate UDF OOOO ICO IAGO ER RE ER RENE RENE ER EE EE a 2k ak include udf h DEFINE_SR_RATE my_rate f t r mw yi rr Thread t0 t gt t0 cell_t c0 F_CO f t real sih4 yi 0 mass fraction of sih
91. define a different unsteady term for each i i 0 is associated with scalar 0 the first scalar equation being solved Example The following UDF named my_uds_unsteady modifies user defined scalar time deriva tives using DEFINE UDS UNSTEADY The source code can be interpreted or compiled in FLUENT k kk k 2k 2k CA 2k 2K 2K 2K 2K K 2K 2K K K 2K 2K FK RAK 2K 2K 2K 2K K K K 2K FK 2K 2K 2K k AR K RK AK 2K 2K LES 2k 2 K 2k K K 2k k K 2k K K UDF for specifying user defined scalar time derivatives EEEE EEE OK KDE DH DH DD 2 3 4 A 4 2A 21 21 DD DH D DO include udf h DEFINE_UDS_UNSTEADY my_uds_unsteady c t i apu su real physical_dt vol rho phi_old physical_dt RP_Get_Real physical time step vol C_VOLUME c t rho C_R_Mi c t apu rho vol physical_dt implicit part phi_old C_STORAGE_R c t SV_UDSI_M1 i su rhoxvol phi_old physical_dt explicit part Hooking a UDS Unsteady Function to FLUENT After the UDF that you have defined using DEFINE_UDS_UNSTEADY is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g my uds unsteady will become visible and selectable in the User Defined Scalars panel in FLUENT See Sec tion 6 6 3 Hooking DEFINE_UDS_UNSTEADY UDFs for details 2 220 Fluent Inc September 11 2006 Chapter 3 Additional Macros for Writing UDFs This chapter provide
92. density based solver Figure 1 9 3 begins with a two step initialization sequence that is executed outside the solution iteration loop This sequence begins by initializing equations to user entered or default values taken from the FLUENT user interface Next PROFILE UDFs are called followed by a call to INIT UDFs Initialization UDFs overwrite initialization values that were previously set The solution iteration loop begins with the execution of ADJUST UDFs Next FLUENT solves the governing equations of continuity and momentum energy and species trans port in a coupled fashion which is simultaneously as a set or vector of equations Tur bulence and other transport equations as required are subsequently solved sequentially and the remaining process is the same as the pressure based segregated solver Fluent Inc September 11 2006 1 13 Overview User Defined Profile User Defined Init Solve U Momentum Solve V lomentum Solve W Momentum Solve Mass Continuity Update Velocity Solve Energy onvergence Solve Turbulence Equation s Solve Other Transport Equations as required Update Properties including User Defined Properties Figure 1 9 1 Solution Procedure for the Pressure Based Segregated Solver 1 14 Fluent Inc September 11 2006 1 9 UDF Calling Sequence in the Solution Process User Defined Profile User Defined Init Solve Mass amp Momentum Solve E
93. directly passed through its arguments DEFINE ADJUST and DEFINE_INIT functions for example are passed mixture domain variables only If a UDF requires a phase domain pointer instead then it will need to utilize macros presented in this section to retrieve it ON DEMAND UDFS aren t directly passed any variables thorugh their arguments Consequently any on demand function that requires access to phase or domain variables will also need to utilize macros presented in this section to retrieve them Recall that when you are writing UDFs for multiphase models you will need to keep in mind the hierarchy of structures within FLUENT see Section 1 10 1 Multiphase specific Data Types for details The particular domain or thread structure that gets passed into your UDF from the solver depends on the DEFINE macro you are using as well as the domain the function is hooked to either through the graphical user interface or hardwired in the code As mentioned above it also may depend on the multiphase model that you are using Refer to Section 1 10 1 Multiphase specific Data Types and in particular Figure 1 10 1 for a discussion on hierarchy of structures within FLUENT 3 58 Fluent Inc September 11 2006 3 3 Looping Macros Phase Domain Pointer DOMAIN_SUB_DOMAIN There are two ways you can get access to a specific phase or subdomain pointer within the mixture domain You can use either the DOMAIN_SUB_DOMAIN macro described below or
94. each of the subdomains In other words for each cell or face thread defined in the superdomain there is a corresponding cell or face thread defined for each subdomain Some of the information defined in one thread of the superdomain is shared with the corresponding threads of each of the subdomains Threads associated with the superdomain are referred to as superthreads while threads associated with the subdomain are referred to as phase level threads or subthreads The domain and thread hierarchy are summarized in Figure 1 10 1 Fluent Inc September 11 2006 1 17 Overview Mixture level thread e g inlet zone Mixture level thread e g fluid zone Mixture domain domain_id 1 Interaction domains domain_id 5 6 7 Primary phase domain domain_id 2 gt gt Secondary phase domain domain_id 3 Secondary phase domain domain_id 4 Phase level threads for inlet zone identified by phase_domain_index Figure 1 10 1 Domain and Thread Structure Hierarchy Figure 1 10 1 introduces the concept of the domain_id and phase_domain_index The domain_id can be used in UDFs to distinguish the superdomain from the primary and secondary phase level domains The superdomain mixture domain domain_id is always assigned the value of 1 Interaction domains are also identified with the domain_id The domain_ids are not necessarily ordered sequentially as show
95. end_c_loop 3 51 7 23 begin end_c_loop_ext 7 23 begin end_c_loop_int 7 23 begin end_f_loop 3 51 7 23 begin_c_loop_all 2 19 body force UDFs 2 149 boiling point UDF 2 172 boundary condition UDFs examples 8 15 8 16 for DPM 2 141 general purpose 2 66 boundary conditions 1 3 Boundary Conditions panel 6 30 6 31 boundary face area normals direction 3 19 boundary face partition 7 9 boundary zone faces partitioned grid 7 31 Fluent Inc September 11 2006 BOUNDARY_FACE_GEOMETRY 3 23 8 47 BOUNDARY FACE THREAD P 2 217 3 24 BOUNDARY_SECONDARY_GRADIENT SOURCE 8 47 building a shared library 5 1 5 2 5 4 5 7 8 11 C compiler 5 2 C preprocessor 4 1 4 5 8 8 C programming 1 1 arrays A 9 casting A 8 commenting code A 2 constants A 3 control statements A 11 for loops A 12 if A ll if else A 11 data types A 2 define A 18 example 8 5 file inclusion A 18 FORTRAN comparison with A 19 functions A 8 A 14 fclose A 16 fopen A 15 fprintf A 16 fscanf A 17 input output I O A 15 mathematical A 14 printf A 16 trigonometric A 14 include A 18 macro substitution A 18 Index 1 Index operators A 13 arithmetic A 13 logical A 13 pointers A 9 as function arguments A 10 variables A 3 declaring A 4 external A 5 global A 3 local A 3 static A 7 typedef A 8 C_CENTROID 2 19 2 20 2 94 3 7 3 54 CCP 2 125 C_D 2 59 2 108 3 9 C_DP 2 137 C_FACE
96. f and f are the mass fraction of the liquid and vapor phase respectively DEFINE_CAVITATION_RATE is used to calculate Maot only The values of Re and Re are computed by the solver accordingly Usage DEFINE_CAVITATION_RATE name c t p rhoV rhoL mafV p_v cigma f_gas m_dot Argument Type Description symbol name UDF name cellt Cell index Thread t Pointer to the mixture level thread real p c Pointer to shared pressure real rhoVic Pointer to vapor density real rhoL c Pointer to liquid density real mafV c Pointer to vapor mass fraction real p_v Pointer to vaporization pressure real cigma Pointer to liquid surface tension coefficient real f_gas Pointer to the prescribed mass fraction of non condensable gases real m dot Pointer to cavitation mass transfer rate Function returns void There are eleven arguments to DEFINE CAVITATION RATE name c t p rhoV rhoL mafV p_v cigma f gas and m dot You supply name the name of the UDF c t p rhoV rhoL mafV p_v cigma f_gas and m_dot are variables that are passed by the FLUENT solver to your UDF Your UDF will need to set the value referenced by the real pointer m_dot to the cavitation rate Fluent Inc September 11 2006 2 1 19 DEFINE Macros Example The following UDF named user_cav_rate is an example of a cavitation model for a multiphase mixture that is different from the default model in FLUENT This cavitation model calculate
97. for NH3 e MOLECON Pollut SPE returns the molar concentration of a species specified by SPE which is either the name of species or IDX i when the species is a pollutant like NO SPE must be replaced by one of the following identifiers FUEL 02 O OH H20 N2 N CH CH2 CH3 IDX NO IDX N20 IDX HCN IDX NH3 For example for O2 molar concentration you can call MOLECON Pollut 02 whereas for NO molar concentration the call should be MOLECON Pollut IDX NO Iden tifier FUEL represents the fuel species as specified in the Fuel Species drop down list under Prompt NO Parameters in the NOx Model panel Fluent Inc September 11 2006 3 35 Additional Macros for Writing UDFs e ARRH Pollut K returns the Arrhenius rate calculated from the constants specified by K K is defined using the Rate_Const data type and has three elements A B and C The Arrhenius rate is given in the form of where T is the temperature R ATP exp C T Note that the units of K must be in m gmol J s SO Macros The following macros can be used in SO model UDFs in the calculation of pollutant rates The are defined in the header file sg nox h which is included in udf h They can be used to return real SO variables in SI units and are available in both the pressure based and the density based solver See Section 2 3 18 DEFINE_SOX_RATE for an example of a DEFINE SOX RATE UDF that utilizes these macros Table 3 2 33 Macros for SO U
98. for details Field values that have been stored in user defined memory will be saved to the data file when you next write one These fields will also appear in the User Defined Memory category in the drop down lists in FLUENT s postprocessing panels They will be named User Memory 0 User Memory 1 etc based on the memory location index The total number of memory locations is limited to 500 For large numbers of user defined memory locations system memory requirements will increase 6 2 Hooking Model Specific UDFs This section contains methods for hooking model specific UDFs to FLUENT that have been defined using DEFINE macros found in Section 2 3 Model Specific DEFINE Macros and interpreted or compiled using methods described in Chapters 4 or 5 respectively 6 14 Fluent Inc September 11 2006 6 2 Hooking Model Specific UDFs 6 2 1 Hooking DEFINE_CHEM_STEP UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_CHEM_STEP UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Function Hooks panel Figure 6 2 1 in FLUENT Define User Defined Function Hooks User Defined Function Hooks Initialization none Edit Adjust none ui Execute at End none Edit Read Case none Edit Write Case none Edit Read Data none Edit Write Data none Edit
99. for single precision and double when running double precision Global Summations Macro Action PRF_GISUM1 x Returns sum of integer x over all compute nodes PRF_GISUM x N iwork Sets x to contain sums over all compute nodes PRF_GRSUM1 x Returns sum of x over all compute nodes float if single precision double if double precision PRF_GRSUM x N iwork Sets x to contain sums over all compute nodes float array if single precision double array if double precision Fluent Inc September 11 2006 7 21 Parallel Considerations Global Maximums and Minimums Macros that can be used to compute global maximums and minimums of variables are identified by the suffixes HIGH and LOW respectively PRF_GIHIGH1 and PRF_GIHIGH com pute the global maximum of integer variables and integer variable arrays respectively PRF_GRHIGH1 x computes the global maximum of a real variable x across all compute nodes The value of the global maximum is of type float when running the single precision version of FLUENT and type double when running the double precision version PRF_GRHIGH x N iwork computes the global maximum of a real variable array similar to the description of PRF_GRSUM x N iwork on the previous page The same naming convention used for PRF_GHIGH macros applies to PRF_GLOW Global Maximums Macro Action PRF_GIHIGH1 x Returns maximum of integer x over all compute nodes PRF_GIHIGH x N iwork Sets x to contain maximums
100. fp s d n plane gt sort_file_name 11 par_fprintf_head fp 10s 10s 10s 10s 10s 10s 10s 10s 10s 10s 10s s n ugu nyu ng ug nyn uy diameter T mass flow time melt index name else sprintf name 4s 4d p gt injection gt name p gt part_id if PARALLEL add try_id and part_id for sorting in parallel par_fprintf fp hd td 410 6g 10 68 10 6g 10 6 10 6g 10 6 410 66 410 68 110 65 10 68 10 6g s n 2 178 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros p gt injection gt try_id p gt part_id p gt state pos 0 p gt state pos 1 p gt state pos 2 p gt state V 0 p gt state V 1 p gt state V 2 p gt state diam p gt state temp p gt flow_rate p gt state time p gt user 0 name else par_fprintf fp 410 6g 10 68 10 68 10 6g 10 6g 10 6g 10 6g 10 6g 10 6g 10 6g 10 6g s n p gt state pos 0 p gt state pos 1 p gt state pos 2 p gt state V 0 p gt state V 1 p gt state V 2 p gt state diam p gt state temp p gt flow_rate p gt state time p gt user 0 name endif Hooking a DPM Scalar Update UDF to FLUENT After the UDF that you have defined using DEFINE DPM SCALAR UPDATE is interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible in the Discre
101. host process or simply the host does not contain grid cells faces or nodes except when using the DPM shared memory model Its primary purpose is to interpret commands from Cortex the FLUENT process responsible for user interface and graphics related functions and in turn to pass those commands and data to a compute node which distributes it to the other compute nodes Fluent Inc September 11 2006 7 1 Parallel Considerations Figure 7 1 1 Partitioned Grid in Parallel FLUENT Figure 7 1 2 Partitioned Grid Distributed Between Two Compute Nodes 7 2 Fluent Inc September 11 2006 7 1 Overview of Parallel FLUENT Cell Threads Compute Node 0 Face Threads Cell Threads Compute Node 1 Face Threads Figure 7 1 3 Domain and Thread Mirroring in a Distributed Grid Compute nodes store and perform computations on their portion of the mesh while a single layer of overlapping cells along partition boundaries provides communication and continuity across the partition boundaries Figure 7 1 2 Even though the cells and faces are partitioned all of the domains and threads in a grid are mirrored on each compute node Figure 7 1 3 The threads are stored as linked lists as in the serial solver The compute nodes can be implemented on a massively parallel computer a multiple CPU workstation or a network of workstations using the same or different operating systems Fluent Inc Septem
102. hour Time in hours real S minute Time in minutes Function returns real There are six arguments to DEFINE_SOLAR_INTENSITY name sun_x sun_y sun_z S hour and S_minute You provide the name of your user defined function The variables sun_x sun_y sun_z S_hour and S_minute are passed by the FLUENT solver to your UDF Your UDF will need to compute the direct or diffuse solar irradiation and return the real value in w m to the solver Example The following source code contains two UDFs sol_direct_intensity computes the direct solar irradiation and returns it to the FLUENT solver and sol_diffuse_intensity computes the diffuse solar irradiation include udf h DEFINE_SOLAR_INTENSITY sol_direct_intensity sun_x sun_y sun_z hour minute real intensity Fluent Inc September 11 2006 2 91 DEFINE Macros intensity 1019 printf solar time f intensity e n minute intensity return intensity DEFINE_SOLAR_INTENSITY sol_diffuse_intensity sun_x sun_y sun_z hour minute real intensity intensity 275 printf solar time f intensity diff e n minute intensity return intensity Hooking a Solar Intensity UDF to FLUENT After the UDF that you have defined using DEFINE_SOLAR_INTENSITY is interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name that you specified e g sol_direct_intensity in the DEFINE macro argument will be come visible and selectabl
103. in read only mode and assign it to fp Fluent Inc September 11 2006 A 15 C Programming Basics fclose int fclose FILE fp The function fclose closes a file that is pointed to by the local pointer passed as an argument e g fp fclose fp close the file pointed to by fp printf int printf char format The function printf is a general purpose printing function that prints to the console in a format that you specify The first argument is the format string It specifies how the remaining arguments are to be displayed in the console window The format string is defined within quotes The value of the replacement variables that follow the format string will be substituted in the display for all instances of Ztype The character is used to designate the character type Some common format characters are d for integers Af for floating point numbers and e for floating point numbers in exponential format with e before the exponent The format string for printf is the same as for fprintf and fscanf In the example below the text Content of variable a is will be displayed in the console window and the value of the replacement variable a will be substituted in the message for all instances of d Example int a 5 printf Content of variable a is d n a n denotes a new line FA UNIX only It is recommended that you use the Fluent Inc Message utility instead of printf for compiled UD
104. library s n NUM_UDM libname Set_User_Memory_Name udm_offset lib1 UDM 0 Set_User_Memory_Name udm_offset 1 lib1 UDM 1 3 46 Fluent Inc September 11 2006 3 2 Data Access Macros Set_User_Memory_Name udm_offset 2 lib1 UDM 2 Message nUDM Offset for Current Loaded Library d udm_offset DEFINE_ON_DEMAND set_udms Domain d Thread x ct cell_t c int i d Get_Domain 1 if udm_offset UDM_UNRESERVED Message Setting UDMs n for i 0 i lt NUM_UDM i thread_loop_c ct d begin_c_loop c ct C_UDMI c ct udm_offset i 3 0 i 10 0 end_c_loop c ct else Message UDMs have not yet been reserved for library 1 n Fluent Inc September 11 2006 3 47 Additional Macros for Writing UDFs BAAR I ICRA ICA A A 1 1 211 21 21 21 21 kkk D HE udm_res2 c contains two UDFs an execute on loading UDF that reserves two UDMs for libudf and renames the UDMs to enhance postprocessing and an on demand UDF that sets the initial value of the UDMs FO HRK HE AK HRK AK OH KO HRK KO HRK aR ak HER 2k ak 3k 2k 2k a ok 2k ak include udf h define NUM_UDM 2 static int udm_offset UDM_UNRESERVED DEFINE_EXECUTE_ON_LOADING on_loading libname if udm_offset UDM_UNRESERVED udm_offset Reserve_User_Memory_Vars NUM_UDM if udm_offset UDM_UNRESERVED Message nYou need to define up to 4d extra UDMs in GUI and then reload current library s n NUM_U
105. library named libudf would appear in FLUENT panels as rrate libudf This distinguishes UDFs that are compiled from those that are interpreted If you write your case file when a UDF library is loaded the library will be saved with the case and will be automatically loaded whenever that case file is subsequently read This process of dynamic loading saves you having to reload the compiled library every time you want to run a simulation Fluent Inc September 11 2006 5 1 Introduction Before you compile your UDF source file s using one of the two methods provided in Sec tions 5 2 and 5 3 you will first need to make sure that the udf h header file is accessible in your path or is saved locally within your working directory Section 5 1 1 Location of the udf h File 5 1 1 Location of the uaf h File UDFs are defined using DEFINE macros see Chapter 2 DEFINE Macros and the defini tions for DEFINE macros are included in udf h Consequently before you compile your source file the udf h header file will need to be accessible in your path or saved locally within your working directory The location of the udf h file is path Fluent Inc fluent6 src udf h where path is the directory in which you have installed the release directory Fluent Inc and x is replaced by the appropriate number for the release you have e g 3 for fluent6 3 FA In general you should not copy udf h from the installation area The c
106. m_dot define DEFINE_EXCHANGE_PROPERTY name c mixture_thread second_column_phase_index first_column_phase_index real name cell_t c Thread mixture_thread int second_column_phase_index int first_column_phase_index define DEFINE_HET_RXN_RATE name c t hr mw yi rr rr_t void name cell_t c Thread t Hetero_Reaction hr real mw MAX_PHASES MAX_SPE_FQNS real yi MAX_PHASES MAX_SPE_EQNS real rr real rr_t define DEFINE_MASS_TRANSFER name c mixture_thread from_phase_index from_species_index to_phase_index to_species_index real name cell_t c Thread mixture_thread int from_phase_index B 4 Fluent Inc September 11 2006 B 4 Dynamic Mesh Model DEFINE Macros int from_species_index int to_phase_index int to_species_index define DEFINE_VECTOR_EXCHANGE_PROPERTY name c mixture_thread second_column_phase_index first_column_phase_index vector_result void name cell_t c Thread mixture_thread int second_column_phase_index int first_column_phase_index real vector_result B 4 Dynamic Mesh Model DEFINE Macros The following definitions for dynamic mesh model DEFINE macros see Section 2 6 Dy namic Mesh DEFINE Macros are taken from the udf h header file define DEFINE_CG_MOTION name dt vel omega time dtime void name Dynamic_Thread dt real vel real omega real time real dtime define DEFINE_GEOM name d dt position void name Domain d
107. moment of inertia SDOF_IYY moment of inertia SDOF_IZZ moment of inertia SDOF_IXY product of inertia SDOF_IXZ product of inertia SDOF_IYZ product of inertia SDOF_LOAD_LOCAL boolean SDOF_LOAD_F_X external force SDOF_LOAD_F_Y external force Fluent Inc September 11 2006 2 205 DEFINE Macros SDOF_LOAD_F_Z SDOF_LOAD_M_X SDOF_LOAD_M_Y SDOF_LOAD_M_Z external force external moment external moment external moment The boolean prop SDOF_LOAD_LOCAL can be used to determine whether the forces and moments are expressed in terms of global coordinates FALSE or body coordinates TRUE The default value for prop SDOF_LOAD_LOCAL is FALSE Custom Transformation Variables The default transformations used by FLUENT are typical for most aerospace and other types of applications However if your model requires custom transformations you can specify these matrices in your SDOF UDF First set the SDOF_CUSTOM_TRANS boolean to TRUE Then use the macros listed below to define custom coordination rotation and derivative rotation matrices CTRANS is the body global coordinate rotation matrix and DTRANS is the body global derivative rotation matrix SDOF_CUSTOM_TRANS SDOF_CTRANS_11 SDOF_CTRANS_12 SDOF_CTRANS_13 SDOF_CTRANS_21 SDOF_CTRANS_22 SDOF_CTRANS_23 SDOF_CTRANS_31 SDOF_CTRANS_32 SDOF_CTRANS_33 SDOF_DTRANS_11 SDOF_DTRANS_12 SD
108. of variables real T Temperature at which the property is to be evaluated used only if a polynomial method is specified Function returns real Fluent Inc September 11 2006 2 81 DEFINE Macros MATERIAL_PROPERTY is defined in materials h and returns a real pointer to the Property array prop for the given material pointer m MATERIAL PROPERTY m Argument Type Description Material m Material pointer Function returns real THREAD MATERIAL is defined in threads h and returns real pointer m to the Material that is associated with the given cell thread t Note that in previous versions of FLUENT THREAD_MATERIAL took two arguments t i but now only takes one t THREAD MATERIAL t Argument Type Description Thread t Pointer to cell thread Function returns real mixture_species_loop is defined in materials h and loops over all of the species for the given mixture material mixture species loop m sp i Argument Type Description Material m Material pointer Material sp Species pointer int i Species index Function returns real 2 82 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros Example 1 Temperature dependent Viscosity Property The following UDF named cell_viscosity generates a variable viscosity profile to simulate solidification The function is called for every cell in the zone The viscosity in the warm T gt 288 K fluid has a molecular value for the liquid
109. options available from the GUI panel A different C function in UDF can be called for each option For example the user defined GUI panel may have a number of buttons Each button may be represented by different integers which when clicked will execute a corresponding C function i DEFINE_EXECUTE_FROM_GUI UDFs must be implemented as compiled UDFs and there can be only one function of this type in a UDF library 2 12 Fluent Inc September 11 2006 2 2 General Purpose DEF INE Macros Example The following UDF named reset_udm resets all user defined memory UDM values when a reset button on a user defined GUI panel is clicked The clicking of the button is represented by 0 which is passed to the UDF by the FLUENT solver PROC AAA AAR RI I I I OKA AREA ACA A A kkk k kkk UDF called from a user defined GUI panel to reset all all user defined memory locations BER HO KE I A A OK KK AK A A ACA A A 21 21 1 1 1 1 2 DH kkk kkk include udf h DEFINE_EXECUTE_FROM_GUI reset_udm myudflib mode Domain domain Get_Domain 1 Get domain pointer Thread t cell_t c int i Return if mode is not zero if mode 0 return Return if no User Defined Memory is defined in FLUENT if n_udm 0 return Loop over all cell threads in domain thread_loop_c t domain Loop over all cells begin_c_loop c t 4 Set all UDMs to zero for i 0 i lt n_udm i C_UDMI c t i
110. ordinates model UDFs diffuse reflectivity 2 36 scattering phase 2 88 source terms 2 38 specular reflectivity 2 40 Index 5 Index Discrete Phase Model panel 6 55 6 57 6 65 6 66 6 69 discrete phase model UDF s body force 2 149 boundary conditions 2 141 defining 2 139 drag coefficient 2 151 erosion and accretion rates 2 153 for sampling device output 2 168 for switching custom laws 2 185 for time step control 2 190 heat and mass transfer 2 159 hooking to FLUENT 6 53 particle equilibrium vapor pressure 2 193 particle initialization 2 162 particle laws 2 166 property 2 172 scalar update 2 176 source term 2 180 spray collide 2 182 dispersed phase properties 2 172 Display Assembly Listing 4 5 DO model UDFs diffuse reflectivity 2 36 scattering phase 2 88 source terms 2 38 specular reflectivity 2 40 Domain data structure 1 10 domain ID 3 62 DOMAIN_ID 3 54 3 62 domain_id 1 18 3 27 domain pointer 1 11 DOMAIN_SUB_DOMAIN 3 59 3 60 DOMAIN_SUPER_DOMAIN 3 61 domains 1 10 interaction 1 17 mixture 1 17 phase 1 17 referencing 1 17 subdomains 1 17 superdomains 1 17 Index 6 dot product 3 67 DPM DEFINE macros quick reference guide 2 139 DPM macros particle cell index thread pointer 3 32 particle material properties 3 32 particle species laws and user scalars 3 32 particles at current position 3 31 particles at entry to cell 3 32 particles at injection into domain
111. over all compute nodes PRF_GRHIGH1 x Returns maximums of x over all compute nodes float if single precision double if double precision PRF_GRHIGH x N iwork Sets x to contain maximums over all compute nodes float array if single precision double array if double precision Global Minimums Macro Action PRF_GILOW1 x Returns minimum of integer x over all compute nodes PRF_GILOW x N iwork Sets x to contain minimums over all compute nodes PRF_GRLOW1 x Returns minimum of x over all compute nodes float if single precision double if double precision PRF_GRLOW x N iwork Sets x to contain minimums over all compute nodes float array if single precision double array if double precision 7 22 Fluent Inc September 11 2006 7 5 Macros for Parallel UDFs Global Logicals Macros that can be used to compute global logical ANDs and logical ORs are identified by the suffixes AND and OR respectively PRF_GLOR1 x computes the global logical OR of variable x across all compute nodes PRF_GLOR x N iwork computes the global logical OR of variable array x The elements of x are set to TRUE if any of the corresponding elements on the compute nodes are TRUE By contrast PRF_GLAND x computes the global logical AND across all compute nodes and PRF_GLAND x N iwork computes the global logical AND of variable array x The elements of x are set to TRUE if any of the corresponding elements on the compute nodes are TRUE Globa
112. p gt cphase compute particle relaxation time if P_DIAM p 0 0 drag_factor DragCoeff p c gt mu P_RHO p P_DIAM p P_DIAM p else drag_factor Liss p_relax_time 1 drag_factor check the condition and return the time step Fluent Inc September 11 2006 2 1 91 DEFINE Macros if dt gt p_relax_time 5 return p_relax_time 5 return dt Hooking a DPM Timestep UDF to FLUENT After the UDF that you have defined using DEFINE DPM TIMESTEP is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible and selectable for DPM Timestep in the Discrete Phase Model panel in FLUENT See Section 6 4 14 Hooking DEFINE DPM TIMESTEP UDFs for details on how to hook your DEFINE_DPM_TIMESTEP UDF to FLUENT 2 1 92 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros 2 5 15 DEFINE_DPM_VP_EQUILIB Description You can use DEFINE DPM VP EQUILIB to specify the equilibrium vapor pressure of vapor izing components of multipcomponent particles Usage DEF INE_DPM_VP_EQUILIB name p cvap_surf Argument Type Description symbol name UDF name Tracked_Particle p Pointer to the Tracked_Particle data structure which contains data related to the particle being tracked real cvap_surf Array that contains the equilibrium vapor concentration
113. particle temperature real pressure p gt cphase pressure gas pressure real molwt_cond 0 reciprocal molecular weight of the particle for is 0 is lt nc ist int gas_index TP_COMPONENT_INDEX_I p is index of vaporizing component in the gas phase if gas_index gt 0 the molecular weight of particle material molwt gas_index MATERIAL_PROP MIXTURE_COMPONENT gas_mix gas_index PROP_mwi molwt_cond TP_COMPONENT_I p is molwt gas_index prevent division by zero molwt_cond MAX molwt_cond DPM_SMALL for is 0 is lt nc ist 2 1 94 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros gas species index of vaporization int gas_index TP_COMPONENT_INDEX_I p is if gas_index gt 0 condensed material Material cond_c MIXTURE_COMPONENT cond_mix is condensed component molefraction real xi_cond TP_COMPONENT_I p is molwt gas_index molwt_cond particle saturation pressure real p_saturation DPM_vapor_pressure p cond_c Tp if p_saturation gt pressure p_saturation pressure else if p_saturation lt 0 0 p_saturation 0 0 vapor pressure over the surface this is the actual Raoult law cvap_surflis xi_cond p_saturation UNIVERSAL_GAS_CONSTANT Tp Hooking a DPM Vapor Equilibrium UDF to FLUENT After the UDF that you have defined using DEFINE_DPM
114. real or do not return any value if they are of type void To determine the return data type for the DEFINE macro you will use to define your UDF look at the macro s corresponding define statement in the udf h file or see Appendix B for a listing C functions cannot alter their arguments They can however alter the variables that their arguments point to A 8 Fluent Inc September 11 2006 A 9 Arrays A 9 Arrays Arrays of variables can be defined using the notation name size where name is the variable name and size is an integer that defines the number of elements in the array The index of a C array always begins at 0 Arrays of variables can be of different data types as shown below Examples int a 10 b 10 10 real radiil 5 a 0 1 a 1 Dimensional array of variable a radiil4 3 14159265 a 1 Dimensional array of variable radii b 10 10 4 a 2 Dimensional array of variable b A 10 Pointers A pointer is a variable that contains an address in memory where the value referenced by the pointer is stored In other words a pointer is a variable that points to another variable by referring to the other variable s address Pointers contain memory addresses not values Pointer variables must be declared in C using the notation Pointers are widely used to reference data stored in structures and to pass data among functions by passing the addresses of the data For example int ip
115. select the process es you want the message to come from This is demonstrated in the following example Example if RP_NODE Message Total Area Before Summing f n total _area endif RP_NODE In this example the message will be sent by the compute nodes It will not be sent by the host or serial process Message0 is a specialized form of the Message utility MessageO will send messages from compute node 0 only and is ignored on the other compute nodes without having to use a compiler directive Note that MessageO will also display messages on a serial process Example Let Compute Node 0 display messages Message0 Total volume f n total_volume Fluent Inc September 11 2006 7 31 Parallel Considerations 7 5 8 Message Passing Macros High level communication macros of the form node_to_host and host_to_node that are described in Section 7 5 2 Communicating Between the Host and Node Processes are typically used when you want to send data from the host to all of the compute nodes or from node 0 to the host You cannot however use these high level macros when you need to pass data between compute nodes or pass data from all of the compute nodes to compute node 0 In these cases you can use special message passing macros described in this section Note that the higher level communication macros expand to functions that perform a number of lower level message passing operations which send se
116. solidification is turned ON Note Concentration in particles x10 kg For mass fraction concentrations in the table above see Equation 20 3 7 of the User s Guide for the defining equation Reynolds Stress Model Macros The macros listed in Table 3 2 18 can be used to return real variables for the Reynolds stress turbulence model in SI units The variables are available in both the pressure based and the density based solver Definitions for these macros can be found in the metric h header file 3 16 Fluent Inc September 11 2006 3 2 Data Access Macros Table 3 2 17 Table of Definitions for Argument i of the Pollutant Species Mass Fraction Function C_POLLUT Table 3 2 18 Macros for Reynolds Stress Model Variables Defined in oa ND OH O m Definitions Mass Mass Mass Mass Soot Fraction Fraction Fraction Fraction of NO of HCN of NH3 of N20 Mass Fraction Normalized Radical Nuclei sg_mem h Macro Argument Types Returns C_RUU c t cell t c Thread t wu Reynolds stress C_RVV c t cell t c Thread xt vv Reynolds stress C_RWW c t cell t c Thread xt ww Reynolds stress C_RUV c t cell t c Thread xt uv Reynolds stress C_RVW c t cell t c Thread xt vw Reynolds stress C_RUW c t cell t c Thread xt uw Reynolds stress Fluent Inc September 11 2006 3 17 Additional Macros for Writing UDFs VOF Multiphase Model Macro The macro C_VOF can be used
117. solver to your UDF Your UDF will need to return the real value of the gray band coefficient to the solver Example The following UDF named user gray band abs specifies the gray band absorption co efficient as a function of temperature that can be used for a non gray Discrete Ordinate model include udf h DEFINE_GRAY_BAND_ABS_COEFF user_gray_band_abs c t nb real abs_coeff 0 real T C_T c t switch nb case 0 abs_coeff 1 3 0 001 T break case 1 abs_coeff 2 7 0 005 T break 2 42 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros return abs_coeff Hooking a Gray Band Coefficient UDF to FLUENT After the UDF that you have defined using DEFINE GRAY BAND ABS COEFF is interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user_gray_band_abs will become visible and selectable in the Materials panel for the Absorption Coefficient See Section 6 2 7 Hooking DEFINE_GRAY_BAND_ABS_COEFF UDFs for details Fluent Inc September 11 2006 2 43 DEFINE Macros 2 3 8 DEFINE_HEAT_FLUX Description You can use DEFINE HEAT FLUX to modify the heat flux at a wall Despite the name a DEFINE HEAT FLUX UDF is not the means to specify the actual heat flux entering a domain from the outside To specify this type of heat flux you would simply use a DEFINE_PROFILE functio
118. suffix can be applied to some of the cell variable macros in Table 3 2 8 to allow access to the value of the variable at the previous time step i e t At These data may be useful in unsteady simulations For example C_T_Mi c t returns the value of the cell temperature at the previous time step Previous time step macros are shown in Table 3 2 11 i Note that data from C_T_M1 is available only if user defined scalars are defined It can also be used with adaptive time stepping See Section 2 7 4 DEFINE UDS UNSTEADY for an example UDF that utilizes C_R_M1 3 12 Fluent Inc September 11 2006 3 2 Data Access Macros Table 3 2 11 Macros for Cell Time Level 1 Defined in mem h Macro Argument Types Returns CRMi c t cell t c Thread t density previous time step CP_Mi c t cell t c Thread t pressure previous time step CUM1 c t cell t c Thread t velocity previous time step C_V_M1 c t cell_t c Thread t velocity previous time step C_W_M1 c t cell t c Thread t velocity previous time step CT M1 c t cell t c Thread t temperature previous time step CYIM1 c t i cell_t c Thread t int i species mass fraction note int i is species index previous time step The M2 suffix can be applied to some of the cell variable macros in Table 3 2 11 to allow access to the value of the variable at the time step before the previous one i e t 2At These data may be useful in unsteady simulations
119. the phases does not have a mixture material associated with it then the mass transfer will be with the bulk fluid of that phase Usage DEFINE MASS TRANSFER name c mixture thread from phase index from species index to_phase_index to_species_index Note that all of the arguments to a DEFINE macro need to be placed on the same line in your source code Splitting the DEFINE statement onto several lines will result in a compilation error Argument Type Description symbol name UDF name cell t c Index of cell on the thread pointed to by mixture thread Thread xmixture thread Pointer to mixture level thread int from phase index Index of phase from which mass is transferred int from species index ID of species from which mass is transferred ID 1 if phase does not have mixture material int to_phase_index Index of phase to which mass is transferred int to_species_index ID of species to which mass is transferred ID 1 if phase does not have mixture material Function returns real There are seven arguments to DEFINE_MASS_TRANSFER name c mixture_thread from_phase_index from_species_index to_phase_index to_species_index You sup ply name the name of the UDF The variables c mixture_thread from_phase_index from species index to phase index and to species index are passed by the FLU ENT solver to your UDF Your UDF will need to return the real value of the mass transfer to the solver in the units of kg m Flue
120. the FLUENT solver to your UDF Your UDF will need to set the values referenced by the real pointer to the slip velocity vector vector_result to the components of the slip velocity vector e g vector_result 0 vector_result 1 for a 2D problem 2 1 36 Fluent Inc September 11 2006 2 4 Multiphase DEF INE Macros Example The following UDF named custom_slip specifies a custom slip velocity in a two phase mixture problem pE kkk kkk kk kkk kkk kkk k k kk k k k kk k kk k k k kk k k k kk k kkk k k k K SE UDF for a defining a custom slip velocity in a 2 phase mixture problem DD OH HE ooo DO DH kkk kkk HO include udf h DEFINE_VECTOR_EXCHANGE_PROPERTY custom_slip c mixture_thread second_column_phase_index first_column_phase_index vector_result real grav 2 0 9 81 real K 5 e4 real pgrad_x pgrad_y Thread pt st thread pointers for primary and secondary phases THREAD_SUB_THREAD mixture_thread second_column_phase_index THREAD_SUB_THREAD mixture_thread first_column_phase_index pt st at this point the phase threads are known for primary 0 and secondary 1 phases C_DP c mixture_thread 0 C_DP c mixture_thread 1 pgrad_x pgrad_y vector_result 0 pgrad_x K C_R c st C_R c pt K grav 0 vector_result 1 pgrad_y K eC C_R c st C_R c pt K grav 1 Fluent Inc September 11 2006 2 1 37 DEFINE Macros Note th
121. the compute node processes send a message to compute node 0 compute node 0 must have a loop to receive the N messages from the N nodes Below is an example of a compiled parallel UDF that utilizes message passing macros PRF_CSEND and PRF_CRECV Refer to the comments in the code for details about the function Example Message Passing include udf h define WALLID 3 DEFINE_ON_DEMAND face_p_list if RP_HOST Host will do nothing in this udf Serial will face_t f Thread tf Domain domain real p_array real x ND_ND x_array ND_ND int n_faces i j domain Get_Domain 1 Each Node will be able to access its part of the domain tf Lookup_Thread domain WALLID Get the thread from the domain The number of faces of the thread on nodes 1 2 needs to be sent to compute node 0 so it knows the size of the arrays to receive from each n_faces THREAD_N_ELEMENTS_INT tf Fluent Inc September 11 2006 7 33 Parallel Considerations No need to check for Principal Faces as this UDF will be used for boundary zones only if RP_NODE if I_AM_NODE_ZERO_P Nodes 1 2 send the number of faces PRF_CSEND_INT node_zero amp n_faces 1 myid endif Allocating memory for arrays on each node p_array real malloc n_faces sizeof real x_array real ND_ND malloc ND_ND n_faces sizeof real begin_f_loop f tf Loop over interior faces in the
122. the face or cell A thread pointer is always required along with the ID to identify which thread the face or cell belongs to Some UDFs are passed the cell index variable c as an argument such as in DEFINE PROPERTY my function c t or the face index variable f such as in DEFINE UDS_FLUX my_function f t i If the cell or face index variable e g cell t c cell_t f isn t passed as an argument and is needed in the UDF the variable is always available to be used by the function once it has been declared locally See Sec tion 2 7 3 DEFINE_UDS_FLUX for an example The data structures that are passed to your UDF as pointers depend on the DEFINE macro you are using and the property or term you are trying to modify For example DEFINE_ADJUST UDFs are general purpose functions that are passed a domain pointer d such as in DEFINE ADJUST my function d DEFINE PROFILE UDFs are passed a thread pointer t to the boundary zone that the function is hooked to such as in DEFINE PROFILE my function thread i Some UDFs such as DEFINE_ON_DEMAND functions aren t passed any pointers to data structures while others aren t passed the pointer the UDF needs If your UDF needs to access a thread or domain pointer that is not directly passed by the solver through an argument then you will need to use a special Fluent supplied macro to obtain the pointer in your UDF For example DEFINE ADJUST is passed only the domain pointer so if your UDF need
123. the following Source Term Variable Unit particle temperature dydt 0 K s particle component mass dydt 1 kg s gas phase enthalpy dzdt gt energy J s gas phase species mass dzdt gt species 0 kg s Fluent Inc September 11 2006 2 1 59 DEFINE Macros PK kkk k kkk OO CR 2K K 2K 2K K FK 2K 2 FK 2K A FK A K 2K 2K FK 2K K FK 2K 2K 2K FK 2K 2K K FK 2k K K FK K K FK FK 2K K K K 2K K UDF for defining the heat and mass transport for multicomponent particle vaporization FO RR HRK a 32k HR 2k 2k ak ok 2k 3k 2k 2k ak ak include udf h DEF INE_DPM_HEAT_MASS multivap p Cp hgas hvap cvap_surf dydt dzdt int ns int nc TP_N_COMPONENTS p number of particle components cell_t cO RP_CELL amp p gt cCell cell and thread Thread tO RP_THREAD amp p gt cCell where the particle is in Material gas_mix THREAD_MATERIAL tO gas mixture material Material cond_mix p gt injection gt material particle mixture material cphase_state_t c amp p gt cphase cell info of particle location real molwt MAX_SPE_EQNS molecular weight of gas species real Tp P_T p particle temperature real mp P_MASS p particle mass real molwt_bulk 0 average molecular weight in bulk gas real Dp DPM_DIAM_FROM_VOL mp P_RHO p particle diameter real Ap DPM_AREA Dp particle surface real Pr c gt sHeat c gt mu c gt
124. the same for printf fprintf and fscanf Note that all of these standard C I O functions are supported by the interpreter so you can use them in either interpreted or compiled UDFs For more information about standard I O functions in C you should consult a reference guide e g 2 Common C I O Functions fopen filename mode opens a file fclose fp closes a file print format 21 4 formatted print to the console fprintf fp format formatted print to a file fscanf fp format formatted read from a file FA It is not possible to use the scanf C function in FLUENT fopen FILE fopen char filename char mode The function fopen opens a file in the mode that you specify It takes two arguments filename and mode filename is a pointer to the file you want to open mode is the mode in which you want the file opened The options for mode are read r write w and append a Both arguments must be enclosed in quotes The function returns a pointer to the file that is to be opened Before using fopen you will first need to define a local pointer of type FILE that is defined in stdio h e g fp Then you can open the file using fopen and assign it to the local pointer as shown below Recall that stdio h is included in the udf h file so you don t have to include it in your function FILE fp define a local pointer fp of type FILE fp fopen data txt r open a file named data txt
125. the source file Section 8 1 5 Step 4 Interpret or Compile the Source File Hook the UDF to FLUENT Section 8 1 6 Step 5 Hook the UDF to FLUENT Run the calculation Section 8 1 7 Step 6 Run the Calculation Analyze the numerical solution and compare it to expected results Section 8 1 8 Step 7 Analyze the Numerical Solution and Compare to Expected Results To begin the process you Il need to define the problem you wish to solve using a UDF Step 1 For example suppose you want to use a UDF to define a custom boundary profile for your model You will first need to define the set of mathematical equations that describes the profile Fluent Inc September 11 2006 8 1 Examples Next you will need to translate the mathematical equation conceptual design into a function written in the C programming language Step 2 You can do this using any text editor Save the file with a c suffix e g udfexample c in your working directory See Appendix A for some basic information on C programming Once you have written the C function you are ready to start FLUENT and read in or set up your case file Step 3 You will then need to interpret or compile the source code debug it Step 4 and then hook the function to FLUENT Step 5 Finally you ll run the calculation Step 6 analyze the results from your simulation and compare them to expected results Step 7 You may loop through this entire process more tha
126. then assign the thread pointer to a thread_name and use it in your UDF i Note that when Lookup Thread is utilized in a multiphase flow problem the domain pointer that is passed to the function depends on the UDF that it is contained within For example if Lookup Thread is used in an adjust function DEFINE ADJUST then the mixture domain is passed and the thread pointer returned is the mixture level thread Example Below is a UDF that uses Lookup_Thread In this example the pointer to the thread for a given zone_ID is retrieved by Lookup_Thread and is assigned to thread The thread pointer is then used in begin_f_loop to loop over all faces in the given thread and and in F_CENTROID to get the face centroid value pE ooo o o ooo kkk kkk kkk kkk Example of an adjust UDF that uses Lookup_Thread Note that if this UDF is applied to a multiphase flow problem the thread that is returned is the mixture level thread FO RK a RR a a HER HE 3k 2k 2k ak ok 2k ak ok include udf h domain passed to Adjust function is mixture domain for multiphase DEFINE_ADJUST print_f_centroids domain real FC 2 face_t f int ID 1 Zone ID for wall 1 zone from Boundary Conditions panel Thread thread Lookup_Thread domain ID begin_f_loop f thread F_CENTROID FC f thread printf x coord f y coord f FC O FC 1 end_f_loop f thread 3 26 Fluent Inc September 11 2006 3 2 Data Access Macros
127. thermal energy via the absorption and emission mechanisms The gradient of the radiative heat flux is therefore a negative source of thermal energy As shown in Section 13 3 3 P 1 Radiation Model Theory of the User s Guide manual the source term for the incident radiation Equation 8 2 7 is equal to the gradient of the radiative heat flux and hence its negative specifies the source term needed to modify the energy equation Now consider how the energy boundary condition at the wall must be modified Locally the only mode of energy transfer from the wall to the fluid that is accounted for by default is conduction With the inclusion of radiation effects radiative heat transfer to and from the wall must also be accounted for This is done automatically if you use FLUENT s built in P1 model The DEFINE HEAT FLUX macro allows the wall boundary condition to be modified to accommodate this second mode of heat transfer by specifying the coefficients of the gir equation discussed in Section 2 3 8 DEFINE_HEAT_FLUX The net radiative heat flux to the wall has already been given as Equation 8 2 9 Comparing this equation with that for gir in Section 2 3 8 DEFINE_HEAT_FLUX will result in the proper coefficients for cir Fluent Inc September 11 2006 8 47 Examples In this example the implementation of the P1 model can be accomplished through six separate UDFs They are all included in a single source file which can be executed as a compi
128. thread filling p_array with face pressure and x_array with centroid p array f F_P f tf F_CENTROID x_array f f tf end_f_loop f tf Send data from node 1 2 to node O Message0 nstart n if RP_NODE if I_AM_NODE_ZERO_P Only SEND data from nodes 1 2 PRF_CSEND_REAL node_zero p_array n_faces myid PRF_CSEND_REAL node_zero x_array 0 ND_ND n_faces myid else endif Node 0 and Serial processes have their own data so list it out first Message0 n nList of Pressures n Same as Message on SERIAL for j 0 j lt n_faces j n_faces is currently node 0 serial value if RP_3D Message0 12 4e 12 4e 12 4e 12 4e n 7 34 Fluent Inc September 11 2006 7 5 Macros for Parallel UDFs x_array j 0 x_array j 1 x_array j 2 p_arrayljl else 2D Message0 12 4e 12 4e 12 4e n x_array j 0 x_array j 1 p_arraylj l endif Node 0 must now RECV data from the other nodes and list that too if RP_NODE if I_AM_NODE_ZERO_P compute_node_loop_not_zero i See para h for definition of this loop A PRF_CRECV_INT i amp n_faces 1 i n_faces now value for node i Reallocate memory for arrays for node i p_array real realloc p_array n_faces sizeof real x_array real ND_ND realloc x_array ND_ND n_faces sizeof real Receive data PRF_CRECV_REAL i p_array n_faces i PRF_
129. time Table 3 5 2 shows the correspondence between solver and RP macros that access the same time dependent variables Table 3 5 2 Solver and RP Macros that Access the Same Time Dependent Variable Solver Macro Equivalent RP Variable Macro CURRENT_TIME RP_Get_Real flow time CURRENT_TIMESTEP RP_Get_Real physical time step N_TIME RP_Get_Integer time step Fa You should not access a scheme variable using any of the RP GET_ func tions from inside a cell or face looping macro c_loop or f loop This type of communication between the solver and cortex is very time consuming and therefore should be done outside of loops Fluent Inc September 11 2006 3 69 Additional Macros for Writing UDFs Example The integer time step count accessed using N_TIME is useful in DEFINE_ADJUST functions for detecting whether the current iteration is the first in the time step paaa o o kkk kkk kkk kkk kk kk kkk kkk kk kkk kkk kkk k k k Example UDF that uses N_TIME DO EE ooo oo DH D DO kkk k kkk kkk static int last_ts 1 Global variable Time step is never lt 0 DEFINE_ADJUST first_iter_only domain int curr_ts curr_ts N_TIME if last_ts curr_ts last_ts curr_ts things to be done only on first iteration of each time step can be put here i There is a new variable named first iteration that can be used in the above if statement first_iteration is true only
130. to FLUENT 6 32 DEFINE RW FILE UDFs defining 2 24 hooking to FLUENT 6 12 DEFINE SCAT PHASE FUNC UDFs defining 2 88 hooking to FLUENT 6 34 DEFINE SDOF PROPERTIES UDF s defining 2 205 hooking to FLUENT 6 76 DEFINE SOLAR INTENSITY UDF s defining 2 91 hooking to FLUENT 6 36 DEFINE_ SOURCE UDFs defining 2 93 example 8 27 hooking to FLUENT 6 37 DEFINE SOX RATE UDFs defining 2 96 hooking to FLUENT 6 40 DEFINE SR RATE UDFs defining 2 101 hooking to FLUENT 6 41 Fluent Inc September 11 2006 DEFINE_TURB_PREMIX_SOURCE UDFs defining 2 105 hooking to FLUENT 6 42 DEFINE_TURBULENT_VISCOSITY UDFs defining 2 107 hooking to FLUENT 6 43 DEFINE_UDS_FLUX UDFs defining 2 215 hooking to FLUENT 6 81 DEFINE_UDS_UNSTEADY UDFs defining 2 219 hooking to FLUENT 6 82 DEFINE_VECTOR_EXCHANGE_PROPERTY UDFs defining 2 136 hooking to FLUENT 6 52 DEFINE_VR_RATE UDFs defining 2 111 example 8 38 hooking to FLUENT 6 44 DEFINE_WALL_FUNCTIONS UDFs defining 2 115 hooking to FLUENT 6 45 defining UDFs 8 2 using DEFINE macros 2 1 deforming zone geometry UDFs 2 200 demo_calc 2 24 density UDF 6 32 derivative variable macros 3 13 derivatives source term 2 93 diffuse reflectivity UDFs 2 36 diffusion coefficient 3 21 diffusive flux 3 21 diffusivity 1 3 diffusivity coefficient UDFs 2 209 dimension utilities 3 63 directory structure UNIX systems 5 11 Windows systems 5 10 discrete
131. to return real variables associated with the VOF mul tiphase model in SI units The variables are available in both the pressure based and the density based solver with the exception of the VOF variable which is available only for the pressure based solver Definitions for these macros can be found in sg mphase h which is included in udf h Table 3 2 19 Macros for Multiphase Variables Defined in sg mphase h Macro Argument Types Returns C_VOF c t cell t c Thread t volume fraction for the has to be a phase phase corresponding to phase thread thread t 3 2 4 Face Macros The macros listed in Table 3 2 20 3 2 23 can be used to return real face variables in SI units They are identified by the F_ prefix Note that these variables are available only in the pressure based solver In addition quantities that are returned are available only if the corresponding physical model is active For example species mass fraction is available only if species transport has been enabled in the Species Model panel in FLUENT Definitions for these macros can be found in the referenced header files e g mem h Face Centroid F CENTROID The macro listed in Table 3 2 20 can be used to obtain the real centroid of a face F_CENTROID finds the coordinate position of the centroid of the face f and stores the coordinates in the x array Note that the array x can be a one two or three dimensional array Table 3 2 20 Macro for F
132. used when the finite rate eddy dissipation chemical reaction mechanism used Note that rr and rr_t are conversion rates in kgmol m s These rates when multiplied by the respec tive stoichiometric coefficients yield the production consumption rates of the individual chemical components Fluent Inc September 11 2006 2 111 DEFINE Macros Example 1 The following UDF named vol_reac_rate specifies a volume reaction rate The function must be executed as a compiled UDF in FLUENT paaa oo oo oo o kkk k k kkk kkk kk kkk UDF for specifying a volume reaction rate The basics of Fluent s calculation of reaction rates only an Arrhenius finite rate reaction rate is calculated from the inputs given by the user in the graphical user interface BEAR AGAR RI I I I A KIRK AK AEA DH A A 1 21 1 21 1 kkk kk kkk kkk kkk kk include udf h DEFINE_VR_RATE vol_reac_rate c t r wk yk rate rr_t real ci prod int i Calculate Arrhenius reaction rate prod 1 for i 0 i lt r gt n_reactants i ci C_R c t yk r gt reactant li wklr gt reactantlil prod pow ci r gt exp_reactant i xrate r gt A exp r gt E UNIVERSAL_GAS_CONSTANT C_T c t pow C_T c t r gt b prod xrr_t rate No return value 2 1 12 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros Example 2 When multiple reactions are specified a volume reaction rate UDF is
133. using a C preprocessor This machine code then executes on an internal emulator or interpreter when the UDF is invoked This extra layer of code incurs a performance penalty but allows an interpreted UDF to be shared effortlessly between different architectures operating systems and FLUENT versions If execution speed does become an issue an interpreted UDF can always be run in compiled mode without modification Fluent Inc September 11 2006 1 5 Interpreting and Compiling UDFs The interpreter that is used for interpreted UDFs does not have all of the capabilities of a standard C compiler which is used for compiled UDFs Specifically interpreted UDFs cannot contain any of the following C programming language elements e goto statements 1 5 1 non ANSI C prototypes for syntax direct data structure references declarations of local structures unions pointers to functions arrays of functions multi dimensional arrays Differences Between Interpreted and Compiled UDFs The major difference between interpreted and compiled UDFs is that interpreted UDFs cannot access FLUENT solver data using direct structure references they can only indi rectly access data through the use of Fluent supplied macros This can be significant if for example you want to introduce new data structures in your UDF A summary of the differences between interpreted and compiled UDFs is presented below See Chapters 4 and 5 for details on
134. writing to a file on all of the data in the same way as the serial solver Figure 7 1 5 Fluent Inc September 11 2006 7 1 Overview of Parallel FLUENT HOST COMPUTE NODES a M Figure 7 1 4 Parallel FLUENT Architecture Fluent Inc September 11 2006 7 5 Parallel Considerations Print messages Figure 7 1 5 Example of Command Transfer in Parallel FLUENT 7 6 Fluent Inc September 11 2006 7 2 Cells and Faces in a Partitioned Grid Interior cells Exterior cell Figure 7 2 1 Partitioned Grid Cells 7 2 Cells and Faces in a Partitioned Grid Some terminology needs to be introduced to distinguish between different types of cells and faces in a partitioned grid Note that this nomenclature applies only to parallel coding in FLUENT Cell Types in a Partitioned Grid There are two types of cells in a partitioned grid interior cells and exterior cells Fig ure 7 2 1 Interior cells are fully contained within a grid partition Exterior cells on one compute node correspond to the same interior cells in the adjacent compute node Figure 7 1 2 This duplication of cells at a partition boundary becomes important when you want to loop over cells in a parallel grid There are separate macros for looping over interior cells exterior cells and all cells See Section 7 5 5 Looping Macros for details Fluent Inc September 11 2006 7 7 Parallel Considerations Boundary zo
135. you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_SCAT_PHASE_FUNC UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Func tions panel Figure 6 2 20 in FLUENT To hook the UDF to FLUENT you will first need to open the User Defined Functions panel from the Material panel by selecting user defined in the drop down list for the Scattering Phase Function property Figure 6 2 19 Define gt Materials Materials Name Material Type Order Materials By air fluid y Name c Chemical Formula Fluent Fluid Materials Chemical Formula air z Fluent Database Mixture User Defined Database none Properties Absorption Coefficient 1 m ana E a 6 Scattering Coefficient 1 m user defined defined Edi i La it ScatPhiB2 Scattering Phase Function lisowopic Edit Refractive Index La Ct r LA Change Create Delete Close Help Figure 6 2 19 The Materials Panel Fluent Inc September 11 2006 6 2 Hooking Model Specific UDFs i The Discrete Ordinates radiation model must be enabled from the Radiation Model panel Next choose the function name e g ScatPhiB2 from the list of UDFs displayed in the User Defined Functions panel and click OK The name of the function will subsequently be displayed under the Scattering Phase Function property in
136. 0 P 1 coeffs 1 for i 1 i lt 7 i P i 1 1 it1 0 2 it 1 c P i ixP i 1 phi coeffs i 1 P i 1 return phi Fluent Inc September 11 2006 2 89 DEFINE Macros DEFINE_SCAT_PHASE_FUNC ScatIso c fsf fsf 0 return 1 0 Hooking a Scattering Phase UDF to FLUENT After the UDF that you have defined using DEFINE SCAT PHASE FUNCTION is interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name that you specified in the DEFINE macro argument e g ScatPhiB will become visible and selectable in the Materials panel in FLUENT See Section 6 2 15 Hooking DEFINE SCAT PHASE FUNC UDF for details 2 90 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros 2 3 16 DEFINE_SOLAR_INTENSITY Description You can use the DEFINE_SOLAR_INTENSITY macro to define direct solar intensity or diffuse solar intensity UDFs for the solar load model See Chapter 13 Modeling Heat Transfer to go to the User s Guide for more information on the solar load model Note that solar intensity UDFs are used with the Solar Model which is available only for the 3d geometries in FLUENT Usage DEFINE_SOLAR_INTENSITY name sum_x sun_y sun_z S_hour S_minute Argument Type Description symbol name UDF name real sun_x x component of the sun direction vector real sun y y component of the sun direction vector real sun z z component of the sun direction vector real S
137. 0 i lt ND_ND i for j 0 j lt ND_ND j Alay hid f i j ND_SUM The utility ND_SUM computes the sum of ND_ND arguments ND_SUM x y z 2D x y 3D x y Z ND_ SET The utility ND_SET generates ND_ND assignment statements ND_SET u v w C_U c t C_V c t C_W c t u C_U c t v C_V c t if 3D 21 w C_W c t 3 64 Fluent Inc September 11 2006 3 4 Vector and Dimension Macros 3 4 3 The NV Macros The NV macros have the same purpose as ND macros but they operate on vectors i e arrays of length ND_ND instead of separate components NV_V The utility NV_V performs an operation on two vectors NV_V a x alO x 0 ali x 1 etc Note that if you use instead of in the above equation then you get alO x 0 etc See Section 2 6 3 DEFINE GRID MOTION for an example UDF that utilizes NV_V NV_VV The utility NV_VV performs operations on vector elements The operation that is per formed on the elements depends upon what symbol is used as an argument in place of the signs in the following macro call NV_VV a x y 2D a 0 x 0 y 0 afi x 1 y 1 See Section 2 6 3 DEFINE_GRID_MOTION for an example UDF that utilizes NV_VV NV_V_VS The utility NV_V_VS adds a vector to another vector which is multiplied by a scalar NV_V_VS a x y 0 5 2D a 0 x 0 y 0 0 5 alt x 1 y 1 0 5 Note that the
138. 006 7 39 Parallel Considerations if RP_NODE if myid node_zero PRF_CSEND_INT node_zero amp noface 1 myid endif 7 40 Fluent Inc September 11 2006 7 8 Parallel UDF Example 7 8 Parallel UDF Example The following is an example of a serial UDF that has been parallelized so that it can run on any version of FLUENT host node serial Explanations for the various changes from the simple serial version are provided in the comments and discussed below The UDF named face av is defined using an adjust function computes a global sum of pressure on a specific face zone and computes its area average Example Global Summation of Pressure on a Face Zone and its Area Average Computation include udf h DEFINE_ADJUST face_av domain Variables used by serial host node versions int surface_thread_id 0 real total_area 0 0 real total_force 0 0 Parallelized Sections if RP_HOST Compile this section for computing processes only serial and node since these variables are not available on the host Thread thread face_t face real area ND_ND endif RP_HOST Get the value of the thread ID from a user defined Scheme variable if RP_NODE SERIAL or HOST surface_thread_id RP_Get_Integer pres_av thread id Message nCalculating on Thread d n surface_thread_id endif RP_NODE To set up this user Scheme variable in cortex ty
139. 2 z 20 20 Gaz where the variable y is 0 0 at the center of the inlet and extends to values of 0 0745 m at the top and bottom Thus the x velocity will be 20 m sec at the center of the inlet and 0 at the edges 8 16 Fluent Inc September 11 2006 8 2 Detailed UDF Examples 5 98e 01 5 42e 01 4 86e 01 4 30e 01 3 74e 01 3 19e 01 2 63e 01 2 07e 01 1 51e 01 9 54e 00 3 96e 00 Turbine Vane 1551 cells 2405 faces 893 nodes Contours of Velocity Magnitude m s Figure 8 2 2 Velocity Magnitude Contours for a Constant Inlet x Velocity 6 11e 01 5 52e 01 4 93e 01 4 34e 01 3 75e 01 3 16e 01 2 57e 01 1 98e 01 1 39e 01 7 96e 00 2 05e 00 Turbine Vane 1551 cells 2405 faces 893 nodes Velocity Vectors Colored By Velocity Magnitude m s Figure 8 2 3 Velocity Vectors for a Constant Inlet x Velocity Fluent Inc September 11 2006 8 17 Examples A UDF is used to introduce this parabolic profile at the inlet The C source code vprofile c isshown below The function makes use of Fluent supplied solver functions that are described in Section 3 2 4 Face Macros The UDF named inlet_x_velocity is defined using DEFINE PROFILE and has two ar guments thread and position Thread is a pointer to the face s thread and position is an integer that is a n
140. 2 162 3 8 3 52 c face loop 2 101 2 103 3 52 C_FACE_THREAD 2 101 2 103 2 162 3 8 3 52 C_FMEAN 2 105 C_H 3 9 C K 2 59 2 108 3 9 CKL 2 125 C_MU_EFF 2 35 C MULL 2 59 2 123 2 125 C_MU_T 2 59 C_NFACES 3 8 C_NNODES 3 8 C_NODE 3 53 c_node_loop 3 53 C_NUT 3 9 CO 3 9 CP 3 9 C_PHASE_DIAMETER 2 125 CR 286 9 103 9 108 2119 9199 D195 2 134 2 137 2 217 3 9 C R M1 2 220 C STORAGE R 2 220 CT 2 21 2 84 2 103 2 134 2 185 3 9 8 32 C_U 2 123 2 125 3 9 C_UDMI 2 21 2 154 3 43 6 14 Index 2 C_UDSI 2 6 3 39 CV 2 123 2 125 3 9 C VOF 2 123 2 125 2 134 3 54 C VOLUME 2 5 2 9 2 21 2 220 3 7 CW 2 125 3 9 C_YI 2 84 2 162 3 9 case file functions reading and writing 2 24 casting A 8 cavitation rate UDFs 2 119 cell 1 10 accessing neighboring thread variables 1 8 values checking accessibility 3 74 cell centroid 3 21 cell centroid macro 3 7 cell face 1 9 cell face index macro 3 8 cell face macros 3 8 cell face thread macro 3 8 cell gradient macros 3 10 cell ID 1 11 cell identifier 3 3 cell looping macro general purpose 7 27 cell looping macros parallel 7 23 cell partition IDs parallel 7 30 cell reconstruction gradient macros 3 11 cell variables macros 3 7 cell volume macro 3 7 cell zone 1 9 cell_t data structure 1 10 center of gravity motion UDFs 2 197 chemistry step UDFs 2 31 coal emissivity 2 173 coal scattering 2 173 communication macros para
141. 2 5 7 DEFINE_DPM_LAW Description You can use DEFINE DPM LAW to customize laws for particles For example your UDF can specify custom laws for heat and mass transfer rates for droplets and combusting particles Additionally you can specify custom laws for mass diameter and temperature properties as the droplet or particle exchanges mass and energy with its surroundings Usage DEFINE DPM LAW name p ci Argument Type Description symbol name UDF name Tracked Particle p Pointer to the Tracked Particle data structure which contains data related to the particle being tracked int ci Variable that indicates whether the continuous and discrete phases are coupled equal to 1 if coupled with continuous phase 0 if not coupled Function returns void There are three arguments to DEFINE_DPM_LAW name p and ci You supply name the name of the UDF p and ci are variables that are passed by the FLUENT solver to your UDF Pointer p can be used as an argument to the macros defined in Sec tion 3 2 7 DPM Macros to obtain information about particle properties e g injection properties 2 1 66 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros Example The following UDF named Evapor_Swelling Law models a custom law for the evapo ration swelling of particles The source code can be interpreted or compiled in FLUENT See Section 2 5 13 Example for another example of DEFINE_DPM_LAW usage DRO ak a
142. 2K 2k K 2k UDF for computing the melting index along a particle trajectory EEEE ooo ooo oo DH DH ED OK DH kkk kk kkk kk include udf h static real viscosity_0 DEFINE_INIT melt_setup domain if memory for the particle variable titles has not been allocated yet do it now if NULLP user_particle_vars Init_User_Particle_Vars now set the name and label strcpy user_particle_vars 0 name melting index strcpy user_particle_vars 0 label Melting Index update the user scalar variables DEFINE_DPM_SCALAR_UPDATE melting_index cell thread initialize p cphase_state_t c amp p gt cphase if initialize this is the initialization call set Fluent Inc September 11 2006 2 1 77 DEFINE Macros p gt user 0 contains the melting index initialize to 0 viscosity_O contains the viscosity at the start of a time step p gt user 0 0 viscosity_0 c gt mu else use a trapezoidal rule to integrate the melting index p gt user 0 P_DT p 5 1 viscosity_0 1 c gt mu save current fluid viscosity for start of next step viscosity_0 c gt mu write melting index when sorting particles at surfaces DEF INE_DPM_OUTPUT melting_output header fp p thread plane char name 100 if header if NNULLP thread par_fprintf_head fp s d n thread gt head gt dpm_summary sort_file_name 11 else par_fprintf_head
143. 2K K FK FKK FK FK 2K K FK FK 2K K FK 2K 2K K FK 26 2k K FK Example of UDF for single phase that uses Get_Domain utility BER EE ooo OH DH DD k k k kkk kkk k kkk include udf h FILE fout void Print_Thread_Face_Centroids Domain domain int id real FC 2 face_t f Thread t Lookup_Thread domain id fprintf fout thread id d n id begin_f_loop f t F_CENTROID FC f t fprintf fout fyd Ye e g n f FC 0 FC 1 FC 2 end_f_loop f t 3 28 Fluent Inc September 11 2006 3 2 Data Access Macros fprintf fout n DEFINE_ON_DEMAND get_coords Domain domain domain Get_Domain 1 fout fopen faces out w Print_Thread_Face_Centroids domain 2 Print_Thread_Face_Centroids domain 4 fclose fout Note that Get_Domain 1 replaces the extern Domain domain expression used in pre vious releases of FLUENT 6 Set Boundary Condition Value F_PROFILE F_PROFILE is typically used in a DEFINE PROFILE UDF to set a boundary condition value in memory for a given face and thread The index i that is an argument to F PROFILE is also an argument to DEFINE_PROFILE and identifies the particular boundary variable e g pressure temperature velocity that is to be set F_PROFILE is defined in mem h Macro F_PROFILE f t i Argument types facet f Thread t int i Function returns void The arguments of F_PROFILE are f the index of the face face_t t a pointer to the f
144. 3 Physical Properties Section 8 2 4 Reaction Rates Section 8 2 5 User Defined Scalars 8 2 1 Boundary Conditions This section contains two applications of boundary condition UDFs e Parabolic Velocity Inlet Profile for a Turbine Vane e Transient Velocity Inlet Profile for Flow in a Tube Fluent Inc September 11 2006 8 15 Examples Parabolic Velocity Inlet Profile in a Turbine Vane Consider the turbine vane illustrated in Figure 8 2 1 An unstructured grid is used to model the flow field surrounding the vane The domain extends from a periodic boundary on the bottom to an identical one on the top a velocity inlet on the left and a pressure outlet on the right DOO P Turbine Vane 1551 cells 2405 faces 893 nodes Grid Figure 8 2 1 The Grid for the Turbine Vane Example A flow field in which a constant x velocity is applied at the inlet will be compared with one where a parabolic x velocity profile is applied While the application of a profile using a piecewise linear profile is available with the boundary profiles option the specification of a polynomial can only be accomplished by a user defined function The results of a constant velocity applied field of 20 m sec at the inlet are shown in Figures 8 2 2 and 8 2 3 The initial constant velocity field is distorted as the flow moves around the turbine vane The inlet x velocity will now be described by the following profile y
145. 3 lt gt bce eee ee ee BE ee Se Bee 2 137 202 DEFINE DPM BODY PORCE 5 44 poces sua drame EN 444 2 145 2 5 3 DEFINE DPMDRAG 2 147 20421 DEFINE DPM EROSION 3 su bin ee seu ps frames du 2 149 2 90 DEFINE DPM HEAT MASS u gt kps 2 lei elE sas 2 155 2 5 6 DEFINE DPM INJECTION INIT 2 158 20 DEFINE DPM LAW RS En dise hr Me RE ia 2 162 20 0 DEFINE DPMIOUTPUT 404 oy doch oe VY ae G OY oe Bac ee eS 2 164 2 0 9 DEFINE DPM PROPERTY eos 4 4 64 4 web kame eee Oe be 2 168 2 5 10 DEFINE DPM SCALAR UPDATE 2 172 2 5 11 DEFINE DPM SOURCE 44 ui era eae LU Babe Sue 2 176 2 5 12 DEFINE DPM SPRAY COLLIDE 4 4 4 4 66 6 Ga deu aa va 2 178 2 9 13 DEFINE_DPM SWITCH 4 4 4 4 60484 62H ee but a 2 181 25 14 DEPINE DPM TIMESTEP EE a at Wn Ati sa dei 2 186 2 0 10 DEFINE DPM VP EQUILIB o 4 6 4408 6 oe de e e pen dou docs 2 189 2 6 Dynamic Mesh DEFINE Macros ce scoct etardi kacs siatt 2 192 2 6 1 DEFINE CG MOTION lt s iis mias m Europ me a he we me he we ee Es 2 193 202 DEPINE GEOM 4 aon s ioietan e bed des Redes we aa uU os 2 196 209 DEFINE GRID MOTION s b a4 ma e ia Peo E EN Ee Ea 2 198 204 DEFINE SDOF PROPERTIES i eoad 44442 amp e a a 2 201 Fluent Inc September 11 2006 CONTENTS 2 7 User Defined Scalar UDS Transport Equation DEFINE Macros 2 205 jel Totroduction cse Goce 4 KGS k Oe Pewee Ra OSG 2 205 2
146. 4 e Section A 14 e Section A 15 Introduction Introduction Commenting Your C Code C Data Types in FLUENT Constants Variables User Defined Data Types Casting Functions Arrays Pointers Control Statements Common C Operators C Library Functions Macro Substitution Directive Using define File Inclusion Directive Using include Comparison with FORTRAN This chapter contains some basic information about the C programming language that may be helpful when writing UDFs in FLUENT It is not intended to be used as a primer on C and assumes that you are an experienced programmer in C There are many topics and details that are not covered in this chapter including for example while and do while control statements unions recursion structures and reading and writing files If you are unfamiliar with C please consult a C language reference guide e g 2 3 before you begin the process of writing UDFs for your FLUENT model Fluent Inc September 11 2006 A 1 C Programming Basics A 2 Commenting Your C Code It is good programming practice to document your C code with comments that are useful for explaining the purpose of the function In a single line of code your comments must begin with the identifier followed by text and end with the identifier as shown by the following This is how I put a comment in my C program Comments that span multiple lines are bracketed by the same identifi
147. 4 at the wall real si2h6 yil1 real sih2 yi 2 real h2 yi 3 real ar yi 4 mass fraction of ar at the wall real rho_w 1 0 site_rho 1 0e 6 T_w 300 0 real si_s yil6 site fraction of si_s real sih_s yil7 site fraction of sih_s T_w F_T f t rho_w C_R c0 t0 C_T c0 t0 T_w sih4 rho_w mw 0 converting of mass fractions to molar concentrations si2h6 rho_w mw 1 sih2 rho_w mw 2 h2 x rho_w mw 3 ar x rho_w mw 4 sis site_rho converting of site fractions to site concentrations sih_s site_rho Fluent Inc September 11 2006 2 1 03 DEFINE Macros if STREQ r gt name reaction 1 rr 100 0 sih4 else if STREQ r gt name reaction 2 rr 0 1 sih_s else if STREQ r gt name reaction 3 rr 100 si2h6 si_s else if STREQ r gt name reaction 4 rr 1 0e10 sih2 Hooking a Surface Reaction Rate UDF to FLUENT After the UDF that you have defined using DEFINE_SR_RATE is interpreted Chapter 4 In terpreting UDFs or compiled Chapter 5 Compiling UDFSs the name of the argu ment that you supplied as the first DEFINE macro argument e g my_rate will become visible and selectable in the User Defined Function Hooks panel in FLUENT See Sec tion 6 2 19 Hooking DEFINE_SR_RATE UDFs for details 2 1 04 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros 2 3 20 DEFINE_TURB_PREMIX_
148. 46 Fluent Inc September 11 2006 6 3 Hooking Multiphase UDFs choose the function name e g user_cav_rate in the Cavitation Mass Rate Function drop down list Figure 6 3 2 and click OK User Defined Function Hooks Initialization none Edit Adjust none Edit Execute at End none Edit Read Case none Edit Write Case none Edit Read Data one Edit Write Data fone Edit Execute at Exit none Edit Wall Heat Flux none Cavitation Mass Rate user cav rate Figure 6 3 2 The User Defined Function Hooks Panel See Section 2 4 1 DEFINE_CAVITATION_RATE for details about DEFINE_CAVITATION_RATE functions Fluent Inc September 11 2006 6 47 Hooking UDFs to FLUENT 6 3 2 Hooking DEFINE EXCHANGE PROPERTY UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_EXCHANGE_RATE UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Func tions panel see below in FLUENT Customized mass transfer UDFs can be applied to VOF Mixture and Eulerian multi phase models Drag coefficient UDF s can be applied to Mixture and Eulerian models while heat transfer and lift coefficient UDFs can be applied only to the Eulerian model You will need to have the multiphase model enabled before you can hook your function To hook an exchange property UDF to FLUENT
149. 5 face threads in domain 3 50 faces in thread 3 51 Fluent Inc September 11 2006 faces of cell 3 52 interior cells parallel 7 24 nodes of cell 3 53 nodes of face 3 53 M PI 2 53 2 55 2 144 2 185 3 76 macro substitution A 18 macros 1 4 adjacent cell index 3 22 adjacent cell thread 3 23 area normal vector 3 23 axisymmetric considerations 3 5 cell diffusion coefficients 3 15 cell face 3 8 cell face index 3 8 cell face thread 3 8 cell thermodynamic properties 3 15 cell variable 3 7 cell volume 3 7 centroid variables 3 7 3 18 data access 3 1 derivative variable 3 13 DPM variable 3 31 dynamic mesh 3 37 error 3 73 face area vector 3 19 face variable 3 6 3 8 3 18 flow variable 3 9 3 20 FLUENT variables accessing 3 1 gradient vector 3 9 input output 3 1 looping 3 1 general purpose 3 50 multiphase specific 3 54 material property 3 15 message 3 73 miscellaneous 3 1 multiphase variables 3 18 node coordinates 3 6 node variable 3 6 3 8 NOx 3 35 particle variable 3 31 previous time step 3 12 reconstruction gradient vector 3 9 Index 9 Index Reynolds Stress Model 3 16 scheme 3 1 SOx 3 36 time dependent 3 1 user defined memory 3 42 3 43 user defined scalars 3 39 vector and dimension 3 1 Makefile 1 6 5 2 makefile udf 5 11 makefile udf2 5 11 makefile_nt udf 5 10 mass transfer coefficient UDFs multiphase 2 133 mass transfer UDFs 2 133 material
150. 6 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros The variables cxboolean buser and char cuser can be used to control the flow of the program in cases of complicated rate definitions ratemin and ratemax hold the minimum and maximum possible values of the variable rate respectively They define the search interval where the numerical algorithm will search for the root of the equation as defined in the function reaction_rate The value of reaction rate rr will be refined until an accuracy specified by the value of tolerance tol is reached The variable ifail will take the value TRUE if the root of the function has not been found Hooking a Particle Reaction Rate UDF to FLUENT After the UDF that you have defined using DEFINE PR RATE is interpreted Chapter 4 In terpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user_pr_rate will become visible and selectable in the User Defined Function Hooks panel in FLUENT See Sec tion 6 2 11 Hooking DEFINE PR RATE UDFs for details Fluent Inc September 11 2006 2 57 DEFINE Macros 2 3 12 DEFINE PRANDTL UDFs The following DEFINE macros can be used to specify Prandtl numbers in FLUENT for single phase flows DEF INE_PRANDTL_D Description You can use DEFINE PRANDTL D to specify Prandtl numbers for turbulent dissipation Usage DEFINE_PRANDTL_D name c t
151. 6 4 7 Interpreting UDFs Fluent Inc September 11 2006 Chapter 5 Compiling UDFs Once you have written your UDF s using any text editor and have saved the source file with a c extension in your working directory you are ready to compile the UDF source file build a shared library from the resulting objects and load the library into FLUENT Once loaded the function s contained in the library will appear in drop down lists in graphical interface panels ready for you to hook to your CFD model Follow the instructions in Section 5 2 Compile a UDF Using the GUI to compile UDF source files using the graphical user interface GUI Section 5 3 Compile a UDF Using the TUI explains how you can use the text user interface TUI to do the same The text interface option provides the added capability of allowing you to link precompiled object files derived from non FLUENT sources e g Fortran sources to your UDF Section 5 4 Link Precompiled Object Files From Non FLUENT Sources This feature is not available in the GUI Section 5 5 Load and Unload Libraries Using the UDF Library Manager Panel describes how you can load and unload multiple UDF libraries using the Library Manager panel The capability of loading more than one UDF library into FLUENT raises the possibility of data contention if multiple libraries use the same user defined scalar UDS and user defined memory UDM locations These clashes can be avoided if libraries reserve
152. 62 THREAD T0 2 101 2 103 2 203 2 217 3 23 THREAD_T1 2 217 3 23 THREAD_TYPE 2 142 term Fluent Inc September 11 2006 Index threads 1 9 cell 1 10 face 1 10 fluid checking 3 75 node 1 10 phase level 1 17 3 60 pointers 3 25 3 60 referencing 1 17 subthreads 1 17 superthreads 1 17 variables and neighboring cell variables 1 8 Time Step Size 8 23 time stepping control for DPM 2 190 time dependent variables 3 68 time stepping control UDFs 2 7 Tracked_Particle 2 172 3 31 transient velocity UDF example 8 21 transport equations custom source for 2 93 trigonometric functions A 14 tube flow 8 21 turbine vane 8 16 turbulence kinetic energy Prandtl num ber UDFs 2 59 turbulent dissipation Prandtl number UDFs 2 58 turbulent viscosity UDFs 2 107 udf h file 1 5 4 2 5 3 location of 4 2 5 3 udf h header file including 1 5 UDFs about 1 1 arguments 1 11 arguments not passed 1 11 calling sequence of 1 12 compiled 1 6 5 4 data structures 1 10 1 17 data types 1 10 defining using DEFINE macros 1 4 2 1 Fluent Inc September 11 2006 definition of 1 1 examples 8 1 boundary condition 8 15 detailed 8 15 property 8 32 reaction rate 8 37 source terms 8 26 step by step 8 1 file inclusion directive 1 1 for multiphase applications 1 17 for UDS transport equations 2 209 header file 1 5 include statement 1 5 interpreted 1 6 interpreted v
153. 7 NO Macros for details about NO macros e g POLLUT_EQN MOLECON ARRH that are used in pollutant rate calculations in this UDF peaa o oo o kkk k kkk kk kkk k kkk UDF example of User Defined NOx Rate For FLUENT Versions 6 3 or above If used with the Replace with UDF radio buttons activated this UDF will exactly reproduce the default fluent NOx rates for prompt NO pathway The flag Pollut_Par gt pollut_io_pdf IN_PDF should always be used for rates other than that from char N so that if requested the contributions will be pdf integrated Any contribution from char must be included within a switch statement of the form Pollut_Par gt pollut_io_pdf OUT_PDF Arguments Fluent Inc September 11 2006 2 49 DEFINE Macros char nox_func_name UDF name cell_t c Cell index Thread t Pointer to cell thread on which the NOx rate is to be applied Pollut_Cell Pollut Pointer to the data structure that contains common data at each cell structure Pollut_Parameter Pollut_Par Pointer to the data structure that contains auxillary data NOx_Parameter NOx Pointer to the data structure that contains data specific to the NOx model KO OX KO X OX X X X E X KF KF KF FOO kkk k kkk k kk k kk k kkk k kkk k kkk k kk RO K k kkk a k 2k 2 2k 21 2k k 2k 2k 2 K KKK 2k ak include udf h DEFINE_NOX_RATE user_nox c t Pollut Pollut_Par NOx Pollut gt fluct fwdrate Pollut gt fluct revrate
154. 9 and the solution re run aak kk CR kk k k k k kkk k kk k k k AK k k A kk k Kk k k k K a a Kk Kk LLC k K k k k 2k 2k LE Implementation of the P1 model using user defined scalars peaa ooo oo kk kkk kkk kk kkk kkk include udf h include sg h Define which user defined scalars to use enum P1 N_REQUIRED_UDS static real abs_coeff 0 2 absorption coefficient static real scat_coeff 0 0 scattering coefficient static real las_coeff 0 0 linear anisotropic scattering coefficient static real epsilon_w 1 0 wall emissivity 8 48 Fluent Inc September 11 2006 8 2 Detailed UDF Examples DEFINE_ADJUST pi_adjust domain Make sure there are enough user defined scalars if n_uds lt N_REQUIRED_UDS Internal_Error not enough user defined scalars allocated DEFINE_SOURCE energy_source c t dS eqn dS eqn 16 abs_coeff SIGMA_SBC pow C_T c t 3 return abs_coeff 4 SIGMA_SBC pow C_T c t 4 C_UDSI c t P1 DEFINE_SOURCE pi_source c t dS eqn dS eqn 16 abs_coeff SIGMA_SBC pow C_T c t 3 return abs_coeff 4 SIGMA_SBC pow C_T c t 4 C_UDSI c t P1 ig DEFINE_DIFFUSIVITY pi_diffusivity c t i return 1 3 abs_coeff 3 las_coeff scat_coeff DEFINE_PROFILE p1_bc thread position face_t f real A ND_ND At real dG ND_ND drO ND_ND es ND_ND ds A_by_es real aterm alpha0O b
155. AK KK KK kk Multiple reaction UDF that specifies different reaction rates for different volumetric chemical reactions FR A HRK DK HER 2k 2 2 2k 2k 2 3k 2k KE KE 2k 2 ok 2k 2k 2 ak 2k 2k ok include udf h DEFINE_VR_RATE myrate c t r mw yi rr rr_t If more than one reaction is defined it is necessary to distinguish between these using the names of the reactions if strcemp r gt name reaction 1 Reaction 1 else if strcmp r gt name reaction 2 Reaction 2 else Message Unknown Reaction n Message Actual Reaction s n r gt name Hooking a Volumetric Reaction Rate UDF to FLUENT After the UDF that you have defined using DEFINE_VR_RATE is interpreted Chapter 4 In terpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argu ment that you supplied as the first DEFINE macro argument e g myrate will become visible and selectable in the User Defined Function Hooks panel in FLUENT See Sec tion 6 2 22 Hooking DEFINE_VR_RATE UDFs for details 2 1 14 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros 2 3 23 DEFINE WALL_FUNCTIONS Description You can use DEFINE_WALL_FUNCTIONS to provide custom wall functions for applications when you want to replace the standard wall functions in FLUENT Note that this is available only for use with the k e turbulence models Usage DEFINE WALL _FUNCTIONS name f t c0 t0 wf_ret yPlus E
156. APPA yPlus yPlus break default printf Wall function return value unavailable n return wf_value Hooking a Wall Function UDF to FLUENT After the UDF that you have defined using DEFINE WALL FUNCTIONS is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user_log_law will become visible and selectable in the Viscous Model panel in FLUENT See Sec tion 6 2 23 Hooking DEFINE WALL FUNCTIONS UDFs for details 2 1 16 Fluent Inc September 11 2006 2 4 Multiphase DEF INE Macros 2 4 Multiphase DEFINE Macros The DEFINE macros presented in this section are used for multiphase applications only Table 2 4 1 provides a quick reference guide to the multiphase specific DEFINE macros the functions they are used to define and the panels where they are activated in FLUENT Definitions of each DEFINE macro are listed in the udf h header file see Appendix C Appendix B contains a list of general purpose DEFINE macros that can also be used to define UDFs for multiphase cases For example the general purpose DEFINE PROPERTY macro is used to define a surface tension coefficient UDF for the multiphase VOF model See Section 2 3 14 DEFINE PROPERTY UDFs for details e Section 2 4 1 DEFINE_CAVITATION_RATE Section 2 4 2 DEFINE EXCHANGE PROPERTY Section 2 4 3 DEFINE_HET_RXN_RATE Section 2 4 4 DEFIN
157. ATE UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_HET_RXN_RATE UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable under Reaction Rate Function in the Reactions tab of the Phase Interaction panel Note that the Reactions tab is enabled only when species transport is enabled and the Reaction Rate Function is accessible when the Total Number of Reactions is greater than 0 Figure 6 3 4 Define Phases Interaction Phase Interaction Drag Lift Collisions Slip Heat Mass Reactions Surface Tension Total Number of Heterogeneous Reactions 2 L Reaction Name net reaction 1 ID fi Number of Reactants fi 4 Number of Products f 4 Phase Species Stoich E Phase Species Stoich Coefficient Coefficient z l Reaction Rate Function user evap_con OK Cancel Help Figure 6 3 4 The Phase Interaction Panel To hook the UDF to FLUENT choose the function name e g user evap con in the Reaction Rate Function drop down list under the Reaction tab Figure 6 3 4 and click OK See Section 2 4 3 DEFINE_ HET _RXN_RATE for details about writing DEFINE HET RXN RATE functions 6 50 Fluent Inc September 11 2006 6 3 Hooking Multiphase UDFs 6 3 4 Hooking DEFINE_MASS_TRANSFER UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com
158. Adjacent Cell Thread Macros Defined in mem h Macro Argument Types Returns THREAD_TO t Thread t cell thread pointer for cell c0 THREAD_T1 t Thread t cell thread pointer for cell c1 Interior Face Geometry INTERIOR FACE GEOMETRY INTERIOR FACE GEOMETRY f t A ds es A by es dr0 dri expands to a function that outputs the following variables to the solver for a given face f on face thread t The macro is defined in the sg h header file which is not included in udf h You will need to include this file in your UDF using the include directive real A ND_ND the area normal vector real ds distance between the cell centroids real es ND_ND the unit normal vector in the direction from cell c0 to cl real by es the value a real drO ND_ND vector that connects the centroid of cell cO to the face centroid real dri ND ND the vector that connects the centroid of cell c1 to the face centroid Note that INTERIOR_FACE_GEOMETRTY can be called to retrieve some of the terms needed to evaluate Equations 3 2 1 and 3 2 3 Boundary Face Geometry BOUNDARY FACE GEOMETRY BOUNDARY FACE GEOMETRY f t A ds es A by es dr0 expands to a function that out puts the following variables to the solver for a given face f on face thread t It is defined in the sg h header file which is not included in udf h You will need to include this file in your UDF using the include directive Fluent Inc September 11 2006 3 23 Addi
159. After you have set up the directory structure and put the files in the proper places you can compile and build the shared library using the TUI Windows Systems 1 Using a text editor edit every user_nt udf file in each version directory to set the following parameters SOURCES VERSION and PARALLEL_NODE SOURCES VERSION PARALLEL_NODE the user defined source file s to be compiled Use the prefix SRC before each filename For example SRC udfexample c for one file and SRC udfexamplel c SRC udfexample2 c for two files the version of the solver you are running which will be the name of the build directory where user_nt udf is located 2d 3d 2ddp 3ddp 2d_host 2d node 3d host 3d_node 2ddp_host 2ddp node 3ddp host or 3ddp node the parallel communications library Specify none for a serial version of the solver or one of the following smpi parallel using shared memory for multiprocessor machines vmpi parallel using shared memory or network with vendor MPI software net parallel using network communicator with RSHD software i If you are using a parallel version of the solver be sure to edit both copies of user_nt udf the one in the host directory and the one in the node direc tory and specify the appropriate SOURCE VERSION and PARALLEL_NODE in each file Set PARALLEL NODE none for the host version and one of the other options smpi vmpi net nmpi for the node version depending on whic
160. BMODULUS sqrt BMODULUS rho_ref 2 86 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros return a Hooking a Property UDF to FLUENT After the UDF that you have defined using DEFINE_PROPERTY is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g sound_speed will become visible and selectable in graphics panels in FLUENT See Section 6 2 14 Hooking DEFINE_PROPERTY UDFs for details Fluent Inc September 11 2006 2 87 DEFINE Macros 2 3 15 DEFINE_SCAT_PHASE_FUNC Description You can use DEFINE SCAT PHASE FUNC to specify the radiation scattering phase function for the Discrete Ordinates DO model The function computes two values the fraction of radiation energy scattered from direction 7 to direction j and the forward scattering factor Usage DEF INE_SCAT_PHASE_FUNC name cosine f Argument Type Description symbol name UDF name real cosine Cosine of the angle between directions and j real f Pointer to the location in memory where the real forward scattering factor is stored Function returns real There are three arguments to DEFINE_SCAT_PHASE_FUNC name cosine and f You supply name the name of the UDF cosine and f are variables that are passed by the FLUENT solver to your UDF Your UDF will need to compute the real fraction of radiation energy scattered fro
161. CRECV_REAL i x_array 0 ND_ND n_faces i for j 0 j lt n_faces j if RP_3D Message0 12 4e 12 4e 12 4e 12 4e n x_array j 0 x_array j 1 x_array j 2 p_arraylj l else 2D Message0 12 4e 12 4e 12 4e n x_array j 0 x_array j 1 p_arraylj l endif endif RP_NODE free p_array Each array has to be freed before function exit free x_array endif RP_HOST Fluent Inc September 11 2006 7 35 Parallel Considerations 7 5 9 Macros for Exchanging Data Between Compute Nodes EXCHANGE_SVAR_MESSAGE and EXCHANGE_SVAR_FACE_MESSAGE can be used to exchange storage variables SV_ between compute nodes EXCHANGE_SVAR_MESSAGE exchanges cell data between compute nodes while EXCHANGE_SVAR_FACE_MESSAGE exchanges face data Note that compute nodes are virtually synchronized when an EXCHANGE macro is used receiving compute nodes wait for data to be sent before continuing Compute Node Exchange Macros EXCHANGE_SVAR_FACE_MESSAGE domain SV_P SV_NULL EXCHANGE_SVAR_MESSAGE domain SV_P SV_NULL EXCHANGE_SVAR_FACE_MESSAGE is rarely needed in UDFs You can exchange multiple storage variables between compute nodes Storage variable names are separated by com mas in the argument list and the list is ended by SV_NULL For example EXCHANGE_SVAR_MESSAGE domain SV_P SV_T SV_NULL is used to exchange cell pres sure and temperature variables You ca
162. DEFINE_DPM_OUTPUT Note that if you need to access other data such as cell values then for the parallel options except Shared Memory you will have access to all fluid and solver variables When you choose the Shared Memory option however you will have access only to the variables defined in the macros SV_DPM_LIST and SV_DPMS_LIST These macro definitions can be found in dpm h 7 12 Fluent Inc September 11 2006 7 5 Macros for Parallel UDFs 7 5 Macros for Parallel UDFs This section contains macros that you can use to parallelize your serial UDF Where applicable definitions for these macros can be found in the referenced header file e g para h 7 5 1 Compiler Directives When converting a UDF to run in parallel some parts of the function may need to be done by the host and some by the compute nodes This distinction is made when the UDF is compiled By using Fluent provided compiler directives you can specify portions of your function to be assigned to the serial process the host or to the compute nodes The UDF that you write will be written as a single file for the serial parallel host and parallel node versions but different parts of the function will be compiled to generate different versions of the dynamically linked shared object file Libudf so 1ibudf d11 on NT Windows Print tasks for example may be assigned exclusively to the host while a task such as computing the total volume of a complete mesh will be ass
163. DFs Defined in sg_nox h Macro Returns POLLUT_EQN Pollut Par MOLECON Pollut SPE NULLIDX Pollut_Par SPE ARRH Pollut K POLLUT_FRATE Pollut POLLUT_RRATE Pollut index of pollutant equation being solved see below molar concentration of species specified by SPE see below TRUE if the species specified by SPE doesn t exist in FLUENT case i e in the Species panel Arrhenius rate calculated from the constants specified by K see below production rate of the pollutant species being solved reduction rate of the pollutant species being solved Fal Pollut Par is a pointer to the Pollut Parameter data structure that con tains auxillary data common to all pollutant species and SOx is a pointer to the SOx_Parameter data structure that contains data specific to the SO model e POLLUT_EQN Pollut_Par returns the index of the pollutant equation currently being solved The indices are EQ_S02 for SO2 and EQ_S03 for SO3 etc 3 36 Fluent Inc September 11 2006 3 2 Data Access Macros e MOLECON Pollut SPE returns the molar concentration of a species specified by SPE SPE is either the name of species or IDX i when the species is a pollutant like SO2 For example for O2 molar concentration you can call MOLECON Pollut 02 whereas for SO2 molar concentration the call should be MOLECON Pollut IDX SO2 e ARRH Pollut K returns the Arrhenius rate calculated from the con
164. DM libname else Message d UDMs have been reserved by the current library s n NUM_UDM libname Set_User_Memory_Name udm_offset lib2 UDM 0 Set_User_Memory_Name udm_offset 1 lib2 UDM 1 Message nUDM Offset for Current Loaded Library 4d udm_offset DEF INE_ON_DEMAND set_udms Domain d Thread x ct cell_t c int i d Get_Domain 1 if udm_offset UDM_UNRESERVED Message Setting UDMs n for i 0 i lt NUM_UDM i 3 48 Fluent Inc September 11 2006 3 2 Data Access Macros thread_loop_c ct d begin_c_loop c ct C_UDMI c ct udm_offset i 2 0 i 10 0 end_c_loop c ct else Message UDMs have not yet been reserved for library 1 n If your model uses a number of UDMs it may be useful to define your variables in an easy to read format either at the top of the source file or in a separate header file using the preprocessor define directive define C_MAG_X c t C_UDMI c t udm_offset define C_MAG_Y c t C_UDMI c t udm_offset 1 Following this definition in the remainder of your UDF you can simply use C MAG _X c t and C_MAG_Y c t to specify the fixed magnetic field components Unreserving UDM variables FLUENT does not currently provide the capability to unreserve UDM variables using a macro Unreserve macros will be available in future versions of FLUENT You will need to exit FLUENT to ensure that all UDM variables are reset Fluent Inc Se
165. DMI c t offset up to C_UDMI c t offset num 1 to store values in user scalars without interference Unreserving UDS Variables FLUENT does not currently provide the capability to unreserve UDS variables using a macro Unreserve macros will be available in future versions of FLUENT N_UDS You can use N_UDS to access the number of user defined scalar UDS transport equations that have been specified in FLUENT The macro takes no arguments and returns the integer number of equations It is defined in models h 3 40 Fluent Inc September 11 2006 3 2 Data Access Macros 3 2 9 User Defined Memory UDM Macros This section contains macros that access user defined memory UDM variables in FLU ENT Before you can store variables in memory using the macros provided below you will first need to allocate the appropriate number of memory location s in the User Defined Memory panel in FLUENT See Section 6 1 8 User Defined Memory Storage for more details Define gt User Defined Memory Note that if you try to use F_UDMI or C_UDMI before you have allocated memory then an error will result A variable will be created for every user defined memory location that you allocate in the graphical user interface For example if you specify 2 as the Number of User Defined Memory then two variables with default names User Memory 0 and User Memory 1 will be defined for your model and the default variable na
166. E PROFILE secondary phase s phase dependent primary and secondary phases primary and secondary phases s primary and secondary phases s mixture mixture mixture Fluid mass source momentum source energy source turbulence dissipation rate source turbulence kinetic energy source species source user defined scalar source turbulence dissipation rate turbulence kinetic energy DEFINE_ SOURCE DEFINE_SOURCE DEFINE_ SOURCE DEFINE_ SOURCE DEFINE SOURCE DEFINE_ SOURCE DEFINE_ SOURCE DEFINE PROFILE DEFINE PROFILE primary and secondary phase s primary and secondary phase s primary and secondary phase s primary and secondary phase s primary and secondary phase s phase dependent mixture primary and secondary phase s primary and secondary phase s Fluent Inc September 11 2006 C 15 Quick Reference Guide for Multiphase DEFINE Macros Table C 5 2 DEFINE Macro Usage for the Eulerian Model Dispersed Tur bulence Flow Variable Macro Phase Specified On Fluid velocity DEFINE_PROFILE primary and secondary phase s temperature DEFINE PROFILE primary and species mass fraction porosity viscous resistance inertial resistance user defined scalar DEFINE_PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE secondary phase s primary and secondary phase s mixture primary and secondary phase s primary and second
167. E UDFs for details Fluent Inc September 11 2006 2 95 DEFINE Macros 2 3 18 DEFINE_SOX_RATE Description You can use DEFINE_SOX_RATE to specify a custom SO rate that can either replace the internally calculated SOx rate in the source term equation or be added to the FLUENT rate The default functionality is to add user defined rates to the FLUENT calculated rates If the Replace with UDF Rate checkbox is checked in the SOx Model panel then the FLUENT calculated rate will not be used and it will instead be replaced by the SO rate you have defined in your UDF When you hook a SO rate UDF to the graphical interface without checking the Replace with UDF Rate box then the user SO rate will be added to the internally calculated rate for the source term calculation Usage DEFINE SOX RATE name c t Pollut Pollut Par SOx Argument Type Description symbol name UDF name cell tc Cell index Thread t Pointer to cell thread on which the SO rate is to be applied Pollut Cell Pollut Pointer to the data structure that contains the common data at each cell Pollut Parameter Pollut Par Pointer to the data structure that contains auxilliary data SOx_Parameter SOx Pointer to the data structure that contains data specific to the SOx model Function returns void There are six arguments to DEFINE_SOX_RATE name c t Pollut Pollut Par and SOx You will supply name the name of the UDF c t Pollut Pollut_Par and SOx are v
168. EFINE Macros Example The following UDF named discrete_phase_sampler samples the size and velocity of discrete phase particles at selected planes downstream of an injection For 2d axisym metric simulations it is assumed that droplets particles are being sampled at planes lines corresponding to constant x For 3d simulations the sampling planes correspond to constant z To remove particles from the domain after they have been sampled change the value of REMOVE_PARCELS to TRUE In this case particles will be deleted following the time step in which they cross the plane This is useful when you want to sample a spray immediately in front of an injector and you don t wish to track the particles further downstream This UDF works with unsteady and steady simulations that include droplet break up or collisions Note that the discrete phase must be traced in an unsteady manner include udf h POR ARIA RI I I AKI AK IK aR I A 42k 4 24 2k kk UDF that samples discrete phase size and velocity distributions within the domain DOO OOO OI LL I CA I kk 3k 3k 3k define REMOVE_PARTICLES FALSE DEF INE_DPM_OUTPUT discrete_phase_sample header fp p t plane if RP_2D real flow_time solver_par flow_time real y if header par_fprintf_head fp Time s R m X velocity m s W velocity m s R velocity m s Drop Diameter m Number of Drops Temperature K Initial Diam m Injection Time s n if NULLP
169. EFINE_PROFILE pressure_profile t i real x ND_ND this will hold the position vector real y face_t f begin_f_loop f t F_CENTROID x f t y x 1 F_PROFILE f t i 1 1e5 y y 0745 0745 0 1e5 end_f_loop f t The function named pressure profile has two arguments t and i t is a pointer to the face s thread and i is an integer that is a numerical label for the variable being set within each loop 2 68 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros Within the function body variable f is declared as a face A one dimensional array x and variable y are declared as real data types Following the variable declarations a looping macro is used to loop over each face in the zone to create a profile or an array of data Within each loop F_CENTROID returns the value of the face centroid array x for the face with index f that is on the thread pointed to by t The y coordinate stored in x 1 is assigned to variable y and is then used to calculate the pressure This value is then assigned to F_PROFILE which uses the integer i passed to it by the solver based on your selection of the UDF as the boundary condition for pressure in the Pressure Inlet panel to set the pressure face value in memory Example 2 Velocity Turbulent Kinetic Energy and Turbulent Dissipation Rate Profiles In the following example DEFINE_PROFILE is used to generate profiles for the x velocity turbulent kin
170. ENT See Section 9 3 User Defined Scalar UDS Transport Equations in the User s Guide for UDS equation theory and details on how to setup scalar equations Descriptions of DEFINE macros for UDS applications are provided below Definitions of DEFINE macros are contained in the udf h header file For your convenience they are also listed in Appendix B Detailed examples of user defined scalar transport UDFs can be found in Section 8 2 5 User Defined Scalars e Section 2 7 1 Introduction e Section 2 7 2 DEFINE_ANISOTROPIC_DIFFUSIVITY e Section 2 7 3 DEFINE_UDS_FLUX e Section 2 7 4 DEFINE UDS UNSTEADY 2 7 1 Introduction For each of the N scalar equations you specified in your FLUENT model you can supply a unique UDF for the diffusion coefficients flux and unsteady terms in the scalar transport equation For multiphase you have the added benefit of specifying UDFs on a per phase basis in both fluid and solid zones Additionally you can specify a UDF for each source term you define for a given scalar equation as well as boundary conditions on wall inflow and outflow boundaries Diffusion Coefficient UDFs For each of the N scalar equations you have specified in your FLUENT model using the User Defined Scalars panel you can supply a unique user defined function UDF for isotropic and anisotropic diffusivity for both fluid and solid materials Recall that FLUENT computes the diffusion coefficient in the UDS equation Isotropic diffus
171. E_MASS_TRANSFER Section 2 4 5 DEFINE VECTOR EXCHANGE PROPERTY Fluent Inc September 11 2006 2 1 17 DEFINE Macros Table 2 4 1 Quick Reference Guide for Multiphase DEFINE Macros Model Function DEFINE Macro Panel Activated VOF mass transfer DEFINE_MASS_TRANSFER Phase Interaction heterogeneous DEFINE_HET_RXN_RATE Phase Interaction reaction rate Mixture mass transfer DEFINE_MASS_TRANSFER Phase Interaction drag coefficient DEFINE EXCHANGE PROPERTY Phase Interaction slip velocity DEFINE VECTOR EXCHANGE Phase Interaction _PROPERTY cavitation rate DEFINE CAVITATION RATE User Defined Function Hooks heterogeneous DEFINE HET RXN RATE Phase Interaction reaction rate Eulerian mass transfer DEFINE_MASS_TRANSFER Phase Interaction heat transfer DEFINE_EXCHANGE_PROPERTY Phase Interaction drag coefficient DEFINE EXCHANGE PROPERTY Phase Interaction lift coefficient DEFINE_EXCHANGE PROPERTY Phase Interaction heterogeneous DEFINE HET _RXN_RATE Phase Interaction reaction rate 2 118 Fluent Inc September 11 2006 2 4 Multiphase DEF INE Macros 2 4 1 DEFINE CAVITATION RATE Description You can use DEFINE CAVITATION RATE to model the cavitation source terms Re and Re in the vapor mass fraction transport equation Equation 23 7 12 in the User s Guide Assuming Maot denotes the mass transfer rate between liquid and vapor phases we have Re MAX Mao 0 fa Re MAX Mqot Olfa where
172. Edit button next to the X Momentum source term This will open the Mass Sources panel where you will select the number of terms you wish to model Figure 6 2 23 Fluent Inc September 11 2006 6 37 Hooking UDFs to FLUENT Zone Name fia Material Name air Edit l Porous Zone M Source Terms Fixed Values Motion Porous Zone Reaction Source Terms Fixed Values Mass kgim3 s 2 sources Edit X Momentum n m3 9 sources Edit Y Momentum n m3 a sources Edit Z Momentum n m3 9 sources Edit Figure 6 2 22 The Fluid Panel 6 38 Fluent Inc September 11 2006 6 2 Hooking Model Specific UDFs Mass Kg m3 s sources Number of Mass kg m3 s sources 2 m 1 udf usr_mass_src1 A 2 judf usr_mass_sre2 Figure 6 2 23 The Fluid Panel Increment the Number of Mass Sources counter e g 2 and then choose the function name e g udf usr mass srcl and udf usr mass src2 from the appropriate drop down list Note that the UDF name that is displayed in the drop down lists is preceeded by the word udf Click OK in the Mass Sources panel to accept the new boundary condition and close the panel The Mass source term in the Fluid panel will now display 2 sources Click OK to close the Fluid panel and fix the new mass source terms for the solution calculation Repeat this step for all of the source terms you wish to customize using a UDF See Section 2 3 17 DEFINE_SOURCE for
173. F 2 172 vaporization temperature UDF 2 172 variables dynamic mesh 3 37 vector cross products 3 67 vector dot products 3 67 vector exchange property UDFs 2 136 vector utilities 3 63 velocity inlet parabolic profile UDF 8 16 transient profile UDF 8 21 Index 16 Velocity Inlet panel 6 29 8 13 8 19 8 22 viscosity property UDF 8 32 Viscous Model panel 6 28 6 43 VOF model DEFINE macro usage C 1 volume reaction rate 1 3 volume reaction rate UDFs 2 111 wall function UDFs 2 115 wall heat flux UDFs 2 44 wall impacts 2 153 wall inflow and outflow boundary condi tion UDFs 2 211 Wall panel 6 53 Windows NT systems 4 5 8 8 Microsoft compiler 4 5 8 8 Windows systems 2 24 directory structure 5 10 working directory 4 2 5 3 writer 2 24 writing files parallel 7 44 writing UDFs for multiphase models 3 58 grid definitions 1 8 ZERO _COMPUTE NODE P 7 18 zone ID 1 9 3 25 3 27 3 71 zones definition of 1 9 ID 3 25 Fluent Inc September 11 2006
174. F is called refer to Figures 1 9 1 1 9 2 and 1 9 3 Usage DEFINE_INIT name d Argument Type Description symbol name UDF name Domain d Pointer to the domain over which the initialization function is to be applied The domain argument provides access to all cell and face threads in the mesh For multiphase flows the pointer that is passed to the function by the solver is the mixture level domain Function returns void There are two arguments to DEFINE_INIT name and d You supply name the name of the UDF d is passed from the FLUENT solver to your UDF Example The following UDF named my_init_func initializes flow field variables in a solution It is executed once at the beginning of the solution process The function can be executed as an interpreted or compiled UDF in FLUENT paaa k kk kkk kkk kk kkk kk k kk kk kkk k kk k k k kk kk k k k k kk kk k kk kk kkk k K k UDF for initializing flow field variables EEEE ooo ooo 2 2 4 A 4 4 21 21 DD DH DH DORE include udf h DEFINE_INIT my_init_func d Fluent Inc September 11 2006 2 19 DEFINE Macros cell_t c Thread t real xc ND_ND loop over all cell threads in the domain thread_loop_c t d loop over all cells begin_c_loop_all c t C_CENTROID xc c t if sqrt ND_SUM pow xc 0 0 5 2 pow xc 1 0 5 2 pow xc 2 0 5 2 lt 0 25 C_T c t 400 else C_T c t 300 end_c_loop_all c t The macro ND SUM
175. F to FLUENT choose the function name e g dpm_ source in the Source drop down list under User Defined Functions Figure 6 4 12 and click OK See Section 2 5 11 DEFINE DPM SOURCE for details about DEFINE DPM SOURCE functions 6 66 Fluent Inc September 11 2006 6 4 Hooking Discrete Phase Model DPM UDFs 6 4 12 Hooking DEFINE_DPM_SPRAY_COLLIDE UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_SPRAY_COLLIDE UDF the name of the function you sup plied as a DEFINE macro argument will become visible and selectable in the Discrete Phase Model panel Figure 6 4 13 in FLUENT Define Models gt Discrete Phase Discrete Phase Model Interaction Particle Treatment MN Interaction with Continuous Phase NV Unsteady Particle Tracking I Update DPM Sources Every Flow Iteration M Track with Fluid Flow Time Step Number of Continuous Phase 299 4l Inject Particles at iteratl per DPM Iteration Particle Time Step on Clear Particles Tracking Physical Models UDF Numerics Parallel User Defined Functions User Variables Body Force none Number of Scalars CS Scalar Update none Source none si Spray Collide Function judf_mean_spray_colli DPM Time Step none OK Injections Cancel Help Figure 6 4 13 The Discrete Phase Model Panel You will need to enable a discrete phase model in the Discre
176. FILE is usually used to specify a profile condition on a boundary face zone it can also be used to specify or fix flow variables that are held constant during computation in a cell zone Click Section 7 27 Fixing the Values of Variables to go to the User s Guide for more information on fixing values in a cell zone boundary condition For these cases the arguments of the macro will change accordingly Note that unlike source term and property UDFs profile UDFs defined using DEFINE PROFILE are not called by FLUENT from within a loop on threads in the bound ary zone The solver passes only the pointer to the thread associated with the boundary zone to the DEFINE_PROFILE macro Your UDF will need to do the work of looping over all of the faces in the thread computing the face value for the boundary variable and then storing the value in memory Fluent has provided you with a face looping macro to loop over all faces in a thread begin_f_loop See Chapter 3 Additional Macros for Writing UDFs for details F PROFILE is typically used along with DEFINE PROFILE and is a predefined macro sup plied by Fluent F_PROFILE stores a boundary condition in memory for a given face and thread and is nested within the face loop as shown in the examples below It is important to note that the index i that is an argument to DEFINE_PROFILE is the same argument to F_PROFILE F PROFILE uses the thread pointer t face identifier f and index i to set the appro
177. FINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE DPM BC phase dependent mixture mixture mixture mixture mixture mixture mixture mixture mixture mixture mixture mixture mixture mixture mixture Other surface tension coefficient mass transfer coefficient heterogeneous reaction rate DEFINE PROPERTY DEFINE MASS TRANSFER DEFINE HET RXN RATE phase interaction phase interaction phase interaction Fluent Inc September 11 2006 Quick Reference Guide for Multiphase DEFINE Macros C 2 Mixture Model Tables C 2 1 C 2 2 list the variables that can be customized using UDFs for the Mixture multiphase model the DEFINE macros that are used to define the UDF and the phase that the UDF needs to be hooked to for the given variable C 4 Fluent Inc September 11 2006 C 2 Mixture Model Table C 2 1 DEFINE Macro Usage for the Mixture Model Variable Macro Phase Specified On Boundary Conditions Inlet Outlet volume fraction DEFINE_PROFILE secondary phase s mass flux DEFINE_PROFILE primary and velocity magnitude pressure temperature species mass fractions user defined scalar boundary value discrete phase boundary condition DEFINE PROFILE DEFINE_PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE secondary phase s primary and secondary phases s mixture mixture phase dependent mixture mixture Fluid ma
178. FLUENT 6 3 UDF Manual September 2006 Copyright 2006 by Fluent Inc All Rights Reserved No part of this document may be reproduced or otherwise used in any form without express written permission from Fluent Inc Airpak FIDAP FLUENT FLUENT for CATIA V5 FloWizard GAMBIT Icemax Icepak Icepro Icewave Icechip MixSim and POLYFLOW are registered trademarks of Fluent Inc All other products or name brands are trademarks of their respective holders CHEMKIN is a registered trademark of Reaction Design Inc Portions of this program include material copyrighted by PathScale Corporation 2003 2004 Fluent Inc Centerra Resource Park 10 Cavendish Court Lebanon NH 03766 Contents Preface i 1 Overview 1 1 1 1 What is a User Defined Function UDF 1 1 t2 Why Use UDES 222 h4 h4R4 4 446844404 44 RE 1 3 Wo Limitations BS senecaene p Ree RES RSE Cee 1 3 1 4 Defining Your UDF Using DEFINE Macros 1 3 1 4 1 Including the udf h Header File in Your Source File 1 5 1 5 Interpreting and Compiling UDFs 4 4 4 44 2 448 eee Gea bo 1 6 1 5 1 Differences Between Interpreted and Compiled UDFs 1 7 1 6 Hooking UDFs to Your FLUENT Model 4 4 4 4 4 42 1 8 La Grd Terminology e sisi dis ati edit sed dk sp 24 4648 5 1 8 1 8 ere Type in FLUENT sis ne eee be LINE SR eR ae Ra 1 10 1 9 UDF Calling Sequence in the Solution Process 1 12 1 10 Special Cons
179. Figure 6 2 26 The User Defined Function Hooks Panel You must have a premixed combustion model enabled in the Species Model panel Fluent Inc September 11 2006 6 2 Hooking Model Specific UDFs To hook the UDF to FLUENT choose the function name e g user_turb_pre_src in the Turbulent Premixed Source Function drop down list in the User Defined Function Hooks panel and click OK See Section 2 3 20 DEFINE TURB PREMIX SOURCE for details about DEF INE_TURB_PREMIX_SOURCE functions 6 2 21 Hooking DEFINE_TURBULENT_VISCOSITY UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_TURBULENT_VISCOSITY UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Viscous Model panel Figure 6 2 27 in FLUENT Define Models Viscous Viscous Model Model Model Constants C Inviscid Laminar Spalart Allmaras 1 eqn k epsilon 2 eqn k omega 2 eqn Reynolds Stress 7 eqn Detached Eddy Simulation Large Eddy Simulation LES 7 1 Spalart Allmaras Options Yorticity Based Production 3 6 StrainfVorticity Based Production User Defined Functions Turbulent Viscosity user_mu_t libudf Figure 6 2 27 The Viscous Model Panel To hook the UDF to FLUENT choose the function name e g user_mu_t in the Turbu lence Viscosity drop down list under User Defined Functions
180. Fs See Section 3 7 Message for details on the Message macro fprintf int fprintf FILE fp char format The function fprintf writes to a file that is pointed to by fp in a format that you specify The first argument is the format string It specifies how the remaining arguments are to be written to the file The format string for fprintf is the same as for printf and fscanf A 16 Fluent Inc September 11 2006 A 13 C Library Functions Example FILE fp fprintf fp 12 4e 12 4e 5d n x_array j 0 x_array j 1 noface int datal 64 25 int data2 97 33 fprintf fp 4 2d 4 2d n data1 data2 fscanf int fscanf FILE fp char format The function fscanf reads from a file that is pointed to by fp in a format that you specify The first argument is the format string It specifies how the data that is to be read is to be interpreted The replacement variables that follow the format string are used to store values that are read The replacement variables are preceded by the amp character Note that the format string for fscanf is the same as for fprintf and printf In the example below two floating point numbers are read from the file pointed to by fp and are stored in the variables f1 and f2 Example FILE fp fscanf fp 4f f amp f1 amp f2 You cannot use the scanf I O function in FLUENT You must use fscanf instead Fluent Inc September 11 2006 A 17 C Pro
181. Get_Domain which is described below DOMAIN SUB DOMAIN has two arguments mixture domain and phase domain index The function returns the phase pointer subdomain for the given phase domain_index Note that DOMAIN_SUB_DOMAIN is similar in implementation to the THREAD_SUB_THREAD macro described in Section 3 3 2 Phase Level Thread Pointer THREAD_SUB_THREAD int phase_domain_index 0 primary phase index is 0 Domain mixture_domain Domain subdomain DOMAIN_SUB_DOMAIN mixture_domain phase_domain_index mixture_domain is a pointer to the mixture level domain It is automatically passed to your UDF by the FLUENT solver when you use a DEFINE macro that contains a domain variable argument e g DEFINE ADJUST and your UDF is hooked to the mixture Oth erwise if the mixture_domain is not explicitly passed to your UDF you will need to use another utility macro to retrieve it e g Get_Domain 1 before calling sub_domain_loop phase_domain_index is an index of subdomain pointers It is an integer that starts with O for the primary phase and is incremented by one for each secondary phase phase domain index is automatically passed to your UDF by the FLUENT solver when you use a DEFINE macro that contains a phase domain index argument DEFINE EXCHANGE PROPERTY DEFINE VECTOR EXCHANGE PROPERTY and your UDF is hooked to a specific interaction phase Otherwise you will need to hard code the in teger value of phase domain index to the DOMA
182. IN SUB DOMAIN macro If your multi phase model has only two phases defined then phase domain index is 0 for the primary phase and 1 for the secondary phase However if you have more than one secondary phase defined for your multiphase model you will need to use the PHASE_DOMAIN_INDEX utility to retrieve the corresponding phase_domain_index for the given domain See Section 3 3 2 Phase Domain Index PHASE_DOMAIN_INDEX for details Fluent Inc September 11 2006 3 59 Additional Macros for Writing UDFs Phase Level Thread Pointer THREAD_SUB_THREAD The THREAD_SUB_THREAD macro can be used to retrieve the phase level thread sub thread pointer given the phase domain index THREAD_SUB_THREAD has two arguments mixture_thread and phase_domain_index The function returns the phase level thread pointer for the given phase domain index Note that THREAD SUB THREAD is similar in implementation to the DOMAIN_SUB_DOMAIN macro described in Section 3 3 2 Phase Do main Pointer DOMAIN_SUB_DOMAIN int phase_domain_index 0 primary phase index is 0 Thread mixture_thread mixture level thread pointer Thread subthread THREAD_SUB_THREAD mixture_thread phase_domain_index mixture_thread is a pointer to a mixture level thread It is automatically passed to your UDF by the FLUENT solver when you use a DEFINE macro that contains a variable thread argument e g DEFINE_PROFILE and the function is hooked to the mixture Otherwi
183. LL_GRID_V amp amp SV_ALLOCATED_P thread SV_WALL_V if RP_2D if rp_axi_swirl d real R sqrt p gt state pos 1 p gt state pos 1 p gt state pos 2 p gt state pos 2 if R gt 1 e 20 idim 3 normal 0 f_normal 0 normal 1 f_normal 1 p gt state pos 1 R normal 2 f_normal 1 p gt state pos 2 R else for i 0 i lt idim i normal i f_normal il else endif for i 0 i lt idim i normal i f_ normallil Set up velocity vectors and calculate the Weber number to determine the regime for i 0 i lt idim i if moving face_vel i WALL_F_VV f thread i WALL_F_GRID_VV f thread i else face_vel i 0 0 Fluent Inc September 11 2006 2 1 45 DEFINE Macros rel_vel i P_VEL p i face_vellil F vmag MAX NV_MAG rel_vel DPM_SMALL rel_dot_n MAX NV_DOT rel_vel normal DPM_SMALL weber_in P_RHO p DPM_SQR rel_dot_n P_DIAM p MAX DPM_SURFTEN p DPM_SMALL Regime where bouncing occurs We_in lt 80 Data from Mundo Sommerfeld and Tropea Int J of Multiphase Flow v21 2 pp151 173 1995 if weber_in lt 80 weber_out 0 6785 weber_in exp 0 04415 weber_in vnew rel_dot_n 1 0 sqrt weber_out MAX weber_in DPM_SMALL The normal component of the velocity is changed based on the experimental paper above i e the Weber number is based on the relative velo
184. MOTION Dynamic Zones grid motion DEFINE GRID MOTION Dynamic Zones geometry deformation DEF INE_GEOM Dynamic Zones properties for Six Degrees of DEFINE_SDOF_PROPERTIES Dynamic Zones Freedom SDOF Solver 2 1 96 Fluent Inc September 11 2006 2 6 Dynamic Mesh DEFINE Macros 2 6 1 DEFINE_CG_MOTION Description You can use DEFINE CG MOTION to specify the motion of a particular dynamic zone in FLUENT by providing FLUENT with the linear and angular velocities at every time step FLUENT uses these velocities to update the node positions on the dynamic zone based on solid body motion Note that UDFs that are defined using DEFINE_CG_MOTION can only be executed as compiled UDFs Usage DEFINE_CG_MOTION name dt vel omega time dtime Argument Type Description symbol name UDF name Dynamic_Thread dt Pointer to structure that stores the dynamic mesh attributes that you have specified or that are calculated by FLUENT real vel Linear velocity real omegal Angular velocity real time Current time real dtime Time step Function returns void There are six arguments to DEFINE CG MOTION name dt vel omega time and dtime You supply name the name of the UDF dt vel omega time and dtime are variables that are passed by the FLUENT solver to your UDF The linear and angular velocities are returned to FLUENT by overwriting the arrays vel and omega respectively Example Consider the following example whe
185. M_UNRESERVED offset Reserve_User_Memory_Vars int num Reserve User Memory Vars defined in sg udms h is designed to be called from an EXECUTE_ON_LOADING UDF Section 2 2 6 DEFINE_EXECUTE_ON_LOADING An on loading UDF as its name implies executes as soon as the shared library is loaded into FLU ENT The macro can also be called from an INIT or ON_DEMAND UDF although this is discouraged except for testing purposes Once reserved UDMs can be set to unique names for the particular library using Set User Memory Name see below for details Once the number of UDMs that are needed by a particular library is set in the GUI and the UDMs are successfully reserved for the loaded library the other functions in the library can safely use C_UDMI c t offset up to C_UDMI c t offset num 1 to store values in memory locations without interference Two example source code files named udm res1i c and udm_res2 c each containing two UDFs are listed below The first UDF is an EXECUTE_ON_LOADING UDF that is used to reserve UDMs for the library and set unique names for the UDM locations so that they can be easily identified in postprocess ing The second UDF is an ON_DEMAND UDF that is used to set the values of the UDM locations after the solution has been initialized The ON_DEMAND UDF sets the initial val ues of the UDM locations using udf offset which is defined in the EXECUTE ON LOADING UDF Note that the on demand UDF must be executed after the solution i
186. Manager panel highlight the shared library name e g libudf that is listed under UDF Libraries or type the Library Name and click Unload Figure 5 5 2 Once unloaded the library e g libudf will be removed from the UDF Libraries list in the panel Repeat this step to unload additional libraries Fluent Inc September 11 2006 5 25 Compiling UDFs 5 6 Common Errors When Building and Loading a UDF Library A common compiler error occurs when you forget to put an include udf h statement at the beginning of your source file You ll get a long list of compiler error messages that include illegal declarations of variables Similarly if your function requires an auxiliary header file e g sg pdf h and you forgot to include it you ll get a similar compiler error message Another common error occurs when the argument list for a DEFINE statement is placed on multiple lines All DEFINE macro arguments must be listed on the same line in a C file The compiler will typically not report any error message but it will report a single warning message in the log file to indicate that this occurred warning no newline at end of file If your compiled UDF library loads successfully then each function contained within the library will be reported to the console and log file For example if you built a shared library named libudf containing two user defined functions superfluid density and speed_sound a successful library load on
187. Model Specific UDFs 6 2 23 Hooking DEFINE_WALL_FUNCTIONS UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_WALL_FUNCTIONS UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Viscous Model panel Figure 6 2 29 in FLUENT Define Models Viscous Viscous Model Model Model Constants C Inviscid C2 Epsilon Laminar 1 9 Spalart Allmaras 1 eqn k epsilon 2 eqn k omega 2 eqn Reynolds Stress 7 eqn Detached Eddy Simulation TKE Prandtl Number eo TDR Prandtl Number Large Eddy Simulation LES 1 2 Energy Prandtl Number ps ot k epsilon Model C Standard C RNG 6 Realizable User Defined Functions Turbulent Viscosity none Near Wall Treatment C Standard Wall Functions C Non Equilibrium Wall Functions Prandtl Numbers C Enhanced Wall Treatment User Defined Wall Functions Options l Viscous Heating TKE Prandtl Number none TDR Prandtl Number none Energy Prandtl Number Law of the Wall luser_log_lawr libudf Figure 6 2 29 The Viscous Model Panel To hook the UDF to FLUENT choose the function name e g user log law in the Law of the Wall drop down list and click OK See Section 2 3 23 DEFINE WALL FUNCTIONS for DEFINE_WALL_FUNCTIONS functions in FLUENT details about defining Fluent Inc September 11 2006 6 45 Hooki
188. NE RW FILE Fluent Inc September 11 2006 2 2 General Purpose DEF INE Macros Table 2 2 1 Quick Reference Guide for General Purpose DEFINE Macros Function DEFINE Macro Panel Activated In manipulates variables time step size for time dependent solutions executes at end of iteration executes at end of a FLUENT session executes from a user defined Scheme routine executes when a UDF library is loaded initializes variables executes asynchronously reads writes variables to case and data files DEFINE ADJUST DEF INE_DELTAT DEF INE_EXECUTE_AT_END DEFINE EXECUTE AT EXIT DEFINE EXECUTE FROM GUI DEFINE EXECUTE ON LOADING DEFINE INIT DEFINE ON DEMAND DEFINE RW FILE User Defined Function Hooks Iterate User Defined Function Hooks N A N A N A User Defined Function Hooks Execute On Demand User Defined Function Hooks Fluent Inc September 11 2006 DEFINE Macros 2 21 DEFINE_ADJUST Description DEFINE_ADJUST is a general purpose macro that can be used to adjust or modify FLUENT variables that are not passed as arguments For example you can use DEFINE_ADJUST to modify flow variables e g velocities pressure and compute integrals You can also use it to integrate a scalar quantity over a domain and adjust a boundary condition based on the result A function that is defined using DEFINE_ADJUST executes at every iteration and is called at the beginning of e
189. NT session while a DEFINE_EXECUTE_ON_LOADING is called whenever a UDF compiled library is loaded Understanding the context in which UDFs are called within FLUENT s solution process may be important when you begin the process of writing UDF code depending on the type of UDF you are writing The solver contains call outs that are linked to user defined functions that you write Knowing the sequencing of function calls within an iteration in the FLUENT solution process can help you determine which data are current and available at any given time Pressure Based Segregated Solver The solution process for the pressure based segregated solver Figure 1 9 1 begins with a two step initialization sequence that is executed outside the solution iteration loop This sequence begins by initializing equations to user entered or default values taken from the FLUENT user interface Next PROFILE UDFs are called followed by a call to INIT UDFs Initialization UDFs overwrite initialization values that were previously set The solution iteration loop begins with the execution of ADJUST UDFs Next momentum equations for u v and w velocities are solved sequentially followed by mass continuity and velocity updates Subsequently the energy and species equations are solved followed by turbulence and other scalar transport equations as required Note that PROFILE and SOURCE UDF are called by each Solve routine for the variable currently under considerati
190. OFILE for details about DEFINE PROFILE functions Fluent Inc September 11 2006 6 29 Hooking UDFs to FLUENT Hooking Profiles for UDS Equations For each of the N scalar equations you have specified in your FLUENT model using the User Defined Scalars panel you can hook a fixed value UDF for a cell zone e g Fluid or Solid and a specified value or flux UDF for all wall inflow and outflow boundaries Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_PROFILE UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the appropriate boundary condition panel Define Boundary Conditions 1 If you are using your UDF to specify a fixed value in a cell zone you will need to turn on the Fixed Values option in the Fluid or Solid panel and click the Fixed Values tab Figure 6 2 15 This will display the fixed values parameters in the scrollable window under the Fixed Values tab Next select the name of the UDF e g fixed_scalar_0 in the appropriate drop down list for the value you wish to set Zone Name fuia Material Name water Edit Porous Zone l Laminar Zone Source Terms V Fixed Values Motion Porous Zone Reaction Source Terms Fixed Values Local Coordinate System for Fixed Velocities Temperature K none E User Scalar 0 udt fixed_scalar_0 User Scalar 1 none
191. OF_DTRANS_13 SDOF_DTRANS_21 SDOF_DTRANS_22 SDOF_DTRANS_23 SDOF_DTRANS_31 SDOF_DTRANS_32 SDOF_DTRANS_33 2 206 boolean coordinate rotation matrices derivative rotation matrices Fluent Inc September 11 2006 2 6 Dynamic Mesh DEFINE Macros Example 1 The following UDF named stage is a simple example of setting mass and moments of inertia properties for a moving object This UDF is typical for applications in which a body is dropped and the SDOF solver computes the body s motion in the flow field PRR OO FO IO I I A 2K K OK 2K K A 2K K kA 2K K 2K 2K K FK FKK FK 2K 2k kk 2K 2K K K 2k K K Simple example of a SDOF property UDF for a moving body BECO AOR kkk I I I IAEA kk kkk kk kkk include udf h DEFINE_SDOF_PROPERTIES stage prop dt time dtime prop SDOF_MASS 800 0 prop SDOF_IXX 200 0 prop SDOF_IYY 100 0 prop SDOF_1ZZ 100 0 printf nstage updated 6DOF properties Example 2 The following UDF named delta_missile specifies case injector forces and moments that are time dependent Specifically the external forces and moments depend on the current angular orientation of the moving object Note that this UDF must be executed as a compiled UDF DRO OOO K 3K 2K 2K k FK 2K K FK 2K 2K K FK 2K 2K FK FK 2K K FK OK kK K KK K FK 4 2k K 2k FK SDOF property compiled UDF with external forces moments EEEE E ooo ooo k kkk k kkk include udf h DEFINE_
192. OLECON Pollut 02 Pollut gt den 1000 Pollut_Par gt sp IDX S02 mw else if POLLUT_EQN Pollut_Par EQ_S03 rf kr MOLECON Pollut 02 MOLECON Pollut IDX S02 rr kf o_eq Pollut gt den 1000 Pollut_Par gt sp IDX S03 mw Pollut gt fluct fwdrate rf Pollut gt fluct revrate rr Hooking a SO Rate UDF to FLUENT After the UDF that you have defined using DEFINE SOX RATE is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user_sox will be come visible and selectable in the SOx Model panel in FLUENT See Section 6 2 18 Hook ing DEFINE SOX RATE UDFs for details 2 1 00 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros 2 3 19 DEFINE SR RATE Description You can use DEFINE SR RATE to specify a custom surface reaction rate A custom surface reaction rate function defined using this macro will overwrite the default reaction rate e g finite rate that is specified in the Materials panel An example of a reaction rate that depends upon gas species mass fractions is provided below Also provided is a reaction rate UDF that takes into account site species Note that the three types of surface reaction species are internally num bered with an integer index i in order Usage DEFINE SR RATE name f t r my yi rr Argument Type Description symbol name
193. ON p cf DPM_CHAR_FRACTION p if mp mpO gt 1 mp mp0 lt 0 if mp mp0 lt 1 vf cf only ash left vf cf 0 return 001 else if mp mp0 lt 1 vf only ash and char left cf 1 1 vf cf mp mp0 vf 0 return 1 0 else volatiles char and ash left cf cf mp mp0 vf 1 1 vf mp mp0 Fluent Inc September 11 2006 2 1 73 DEFINE Macros return 1 0 return 1 0 DEFINE_DPM_PROPERTY coal_scattering c t p real mp0 P_INIT_MASS p real mp P_MASS p real cf vf get the original char and volatile fractions and store them in vf and cf vf DPM_VOLATILE_FRACTION p cf DPM_CHAR_FRACTION p if mp mpO gt 1 mp mp0 lt 0 if mp mp0 lt 1 vf cf only ash left vf cf 0 return 1 1 else if mp mp0 lt 1 vf only ash and char left cf 1 1 vf cf mp mp0 vf 0 7 return 0 9 else volatiles char and ash left cf cf mp mp0 vf 1 1 vf mp mp0 return 1 0 return 1 0 i 2 1 74 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros Hooking a DPM Material Property UDF to FLUENT After the UDF that you have defined using DEFINE_DPM_PROPERTY is interpreted Chap ter 4 Interpreting UDF
194. ON for an example of a UDF that uses f node loop 3 3 1 Multiphase Looping Macros This section contains a description of looping macros that are to be used for multiphase UDFs only They enable your function to loop over all cells and faces for given threads or domains Refer to Section 1 10 1 Multiphase specific Data Types and in particular Figure 1 10 1 for a discussion on hierarchy of structures within FLUENT Looping Over Phase Domains in Mixture sub_domain_loop The sub_domain_loop macro loops over all phase domains subdomains within the mix ture domain The macro steps through and provides each phase domain pointer defined in the mixture domain as well as the corresponding phase domain index As discussed in Section 1 10 1 Multiphase specific Data Types the domain pointer is needed in part to gain access to data within each phase Note that sub_domain_loop is similar in im plementation to the sub_thread_loop macro described below int phase_domain_index index of subdomain pointers Domain mixture_domain Domain subdomain sub_domain_loop subdomain mixture_domain phase_domain_index The variable arguments to sub_domain_loop are subdomain mixture_domain and phase_domain_index subdomain is a pointer to the phase level domain and mixture_domain is a pointer to the mixture level domain The mixture_domain is auto matically passed to your UDF by the FLUENT solver when you use a DEFINE macro that contains a domain v
195. P_TIME p gt TSTART if i 0 bforce Q BZ P_VEL p 1 else if i 1 bforce Q BZ P_VEL p 0 else bforce 0 0 an acceleration should be returned return bforce P_MASS p Hooking a DPM Body Force UDF to FLUENT After the UDF that you have defined using DEFINE_DPM_BODY_FORCE is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible in the Discrete Phase Model panel in FLUENT See Section 6 4 2 Hooking DEFINE_DPM_BODY_FORCE UDFs for details on how to hook your DEFINE_DPM_BODY_FORCE UDF to FLUENT 2 1 50 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros 2 5 3 DEFINE_DPM_DRAG Description You can use DEFINE_DPM_DRAG to specify the drag coefficient Cp between particles and fluid defined by the following equation 18u CpRe Fp 5 PpD 24 Usage DEFINE_DPM_DRAG name Re p Argument Type Description symbol name UDF name real Re particle Reynolds number based on the particle diameter and relative gas velocity Tracked Particle p Pointer to the Tracked Particle data structure which contains data related to the particle being tracked Function returns real There are three arguments to DEFINE_DPM_DRAG name Re and p You supply name the name of the UDF Re and p are variables that are passed by the FLUENT solver to your UDF Your UDF wil
196. Par SOx_Parameter S0x DEFINE_SOX_RATE user_sox c t Pollut Pollut_Par SOx Pollut gt fluct fwdrate Pollut gt fluct revrate O O we switch Pollut_Par gt pollut_io_pdf case IN_PDF Source terms other than those from char must be included here if SOx gt user_replace This rate replaces the default FLUENT rate so2_so3_rate c t Pollut Pollut_Par SOx else This rate is added to the default FLUENT rate so2_so3_rate c t Pollut Pollut_Par SOx break case OUT_PDF Char Contributions that do not go into pdf loop must be included here break void so2_so3_rate cell_t c Thread t Pollut_Cell Pollut Pollut_Parameter Pollut_Par SOx_Parameter SUx real kf kr rf 0 rr 0 real xc_o2 0_eq real r_volatile Ys_volatile fuels_so2_frac Rate_Const K_F Rate_Const K_R Rate_Const K_O 11 286 0 0 89765 5753 1 0e4 1 0 10464 625 36 64 0 5 27123 0 S03 0 lt gt S02 02 Fluent Inc September 11 2006 2 99 DEFINE Macros kf kr ARRH Pollut K_F ARRH Pollut K_R MOLECON Pollut 02 ARRH Pollut K_0 sqrt MOLECON Pollut 02 XC_O2 o_eq if POLLUT_EQN Pollut_Par EQ_S02 r_volatile Pollut gt r_volatile Ys_volatile 1 e 04 fuels_so2_frac 1 rf r_volatile Ys_volatile fuels_so2_frac 1000 Pollut_Par gt sp S mw Pollut gt cell_V rf kf o_eq MOLECON Pollut IDX S03 rr kr M
197. Returns P_POSO p i P_VELO p i P_DIAMO p P_TO p P_RHOO p P_MASSO p P_TIMEO p P_LFO p Tracked_Particle Tracked_Particle Tracked_Particle Tracked_Particle Tracked_Particle Tracked_Particle Tracked_Particle Tracked_Particle p int i p int i p p p p p p position i 0 1 2 velocity i 0 1 2 diameter temperature density mass particle time at entry liquid fraction wet combusting particles only Note that when you are the using the macros listed in Table 3 2 27 to track transient particles the particle state is the beginning of the fluid flow time step only if the particle does not cross a cell boundary Table 3 2 28 Macros for Particles at Injection into Domain Defined in dpm h Name Arguments Argument Types Returns P_CELL p P_CELL_THREAD p Tracked_Particle p Tracked_Particle p cell index of the cell that the particle is currently in pointer to the thread of the cell that the particle is currently in 3 32 Fluent Inc September 11 2006 3 2 Data Access Macros Table 3 2 29 Macros for Particle Cell Index and Thread Pointer Defined in dpm h Macro Argument Types Returns P_INIT_POS p i P_INIT_VEL p i P_INIT_DIAM p P_INIT_TEMP p P_INIT_RHO p P_INIT_MASS p P_INIT_LF p Tracked_Particle Tracked_Particle Tracked_Particle Tracked_Particle Tracked_Particle Tracked_Particle Tr
198. S UNSTEADY name c t i apu su Argument Type Description symbol name UDF name cellt c Cell index Thread t Pointer to cell thread on which the unsteady term for the user defined scalar transport equation is to be applied int i Index that identifies the user defined scalar for which the unsteady term is to be set real apu Pointer to central coefficient real su Pointer to source term Function returns void There are six arguments to DEFINE UDS UNSTEADY name c t i apu and su You supply name the name of the UDF c t and i are variables that are passed by the FLUENT solver to your UDF Your UDF will need to set the values of the unsteady terms referenced by the real pointers apu and su to the central coefficient and source term respectively The FLUENT solver expects that the transient term will be decomposed into a source term su and a central coefficient term apu These terms are included in the equation set in a similar manner to the way the explicit and implicit components of a source term might be handled Hence the unsteady term is moved to the right hand side and discretized as follows f o av TA eo L E ay unsteady term Fluent Inc September 11 2006 2 219 DEFINE Macros _ PAV payer At At S apu su g 2 7 3 Equation 2 7 3 shows how su and apu are defined Note that if more than one scalar is being solved a conditional if statement can be used in your UDF to
199. SDOF_PROPERTIES delta_missile prop dt time dtime prop SDOF_MASS 907 185 prop SDOF_1IXX 27 116 prop SDOF_IYY 488 094 prop SDOF_1ZZ 488 094 add injector forces moments register real dfront fabs DT_CG at 2 Fluent Inc September 11 2006 2 207 DEFINE Macros 0 179832 DT_THETA dt 1 register real dback fabs DT_CG dt 2 0 329184 DT_THETA dt 1 if dfront lt 0 100584 prop SDOF_LOAD_F_Z prop SDOF_LOAD_M_Y F 10676 0 1920 0 if dback lt 0 100584 prop SDOF_LOAD_F_Z 42703 0 prop SDOF_LOAD_M_Y 14057 0 t printf ndelta_missile updated 6DOF properties Hooking a DEFINE_SDOF_PROPERTIES UDF to FLUENT After the UDF that you have defined using DEFINE_SDOF_PROPERTIES is interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become vis ible in the Six DOF UDF drop down list in the Dynamic Zones panel in FLUENT See Section 6 5 4 Hooking DEFINE_SDOF_PROPERTIES UDF s for details on how to hook your DEFINE_SDOF_PROPERTIES UDF to FLUENT 2 208 Fluent Inc September 11 2006 2 7 User Defined Scalar UDS Transport Equation DEFINE Macros 2 7 User Defined Scalar UDS Transport Equation DEFINE Macros This section provides information on how you can define UDFs that can be used in UDS transport equations in FLU
200. SOURCE Description You can use DEFINE_TURB_PREMIX_SOURCE to customize the turbulent flame speed and source term in the premixed combustion model Chapter 16 Modeling Premixed Combustion in the User s Guide and the partially premixed combustion model Chapter 17 Mod eling Partially Premixed Combustion in the User s Guide Usage DEFINE TURB PREMIX SOURCE name c t turb flame speed source Argument Type Description symbol name UDF name cellt c Cell index Thread t Pointer to cell thread on which the turbulent premixed source term is to be applied real turb_flame speed Pointer to the turbulent flame speed real source Pointer to the reaction progress source term Function returns void There are five arguments to DEFINE_TURB_PREMIX_SOURCE name c t turb_ flame speed and source You supply name the name of the UDF c t turb_ flame speed and source are variables that are passed by the FLUENT solver to your UDF Your UDF will need to set the turbulent flame speed to the value referenced by the turb flame speed pointer It will also need to set the source term to the value referenced by the source pointer Example The following UDF named turb_flame_src specifies a custom turbulent flame speed and source term in the premixed combustion model The source code must be executed as a compiled UDF in FLUENT In the standard premixed combustion model in FLUENT the mean reaction rate of the progress variable tha
201. ST or RP_NODE are true then PARALLEL is also true Fluent Inc September 11 2006 7 13 Parallel Considerations DRO E k k k kkk k kkk kkk k kkk I k kkk K kkk k kK k Kk k 2k 24 2k k kkk kK 2k K KK k 2k 2 2k 2k 2k k Compiler Directives DRO kkk ak akk k OR I 2K K FK A K FK 2K 2K 2K 2K FK FKK FK 2k 24 K FK 2k 2K 2k 2K 2k K 2k 2k KK K LES K if RP_HOST only host process is involved endif if RP_NODE only compute nodes are involved endif if PARALLEL both host and compute nodes are involved but not serial equivalent to if RP_HOST RP_NODE endif DRO OO kkk k kkk kkk k kkk k kkk kkk k kkk k 2 LL LL k kkk 2k 21 2k k 2k 2k 2k k 2k 2k 2 2k 6 2k ak k Negated forms that are more commonly used PROC HE HO OK AA AGAR RR I I I III AKER CA A A A A KKK KEK A ACA A A 2K 1 KK KK kkk if RP_HOST either serial or compute node process is involved endif if RP_NODE either serial or host process is involved endif if PARALLEL only serial process is involved endif The following simple UDF shows the use of compiler directives The adjust function is used to define a function called where am i This function queries to determine which type of process is executing and then displays a message on that computed node s mon itor 7 14 Fluent Inc September 11 2006 7 5 Macros for Parallel UDFs Example RTC Ce CLC RENE RER ER RER RER errr rere ee EEK Simple
202. STEP to compute the homogeneous net mass reaction rate of all species integrated over a time step t dY 2 3 1 q 2 3 1 A ie 0 where Y is the initial mass fraction of species i t is time At is the given time step and oi is the net mass reaction rate Yt is ith species mass fraction at the end of the integration DEFINE_CHEM_STEP UDFs are used for the EDC and PDF Transport models Usage DEFINE CHEM STEP name c t p num_p n_spe dt pres temp yk Argument Type Description symbol name UDF name cellt c Cell index of current particle Thread t Pointer to cell thread for particle Particle p Pointer to particle data structure that contains data related to the particle being tracked int num p Not Used int n_spec Number of volumetric species double dt Time step double pres Pointer to pressure double temp Pointer to temperature double yk Pointer to array of initial species mass fractions Function returns void There are nine arguments to DEFINE CHEM_ STEP name c p num_p n_spe dt pres temp and yk You supply name the name of the UDF c p n spe dt pres temp and yk are variables that are passed by the FLUENT solver to your UDF num_p is not used by the function and can be ignored The output of the function is the array of mass fractions yk after the integration step The initial mass fractions in array yk are overwritten Fluent Inc September 11 2006 2 31 DEFINE Macros
203. T choose the function name e g dpm_output in the Output drop down list under User Defined Functions and click Start and Close See Section 2 5 8 DEFINE_DPM_OUTPUT for details about DEFINE_DPM_OUTPUT functions 6 62 Fluent Inc September 11 2006 6 4 Hooking Discrete Phase Model DPM UDFs 6 4 9 Hooking DEFINE_DPM_PROPERTY UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_PROPERTY UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Func tions panel Figure 6 4 10 To hook the UDF to FLUENT you will first need to open the User Defined Functions panel by choosing user defined in the drop down list for the appropriate property e g Particle Emissivity in the Materials panel Figure 6 4 9 Define Materials Materials Name Material Type Order Materials By anthracite inert particle Name C A Chemical Formula Fluent Inert Particle Materials Chemical Formula anthracite z Fluent Database Mixture User Defined Database none v al Thermal Conductivity wil constant Ct 6 6454 Viscosity kg m s constat Edit 72e Particle Emissivity user defined Edit anthracite_emissivity Particle Scattering Factor constant Edit eS Change Create Delete Close Help Figure 6 4 9 The Materials Panel i I
204. T models e g discrete phase model multiphase mixture model discrete ordinates radiation model Simple examples of UDFs that demonstrate usage are provided with most DEFINE macro descriptions in Chapter 2 DEFINE Macros In addition a step by step example mini tutorial and detailed examples can be found in Chapter 8 Examples 1 3 Limitations Although the UDF capability in FLUENT can address a wide range of applications it is not possible to address every application using UDFs Not all solution variables or FLUENT models can be accessed by UDFs Specific heat values for example cannot be modified this would require additional solver capabilities If you are unsure whether a particular problem can be handled using a UDF you can contact your technical support engineer for assistance FA Note that you may need to update your UDF when using a new version of FLUENT Fluent Inc September 11 2006 1 3 Overview 1 4 Defining Your UDF Using DEFINE Macros UDFs are defined using Fluent supplied function declarations These function declara tions are implemented in the code as macros and are referred to in this document as DEFINE all capitals macros Definitions for DEFINE macros are contained in the udf h header file see Appendix B for a listing For a complete description of each DEFINE macro and an example of its usage refer to Chapter 2 DEFINE Macros The general format of a DEFINE macro is DEFINE_MACRONAME udf_n
205. There are three arguments to C_UDMI c thread and i c is the cell identifier thread is a pointer to the cell thread and i is an integer index that identifies the memory location where data is to be stored An index i of 0 corresponds to user defined memory location 0 or User Memory 0 Example UDF that Utilizes UDM and UDS Variables UDMs are often used to store diagnostic values derived from calculated values of a UDS Below is an example that shows a technique for plotting the gradient of any flow variable In this case the volume fraction of a phase is loaded into a user scalar If an iteration is made such that the UDS is not calculated the gradients of the scalar will nevertheless be updated without altering the values of the user scalar The gradient is then available to be copied into a User Memory variable for displaying include udf h define domain_ID 2 DEFINE_ADJUST adjust_gradient domain Thread t cell_t c face_t f domain Get_Domain domain_ID Fill UDS with the variable thread_loop_c t domain Fluent Inc September 11 2006 3 43 Additional Macros for Writing UDFs begin_c_loop c t C_UDSI c t 0 C_VOF c t end_c_loop c t thread_loop_f t domain if THREAD_STORAGE t SV_UDS_I O NULL begin_f_loop f t F_UDSI f t 0 F_VOF f t end_f_loop f t DEFINE_ON_DEMAND store_gradient Domain domain cell_t c Thread t domain Get_Domain 1
206. Thread domain is passed by FLUENT and is the pointer to the domain structure You supply the integer value of zone_ID For example the code int zone_ID 2 Thread thread_name Lookup_Thread domain zone_ID passes a zone ID of 2 to Lookup_Thread A zone ID of 2 may for example correspond to a wall zone in your case Now suppose that your UDF needs to operate on a particular thread in a domain instead of looping over all threads and the DEFINE macro you are using to define your UDF doesn t have the thread pointer passed to it from the solver e g DEFINE_ADJUST You can use Lookup_Thread in your UDF to get the desired thread pointer This is a two step process First you will need to get the integer ID of the zone by visiting the boundary condition panel e g Fluid and noting the zone ID You can also obtain the value of the Zone ID from the solver using RP_Get_Integer Note that in order to use RP_Get_Integer you will have had to define the zone ID variable first either in another UDF using RP_Set_Integer or on the Scheme side using rp var define see Section 3 6 Scheme Macros for details Fluent Inc September 11 2006 3 25 Additional Macros for Writing UDFs Next you supply the zone_ID as an argument to Lookup_Thread either as a hard coded integer e g 1 2 or as the variable assigned from RP_Get_Integer Lookup_Thread returns the pointer to the thread that is associated with the given zone ID You can
207. Time 1 8840e 00 Figure 8 2 7 Average Velocity Magnitude at the Pressure Outlet The figure nicely illustrates that the velocity oscillates around the equilibrium value 20 m s with an amplitude of 5 m s as expected 8 2 2 Source Terms This section contains an application of a source term UDF It is executed as an interpreted UDF in FLUENT Adding a Momentum Source to a Duct Flow When a source term is being modeled with a UDF it is important to understand the context in which the function is called When you add a source term FLUENT will call your function as it performs a global loop on cells Your function should compute the source term and return it to the solver In this example a momentum source will be added to a 2D Cartesian duct flow The duct is 4 m long and 2 m wide and will be modeled with a symmetry boundary through the middle Liquid metal with properties listed in Table 8 2 1 enters the duct at the left with a velocity of 1 mm s at a temperature of 290 K After the metal has traveled 0 5 m along the duct it is exposed to a cooling wall which is held at a constant temperature of 280 K To simulate the freezing of the metal a momentum source is applied to the metal as soon as its temperature falls below 288 K The momentum source is proportional to the x component of the velocity vz and has the opposite sign 8 26 Fluent Inc September 11 2006 8 2 Detailed UDF Examples Sz Ouz 8 2 1 wher
208. Tracked Particle data structure which contains data related to the particle being tracked Function returns real There are four arguments to DEFINE DPM PROPERTY name c t and p DEFINE DPM PROPERTY has the same arguments as the DEFINE PROPERTY function de scribed in Section 2 3 14 DEFINE PROPERTY UDFs with the addition of the pointer to the Tracked_Particle p You supply name the name of the UDF c t and p are variables that are passed by the FLUENT solver to your UDF Your UDF will need to compute the real value of the discrete phase property and return it to the solver Pointer p can be used as an argument to the macros defined in Sec tion 3 2 7 DPM Macros to obtain information about particle properties e g injection properties 2 1 72 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros Example In the following example two discrete phase material property UDFs named coal_emissivity and coal_scattering respectively are concatenated into a single C source file These UDFs must be executed as compiled UDFs in FLUENT peaa oo ooo kk kkk kkk kkk kkk kk kkk kk kkk UDF that specifies discrete phase materials EEEE o ooo ooo DD D kkk DH kkk kk kk kkk include udf h DEFINE_DPM_PROPERTY coal_emissivity c t p real mp0 P_INIT_MASS p real mp P_MASS p real vf cf get the material char and volatile fractions and store them in vf and cf vf DPM_VOLATILE_FRACTI
209. UDF name facet f Index that identifies a face within the given thread or cell in the case of surface reaction in a porous zone Thread t Pointer to face thread on which the surface rate reaction is to be applied Reaction r Pointer to data structure for the reaction real mw Pointer to array of species molecular weights real yi Pointer to array of mass fractions of gas species at the surface and the coverage of site species or site fractions real rr Pointer to reaction rate Function returns void There are seven arguments to D FINE_SR_ RATE name f t r my yi and rr You supply name the name of the UDF Once your UDF is compiled and linked the name that you have chosen for your function will become visible and selectable in the graphical user interface in FLUENT f t r my and yi are variables that are passed by the FLUENT solver to your UDF Your UDF will need to set the reaction rate to the value referenced by the real pointer rr as shown in the examples below Example 1 Surface Reaction Rate Using Species Mass Fractions The following compiled UDF named arrhenius defines a custom surface reaction rate using species mass fractions in FLUENT Fluent Inc September 11 2006 2 1 01 DEFINE Macros DOR OOOO HRK HE HR HRK RR RR ak HER HE Custom surface reaction rate UDF KR HRK A HRK HRK AK OK ER KO HRK HRK HER 2k 2k a 2k 2k ak ok include udf h ARRHENIUS CONSTANTS define PRE_EXP 1e 15
210. UDF that uses compiler directives OOOO OCIA HER ER RENE RA I RK I Ka kk include udf h DEFINE_ADJUST where_am_i domain if RP_HOST Message I am in the host process n endif RP_HOST if RP_NODE Message I am in the node process with ID d n myid myid is a global variable which is set to the multiport ID for each node endif RP_NODE if PARALLEL Message I am in the serial process n endif PARALLEL This simple allocation of functionality between the different types of processes is useful in a limited number of practical situations For example you may want to display a message on the compute nodes when a particular computation is being run by using RP_NODE or RP_HOST Or you can also choose to designate the host process to display messages by using RP_HOST or RP_NODE Usually you want messages written only once by the host process and the serial process Simple messages such as Running the Adjust Function are straightforward Alternatively you may want to collect data from all the nodes and print the total once from the host To perform this type of operation your UDF will need some form of communication between processes The most common mode of communication is between the host and the node processes Fluent Inc September 11 2006 7 15 Parallel Considerations 7 5 2 Communicating Between the Host and Node Processes There are two sets of similar macr
211. UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DOM_DIFFUSE_REFLECTIVITY UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Function Hooks panel Figure 6 2 5 in FLUENT Define User Defined Function Hooks User Defined Function Hooks Initialization none Edit Adjust hone Edit Execute at End none Edit Read Case none Edit Write Case none Edit Read Data none Edit Write Data none Edit Execute at Exit none Edit Wall Heat Flux mone DO Source mone DO Diffuse Reflectivity DO Specular Reflectivity mone Figure 6 2 5 The User Defined Function Hooks Panel The Discrete Ordinates radiation model must be enabled from the Radiation Model panel To hook the UDF to FLUENT choose the function name e g user dom diff refl in the DO Diffuse Reflectivity drop down list in the User Defined Function Hooks panel and click OK See Section 2 3 4 DEFINE DOM DIFFUSE REFLECTIVITY for details about DEFINE DOM DIFFUSE REFLECTIVITY functions Fluent Inc September 11 2006 6 19 Hooking UDFs to FLUENT 6 2 5 Hooking DEFINE_DOM_SOURCE UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DOM_SOURCE UDF compiled your DEFINE DOM SOURCE UDF see Chapter 5 Compiling UDF
212. UNC DEFINE SOLAR INTENSITY DEFINE SOURCE DEFINE SOX RATE DEFINE SR RATE DEF INE_TURB_PREMIX_SOURCE DEF INE_TURBULENT_VISCOSITY DEFINE_VR_RATE DEFINE_WALL_FUNCTIONS Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros Table 2 3 1 Quick Reference Guide for Model Specific DEFINE Functions Function DEFINE Macro Panel Activated In mixing constant homogeneous net mass reaction rate for all species integrated over a time step species mass or UDS diffusivity diffusive reflectivity for discrete ordinates DO model source for DO model specular reflectivity for DO model gray band absorption coefficient for DO model wall heat flux homogeneous net mass reaction rate for all species NO formation rates for Thermal NO Prompt NO Fuel NO and N20 Pathways particle surface reaction rate Prandtl numbers species mass fraction DEF INE_CPHI DEF INE_CHEM_STEP DEFINE_DIFFUSIVITY DEF INE_DOM_DIFFUSE_ REFLECTIVITY DEFINE DOM SOURCE DEFINE DOM SPECULAR REFLECTIVITY DEFINE GRAY BAND_ ABS_COEFF DEFINE HEAT FLUX DEF INE_NET_ REACTION_RATE DEFINE NOX RATE DEFINE PR RATE DEFINE PRANDTL DEFINE PROFILE User Defined Function Hooks User Defined Function Hooks Materials User Defined Function Hooks User Defined Function Hooks User Defined Function Hooks Materials User Defined Function Hooks User Defined Function Hooks NOx Model User Defined Function Hooks Viscous Mod
213. UNIX code define addab_ ADDAB endif typedef struct float r i Complex typedef struct double r i DComplex typedef struct long double r i QComplex FORTRAN QUAD PRECISION FORTRAN FUNCTION extern double addab_ float a double b int c NOTE on SUN machines that FORTRAN functions returning a complex number are actually implemented as void but with an extra initial argument extern void ccmplx_ Complex z float a float b Fluent Inc September 11 2006 5 4 Link Precompiled Object Files From Non FLUENT Sources extern void qcmplx_ QComplex z float a float b BLANK COMMON BLOCK extern struct int size float array 10 _BLNK__ FORTRAN NAMED COMMON BLOCK extern struct int int_c float float_a double double_b float cmplx_r float cmplx_i tstcom_ DEFINE_ON_DEMAND fort_test float a 3 0 float_b double d b 1 5 int i c 2 Complex Z QComplex qz d addab_ amp a amp b amp c Message n nFortran code gives 4 f d f f n a c b d Message Common Block TSTCOM set to g hg d n tstcom_ float_a tstcom_ double_b tstcom_ int_c Message Common Complex Number is f fj n tstcom_ cmplx_r tstcom_ cmplx_i Message BLANK Common Block has an array of size 4d n BLNK__ size for i 0 i lt _BLNK__ size i Message arrayl d g n i _BLNK__ arraylil float_b float b ccmplx_ amp z amp a
214. UX f t Sec tion 3 2 4 Face Macros The sign of flux that is computed by the FLUENT solver is positive if the flow direction is the same as the face area normal direction as determined by F_AREA see Section 3 2 4 Face Area Vector F_AREA and is negative if the flow direction and the face area normal directions are opposite By convention face area nor mals always point out of the domain for boundary faces and they point in the direction from cell cO to cell c1 for interior faces The UDF must be executed as a compiled UDF RTC LC Ti Cori CLT rrCLoLrreCerrrrerrr errr RER RER rer errr rer errr re ee Ly UDF that implements a simplified advective term in the scalar transport equation 1 PR RHERHERRHER HER HN RENE EEE EEE EEE RE RER RE ER EEE EEE EEK include udf h DEFINE_UDS_FLUX my_uds_flux f t i cell_t c0 ci 1 Thread xtO xti NULL real NV_VEC psi_vec NV_VEC A flux 0 0 c0 F_CO f t tO F_CO_THREAD f t F_AREA A f t If face lies at domain boundary use face values If face lies IN the domain use average of adjacent cells if BOUNDARY_FACE_THREAD_P t Most face values will be availablex real dens Fluent Inc September 11 2006 2 217 DEFINE Macros Depending on its BC density may not be set on face thread if NNULLP THREAD_STORAGE t SV_DENSITY dens F_R f t Set dens to face value if available else dens C_R cO t0
215. User Defined Functions panel Choose the UDF name from the list of UDFs displayed and click OK See Section 2 5 15 DEFINE_DPM_VP_EQUILIB for details about DEFINE_DPM_VP_EQUILIBRIUM functions 6 5 Hooking Dynamic Mesh UDFs This section contains methods for hooking UDF s to FLUENT that have been defined using DEFINE macros described in Section 2 6 Dynamic Mesh DEFINE Macros and interpreted or compiled using methods described in Chapters 4 or 5 respectively 6 5 1 Hooking DEFINE_CG_MOTION UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_CG_MOTION UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Dynamic Mesh Zones panel Figure 6 5 1 To hook the UDF to FLUENT you will first need to enable the dynamic mesh model Define Dynamic Mesh Parameters To enable the dymanic mesh model select Dynamic Mesh under Model and click OK i The Dynamic Mesh panel will be accessible only when you choose Unsteady as the time method in the Solver panel Next open the Dynamic Mesh Zones panel Define Dynamic Mesh Zones Fluent Inc September 11 2006 6 71 Hooking UDFs to FLUENT Dynamic Mesh Zones Zone Names Dynamic Zones axis Type C Stationary Rigid Body Deforming C User Defined Motion Attributes Geometry Definition Meshi
216. X PHASES MAX_SPE_EQNS Matrix of species mass fractions yi i j will give mass fraction of species with ID j in phase with index i For phase which has fluid material yi i 0 will be 1 real rr Pointer to laminar reaction rate real rr_t Currently not used Provided for future use Function returns void There are eight arguments to DEFINE HET RXN RATE name c t r mw yi rr and rr t You supply name the name of the UDF c t r mw yi rr and rr_t are variables that are passed by the FLUENT solver to your UDF Your UDF will need to set the values referenced by the real pointer rr The values must be specified in Dis where the volume is the cell volume 2 1 28 Fluent Inc September 11 2006 2 4 Multiphase DEF INE Macros Example The following compiled UDF named user_evap_condens_react defines the reaction rate required to simulate evaporation or condensation on the surface of droplets Such a reaction can be formally described by the following HO dig H20 gas 2 4 1 Here gas is a primary phase mixture of two species H30 gas and air Droplets constitute the secondary phase and represent a mixture of one species HzO iq Single species mixtures are allowed in multiphase models The forumlation for the reaction rate follows the model for particle evaporation that is defined in Section 22 9 2 Droplet Vaporization Law 2 of the User s Guide Constants used in psat_h2o to calculate saturation
217. XVelocity m9 udt x_velociy Y Yelocity m s g constant v Z Velocity m s g constant X Figure 8 1 8 The Velocity Inlet Panel Fluent Inc September 11 2006 8 13 Examples 8 1 7 Step 6 Run the Calculation Run the calculation as usual Solve Iterate 8 1 8 Step 7 Analyze the Numerical Solution and Compare to Expected Results Once the solution is run to convergence obtain a revised velocity field The velocity magnitude contours for the parabolic inlet x velocity are shown in Figure 8 1 9 and can be compared to the results of a constant velocity field of 20 m sec Figure 8 1 2 For the constant velocity condition the flow field is distorted as the flow moves around the turbine vane The velocity field for the imposed parabolic profile however shows a maximum at the center of the inlet which drops to zero at the edges 4 460401 4 05e 01 3 64e 01 3 28e 01 2 83e 01 420401 2 01e 01 1 60e 01 1 19e 01 7 78e 00 3 68e 00 Turbine Vane 1551 cells 2405 faces 893 nodes Contours of Velocity Magnitude m s Figure 8 1 9 Velocity Magnitude Contours for a Parabolic Inlet x Velocity 8 14 Fluent Inc September 11 2006 8 2 Detailed UDF Examples 8 2 Detailed UDF Examples This section contains detailed examples of UDFs that are used in typical FLUENT appli cations e Section 8 2 1 Boundary Conditions Section 8 2 2 Source Terms Section 8 2
218. Y UDFs 6 57 6 4 Hooking Discrete Phase Model DPM UDFs 6 59 6 4 1 Hooking DEFINE DPM BC UDFs 6444 6444444845 6 59 6 4 2 Hooking DEFINE DPM BODY FORCE UDFs 6 61 64 5 Hooking DEFINE DPM_ORAG UDES oc 4 4 Le 6 t eee avenues 6 62 6 4 4 Hooking DEFINE DPM_EROSION UDFs 6 63 6 4 5 Hooking DEFINE DPM HEAT MASS UDFs 6 64 6 4 6 Hooking DEFINE DPM_INJECTION_INIT UDFs 6 66 6 4 7 Hooking DEFINE DPM LAW UDFs 6 68 64 8 Hooking DEFINE DPMOUTPUT UDFs 2 4 24 44 444844 6 69 6 4 9 Hooking DEFINE DPM PROPERTY UDFs 6 70 6 4 10 Hooking DEFINE_DPM_ SCALAR_ UPDATE UDFs 6 72 6 4 11 Hooking DEFINE DPM SOURCE UDFs 4 4 4 44 qu sua aa 6 73 6 4 12 Hooking DEFINE DPM SPRAY_COLLIDE UDFs 6 74 64 13 Hooking DEFINE_DPM SWITCH UDFs 44 4 sh ses uvaean 6 76 6 4 14 Hooking DEFINE DPM_TIMESTEP UDFs 6 77 6 4 15 Hooking DEFINE DPM_VP_EQUILIB UDFs 6 78 Fluent Inc September 11 2006 Vil CONTENTS oo Hooking Dynamic Mesk UDFS 44 dus lt 4 wae ed wee ae ee eS 6 79 6 5 1 Hooking DEFINE_CG_ MOTION UDFs 6 79 6 5 2 Hooking DEFINE GEOM UDPs 2 lt 4 224242 ee ween 6 81 6 5 3 Hooking DEFINE GRID MOTION UDFs 4 4 66 6 4 4244 6 83 6 5 4 Hooking DEFINE_SDOF PROPERTIES UDFs 6 85 6 6 Hooking User Defined Scalar UDS Transport Equation UDFs 6 87 6 6 1 Hookin
219. Zone ID THREAD_ID You can use THREAD_ID when you want to retrieve the integer zone ID number displayed in a boundary conditions panel such as Fluid that is associated with a given thread pointer t Note that this macro does the inverse of Lookup_Thread see above int zone_ID THREAD_ID t Domain Pointer Get Domain You can use the Get Domain macro to retrieve a domain pointer when it is not explicitly passed as an argument to your UDF This is commonly used in ON_DEMAND functions since DEFINE_ON_DEMAND is not passed any arguments from the FLUENT solver It is also used in initialization and adjust functions for multiphase applications where a phase domain pointer is needed but only a mixture pointer is passed Get_Domain domain_id domain_id is an integer whose value is 1 for the mixture domain but the values for the phase domains can be any integer greater than 1 The ID for a particular phase can be found be selecting it in the Phases panel in FLUENT Define Phases Single Phase Flows In the case of single phase flows domain_id is 1 and Get_Domain 1 will return the fluid domain pointer DEF INE_ON_DEMAND my_udf Domain domain domain is declared as a variable domain Get_Domain 1 returns fluid domain pointer Multiphase Flows In the case of multiphase flows the value returned by Get_Domain is either the mixture level a phase level or an interaction phase level domain
220. _COEFF vof k nu d vof 6 k Nu d d static real heat_ranz_marshall cell_t c Thread ti Thread tj real h real d C_PHASE_DIAMETER c tj real k C_K_L c ti real NV_VEC v vel Re Pr Nu NV_DD v C_U c tj C_V c tj C_W c tj C_U c ti C_V c ti C_W c ti vel NV_MAG v Re RE_NUMBER C_R c ti vel d C_MU_L c ti Pr PR_NUMBER C_CP c ti C_MU_L c ti k Nu 2 0 6 sqrt Re pow Pr 1 3 Fluent Inc September 11 2006 2 1 25 DEFINE Macros h IP_HEAT_COEFF C_VOF c tj k Nu d return h Zz DEFINE_EXCHANGE_PROPERTY heat_udf c t i j Thread ti THREAD_SUB_THREAD t i Thread tj THREAD_SUB_THREAD t j real val val heat_ranz_marshall c ti tj return val Hooking an Exchange Property UDF to FLUENT After the UDF that you have defined using DEFINE_EXCHANGE_PROPERTY is interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g heat_udf will become visible and selectable in the Phase Interaction panel in FLUENT See Sec tion 6 3 2 Hooking DEFINE_EXCHANGE_PROPERTY UDF for details 2 1 26 Fluent Inc September 11 2006 2 4 Multiphase DEF INE Macros 2 4 3 DEFINE_HET_RXN_RATE Description You need to use DEFINE_HET_RXN_RATE to specify reaction rates for heterogeneous reac tions A heterogeneous reaction is one that involves reactants and p
221. _CRECV 7 32 PRF_CRECV_INT 7 44 PRF_CRECV_REAL 7 44 PRF_CSEND 7 32 PRF_CSEND_INT 7 44 PRF_CSEND_REAL 7 44 PRF_GIHIGH 7 19 7 22 PRF_GILOW 7 22 PRF_GISUM 7 19 7 21 PRF_GLAND 7 23 PRF_GLOR 7 23 PRF_GRHIGH 7 22 PRF_GRLOW 7 22 Fluent Inc September 11 2006 Index PRF_GRSUM 7 21 PRF_GRSUM1 7 43 PRF_GSYNC 7 23 PRINCIPAL_FACE_P 7 9 7 28 7 43 printf 2 9 2 24 2 177 A 16 profile UDFs external emissivity 2 66 heat generation rate 2 66 inertial resistance 2 66 porosity 2 66 porous resistance 2 66 species mass fraction 2 66 specific dissipation rate 2 66 stress condition 2 66 temperature 2 66 turbulence dissipation rate 2 66 turbulence kinetic energy 2 66 velocity 2 66 viscous resistance 2 66 volume fraction 2 66 wall shear 2 66 PROP ktc 2 81 PROP_mu 2 81 PROP rho 2 81 property UDFs absorption and scattering coefficient 2 79 density 2 79 diameter 2 79 elasticity modulus 2 79 example 8 32 for DPM 2 172 frictional pressure 2 79 frictional viscosity 2 79 general 2 79 granular conductivity 2 79 viscosity 2 79 radial distribution 2 79 rate of strain 2 79 six degrees of freedom solver 2 205 solids pressure 2 79 Fluent Inc September 11 2006 thermal conductivity 2 79 user defined mixing laws conductivity 2 79 density 2 79 viscosity 2 79 viscosity 2 79 Radiation Model panel 6 36 radiation scattering phase function 2 88 radiative transport equati
222. _DPM_EROSION UDFs for details on how to hook your DEFINE_DPM_EROSION UDF to FLUENT 2 1 58 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros 2 5 5 DEFINE_DPM_HEAT_MASS Description You can use DEFINE DPM HEAT MASS to specify the heat and mass transfer of multicom ponent particles to the gas phase Usage DEFINE_DPM_HEAT_MASS name p C_p hgas hvap cvap_surf dydt dzdt Argument Type Description symbol name UDF name Tracked_Particle p Pointer to the Tracked_Particle data structure which contains data related to the particle being tracked real Cp Particle heat capacity real hgas Enthalpies of vaporizing gas phase species real hvap Vaporization enthalpies of vaporizing components real cvap_surf Vapor equilibrium concentrations of vaporizing components real dydt Source terms of the particle temperature and component masses dpms_t dzdt Source terms of the gas phase enthalpy and species masses Function returns void There are eight arguments to DEFINE_DPM_HEAT_MASS name e p C_p hgas hvap cvap_surf dydt and dzdt You supply name the name of the UDF e p C_p hgas hvap and cvap surf are variables that are passed by the FLUENT solver to your UDF Your UDF will need to compute the particle and gas phase source terms and store the values in dydt and dzdt respectively Example The following is an example of a compiled UDF that uses DEFINE_DPM_HEAT_MASS It implements the source terms for
223. _ND loop over all subdomains phases in the superdomain mixture sub_domain_loop subdomain mixture_domain phase_domain_index loop if secondary phase if DOMAIN_ID subdomain 3 loop over all cell threads in the secondary phase domain thread_loop_c cell_thread subdomain loop over all cells in secondary phase cell threads begin_c_loop_all cell cell_thread C_CENTROID xc cell cell_thread if sqrt ND_SUM pow xc 0 0 5 2 pow xc 1 0 5 2 pow xc 2 0 5 2 lt 0 25 set volume fraction to 1 for centroid C_VOF cell cell_thread 1 else otherwise initialize to zero C_VOF cell cell_thread 0 end_c_loop_all cell cell_thread eg Fluent Inc September 11 2006 3 55 Additional Macros for Writing UDFs Looping Over Phase Threads in Mixture sub_thread_loop The sub_thread_loop macro loops over all phase level threads subthreads associated with a mixture level thread The macro steps through and returns the pointer to each subthread as well as the corresponding phase domain index As discussed in Sec tion 1 10 1 Multiphase specific Data Types if the subthread pointer is associated with an inlet zone then the macro will provide the pointers to the face threads associated with the inlet for each of the phases int phase_domain_index Thread subthread Thread mixture_thread sub_thread_loop subthread mixture_thread phase_domain_index The
224. _PRANDTL_O name c and t You supply name the name of the UDF c and t are variables that are passed by the FLUENT solver to your UDF Your UDF will need to return the real value for the specific dissipation Prandtl number to the solver Example Specifying a Constant Specific Dissipation Prandtl Number include udf h DEFINE_PRANDTL_O user_pr_o c t real pr_o pr_o 2 return pr_o 2 62 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros Hooking a Prandtl Number UDF to FLUENT After the UDF that you have defined using DEFINE_PRANDTL_O is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user pro will become visible and selectable in the Viscous Model panel in FLUENT See Sec tion 6 2 12 Hooking DEFINE_PRANDTL UDFs for details DEFINE_PRANDTL_T Description You can use DEFINE_PRANDTL_T to specify Prandtl numbers that appear in the tempera ture equation diffusion term Usage DEFINE_PRANDTL_T name c t Argument Type Description symbol name UDF name cell_t c Index that identifies the cell on which the Prandtl number function is to be applied Thread t Pointer to cell thread Function returns real There are three arguments to DEFINE_PRANDTL_T name c and t You supply name the name of the UDF c and t are variables that are passed by the FLUENT solv
225. _SUPER_DOMAIN when your UDF has access to a particular phase level domain subdomain pointer and you want to retrieve the mixture level domain pointer DOMAIN_SUPER_DOMAIN has one argument subdomain Note that DOMAIN_SUPER_DOMAIN is similar in implementation to the THREAD_SUPER_THREAD macro described in Section 3 3 2 Mix ture Thread Pointer THREAD_SUPER_THREAD Domain subdomain Domain mixture_domain DOMAIN_SUPER_DOMAIN subdomain subdomain is a pointer to a phase level domain within the multiphase mixture It is automatically passed to your UDF by the FLUENT solver when you use a DEFINE macro that contains a domain variable argument e g DEFINE_ADJUST and the function is hooked to a primary or secondary phase in the mixture Note that in the current ver sion of FLUENT DOMAIN_SUPER_DOMAIN will return the same pointer as Get_Domain 1 Fluent Inc September 11 2006 3 61 Additional Macros for Writing UDFs Therefore if a subdomain pointer is available in your UDF it is recommended that the DOMAIN_SUPER_DOMAIN macro be used instead of the Get_Domain macro to avoid potential incompatibility issues with future releases of FLUENT Mixture Thread Pointer THREAD SUPER THREAD You can use the THREAD_SUPER_THREAD macro when your UDF has access to a particular phase level thread subthread pointer and you want to retrieve the mixture level thread pointer THREAD_SUPER_THREAD has one argument subthread Thread subthrea
226. _THREAD dt face_t f Node v real NV_VEC omega NV_VEC axis NV_VEC dx real NV_VEC origin NV_VEC rvec real sign int n set deforming flag on adjacent cell zone SET_DEFORMING_THREAD_FLAG THREAD_TO tf sign 5 0 sin 26 178 time Message time f omega f n time sign NV_S omega 0 0 NV_D axis 0 0 1 0 0 0 Fluent Inc September 11 2006 2 203 DEFINE Macros NV_D origin 0 0 0 0 0 152 begin_f_loop f tf f_node_loop f tf n t v F_NODE f tf n update node if x position is greater than 0 02 and that the current node has not been previously visited when looping through previous faces if NODE_X v gt 0 020 amp amp NODE_POS_NEED_UPDATE v indicate that node position has been update so that it s not updated more than once NODE_POS_UPDATED v omega 1 sign pow NODE_X v 0 230 0 5 NV_VV rvec NODE_COORD v origin NV_CROSS dx omega rvec NV_S dx dtime NV_V NODE_COORD v dx J end_f_loop f tf Hooking a DEFINE_GRID_MOTION to FLUENT After the UDF that you have defined using DEFINE_GRID_MOTION is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible in the Dynamic Zones panel in FLUENT See Section 6 5 3 Hooking DEFINE_GRID_MOTION UDFs for details on how
227. _USER_REAL p 0 0 Simple initialization Used later for stopping trajectory calculation DEFINE_DPM_EROSION dpm_accr p t f normal alpha Vmag Mdot real A ND_ND area int num_in_data Thread t0 cell_t cO real radi_pos 2 radius imp_vel 2 vel_ortho 2 1 56 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros The following is ONLY valid for 2d axisymmetric calculations Additional effort is necessary because DPM tracking is done in THREE dimensions for TWO dimensional axisymmetric calculations radi_pos 0 radi_pos 1 p gt state pos 1 Radial location vector p gt state pos 2 Y and Z in O and 1 radius NV_MAG radi_pos NV_VS radi_pos radi_pos radius Normalized radius direction vector imp_vel 0 P_VEL p 0 Axial particle velocity component imp_vel 1 NVD_DOT radi_pos P_VEL p 1 P_VEL p 2 0 Dot product of normalized radius vector and y amp z components of particle velocity vector gives _radial_ particle velocity component vel_ortho NV_DOT imp_vel normal velocity orthogonal to wall if vel_ortho lt MIN_IMPACT_VELO See above MIN_IMPACT_VELO return if UDM_checked We will need some UDMs if check_for_UDM so check for their availability return Using int variable for speed could even just call check_for UDFM
228. _VP_EQUILIBRIUM is interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible and selectable in the Materials panel in FLUENT Note that before you hook the UDF you ll need to create particle injections in the Injections panel with the type Multicomponent chosen See Section 6 4 15 Hooking DEFINE_DPM_VP_EQUILIB UDFs for details on how to hook your DEFINE_DPM_VP_EQUILIB UDF to FLUENT Fluent Inc September 11 2006 2 1 95 DEFINE Macros 2 6 Dynamic Mesh DEFINE Macros This section contains descriptions of DEFINE macros that you can use to define UDFs that control the behavior of a dynamic mesh Note that dynamic mesh UDFS that are defined using DEFINE_CG_MOTION DEFINE_GEOM and DEFINE GRID MOTION can only be executed as compiled UDFs Table 2 6 1 provides a quick reference guide to the dynamic mesh DEFINE macros the functions they define and the panels where they are activated in FLUENT Definitions of each DEFINE macro are contained in the udf h header file For your convenience they are listed in Appendix B e Section 2 6 1 DEFINE_CG_MOTION e Section 2 6 2 DEFINE_GEOM e Section 2 6 3 DEFINE_GRID_MOTION e Section 2 6 4 DEFINE_SDOF_PROPERTIES Table 2 6 1 Quick Reference Guide for Dynamic Mesh Specific DEFINE Macros Function DEFINE Macro Panel Activated In center of gravity motion DEF INE_CG_
229. _dot real p_vapor p_v real dp dp0 source p_vapor MIN 0 195 C_R c t C_K c t 5 0 p_vapor dp p_vapor ABS_P plcl op_pres dpO MAX 0 1 ABS dp source sqrt 2 0 3 0 rhoL c dp0 if dp gt 0 0 m_dot c_evap rhoV c source else m_dot c_con rhoL c source Note that all of the arguments to a DEFINE macro need to be placed on the same line in your source code Splitting the DEFINE statement onto several lines will result in a compilation error Hooking a Cavitation Rate UDF to FLUENT After the UDF that you have defined using DEFINE CAVITATION RATE is interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user_cav_rate will become visible and selectable in the User Defined Function Hooks panel in FLUENT See Section 6 3 1 Hooking DEFINE_CAVITATION_RATE UDFs for de tails Fluent Inc September 11 2006 2 1 21 DEFINE Macros 2 4 2 DEFINE EXCHANGE PROPERTY Description You can use DEFINE EXCHANGE PROPERTY to specify UDFs for some phase interaction variables in multiphase models These include net heat transfer rates between phases and drag and lift coefficient functions Below is a list of user defined functions that can be specified using DEFINE_ EXCHANGE PROPERTY for the multiphase models in FLUENT Note that there are some phase interaction variables such as vaporization pr
230. a grid point face_t is an integer data type that identifies a particular face within a face thread cell_t is an integer data type that identifies a particular cell within a cell thread Thread is a structure data type that stores data that is common to the group of cells or faces that it represents For multiphase applications there is a thread structure for each phase as well as for the mixture See Section 1 10 1 Multiphase specific Data Types for details Domain is a structure data type that stores data associated with a collection of node face and cell threads in a mesh For single phase applications there is only a single domain structure For multiphase applications there are domain structures for each phase the interaction between phases as well as for the mixture The mixture level domain is the highest level structure for a multiphase model See Section 1 10 1 Multiphase specific Data Types for details FA Note that all of the FLUENT data types are case sensitive 1 10 Fluent Inc September 11 2006 1 8 Data Types in FLUENT When you use a UDF in FLUENT your function can access solution variables at individual cells or cell faces in the fluid and boundary zones UDFs need to be passed appropriate arguments such as a thread reference i e pointer to a particular thread and the cell or face ID in order to allow individual cells or faces to be accessed Note that a face ID or cell ID alone does not uniquely identify
231. ace s thread t and i an integer index to the particular face variable that is to be set i is defined by FLUENT when you hook a DEFINE PROFILE UDF to a particular variable e g pressure temperature velocity in a boundary condition panel This index is passed to your UDF by the FLUENT solver so that the function knows which variable to operate on Suppose you want to define a custom inlet boundary pressure profile for your FLUENT case defined by the following equation 2 1 1x 105 0 1 x 10 Y p y 4 j 0 0745 Fluent Inc September 11 2006 3 29 Additional Macros for Writing UDFs You can set the pressure profile using a DEFINE_PROFILE UDF Since a profile is an array of data your UDF will need to create the pressure array by looping over all faces in the boundary zone and for each face set the pressure value using F_PROFILE In the sample UDF source code shown below the y coordinate of the centroid is obtained using F_CENTROID and this value is used in the pressure calculation that is stored for each face The solver passes the UDF the right index to the pressure variable because the UDF is hooked to Gauge Total Pressure in the Pressure Inlet boundary condition panel See Section 2 3 13 DEFINE_PROFILE for more information on DEFINE_PROFILE UDFs DRO OO RR OO A 3K 2K A KA K K 2k 2K 24 FK 24 K 24 2k 24 K FK 2k 2K 2k FK 2k K 2k FK 2k K 2 2K 2 2k 2k 2k 2K K UDF for specifying a parabolic pressure profile boundary p
232. ace Centroids Defined in metric h Macro Argument Types Outputs F_CENTROID x f t real x ND_ND face_t f Thread t x face centroid 3 18 Fluent Inc September 11 2006 3 2 Data Access Macros 1 A co using Right Hand 0 Rule Figure 3 2 1 FLUENT Determination of Face Area Normal Direction 2D Face The ND_ND macro returns 2 or 3 in 2D and 3D cases respectively as defined in Sec tion 3 4 2 The ND Macros Section 2 3 13 DEFINE_PROFILE contains an example of F_CENTROID usage Face Area Vector F_AREA F_AREA can be used to return the real face area vector or face area normal of a given face f in a face thread t See Section 2 7 3 DEFINE_UDS_FLUX for an example UDF that utilizes F_AREA Table 3 2 21 Macro for Face Area Vector Defined in metric h Macro Argument Types Outputs F_AREA A f t ALND_ND face_t f Thread t A area vector By convention in FLUENT boundary face area normals always point out of the domain FLUENT determines the direction of the face area normals for interior faces by applying the right hand rule to the nodes on a face in order of increasing node number This is shown in Figure 3 2 1 FLUENT assigns adjacent cells to an interior face c0 and c1 according to the following convention the cell out of which a face area normal is pointing is designated as cell CO while the cell in to which a face area normal is pointing is cell c1 Fig
233. acked_Particle p int i p int i p p p p p position i 0 1 2 velocity i 0 1 2 diameter temperature density mass liquid fraction wet combusting particles only Table 3 2 30 Macros for Particle Species Laws and User Scalars Defined in dpm h Macro Argument Types Returns P_EVAP_SPECIES_INDEX p P_DEVOL SPECIES INDEX p P_OXID_SPECIES_INDEX p P_PROD_SPECIES_INDEX p P_CURRENT_LAW p P_NEXT_LAW p P_USER_REAL p i Tracked_Particle Tracked_Particle Tracked_Particle Tracked_Particle Tracked_Particle Tracked_Particle Tracked_Particle p p p p p p p evaporating species index in mixture devolatilizing species index in mixture oxidizing species index in mixture combustion products species index in mixture current particle law index next particle law index storage array for user defined values indexed by i Fluent Inc September 11 2006 3 33 Additional Macros for Writing UDFs Table 3 2 31 Macros for Particle Material Properties Defined in dpm h Macro Argument Types Returns P_MATERIAL p DPM_BOILING_TEMPERATURE p m DPM_CHAR_FRACTION p DPM_DIFFUSION_COEFF p t DPM_EMISSIVITY p m DPM EVAPORATION TEMPERATURE p m DPM_HEAT_OF_PYROLYSIS p DPM_HEAT_OF_REACTION p DPM_LATENT_HEAT p DPM LIQUID SPECIFIC HEAT pst DPM_MU p DPM_SCATT_FACTOR p m DPM_SPECIFIC_HEAT p t
234. acros are provided that enable your function to loop over nodes cells and faces in a thread or domain in order to retrieve and or set values Finally data access macros that are specific to a particular model e g DPM NO are presented as well as macros that perform vector time dependent Scheme and I O operations Function definitions for the macros provided in this chapter are contained in header files Header files are identified by the h suffix as in mem h metric h and dpm h and are stored in the source code directory Fluent Inc fluent6 x src The header files unless explicitly noted are included in the udf h file so your UDF does not need to contain a special include compiler directive You must however remember to include the include udf h directive in any UDF that you write Access to data from a FLUENT solver is accomplished by hooking your UDF C function once it is compiled or interpreted to the code through the graphical user interface GUI Once the UDF is correctly hooked the solver s data is passed to the function and is available to use whenever it is called These data are automatically passed by the solver to your UDF as function arguments Note that all solver data regardless of whether they are passed to your UDF by the solver or returned to the solver by the UDF are specified in SI units Macros in this chapter are listed with their arguments argument types returned value s if applicable and head
235. acros defined in Sec tion 3 2 7 DPM Macros to obtain information about particle properties e g injection properties Example See Section 2 5 13 Example for an example of DEFINE_DPM_SOURCE usage 2 1 80 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros Hooking a DPM Source Term UDF to FLUENT After the UDF that you have defined using DEFINE_DPM_SOURCE is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible in the Discrete Phase Model panel in FLUENT See Section 6 4 11 Hooking DEFINE DPM SOURCE UDFs for details on how to hook your DEFINE_DPM_SOURCE UDF to FLUENT Fluent Inc September 11 2006 2 1 81 DEFINE Macros 2 5 12 DEFINE_DPM_SPRAY_COLLIDE Description You can use DEFINE DPM SPRAY COLLIDE to side step the default FLUENT spray collision algorithm When droplets collide they may bounce in which case their velocity changes or they may coalesce in which case their velocity is changed as well as their diameter and number in the DPM parcel A spray collide UDF is called during droplet tracking after every droplet time step and requires that collision is enabled in the DPM panel Usage DEFINE_DPM_SPRAY_COLLIDE name tp p Argument Type Description symbol name UDF name Tracked Particle tp Pointer to the Tracked Particle data structure which cont
236. ad tc tc Lookup_Thread domain fluid_chamber_ID radius RP_Get_Real spark radius vol 0 begin_c_loop_int c tc C_CENTROID xc c tc NV_VV dis xc spark_center if NV_MAG dis lt radius vol C_VOLUME c tc end_c_loop_int c tc vol PRF_GRSUM1 vol begin_c_loop_int c tc Fluent Inc September 11 2006 7 37 Parallel Considerations C_UDMI c tc 1 vol end_c_loop_int c tc DEFINE_SOURCE energy_source c t dS eqn if RP_HOST real xc ND_ND dis ND_ND real source radius vol CA rpm start_CA rpm RP_Get_Real dynamesh in cyn crank rpm start_CA RP_Get_Real spark start ca CA rpm CURRENT_TIME 6 RP_Get_Real dynamesh in cyn crank start angle if CA gt start_CA amp amp CA lt start_CA RP_Get_Real spark duration rpm 6 radius RP_Get_Real spark radius vol C_UDMI c t 1 C_CENTROID xc c t NV_VV dis xc spark_center if NV_MAG dis lt radius source RP_Get_Real spark energy RP_Get_Real spark duration vol return source else return 0 else return 0 endif 7 38 Fluent Inc September 11 2006 7 7 Process Identification il Interpreted UDFs cannot be used while running in parallel with an Infini band interconnect The compiled UDF approach should be used in this case 7 7 Process Identification Each process in parallel FLUENT has a un
237. ad t int i laminar species int j diffusivity C_DIFF_EFF c t i cell_t c Thread t int i effective species diffusivity Table 3 2 15 Macros for Thermodynamic Properties Defined in mem h Name Arguments Argument Types Returns CCP Cet cell t c Thread t specific heat C_RGAS c t cellt c Thread t universal gas constant molecular weight C_NUT c t cell_t c Thread t turbulent viscosity for Spalart Allmaras Fluent Inc September 11 2006 3 15 Additional Macros for Writing UDFs Table 3 2 16 Additional Material Property Macros Defined in sg mem h Macro Argument Types Returns C_FMEAN c t cell t c Thread t primary mean mixture fraction C_FMEAN2 c t cell_t c Thread t secondary mean mixture fraction C_FVAR c t cell t c Thread t primary mixture fraction variance C_FVAR2 c t cell_t c Thread t secondary mixture fraction variance C_PREMIXC c t cell_t c Thread t reaction progress variable C LAM FLAME SPEED c t cell t c Thread t laminar flame speed C_SCAT_COEFF c t cell_t c Thread t scattering coefficient C_ABS COEFF c t cell t c Thread t absorption coefficient C_CRITICAL_STRAIN_ cell_t c Thread t critical strain rate RATE Cc t C_LIQF c t cell t c Thread t liquid fraction in a cell C POLLUT c t i cell t c Thread t int i ith pollutant species mass fraction see table below il C_LIQF is available only in fluid cells and only if
238. ader file Consequently before you can interpret a UDF source file udf h will need to be accessible in your path or saved locally within your working directory The location of the udf h file is path Fluent Inc fluent 6 src udf h where path is the directory in which you have installed the release directory Fluent Inc and x is replaced by the appropriate number for the release you have e g 2 for fluent6 2 EH In general you should not copy udf h from the installation area The compiler is designed to look for this file locally in your current directory first If it is not found in your current directory the compiler will look in the src directory automatically In the event that you upgrade your release area but do not remove an old copy of udf h from your working directory you will not be accessing the most recent version of this file FA You should not under any circumstances alter the udf h file 4 1 2 Limitations Due to limitations in the interpreter used to compile interpreted UDF source code in FLUENT interpreted UDFs are limited in their use of the C programming language In particular the following elements of C cannot be used in interpreted UDFs e goto statements e non ANSI C prototypes for syntax e direct data structure references e declarations of local structures e unions e pointers to functions e arrays of functions e multi dimensional arrays Fluent Inc September 11 2006 4 2
239. ag coefficient 2 151 emissivity UDF 2 172 equilibrium vapor pressure UDF 2 193 erosion and accretion rate 2 153 injection initialization 2 162 law UDFs for DPM 2 166 location 2 162 material property UDFs 2 172 reaction rate UDFs 2 52 sampling output UDF 2 168 scalar update UDFs 2 176 scattering factor UDF 2 172 source term UDF 2 180 source terms 2 180 spray collide UDFs 2 182 surface tension UDF 2 172 switching law UDFs 2 185 time step control UDF 2 190 velocity 2 162 viscosity UDF 2 172 particle or droplet diameter 2 80 partitioned grid terms 7 7 partitions 7 1 Index 12 phase domain subdomain pointer 3 59 phase domain index 3 62 Phase Interaction panel 6 48 6 50 6 52 phase thread subthread pointer 3 60 phase level threads 1 17 3 61 PHASE_DOMAIN_INDEX 3 56 3 57 3 59 3 62 phase_domain_index 1 18 3 60 3 62 pointer array 3 56 3 61 pointers 1 11 A 9 domain 1 11 phase domain 3 60 3 62 phase thread 3 60 thread 1 11 POLLUT EQN 3 35 3 36 POLLUT_EQN Pollut_Par 3 35 3 36 POLLUT_FRATE 3 35 3 36 POLLUT_RRATE 3 35 3 36 postprocessing UDF example 8 43 postprocessing UDF parallel 7 44 Prandtl number UDFs specific dissipation 2 62 temperature equation diffusion term 2 63 thermal wall function 2 64 turbulence kinetic energy 2 59 turbulent dissipation 2 58 predicates parallel UDFs 7 18 premixed combustion model UDFs source term 2 105 turbulent flame speed 2 105 PRF
240. age variable Fluent Inc September 11 2006 3 75 Additional Macros for Writing UDFs MPI The macro M_PI returns the value of r UNIVERSAL_GAS_CONSTANT UNIVERSAL_GAS_CONSTANT returns the value of the universal gas constant 8314 34 J Kmol K EA Note that this constant is not expressed in SI units See Section 2 3 22 DEFINE_VR_RATE for an example UDF that utilizes UNIVERSAL_GAS_CONSTANT SQR k SQR k returns the square of the given variable k or k x k 3 76 Fluent Inc September 11 2006 Chapter 4 Interpreting UDFs Once you have written your UDF using any text editor and have saved the source code file it with a c extension in your working directory you are ready to interpret the source file Follow the instructions below in Section 4 2 Interpreting a UDF Source File Using the Interpreted UDFs Panel Once interpreted the UDF function name s that you supplied in the DEFINE macro s will appear in drop down lists in graphical panels in FLUENT ready for you to hook to your CFD model Alternatively if you wish to compile your UDF source file see Chapter 5 Compiling UDFs for details Section 4 1 Introduction Section 4 2 Interpreting a UDF Source File Using the Interpreted UDFs Panel Section 4 3 Common Errors Made While Interpreting A Source File Section 4 4 Special Considerations for Parallel FLUENT 4 1 Introduction An interpreted UDF is a function that is interpreted directly from a source
241. ail FALSE real ash_mass P_INIT_MASS p 1 DPM_CHAR_FRACTION p DPM_VOLATILE_FRACTION p real one_minus_conv MAX O P_MASS p ash_mass P_INIT_MASS p DPM_CHAR_FRACTION p Fluent Inc September 11 2006 2 55 DEFINE Macros real ruser 3 int iuser 1 cxboolean buser 1 char cuser 30 real ratemin ratemax root ruser 0 ppldif_i ruser 1 MAX 1 E 15 c1 pow 0 5 P_T p C_T c t 0 75 P_DIAM p ruser 2 Al exp E1 UNIVERSAL_GAS_CONSTANT P_T p strcpy cuser reaction 2 ratemin 0 ratemax ruser 1 pp dif_il arguments for auxiliary function zbrent_pr_rate root zbrent_pr_rate reaction_rate ruser iuser buser cuser ratemin ratemax tolerance amp ifail if ifail root MAX 1 E 15 ruser 1 rr root P_DIAM p P_DIAM p M_PI sf 0 one_minus_conv Message Fail status d n ifail Message Reaction rate for reaction s g n cuser rr In this example a real function named reaction_rate is defined at the top of the UDF The arguments of reaction_rate are real rate and the pointer arrays real ruser integer iuser cxboolean buser and char cuser which must be declared and defined in the main body of the DEFINE PR RATE function Typically if the particle surface reaction rate is described by rate f ruser iuser rate then the real function in this example reaction_rate should return f ruser iuser rate rate 2 5
242. ains data related to the particle being tracked Particle p Pointer to the Particle data structure where particles p are stored in a linked list Function returns void There are three arguments to DEFINE_DPM_SPRAY_COLLIDE name tp and p You supply name the name of the UDF tp and p are variables that are passed by the FLUENT solver to your UDF When collision is enabled this linked list is ordered by the cell that the particle is currently in As particles from this linked list are tracked they are copied from the particle list into a Tracked_Particle structure 2 1 82 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros Example The following UDF named man_spray_collide is a simple and non physical exam ple that demonstrates the usage of DEFINE_SPRAY_COLLIDE The droplet diameters are assumed to relax to their initial diameter over a specified time t_relax The droplet velocity is also assumed to relax to the mean velocity of all droplets in the cell over the same time scale peaa oo o kkk k kkk kk kk kkk kk kkk kkk kkk DPM Spray Collide Example UDF BOO ooo o kkk k k kkk kk kkk kkk include udf h include dpm h include surf h DEFINE_DPM_SPRAY_COLLIDE man_spray_collide tp p non physical collision UDF that relaxes the particle velocity and diameter in a cell to the mean over the specified time scale t_relax const real t_relax 0 001 seconds get
243. al source source total_source volume return source Fluent Inc September 11 2006 A 5 Variables A 5 3 Static Variables The static operator has different effects depending on whether it is applied to local or global variables When a local variable is declared as static the variable is prevented from being destroyed when a function returns from a call In other words the value of the variable is preserved When a global variable is declared as static the variable is file global It can be used by any function within the source file in which it is declared but is prevented from being used outside the file even if is declared as external Functions can also be declared as static A static function is visible only to the source file in which it is defined static variables and functions can be declared only in compiled UDF source files Example Static Global Variable mysource c include udf h static real abs_coeff 1 0 static global variable used by both functions in this source file but is not visible to the outside DEFINE_SOURCE energy_source c t dS eqn real source local variable int Pi local variable value is not preserved when function returns dS eqn 16 abs_coeff SIGMA _SBC pow C_T c t 3 source abs_coeff 4 SIGMA_SBC pow C_T c t 4 C_UDSI c t P1 return source DEFINE_SOURCE p1_source c t dS eqn real source in
244. ame fluid Material Name liquid metal Edit Porous Zone M Source Terms l Fixed Values Motion Porous Zone Reaction Source Terms Fixed Values Mass kgim3 s 9 sources Edit X Momentum n m3 1 source Edit Y Momentum n m3 a sources Edit Energy wlm3 6 sources Edit Figure 8 2 9 The Fluid Panel 2 90e 02 2 89e 02 2 87e 02 2 86e 02 2 84e 02 2 83e 02 2 81e 02 2 80e 02 2 78e 02 2 77e 02 2 75e 02 Contours of Static Temperature k Source Term Application Figure 8 2 10 Temperature Contours Illustrating Liquid Metal Cooling 8 30 Fluent Inc September 11 2006 8 2 Detailed UDF Examples 2 13e 03 1 92e 03 1 70e 03 1 49e 03 1 28e 03 1 06e 03 8 51e 04 6 38e 04 4 26e 04 2 13e 04 0 00e 00 Contours of Velocity Magnitude m s Source Term Application Figure 8 2 11 Velocity Magnitude Contours Suggesting Solidification 8 00e 00 7 20e 00 6 40e 00 5 60e 00 4 80e 00 4 00e 00 3 20e 00 2 40e 00 1 60e 00 8 00e 01 0 00e 00 Contours of Stream Function kg s Source Term Application Figure 8 2 12 Stream Function Contours Suggesting Solidification Fluent Inc September 11 2006 8 31 Examples 8 2 3 Physical Properties This section contains an application of a ph
245. ame passed in variables where the first argument in the parentheses is the name of the UDF that you supply Name arguments are case sensitive and must be specified in lowercase The name that you choose for your UDF will become visible and selectable in drop down lists in graphical user interface panels in FLUENT once the function has been interpreted or compiled The second set of input arguments to the DEFINE macro are variables that are passed into your function from the FLUENT solver For example the macro DEFINE_PROFILE inlet_x_velocity thread index defines a boundary profile function named inlet_x_velocity with two variables thread and index that are passed into the function from FLUENT These passed in variables are the boundary condition zone ID as a pointer to the thread and the index identifying the variable that is to be stored Once the UDF has been interpreted or compiled its name e g inlet_x_velocity will become visible and selectable in drop down lists in the appropriate boundary condition panel e g Velocity Inlet in FLUENT Note that all of the arguments to a DEFINE macro need to be placed on the same line in your source code Splitting the DEFINE statement onto several lines will result in a compilation error Do not include a DEFINE macro statement e g DEFINE PROFILE within a comment in your source code This will cause a compilation error Fluent Inc September 11 2006 1 4 Defining Your UDF Usin
246. amp float_b Message Function CCMPLX returns Complex Number Fluent Inc September 11 2006 5 21 Compiling UDFs Che Fei Va er 21 qcmplx_ amp qz amp a amp float_b Message Function QCMPLX returns Complex Number he hej n qz r qz i 3 The makefile is then modified to specify the UDF C source file test_use c and the external object file test o as shown below fo re User modifiable section fo re SOURCES test_use c FLUENT_INC usr local Fluent Inc Precompiled User Object files for example o files from f sources USER_OBJECTS test o 4 Finally the Makefile is executed by issuing the following command in the libudf directory make FLUENT_ARCH ultra UNIX and Linux Systems 1 Follow the procedure for setting up the directory structure described in Section 5 3 1 Set Up the Directory Structure 2 Copy your precompiled object files e g myobjecti o myobject2 0 to all of the architecture version directories you created in Step 1 e g ultra 2d and ultra 3d il The object files should be compiled using similar flags to those used for FLUENT Common flags used by FLUENT are KPIC 0 and ansi which often have equivalents such as fpic 03 and xansi 3 Using a text editor edit the file makefile in your src directory to set the following three parameters SOURCES FLUENT_INC and USER OBJECTS 5 22 Fluent Inc September 11 2006 5 4 Link Precompiled Object Fil
247. an structure using DEFINE_RW_FILE It is often useful to save dynamic information e g number of occurrences in conditional sampling while your solution is being calculated which is another use of this function Note that the read order and the write order must be the same when you use this function Usage DEFINE_RW_FILE name fp Argument Type Description symbol name UDF name FILE fp Pointer to the file you are reading or writing Function returns void There are two arguments to DEFINE_RW_FILE name and fp You supply name the name of the UDF fp is passed from the solver to the UDF DEFINE_RW_FILE cannot be used in UDFs that are executed on Windows systems Example The following C source code listing contains examples of functions that write information to a data file and read it back These functions are concatenated into a single source file that can be interpreted or compiled in FLUENT LR HRK CTT HEROK CCCP HEROK HRK HRK IR RERO ER KR EEK UDFs that increment a variable write it to a data file and read it back in FOR ER aK a 32k 2 HER 2k 2k a ok 2k 2 ok 2k 2k ak ak include udf h int kount 0 define global variable kount 2 24 Fluent Inc September 11 2006 2 2 General Purpose DEF INE Macros DEFINE_ADJUST demo_calc d kount printf kount d n kount DEFINE_RW_FILE writer fp printf Writing UDF data to data file n fprintf fp d kount write out kount t
248. an example of F_UDSI usage Table 3 2 35 Accessing User Defined Scalar Face Variables mem h Macro Argument Types Returns FUDSICE 6 1 face t f Thread t int i UDS face variables Note i is index of scalar HI Note that F_UDSI is available for wall and flow boundary faces only If a UDS attempts to access any other face zone then an error will result C_UDSI You can use C_UDSI when you want to access cell variables that are computed for user defined scalar transport equations Macros for accessing UDS cell variables are listed in Table 3 2 36 Some examples of usage for these macros include defining non constant source terms for UDS transport equations and initializing equations See Sec tion 3 2 9 Example UDF that Utilizes UDM and UDS Variables for an example of C_UDSI usage Table 3 2 36 C_UDSI for Accessing UDS Transport Cell Variables mem h Macro Argument Types Returns C UDSI c t i cell t c Thread t int i UDS cell variables C UDSI G c t i cell t c Thread t int i UDS gradient C_UDSI_M1 c t i cell_t c Thread t int i UDS previous time step C_UDSI_M2 c t i cell_t c Thread t int i UDS second previous time step C_UDSI_DIFF c t i cell_t c Thread t int i UDS diffusivity Note i is index of scalar Fluent Inc September 11 2006 3 39 Additional Macros for Writing UDFs Reserving UDS Variables Reserve User Scalar Vars The new capability of l
249. and e interpreted or compiled using methods described in Chapters 4 or 5 respectively 6 4 1 Hooking DEFINE_DPM_BC UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_BC UDF the name of the function you supplied as a DE FINE macro argument will become visible and selectable in the appropriate boundary condition panel Figure 6 4 1 in FLUENT Define Boundary Conditions Suppose that your UDF defines a particle velocity boundary condition at a wall To hook the UDF to FLUENT first open the Wall boundary condition panel and select the DPM tab Figure 6 4 1 Then choose user_defined as Boundary Cond Type under Discrete Phase Model Conditions This will expand the panel to allow you to choose the function name e g user_dpm_bc from the Boundary Cond Function drop down list Figure 6 4 1 Click OK See Section 2 5 1 DEFINE DPM BC for details about DEFINE DPM BC functions Fluent Inc September 11 2006 6 53 Hooking UDFs to FLUENT Wall wall bottom Figure 6 4 1 The Wall Panel 6 54 Fluent Inc September 11 2006 6 4 Hooking Discrete Phase Model DPM UDFs 6 4 2 Hooking DEFINE_DPM_BODY_FORCE UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_BODY_FORCE UDF the name of the function you supplied as a DEFINE macro argument will become visible and selec
250. ari ables that are passed by the FLUENT solver to your function A DEFINE_SOX_RATE func tion does not output a value The calculated SO2 rates or other pollutant species rates are returned through the Pollut structure as the forward rate Pollut gt fluct fwdrate and reverse rate Pollut gt fluct revrate respectively 2 96 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros i The data contained within the SO structure is specific only to the SO model Alternatively the Pollut structure contains data at each cell that are useful for all pollutant species e g forward and reverse rates gas phase temperature density The Pollut Par structure contains auxiliary data common for all pollutant species e g equation solved universal gas con stant species molecular weights Note that molecular weights extracted from the Pollut Par structure i e Pollut _Par gt sp IDX i mw for pol lutant species and Pollut_Par gt sp i mw for other species such as O2 has units of kg kg mol The reverse rate calculated by user must be di vided by the respective species mass fraction in order to be consistent with the FLUENT 6 3 implementation prior versions of FLUENT used explicit division by species mass fraction internally Example The following compiled UDF named user_sox computes the rates for SO and SO formation according to the reaction given in Equation 2 3 8 Note that this UDF will replace the FLUENT rate only i
251. ariable argument e g DEFINE ADJUST and your UDF is hooked to the mixture If mixture_domain is not explicitly passed to your UDF you will need to use another utility macro to retrieve it e g Get_Domain 1 before calling sub_domain_loop see Section 3 2 6 Domain Pointer Get_Domain phase_domain_index is an index of subdomain pointers phase domain index is O for the primary phase and is incre mented by one for each secondary phase in the mixture Note that subdomain and phase_domain_index are set within the sub_domain_loop macro Example The following interpreted UDF patches an initial volume fraction for a particular phase in a solution It is executed once at the beginning of the solution process The function sets up a spherical volume centered at 0 5 0 5 0 5 with a radius of 0 25 A secondary phase volume fraction of 1 is then patched to the cells within the spherical volume while the volume fraction for the secondary phase in all other cells is set to 0 3 54 Fluent Inc September 11 2006 3 3 Looping Macros DOR OO OC OG 2K 2K K 2K 2K K I RAK 2K 2K FK FK 2k K 2k 2K 2k K FK 26 2k K FK UDF for initializing phase volume fraction BER ooo OO DH A 21 21 1 1 KK KK kkk k kkk kkk kk k kkk include udf h domain pointer that is passed by INIT function is mixture domain DEFINE_INIT my_init_function mixture_domain int phase_domain_index cell_t cell Thread cell_thread Domain subdomain real xc ND
252. ary faces In other words although each face can appear on one or two partitions it can only officially belong to one of them The boolean macro PRINCIPAL FACE P f t returns TRUE if the face f is a principal face on the current compute node PRINCIPAL FACE P You can use PRINCIPAL FACE _P to test whether a given face is the principal face before including it in a face loop summation In the sample source code below the area of a face is added to the total area only if it is the principal face Note that PRINCIPAL_FACE_P is always TRUE for the serial version FA PRINCIPAL FACE_P can be used only in compiled UDFs Example begin_f_loop f t if PRINCIPAL_FACE_P f t tests if the face is the principle face FOR COMPILED UDFs ONLY F_AREA area f t computes area of each face total_area NV_MAG area computes total face area by accumulating magnitude of each face s area end_f_loop f t Fluent Inc September 11 2006 7 9 Parallel Considerations THREAD_N_ELEMENTS_EXT THREAD_N_ELEMENTS_INT Data Array for pressure on thread C_P c t THREAD_N_ELEMENTS Figure 7 2 3 Exterior Thread Data Storage at End of a Thread Array Exterior Thread Storage Each thread stores the data associated with its cells or faces in a set of arrays For example pressure is stored in an array and the pressure for cell c is obtained by accessing element c of that array Storage for exterior cell and face d
253. ary phase s mixture Wall species mass fraction shear stress components moving velocity components heat flux temperature heat generation rate heat transfer coefficient external emissivity external radiation temperature free stream temperature granular flux granular temperature user defined scalar boundary value discrete phase boundary value DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE DPM_BC mixture primary and secondary phase s mixture mixture mixture mixture mixture mixture mixture mixture secondary phase s secondary phase s mixture mixture Material Properties granular diameter granular viscosity granular bulk viscosity granular frictional viscosity granular conductivity granular solids pressure granular radial distribution granular elasticity modulus turbulent viscosity DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE TURBULENT_ VISCOSITY secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s mixture primary and secondary phase s Fluent Inc September 11 2006 C 5 Eulerian Model Dispersed Turbule
254. ary will reside for each of the versions of FLUENT you wish to run e g 2d 3d You will then modify the file named makefile to setup source file parameters Subsequently you will execute the Makefile which compiles the source file and builds the shared library from the resulting object files Finally you will load the UDF library into FLUENT Using the TUI option allows you the added advantage of building a shared library for precompiled object file s that are derived from non FLUENT sources e g o objects from f sources See Section 5 4 Link Precompiled Object Files From Non FLUENT Sources for details i Note that if you are running serial or parallel FLUENT on a Windows system then you must have Microsoft Visual Studio installed on your ma chine and have launched FLUENT from the Visual Studio console window to compile a UDF 5 3 1 Set Up the Directory Structure The directory structures for UNIX and Windows systems are different so the procedure for setting up the directory structure is described separately for each Windows Systems For compiled UDFs on Windows systems two Fluent Inc files are required to build your shared UDF library makefile nt udf and user_nt udf The file user nt udf has a user modifiable section that allows you to specify source file parameters The procedure below outlines steps that you need to follow in order to set up the directory structure required for the shared library 1 In your working d
255. at the first iteration of a timestep Since the adjust UDF is also called before timestepping begins the two methods vary slightly as to when they are true You must decide which behavior is more appropriate for your case 3 70 Fluent Inc September 11 2006 3 6 Scheme Macros 3 6 Scheme Macros The text interface of FLUENT executes a Scheme interpreter which allows you to define your own variables that can be stored in FLUENT and accessed via a UDF This capability can be very useful for example if you want to alter certain parameters in your case and you do not want to recompile your UDF each time Suppose you want to apply a UDF to multiple zones in a grid You can do this manually by accessing a particular Zone ID in the graphical user interface hardcoding the integer ID in your UDF and then recompiling the UDF This can be a tedious process if you want to apply the UDF toa number of zones By defining your own scheme variable if you want to alter the variable later then you can do it from the text interface using a Scheme command Macros that are used to define and access user specified Scheme variables from the text interface are identified by the prefix rp e g rp var define Macros that are used to access user defined Scheme variables in a FLUENT solver are identified by the prefix RP e g RP_Get_Real These macros are executed within UDFs 3 6 1 Defining a Scheme Variable in the Text Interface To define a scheme
256. at the pressure gradient macro C_DP is now obsolete A more current pressure gradient macro can be found in Table 3 2 4 Hooking a Vector Exchange Property UDF to FLUENT After the UDF that you have defined using DEFINE_VECTOR_EXCHANGE_PROPERTY is in terpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g custom slip will become visible and selectable in the Phase Interaction panel in FLU ENT See Section 6 3 5 Hooking DEFINE_VECTOR_EXCHANGE PROPERTY UDFs for details 2 138 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros 2 5 Discrete Phase Model DPM DEFINE Macros This section contains descriptions of DEFINE macros for the discrete phase model DPM Table 2 5 1 provides a quick reference guide to the DPM DEFINE macros the functions they define and the panels where they are activated in FLUENT Definitions of each DEFINE macro are contained in the udf h header file For your convenience they are listed in Appendix B e Section 2 5 1 e Section 2 5 2 e Section 2 5 3 e Section 2 5 4 e Section 2 5 5 e Section 2 5 6 e Section 2 5 7 e Section 2 5 8 e Section 2 5 9 e Section 2 5 10 e Section 2 5 11 e Section 2 5 12 e Section 2 5 13 e Section 2 5 14 e Section 2 5 15 DEF INE_DPM_BC DEFINE DPM BODY FORCE DEFINE DPM DRAG DEF INE_DPM_EROSION DEF INE_DPM_HEAT_MASS
257. ata occurs at the end of every thread data array as shown in Figure 7 2 3 7 10 Fluent Inc September 11 2006 7 3 Parallelizing Your Serial UDF 7 3 Parallelizing Your Serial UDF FLUENT s serial solver contains Cortex and only a single FLUENT process The parallel solver on the other hand contains three types of executable Cortex host and compute node or simply node for short When FLUENT runs in parallel an instance of Cortex starts followed by one host and n compute nodes thereby giving a total of n 2 running processes For this reason when you are running in parallel you will need to make sure that your function will successfully execute as a host and a node process At first it may appear that you should write three different versions of your UDF one for serial host and node Good programming practice however would suggest that you write a single UDF that when compiled can execute on any of the three versions This process is referred to in this manual as parallelizing your serial UDF You can do this by adding special macros for parallel as well as compiler directives to your UDF as described below Compiler directives e g if RP_NODE RP_HOST PARALLEL and their negated forms direct the compiler to include only portions of the function that apply to a particular process and ignore the rest see Section 7 5 1 Compiler Directives A general rule of thumb is that your serial UDF needs to be
258. ates Model real n_a Refractive index of medium a real n_b Refractive index of medium b real ray_direction Direction vector s defined in Equation 13 3 55 in the User s Guide real en Interface normal vector n defined in Equation 13 3 55 in the User s Guide int internal_reflection Variable used to flag the code that total internal reflection has occurred real specular_reflectivity Specular reflectivity for the given direction s real specular transmissivity Specular transmissivity for the given direction s Function returns void 2 40 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros There are eleven arguments to DEFINE_DOM_SPECULAR_REFLECTIVITY name f t nband n_a nb ray direction en internal_reflection specular_reflectivity and specular_transmissivity You supply name the name of the UDF f t nband n_a n_b ray direction en internal reflection specular reflectivity and specular_transmissivity are variables that are passed by the FLUENT solver to your UDF Example In the following UDF named user_dom_spec_ref1l specular reflectivity and transmis sivity values are altered for a given ray direction s at face f UDF to alter the specular reflectivity and transmissivity at semi transparent walls along direction s at face f include udf h DEFINE_DOM_SPECULAR_REFLECTIVITY user_dom_spec_refl f t nband n_a n_b ray_direction en internal_reflection specular_reflectivit
259. be looped over with c_face_loop The macro is defined in mem h Table 3 2 7 Macro for Cell Face Index Defined in mem h Macro Argument Types Returns C_FACE_THREAD cell_t c Thread t int i Thread t of face_t f returned by C_FACE 3 8 Fluent Inc September 11 2006 3 2 Data Access Macros Flow Variable Macros for Cells You can access flow variables using macros listed in Table 3 2 8 Table 3 2 8 Macros for Cell Flow Variables Defined in mem h Macro Argument Types Returns CR c t cell_t c Thread t density C_P c t cell_t c Thread t pressure CU c t cell t c Thread t u velocity CVCc t cell t c Thread t v velocity C_W c t cell_t c Thread t w velocity CT c t cell_t c Thread t temperature CH c t cellt c Thread t enthalpy CK c t cell t c Thread t turb kinetic energy C_NUT c t cell t c Thread t turbulent viscosity for Spalart Allmaras CD c t cell_t c Thread t turb kinetic energy dissipation rate C 0 c t cell t c Thread t specific dissipation rate C YI c t i cell_t c Thread t int i species mass fraction note int i is species index Gradient G and Reconstruction Gradient RG Vector Macros You can access gradient and reconstruction gradient vectors and components for many of the cell variables listed in Table 3 2 8 FLUENT calculates the gradient of flow in a cell based on the divergence theory and stores this value in the variabl
260. ber 11 2006 7 3 Parallel Considerations 7 1 1 Command Transfer and Communication The processes that are involved in a FLUENT session running in parallel are defined by Cortex a host process and a set of n compute node processes referred to as compute nodes with compute nodes being labeled from 0 to n 1 Figure 7 1 4 The host receives commands from Cortex and passes commands to compute node 0 Compute node 0 in turn sends commands to the other compute nodes All compute nodes except 0 receive commands from compute node 0 Before the compute nodes pass messages to the host via compute node 0 they synchronize with each other Figure 7 1 4 shows the relationship of processes in parallel FLUENT Each compute node is virtually connected to every other compute node and relies on its communicator to perform such functions as sending and receiving arrays synchro nizing performing global reductions such as summations over all cells and establishing machine connectivity A FLUENT communicator is a message passing library For ex ample it could be a vendor implementation of the Message Passing Interface MPI standard as depicted in Figure 7 1 4 All of the parallel FLUENT processes as well as the serial process are identified by a unique integer ID The host process is assigned the ID node_host 999999 The host collects messages from compute node 0 and performs operation such as printing displaying messages and
261. ble value if the node is compute node 0 and the function is compiled as a node version e do nothing if the function is compiled as a node version but the node is not compute node 0 e receive and set variables if the function is compiled as the host version e do nothing for the serial version Fluent Inc September 11 2006 7 17 Parallel Considerations The most common usage for this set of macros is to pass global reduction results from compute node 0 to the host process In cases where the value that is to be passed is computed by all of the compute nodes there must be some sort of collection such as a summation of the data from all the compute nodes onto compute node 0 before the single collected summed value can be sent Refer to the example UDF in Section 7 8 Parallel UDF Example for a demonstration of usage and Section 7 5 4 Global Reduction Macros for a full list of global reduction operations 7 5 3 Predicates There are a number of macros available in parallel FLUENT that expand to logical tests These logical macros referred to as predicates are denoted by the suffix P and can be used as test conditions in your UDF The following predicates return TRUE if the condition in the parenthesis is met predicate definitions from para h header file define MULTIPLE_COMPUTE_NODE_P compute_node_count gt 1 define ONE_COMPUTE_NODE_P compute_node_count 1 define ZERO_COMPUTE_NODE_P compute_node_coun
262. bout DEFINE DPM SWITCH functions 6 68 Fluent Inc September 11 2006 6 4 Hooking Discrete Phase Model DPM UDFs 6 4 14 Hooking DEFINE_DPM_TIMESTEP UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_TIMESTEP UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Discrete Phase Model panel under the UDF tab for DPM Timestep Figure 6 4 15 Define Models Discrete Phase Discrete Phase Model Interaction Particle Treatment M Interaction with Continuous Phase Unsteady Particle Tracking l Update DPM Sources Every Flow Iteration oo Number of Continuous Phase 2 99 Iterations per DPM Iteration Tracking Physical Models UDF Numerics Parallel User Defined Functions User Variables Body Force none Number of Scalars e E Scalar Update jones Source none DPM Time Step dpm_timestep libudt OK Injections Cancel Help Figure 6 4 15 The Discrete Phase Model Panel To hook the UDF to FLUENT choose the function name e g dpm timestep in the DPM Time Step drop down list under the UDF tab Figure 6 4 15 and click OK See Section 2 5 14 DEFINE DPM TIMESTEP for details about DEFINE DPM TIMESTEP func tions Fluent Inc September 11 2006 6 69 Hooking UDFs to FLUENT 6 4 15 Hooking DEFINE_DPM_VP_EQUILIB UDFs Once you have
263. budf Figure 6 2 9 The User Defined Function Hooks Panel i The Energy Equation must be enabled To hook the UDF to FLUENT simply choose the function name e g user_heat_flux in the Wall Heat Flux drop down list in the User Defined Function Hooks panel and click OK See Section 2 3 8 DEFINE_HEAT_FLUX for details about DEFINE_HEAT_FLUX functions Fluent Inc September 11 2006 6 23 Hooking UDFs to FLUENT 6 2 9 Hooking DEFINE_NET_REACTION_RATE UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_NET_REACTION_RATE UDF the name of the function you sup plied as a DEFINE macro argument will become visible and selectable in the User Defined Function Hooks panel Figure 6 2 10 in FLUENT Define User Defined Function Hooks User Defined Function Hooks Initialization none Edit Adjust none Edit Execute at End none Edit Read Case one Edit Write Case none Edit Read Data none Edit Write Data none Edit Execute at Exit none Edit Wall Heat Flux none Net Reaction Rate Particle Reaction Rate mone Chemistry Step mone Mixing Model Constant Cphi none tits Figure 6 2 10 The User Defined Function Hooks Panel 6 24 Fluent Inc September 11 2006 6 2 Hooking Model Specific UDFs i Net reaction rate UDFs may be used for the EDC and PDF Transport models as well as f
264. builds a shared library e g libudf with the object files If you compile your source file using the GUI this compile build process is executed when you click the Build pushbutton in the Compiled UDFs panel The shared library that you name e g Libudf is automatically built for the architecture and version of FLUENT you are running during that session e g hpux11 2d and will store the UDF object file s If you compile your source file using the TUI you will first need to setup target directories for the shared libraries modify a file named makefile to specify source parameters and then execute the Makefile which directs the compile build process Compiling a UDF using the TUI has the added advantage of allowing precompiled object files derived from non FLUENT sources to be linked to FLUENT Section 5 4 Link Precompiled Object Files From Non FLUENT Sources This option is not available using the GUI Once the shared library is built using the TUI or GUI you will need to load the UDF library into FLUENT before you can use it This can be done using the Load pushbutton in the Compiled UDFs panel Once loaded all of the compiled UDFs that are contained within the shared library will become visible and selectable in graphics panels in FLUENT Note that compiled UDFs are displayed in FLUENT panels with the associated UDF library name separated by two colons For example a compiled UDF named rrate that is associated with a shared
265. c t C_UDSI c t MAG_GRAD_T4 NV_MAG C_UDSI_G c t T4 end_c_loop c t 8 44 Fluent Inc September 11 2006 8 2 Detailed UDF Examples thread_loop_f t domain if NULL THREAD_STORAGE t SV_UDS_I T4 amp amp NULL T_STORAGE_R_NV t gt t0 SV_UDSI_G T4 begin_f_loop f t F_UDSI f t MAG_GRAD_T4 C_UDSI F_CO f t t gt t0 MAG_GRAD_T4 end_f_loop f t The conditional statement if NULL THREAD_STORAGE t SV_UDS_I T4 is used to check if the storage for the user defined scalar with index T4 has been allocated while NULL T_STORAGE_R_NV t SV_UDSI_G T4 checks whether the storage of the gradient of the user defined scalar with index T4 has been allocated In addition to compiling this UDF as described in Chapter 5 Compiling UDFs you will need to enable the solution of a user defined scalar transport equation in FLUENT Define User Defined Scalars Refer to Section 9 3 User Defined Scalar UDS Transport Equations of the User s Guide for UDS equation theory and details on how to setup scalar equations Fluent Inc September 11 2006 8 45 Examples Implementing FLUENT s P 1 Radiation Model Using User Defined Scalars This section provides an example that demonstrates how the P1 radiation model can be implemented as a UDF utilizing a user defined scalar transport equation In the P1 model the variation of the incident radiation G in the do
266. cal solution for the overall particle reaction rate It uses Brent s method to find the root of a function known to lie between x1 and x72 The root will be refined until its accuracy has reached tolerance tol This is demonstrated in Example 2 Auxiliary function zbrent_pr_rate real func real real int cxboolean char real ruser int iuser cxboolean buser char cuser real x1 real x2 real tol cxboolean ifail Auxiliary function returns real Example 1 The following UDF named user_pr_rate specifies a particle reaction rate given by Equation 14 3 9 of the User s Guide where the effectiveness factor 7 is defined as ls where x is the fractional conversion of the particle char mass In this case the UDF will be applied to all surface particle reactions defined in the FLUENT model Fluent Inc September 11 2006 2 53 DEFINE Macros UDF of specifying the surface reaction rate of a particle include udf h define A1 0 002 define El 7 9e7 DEFINE_PR_RATE user_pr_rate c t r mw pp p sf dif_i cat_i rr Argument types cell_t c Thread t Reaction r reaction structure real mw species molecular weight real pp gas partial pressures Tracked_Particle p particle structure real sf current mass fractions of solid species in particle char mass int dif_i index of diffusion controlled species int cat_i index of catalyst species real rr rate of reaction kg s
267. can be used as an argument to the macros defined in Sec tion 3 2 7 DPM Macros to obtain information about particle properties e g injection properties Example The following UDF named particle_body_force computes the magnetic force on a charged particle DEFINE_DPM_BODY_FORCE is called at every particle time step in FLUENT and requires a significant amount of CPU time to execute For this reason the UDF should be executed as a compiled UDF In the UDF presented below a charged particle is introduced upstream into a laminar flow and travels downstream until t tstart when a magnetic field is applied The particle takes on an approximately circular path not an exact circular path because the speed and magnetic force vary as the particle is slowed by the surrounding fluid Fluent Inc September 11 2006 2 1 49 DEFINE Macros The macro P_TIME p gives the current time for a particle traveling along a trajectory which is pointed to by p UDF for computing the magnetic force on a charged particle include udf h define Q 1 0 particle electric charge define BZ 3 0 z component of magnetic field define TSTART 18 0 x field applied at t tstart Calculate magnetic force on charged particle Magnetic force is particle charge times cross product of particle velocity with magnetic field Fx q bz Vy Fy q bz Vx DEF INE_DPM_BODY_FORCE particle_body_force p i real bforce if
268. city for i 0 i lt idim i P_VEL p i rel_vel i vnew normal i face_vel i if weber_in gt 80 alpha acos rel_dot_n vmag Get one tangent vector by subtracting off the normal component from the impingement vector then cross the normal with the tangent to get an out of plane vector 2 1 46 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros for i 0 i lt idim i tan_1 il rel_vel i rel_dot_n normal i UNIT_VECT tan_1 tan_1 V_CROSS tan_1 normal tan_2 beta is calculated by neglecting the coth alpha term in the paper it is approximately right beta MAX M_PI sqrt sin alpha 1 0 sin alpha DPM_SMALL phi M_PI betaxlog 1 0 cheap_uniform_random 1 0 exp beta if cheap_uniform_random gt 0 5 phi phi vnew vmag cp cos phi sp sin phi for i 0 i lt idim i P_VEL p i vnew tan_1 i cp tan_2 i sp face_vel i Subtract off from the original state for i 0 i lt idim i P_VELO p i P_VEL p i if DPM_STOCHASTIC_P p gt injection Reflect turbulent fluctuations also Compute normal velocity dum 0 for i 0 i lt idim i Fluent Inc September 11 2006 2 1 47 DEFINE Macros dum p gt V_prime i normal i Subtract off normal velocity for i 0 i lt idim i p gt V_prime i 2 d
269. ck OK The name of the function will subsequently be displayed under the selected property e g Viscosity in the Materials panel FA If you plan to define density using a UDF note that the solution conver gence will become poor as the density variation becomes large Specifying a compressible law density as a function of pressure or multiphase behav ior spatially varying density may lead to divergence It is recommended that you restrict the use of UDFs for density to weakly compressible flows with mild density variations See Section 2 3 14 DEFINE PROPERTY UDF s for details about DEFINE PROPERTY functions 6 32 Fluent Inc September 11 2006 6 2 Hooking Model Specific UDFs Materials Name Material Type Order Materials By air fluid Name Chemical Formula Fluent Fluid Materials C Chemical Formula air Fluent Database Mixture User Defined Database none Density kg m3 constant Edit A Pz ooo Cp j kg k constant Edit 1006 43 Thermal Conductivity w m k constant Edit 0 0242 Properties Viscosity kg m s defined cell_viscosity F2 Change Create Delete Close Help Figure 6 2 17 The Materials Panel User Defined Functions fx cell viscosi Figure 6 2 18 The User Defined Functions Panel Fluent Inc September 11 2006 6 33 Hooking UDFs to FLUENT 6 34 6 2 15 Hooking DEFINE_SCAT_PHASE_FUNC UDFs Once
270. ck OK to accept the new boundary condition and close the panel The user profile will be used in the subsequent solution calculation Velocity Inlet Zone Name velocity inlet 2 Momentum Thermal Radiation Species DPM Multiphase UDS Velocity Specification Method Components Reference Frame Absolute X Velocity m s udt unsteady_velocit Y Velocity m s g constant The time stepping parameters are set in the Iterate panel Solve lIterate 8 22 Fluent Inc September 11 2006 8 2 Detailed UDF Examples lterate Time Time Step Size s 8 6134 Number of Time Steps 64 4j Time Stepping Method Fixed C Adaptive Variable Options l Data Sampling for Time Statistics Iteration Max Iterations per Time Step 28 Reporting Interval fi UDF Profile Update Interval fi Iterate Apply Close Help In this example a Time Step Size of 0 0314 s is used so that 20 time steps will complete a full period of oscillation in the inlet velocity The UDF Profile Update Interval is set to 1 so that the velocity will be updated every iteration After 60 time steps or 3 periods are complete you can examine the velocity magnitude across the pressure outlet for its response to the oscillating inlet condition Fluent Inc September 11 2006 8 23 Examples To collect this information during the calculation open the Surface Monitors panel before begi
271. come visible and selectable under Mass Transfer when you select the Mass tab option in the Phase Interaction panel and specify the Number of Mass Transfer Functions See Section 6 3 4 Hooking DEFINE_MASS_TRANSFER UDFs for details Fluent Inc September 11 2006 2 1 35 DEFINE Macros 2 4 5 DEFINE_VECTOR_EXCHANGE_PROPERTY Description You can use DEFINE VECTOR EXCHANGE PROPERTY to specify custom slip velocities for the multiphase Mixture model Usage DEFINE_VECTOR_EXCHANGE_PROPERTY name c mixture_thread second_column_phase_index first_column_phase_index vector_result Note that all of the arguments to a DEFINE macro need to be placed on the same line in your source code Splitting the DEFINE statement onto several lines will result in a compilation error Argument Type Description symbol name UDF name cell_t c Cell index Thread mixture_thread Pointer to cell thread of mixture domain int second column phase index Index of second phase in phase interaction int first column phase index Index of first phase in phase interaction real vector_ result Pointer to slip velocity vector Function returns void There are six arguments to DEFINE VECTOR EXCHANGE PROPERTY name c mixture thread second column phase index first column phase index and vector result You supply name the name of the UDF c mixture thread second column phase _ index first column phase index and vector result are vari ables that are passed by
272. ctions of data as single arrays from one process to another process These lower level message passing macros can be easily identified in the macro name by the characters SEND and RECV Macros that are used to send data to processes have the prefix PRF_CSEND whereas macros that are used to receive data from processes have the prefix PRF_CRECV Data that is to be sent or received can belong to the following data types character CHAR integer INT REAL and logical BOOLEAN BOOLEAN variables are TRUE or FALSE REAL variables are assigned as float data types when running a single precision version of FLUENTand double when running double precision Message passing macros are defined in the prf h header file and are listed below message passing macros PRF_CSEND_CHAR to buffer nelem tag PRF_CRECV_CHAR from buffer nelem tag PRF_CSEND_INT to buffer nelem tag PRF_CRECV_INT from buffer nelem tag PRF_CSEND_REAL to buffer nelem tag PRF_CRECV_REAL from buffer nelem tag PRF_CSEND_BOOLEAN to buffer nelem tag PRF_CRECV_BOOLEAN from buffer nelem tag There are four arguments to the message passing macros For send messages the argument to is the node ID of the process that data is being sent to buffer is the name of an array of the appropriate type that will be sent nelem is the number of elements in the array and tag is a user defined message tag The tag convention is to use myid when sending messages and t
273. d Thread mixture_thread THREAD_SUPER_THREAD subthread subthread is a pointer to a particular phase level thread within the multiphase mix ture It is automatically passed to your UDF by the FLUENT solver when you use a DEFINE macro that contains a thread variable argument e g DEFINE PROFILE and the function is hooked to a primary or secondary phase in the mixture Note that THREAD_SUPER_THREAD is similar in implementation to the DOMAIN_SUPER_DOMAIN macro described in Section 3 3 2 Mixture Domain Pointer DOMAIN_ SUPER DOMAIN Domain ID DOMAIN ID You can use DOMAIN_ID when you want to access the domain_id that corresponds to a given phase level domain pointer DOMAIN_ID has one argument subdomain which is the pointer to a phase level domain The default domain_id value for the top level domain mixture is 1 That is if the domain pointer that is passed to DOMAIN_ID is the mixture level domain pointer then the function will return a value of 1 Note that the domain_id that is returned by the macro is the same integer ID that is displayed in the graphical user interface when you select the desired phase in the Phases panel in FLUENT Domain subdomain int domain_id DOMAIN_ID subdomain Phase Domain Index PHASE DOMAIN INDEX The PHASE DOMAIN_INDEX macro retrieves the phase domain index for a given phase level domain subdomain pointer PHASE DOMAIN INDEX has one argument subdomain which is the pointer to a phase le
274. d ct cell_t c int i d Get_Domain 1 if udm_offset UDM_UNRESERVED Message Setting UDMs n for i 0 i lt NUM_UDM i thread_loop_c ct d begin_c_loop c ct C_UDMI c ct udm_offset i 3 0 i 10 0 end_c_loop c ct else Message UDMs have not yet been reserved for library 1 n Fluent Inc September 11 2006 2 17 DEFINE Macros Hooking an Execute On Loading UDF to FLUENT After the UDF that you have defined using DEFINE_EXECUTE_ON_LOADING is compiled Chapter 5 Compiling UDFs the function will not need to be hooked to FLUENT through any graphics panels Instead FLUENT searches the newly loaded library for any UDFs of the type EXECUTE_ON_LOADING and will automatically execute them in the order they appear in the library 2 18 Fluent Inc September 11 2006 2 2 General Purpose DEF INE Macros 2 2 7 DEFINE_INIT Description DEFINE_INIT is a general purpose macro that you can use to specify a set of initial values for your solution DEFINE_INIT accomplishes the same result as patching but does it in a different way by means of a UDF A DEFINE_INIT function is executed once per initialization and is called immediately after the default initialization is performed by the solver Since it is called after the flow field is initialized it is typically used to set initial values of flow quantities For an overview of the FLUENT solution process which shows when a DEFINE_INIT UD
275. d tO are variables that are passed by the FLUENT solver to your UDF Arrays cir and cid contain the linearizations of the radiative and diffusive heat fluxes respectively computed by FLUENT based on the activated models These arrays allow you to modify the heat flux in any way that you choose FLUENT computes the heat flux at the wall using these arrays after the call to DEFINE_HEAT_FLUX so the total heat flux at the wall will be the currently computed heat flux based on the activated models with any modifications as defined by your UDF The diffusive heat flux qid and radiative heat flux qir are computed by FLUENT according to the following equations cid 0 cid 1 C_T c0 t0 cid 2 F_T f t cid 3 pow F_T f t 4 cir 0 cir 1 C T c0 t0 cir 2 F_T f t cir 3 pow F_T f t 4 qid qir The sum of gid and qir defines the total heat flux from the fluid to the wall this direction being positive flux and from an energy balance at the wall equals the heat flux of the surroundings exterior to the domain Note that heat flux UDFs defined using DEFINE_HEAT_FLUX are called by FLUENT from within a loop over wall faces In order for the solver to compute C_T and F_T the values you supply to cid 1 and cid 2 should never be zero Example Section 8 2 5 Implementing FLUENT s P 1 Radiation Model Using User Defined Scalars provides an example of the P 1 radiation model implementation through a user defined scalar
276. d within mp_thread_loop_c you can loop over all cells in all phase cell threads within a mixture Looping Over Phase Face Threads in Mixture mp_thread_loop_f The mp_thread_loop_f macro loops through all face threads at the mixture level within the mixture domain and provides the pointers of the phase level face threads associated with each mixture level thread This is nearly identical to the thread loop f macro when applied to the mixture domain The difference is that in addition to stepping through each face thread the macro also returns a pointer array pt that identifies the corresponding phase level threads The pointer to the face thread for the ith phase is ptLi where i is the phase domain index pt i can be used as an argument to macros requiring the phase level thread pointer The phase domain index can be re trieved using the PHASE_DOMAIN_INDEX macro See Section 3 3 2 Phase Domain Index PHASE_DOMAIN_INDEX for details Thread pt Thread face_threads Domain mixture_domain mp_thread_loop_f face_threads mixture_domain pt The variable arguments to mp_thread_loop_f are face threads mixture domain and pt face threads is a pointer to the face threads and mixture domain is a pointer to the mixture level domain pt is an array pointer whose elements contain pointers to phase level threads Fluent Inc September 11 2006 3 57 Additional Macros for Writing UDFs mixture_domain is automatically passed
277. d_Particle data structure which contains data related to the particle being tracked Function returns void There are five arguments to DEFINE_DPM_SCALAR_UPDATE name c t initialize and p You supply name the name of the UDF c t initialize and p are variables that are passed by the FLUENT solver to your UDF Pointer p can be used as an argument to the macros defined in Sec tion 3 2 7 DPM Macros to obtain information about particle properties e g injection properties Also the real array user is available for stor age The size of this array should be set in the Discrete Phase Model panel in the Number of Scalars field 2 1 76 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros Example The following compiled UDF computes the melting index along a particle trajectory The DEF INE_DPM_SCALAR_UPDATE function is called at every particle time step in FLUENT and requires a significant amount of CPU time to execute The melting index is computed from a melting index ay dt 2 5 1 o p Also included in this UDF is an initialization function DEFINE INIT that is used to initialize the scalar variables DPM_OUTPUT is used to write the melting index at sample planes and surfaces The macro NULLP which expands to p NULL checks if its argument is a null pointer DRC CO 2k K K FK 2K K 3K 2K K gt k 2K 2K K IO I FK 2K LL FK 2K 2K K FK 2K K FK FKK FK FK A 2k FK 2k 2K 2k FK 2k LL SL 2K 2 2k
278. dd Delete Library Name ibua Build Figure 5 2 1 The Compiled UDFs Panel 5 In the Compiled UDFs panel click on Add under Source Files to select the UDF source file or files you want to compile This will open the Select File panel shown in Figure 5 2 2 for Linux Unix systems 6 In the Select File panel highlight the directory path under Directories and the desired file e g udfexample c under Files Once highlighted the complete path to the source file will be displayed under Source File s Click OK The Select File panel will close and the file you added e g udfexample c will appear in the Source Files list in the Compiled UDFs panel Figure 5 2 3 You can delete a file after adding it by selecting the source file and then clicking Delete in the Compiled UDFs panel Repeat this step until all source files have been added Fluent Inc September 11 2006 5 5 Compiling UDFs Select File Look in amp mywork e a e a P 4 My Recent Documents My Network Places Files of type Source Files Cancel Source File s Remove 2 mywork udfexample c Figure 5 2 2 The Select File Panel Compiled UDFs Source Files Header Files udfexample c _ Add Delete _ Add Delete Library Name ibua Build Figure 5 2 3 The Compiled UDFs Panel 5 6 Fluent Inc September 11 2006 5 2 Compile a UDF Using the GUI il If you ar
279. details about DEFINE_SOURCE functions Fluent Inc September 11 2006 6 39 Hooking UDFs to FLUENT 6 2 18 Hooking DEFINE_SOX_RATE UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_SOX_RATE UDF in FLUENT the function name you supplied in the DEFINE macro argument will become visible and selectable for the SOx Rate in the SOx Model panel Figure 6 2 24 Define Models gt Species SOx SOx Model Model Formation Model Parameters M SOx Formation Fuel Type Turbulence Interaction C Solid Liquid Gas PDF Mode none I Include 03 Product Include SH and SO Intermediates User Defined Functions S Intermediate h2s 50x Rate user sox libudf i ELLES b Fuel S Mass Fraction g Replace with UDF Rate Conversion Fraction 0 Model equilibrium X OH Model partial equilibrium Close Help Figure 6 2 24 The SOx Model Panel FA Note that the UDF name will not appear in the list until the function has been interpreted or compiled and loaded Recall that a single UDF can be used to define custom rates for SOx Formation To replace the internally calculated SO rate with a UDF rate you will first need to choose the UDF name e g user_sox from the SOx Rate drop down list check the Replace with UDF Rate box and then click Apply Note that the Replace with UDF Rate checkbox appears only after y
280. dex gradient vector 3 10 Fluent Inc September 11 2006 3 2 Data Access Macros i Note that you can access vector components of each of the variables listed in Table 3 2 9 by using the integer index i for each macro listed in Table 3 2 9 For example C_T_G c t i will access a component of the temperature gradient vector FH C_R_G can be used only in the density based solver and C_P_G can be used only in the pressure based solver C_YILG can be used only in the density based solver To use this in the pressure based solver you will need to set the rpvar species save gradients to t Reconstruction Gradient RG Vector Macros Table 3 2 10 shows a list of cell reconstruction gradient vector macros Like gradient variables RG variables are available only when the equation for that variable is being solved As in the case of gradient variables you can retain all of the reconstruction gradient data by issuing the text command solve set expert and then answering yes to the question Keep temporary solver memory from being freed Note that when you do this the reconstruction gradient data is retained but the calculation requires more memory to run You can access a component of a reconstruction gradient vector by specifying it as an argument in the reconstruction gradient vector call 0 for the x component 1 for y and 2 for z For example C_T_RG c t 0 returns the x component of the cell temperatur
281. dimensions in your UDF The first is to use an explicit method to direct the compiler to compile separate sections of the code for 2D and 3D respectively This is done using RP_2D and RP_3D in conditional if statements The second method allows you to include general 3D expressions in your UDF and use ND and NV macros that will remove the z components when compiling with RP_2D NV macros operate on vectors while ND macros operate on separate components RP_2D and RP_3D The use of a RP_2D and RP_3D macro in a conditional if statement will direct the compiler to compile separate sections of the code for 2D and 3D respectively For example if you want to direct the compiler to compute swirl terms for the 3D version of FLUENT only then you would use the following conditional compile statement in your UDF if RP_3D compute swirl terms endif 3 4 2 The ND Macros The use of ND macros in a UDF allows you to include general 3D expressions in your code and the ND macros take care of removing the z components of a vector when you are compiling with RP_2D Fluent Inc September 11 2006 3 63 Additional Macros for Writing UDFs ND_ND The constant ND_ND is defined as 2 for RP_2D FLUENT 2D and RP_3D FLUENT 3D It can be used when you want to build a 2 x 2 matrix in 2D and a 3 x 3 matrix in 3D When you use ND_ND your UDF will work for both 2D and 3D cases without requiring any modifications real A ND_ND ND_ND for i
282. ds_unsteady Figure 6 6 4 The User Defined Scalars Panel To hook the UDF to FLUENT first specify the Number of User Defined Scalars e g 2 in the User Defined Scalars panel Figure 6 6 4 As you enter the number of user defined scalars the panel will expand to show the Unsteady Function settings Next for each scalar you have defined increment the UDS Index and choose the Zone Type e g all fluid zones select the function e g my_uds_unsteady from the Unsteady Function drop down list and click OK 6 82 Fluent Inc September 11 2006 6 7 Common Errors While Hooking a UDF to FLUENT 6 7 Common Errors While Hooking a UDF to FLUENT In some cases if you select user defined as an option in a graphics panel but have not previously interpreted or compiled loaded a UDF you will get an error message In other graphics panels the user defined option will only become visible as an option for a parameter after you have interpreted or compiled the UDF Once you have interpreted or compiled the UDF you can then select user defined option and the list of interpreted and compiled loaded UDFs will be displayed If you inadvertently hook a UDF to the wrong parameter in a FLUENT graphics panel e g profile UDF for a material property you will either get a real time error message or when you go to initialize or iterate the solution FLUENT will report an error in the dialog box Figure 6 7 1 Figure 6 7 1 The Error Dia
283. dulus 2 79 Eulerian model C 7 C 11 C 14 C 18 exchange property 2 122 frictional properties 2 79 granular properties 2 79 heat transfer coefficient 2 79 heterogeneous reaction rate 2 127 hooking to FLUENT 6 46 lift coefficient 2 122 mass transfer 2 133 material properties 2 79 Fluent Inc September 11 2006 Index Mixture model C 4 net mass transfer rate 2 122 particle or droplet diameter 2 79 radial distribution 2 79 slip velocity 2 136 solids pressure 2 79 speed of sound 2 79 surface tension coefficient 2 79 threads 1 17 vector exchange property 2 136 VOF model C 1 writing 1 17 multiphase variables macros for accessing 3 18 MULTIPLE COMPUTE_NODE_P 7 18 myid 7 39 N_DOT 2 105 N_REQ_UDM 2 185 N_TIME 3 70 N_UDM 3 74 N_UDS 3 40 3 74 ND_DOT 3 67 ND_ND 2 19 2 68 2 69 2 73 2 94 2 101 2 103 2 105 3 64 ND_SET 3 64 ND_SUM 2 19 2 20 3 54 3 64 NNULLP 2 142 2 154 2 177 3 75 Node data structure 1 10 node index number 3 53 3 54 node pointer 3 3 node variable macros 3 8 node_to_host 7 17 NODE X 2 203 nodes 1 10 NOx macros 3 35 NOx rate UDFs 2 48 NULLIDX 3 35 3 36 NULLP 2 177 3 75 number of faces in cell macro for 3 8 number of nodes in face macro for 3 8 NV_CROSS 2 203 NV_D 2 203 2 216 NV_DOT 2 41 2 142 2 144 Fluent Inc September 11 2006 NV_MAG 2 101 2 103 2 125 2 142 2 144 3 66 7 9 NV_MAG2
284. e 22 0544 dau ia bebe bee es B 4 B 4 Dynamic Mesh Model DEFINE Macros B 6 B 5 Discrete Phase Model DEFINE Macros B 7 B 6 User Defined Scalar UDS DEFINE Macros B 8 X Fluent Inc September 11 2006 CONTENTS C Quick Reference Guide for Multiphase DEFINE Macros C 1 Col NOP Model 2 2 3 enes sa muas Oe Ro E WES Pewee aes Os C 1 C 2 Mixture Model 2b ss ce ee ene eee Se ad ey Eke eG C 4 C3 Eulerian Model Laminar Mow lt s stoei ee soei sa sde Ware C 7 C 4 Eulerian Model Mixture Turbulence Flow C 11 C 5 Eulerian Model Dispersed Turbulence Flow C 14 C 6 Eulerian Model Per Phase Turbulence Flow C 18 Fluent Inc September 11 2006 XI CONTENTS XII Fluent Inc September 11 2006 About This Document User defined functions UDFs allow you to customize FLUENT and can significantly enhance its capabilities This UDF Manual presents detailed information on how to write compile and use UDFs in FLUENT Examples have also been included where available General information about C programming basics is included in an appendix Information in this manual is presented in the following chapters e Chapter 1 Overview e Chapter 2 DEFINE Macros e Chapter 3 Additional Macros for Writing UDFs e Chapter 4 Interpreting UDFs e Chapter 5 Compiling UDFs e Chapter 6 Hooking UDFs to FLUENT e Chapter 7 Parallel C
285. e name of the UDF c mixture thread second column phase _ index and first_ column phase _index are variables that are passed by the FLUENT solver to your UDF Your UDF will need to return the real value of the lift coefficient drag exchange coefficient heat or mass transfer to the solver Example 1 Custom Drag Law The following UDF named custom_drag can be used to customize the default Syam lal drag law in FLUENT The default drag law uses 0 8 for void lt 0 85 and 2 65 void gt 0 85 for bfac This results in a minimum fluid velocity of 25 cm s The UDF modifies the drag law to result in a minimum fluid velocity of 8 cm s using 0 28 and 9 07 for the bfac parameters J EK 2K aK K K 2K 2k 3k 3k 3k ak 3k 3k aK 2 a 2K 2 2K aK aK K K K K 2K K K 2K 3K 2K 3K 3K 3K 3K 3K 3K 2K 3K 2K 2k 2K 2K 2K gt K aK 2K 2K K I K 2K 2K 2K 3K 4 4 4 4 UDF for customizing the default Syamlal drag law in Fluent EEEE ooo OO D DH D DE kkk kkk kkk kk kk include udf h define pi 4 atan 1 define diam2 3 e 4 DEFINE_EXCHANGE_PROPERTY custom_drag cell mix_thread s_col f_col Fluent Inc September 11 2006 2 1 23 DEFINE Macros Thread thread_g thread_s real x_vel_g x_vel_s y_vel_g y_vel_s abs_v slip_x slip_y rho_g rho_s mu_g reyp afac bfac void_g vfac fdrgs taup k_g_s find the threads for the gas primary and solids secondary phases thread_g THREAD_SUB_THREAD mix_thread s_col gas pha
286. e reconstruction gradient vector returns the x component of the temperature reconstruction gradient vector FH Note that you can access vector components by using the integer index i for each macro listed in Table 3 2 10 For example CT RG c t il will access a component of the temperature reconstruction gradient vector i C_P_RG can be used in the pressure based solver only when the second order discretization scheme for pressure is specified i C_YI_RG can be used only in the density based solver Fluent Inc September 11 2006 3 11 Additional Macros for Writing UDFs Table 3 2 10 Macros for Cell Reconstruction Gradients RG Defined in mem h Macro Argument Types Returns CRRG cC t cell t c Thread t density RG vector C_P_RG c t cell t c Thread t pressure RG vector C_U_RG c t cell_t c Thread t velocity RG vector C_V_RG c t cell_t c Thread t velocity RG vector C_W_RG c t cell_t c Thread t velocity RG vector CT RG c t cell t c Thread t temperature RG vector C_H_RG c t cell_t c Thread t enthalpy RG vector C_NUT_RG c t cell_t c Thread t turbulent viscosity for Spalart Allmaras RG vector C_K_RG c t cell_t c Thread t turbulent kinetic energy RG vector CD RG c t cell t c Thread t turbulent kinetic energy dissipation rate RG vector C_YI_RG c t i cell t c Thread t int i species mass fraction RG vector note int i is species index Previous Time Step Macros The M1
287. e C is a constant As the liquid cools its motion will be reduced to zero simulating the formation of the solid In this simple example the energy equation will not be customized to account for the latent heat of freezing The velocity field will be used only as an indicator of the solidification region The solver linearizes source terms in order to enhance the stability and convergence of a solution To allow the solver to do this you need to specify the dependent relationship between the source and solution variables in your UDF in the form of derivatives The source term Sy depends only on the solution variable v Its derivative with respect to Ur is OS Ov e 8 2 2 The following UDF specifies a source term and its derivative The function named cell x source is defined on a cell using DEFINE SOURCE The constant C in Equa tion 8 2 1 is called CON in the function and it is given a numerical value of 20 kg m s which will result in the desired units of N m for the source The temperature at the cell is returned by C_T cell thread The function checks to see if the temperature is below or equal to 288 K If it is the source is computed according to Equation 8 2 1 C_U returns the value of the x velocity of the cell If it is not the source is set to 0 0 At the end of the function the appropriate value for the source is returned to the FLUENT solver Table 8 2 1 Properties of the Liquid Metal P
288. e Chapter 6 Hooking UDFs to FLUENT for details on how to hook a UDF to FLUENT 1 7 Grid Terminology Most user defined functions access data from a FLUENT solver Since solver data is defined in terms of grid components you will need to learn some basic grid terminology before you can write a UDF A mesh is broken up into control volumes or cells Each cell is defined by a set of grid points or nodes a cell center and the faces that bound the cell Figure 1 7 1 FLUENT uses internal data structures to define the domain s of the mesh to assign an order to cells cell faces and grid points in a mesh and to establish connectivity between adjacent cells 1 8 Fluent Inc September 11 2006 1 7 Grid Terminology A thread is a data structure in FLUENT that is used to store information about a bound ary or cell zone Cell threads are groupings of cells and face threads are groupings of faces Pointers to thread data structures are often passed to functions and manipulated in FLUENT to access the information about the boundary or cell zones represented by each thread Each boundary or cell zone that you define in your FLUENT model in a bound ary conditions panel has an integer Zone ID that is associated with the data contained within the zone You won t see the term thread in a graphics panel in FLUENT so you can think of a zone as being the same as a thread data structure when programming UDFs Cells and cell
289. e YMAX 0 4064 define UMEAN 1 0 define B 1 7 define DELOVRH 0 5 define VISC 1 7894e 05 define CMU 0 09 define VKC 0 41 profile for x velocity DEFINE_PROFILE x_velocity t i real y del h x ND_ND ufree variable declarations face_t f h YMAX YMIN del DELOVRH h ufree UMEAN B 1 begin_f_loop f t 2 70 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros end_ F_CENTROID x f t y x 1 if y lt del F_PROFILE f t i else F_PROFILE f t i ufree pow h y del B ufree pow y del B f_loop f t profile for kinetic energy DEFINE_PROFILE k_profile t i real y del h ufree x ND_ND real ff utau knw kinf face_t f h del YMAX YMIN DELOVRH h ufree UMEAN B 1 ff 0 045 pow ufree del VISC 0 25 utau sqrt ff pow ufree 2 2 0 knw pow utau 2 sqrt CMU kinf 0 002 pow ufree 2 begin_f_loop f t F_CENTROID x f t y x 1 if y lt del F_PROFILE f t i knw y del kinf knw else F_PROFILE f t i knw h y del kinf knw end_f_loop f t profile for dissipation rate Fluent Inc September 11 2006 2 71 DEFINE Macros DEFINE_PROFILE dissip_profile t i 2 72 real y x ND_ND del h ufree real ff utau knw kinf real mix kay face_t f h YMAX YMIN del DELOVRH h ufree UMEAN
290. e arguments to DEFINE_PRANDTL_K name c and t You supply name the name of the UDF c and t are variables that are passed by the FLUENT solver to your UDF Your UDF will need to return the real value for the kinetic energy Prandtl number to the solver Example The following UDF implements a high Re version of the RNG model using the k e option that is activated in FLUENT Three steps are required 1 Set Cmu Cleps and C2eps as in the RNG model 2 Calculate Prandtl numbers for k and using the UDF 3 Add the r source term in the equation In the RNG model diffusion in k and equations appears as u fe a while in the standard k e model it is given by Fluent Inc September 11 2006 2 59 DEFINE Macros Ht Bree For the new implementation a UDF is needed to define a Prandtl number Pr as Pr Ht u pu u in order to achieve the same implementation as the original RNG Model The following functions which are concatenated into a single C source code file demon strate this usage Note that the source code must be executed as a compiled UDF include udf h DEFINE_PRANDTL_K user_pr_k c t real pr_k alpha real mu C_MU_L c t real mu_t C_MU_T c t alpha rng_alpha 1 mu mu_t mu pr_k mu_t mutmu_t alpha mu return pr_k DEFINE_PRANDTL_D user_pr_d c t real pr_d alpha real mu C_MU_L c t real mu_t C_MU_T c t a
291. e capital form in FORTRAN e g ADDAB goes to addab_ This name mangling is done by the compiler and is strongly system dependent Note also that functions returning complex numbers have dif ferent forms on different machine types since C can return only single values and not structures Consult your system and compiler manuals for details 1 In the first step of this example a FORTRAN source file named test f is compiled and the resulting object file test o is placed in the shared library directory for the ultra 2d version libudf ultra 2d The source listing for test f is shown below FORTRAN function test f compile to o file using 77 KPIC n32 0 c test f irix6 amp suns REAL 8 FUNCTION ADDAB A B C REAL A REAL 8 B REAL 8 YCOM COMPLEX ZCOM INTEGER C INTEGER SIZE COMMON SIZE ARRAY 10 COMMON TSTCOM ICOM XCOM YCOM ZCOM ICOM C XCOM A YCOM B ZCOM CMPLX A REAL B SIZE 10 DO 100 I 1 S5IZE Fluent Inc September 11 2006 5 19 Compiling UDFs ARRAY 1 I A 100 CONTINUE ADDAB A C B END COMPLEX FUNCTION CCMPLX A B REAL A B CCMPLX CMPLX A B END 2 The UDF C source file named test_use c is placed in the source directory for the ultra 2d version src ultra 2d The source listing for test_use c is as follows 5 20 include udf h if defined _WIN32 Visual Fortran makes uppercase functions provide lowercase mapping to be compatible with
292. e deflection due to fluid structure interaction Note that UDFs that are defined using DEFINE_GRID_MOTION can be executed only as compiled UDFs Usage DEFINE_GRID_MOTION name d dt time dtime Argument Type Description symbol name UDF name Domain d Pointer to domain Dynamic_Thread dt Pointer to structure that stores the dynamic mesh attributes that you have specified or that are calculated by FLUENT real time Current time real dtime Time step Function returns void There are five arguments to DEFINE_GRID_MOTION name d dt time and dtime You supply name the name of the UDF d dt time and dtime are variables that are passed by the FLUENT solver to your UDF 2 202 Fluent Inc September 11 2006 2 6 Dynamic Mesh DEFINE Macros Example Consider the following example where you want to specify the deflection on a cantilever beam based on the x position such that w x 10 4Yxsin26 178t x gt 0 02 2 6 3 wyr 0 x lt 0 02 2 6 4 where w x is the y component of the angular velocity at a position x The node position is updated based on rt P Os r At 2 6 5 where Q is the angular velocity and 7 is the position vector of a node on the dynamic zone peaa oo o kkk kkk kk kkk kkk kk kk kkk kkk kk node motion based on simple beam deflection equation compiled UDF EEEE o ooo k kk 2 KK 2 kkk include udf h DEFINE_GRID_MOTION beam domain dt time dtime Thread tf DT
293. e end of the function the computed value for the viscosity mu_lam is returned to the solver Fluent Inc September 11 2006 2 83 DEFINE Macros 2 84 Example 2 User defined Mixing Law for Thermal Conductivity You can use DEFINE_PROPERTY to define custom user defined mixing laws for density viscosity and conductivity of mixture materials In order to access species material properties your UDF will need to utilize auxiliary utilities that are described above The following UDF named mass_wtd_k is an example of a mass fraction weighted con ductivity function The UDF utilizes the generic_property function to obtain properties of individual species It also makes use of MATERIAL_PROPERTY and THREAD_MATERIAL PK kkk ak ak kk 3k ak k ak 2k 2k K ak 2k K K FK 2K K 3K 2K K gt K 2K 2K K FK 2K 2K 2K 3K 2K LL FK 2K K K FK 2K K FK FKK FK FK 2K K FK FK 2K FK FK 2K LL LL LS FK 2K K K FK UDF that specifies a custom mass fraction weighted conductivity EEEE ooo OK HD DD DK kkk kkk kkk kkk kk include udf h DEFINE_PROPERTY mass_wtd_k c t real sum 0 int i Material sp real ktc Property prop mixture_species_loop THREAD_MATERIAL t sp i prop MATERIAL_PROPERTY sp ktc generic_property c t prop PROP_ktc C_T c t sum C_YI c t i ktc return sum Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros Example 3 Surface Tension Coefficient UDF DEFINE_PROPERTY can also be
294. e following utilities compute the dot product of two sets of vector components ND_DOT x y z u v w 2D x u y v 3D x u y v z w NV_DOT x u 2D x 0 u 0 x 1 u 1 3D x 0 u 0 x 1 xu 1 x 2 u 2 NVD_DOT x u v w 2D x 0 u x 1 v 3D xf O u x 1 xv x 2 w See Section 2 3 6 DEFINE_DOM_SPECULAR_REFLECTIVITY for an example UDF that utilizes NV_DOT Cross Product For 3D the CROSS macros return the specified component of the vector cross product For 2D the macros return the cross product of the vectors with the z component of each vector set to 0 ND_CROSS_X x0 x1 x2 y0 y1 y2 2D 0 0 3D C x1 y2 y1 x2 ND_CROSS_Y x0 x1 x2 y0 y1 y2 2D 0 0 3D x2 y0 y2 x0 ND_CROSS_Z x0 x1 x2 y0 y1 y2 2D and 3D x0 y1 y0 x1 NV_CROSS_X x y Fluent Inc September 11 2006 3 67 Additional Macros for Writing UDFs ND_CROSS_X x 0 x 1 x 2 u 0 y 1 y 2 NV_CROSS_Y x y ND_CROSS_X x 0 x 1 x 2 u 0 y 1 y 2 NV_CROSS_Z x y ND_CROSS_X x 0 x 1 x 2 u 0 y 1 y 2 NV_CROSS a x y a 0 NV_CROSS_X x y a 1 NV_CROSS_Y x y a 2 NV_CROSS_Z x y See Section 2 6 3 DEFINE GRID MOTION for an example UDF that utilizes NV CROSS 3 5 Time Dependent Macros You can access time dependent variables in your UDF in two different ways direct access using a solver macro or indirect access using an RP va
295. e for Direct Solar Irradiation and Diffuse Solar Irradiation in the Radiation Model panel in FLUENT Note that the solar load model must be enabled See Section 6 2 16 Hooking DEFINE_SOLAR_INTENSITY UDFs for details 2 92 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros 2 3 17 DEFINE SOURCE Description You can use D FINE SOURCE to specify custom source terms for the different types of solved transport equations in FLUENT except the discrete ordinates radiation model including e mass e momentum e k e energy also for solid zones e species mass fractions e PI radiation model e user defined scalar UDS transport e granular temperature Eulerian Mixture multiphase models Usage DEFINE_SOURCE name c t dS eqn Argument Type Description symbol name UDF name cellt c Index that identifies cell on which the source term is to be applied Thread t Pointer to cell thread real dS Array that contains the derivative of the source term with respect to the dependent variable of the transport equation int eqn Equation number Function returns real There are five arguments to DEFINE_SOURCE name c t dS and eqn You supply name the name of the UDF c t dS and eqn are variables that are passed by the FLUENT solver to your UDF Note that the source term derivatives may be used to linearize the source term if they enhance the stability of the solver To illustrate this note that the sou
296. e identified by the suffix G For example cell temperature is stored in the variable C_T and the temperature gradient of the cell is stored in C_T_G The gradients stored in variables with the G suffix are non limited values and if used to reconstruct values within the cell at faces for example may potentially result in values that are higher or lower than values in the surrounding cells Therefore if your UDF needs to compute face values from cell gradients you should use the reconstruction gradient RG values instead of non limited gradient G values Reconstruction gradient variables are identified by the suffix RG and use the limiting method that you have activated in your FLUENT model to limit the cell gradient values Fluent Inc September 11 2006 3 9 Additional Macros for Writing UDFs Gradient G Vector Macros Table 3 2 9 shows a list of cell gradient vector macros Note that gradient variables are available only when the equation for that variable is being solved For example if you are defining a source term for energy your UDF can access the cell temperature gradient using C_T_G but it cannot get access to the x velocity gradient using C_U_G The reason for this is that the solver continually removes data from memory that it doesn t need In order to retain the gradient data when you want to set up user defined scalar transport equations for example you can prevent the solver from freeing up memory by i
297. e methods e g piecewise linear polynomial in the Materials panel as a general guideline you should define a speed of sound function along with your density UDF using the formulation Vap For simplicity it is recommended that you concatenate the density and speed of sound functions into a single UDF source file Fluent Inc September 11 2006 2 85 DEFINE Macros The following UDF source code example contains two concatenated functions a density function named superfluid_density that is defined in terms of pressure and a custom speed of sound function named sound_speed peaa o oo o kkk k kk kkk kkk k kkk kkk kkk k kkk Density and speed of sound UDFs for compressible liquid flows For use with pressure based solver for single phase multiphase mixture or cavitation models only Note that for density function dp is the difference between a cell absolute pressure and reference pressure EEEE ooo ooo DO kkk D kkk kk kkk kkk include udf h define BMODULUS 2 2e9 define rho_ref 1000 0 define p_ref 101325 DEFINE_PROPERTY superfluid_density c t real rho real p dp real p_operating p_operating RP_Get_Real operating pressure p C_P c t p_operating dp p p_ref rho rho_ref 1 0 dp BMODULUS return rho DEFINE_PROPERTY sound_speed c t real a real p dp p_operating p_operating RP_Get_Real operating pressure p C_P c t p_operating d p p p_ref 1 dp
298. e of all the compute nodes These operations are directed for the compute nodes using if RP_NODE Fluent Inc September 11 2006 7 43 Parallel Considerations 7 9 Writing Files in Parallel Although compute nodes can perform computations on data simultaneously when FLU ENT is running in parallel when data is written to a single common file the writing operations have to be sequential The file has to be opened and written to by processes that have access to the desired file system It is often the case that the compute nodes are running on a dedicated parallel machine without disk space This means that all of the data has to be written from the host process which always runs on a machine with access to a file system since it reads and writes the case and data files This implies that unlike the example in Section 7 5 8 Message Passing Macros where data is only passed to compute node 0 to be collated data must now be passed from all the compute nodes to compute node 0 which then passes it on to the host node which writes it to the file This process is known as marshalling Thus file writing in parallel is done in the following stages 1 The host process opens the file 2 Compute node 0 sends its data to the host 3 The other compute nodes send their data to compute node 0 4 Compute node 0 receives the data from the other compute nodes and sends it to the host 5 The host receives the data sent from all the comp
299. e running FLUENT on a network of Windows machines you may need to type the file s complete path in the Source File Name field in the Interpreted UDFs panel instead of using the browser option For example to compile udfexample c from a shared working directory named mywork you would enter the following in the Source File Name field lt fileserver gt mywork udfexample c Here you replace lt fileserver gt with the name of the computer on which your working directory mywork and source file udfexample c are lo cated 7 In the Compiled UDFs panel select additional header files that you want to include in the compilation by clicking Add under Header File s and repeat the previous step 8 In the Compiled UDFs panel Figure 5 2 3 enter the name of the shared library you want to build in the Library Name field or leave the default name libudf and click Build All of the UDFs that are contained within each C source file you selected will be compiled and the build files will be stored in the shared library you specified e g libudf As the compile build process begins a Warning dialog box Figure 5 2 4 will appear reminding you that the source file s need to be in the same directory as the case and data files Click OK to close the dialog and continue with the build Warning Make sure that UDF source files are in the directory that contains your case and data files Cancel Figure 5 2 4 The Warning Dialog Box
300. ection Properties Set Injection Properties Custom Laws Sample Trajectories Materials Discrete Phase Model Discrete Phase Model User Defined Function Hooks Custom Laws Discrete Phase Model Materials 2 140 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros 2 5 1 DEFINE DPM BC Description You can use DEFINE DPM BC to specify your own boundary conditions for particles The function is executed every time a particle touches a boundary of the domain except for symmetric or periodic boundaries You can define a separate UDF using DEFINE_DPM_BC for each boundary Usage DEFINE DPM BC name p t f f normal dim Argument Type Description symbol name UDF name Tracked Particle p Pointer to the Tracked Particle data structure which contains data related to the particle being tracked Thread t Pointer to the face thread the particle is currently hitting face_t f Index of the face that the particle is hitting real f normal Array that contains the unit vector which is normal to the face int dim Dimension of the flow problem The value is 2 in 2d for 2d axisymmetric and 2d axisymmetric swirling flow while it is 3 in 3d flows Function returns int There are six arguments to DEFINE_DPM_BC name p t f f normal and dim You supply name the name of the UDF p t f f normal and dim are variables that are passed by the FLUENT solver to your UDF Your UDF will need
301. ed Memory UDM Macros Axisymmetric Considerations for Data Access Macros C side calculations for axisymmetric models in FLUENT are made on a 1 radian basis Therefore when you are utilizing certain data access macros e g F_AREA or F_FLUX for axissymetric flows your UDF will need to multiply the result by 2 PI utilizing the macro M_PI to get the desired value Fluent Inc September 11 2006 3 5 Additional Macros for Writing UDFs 3 2 2 Node Macros A grid in FLUENT is defined by the position of its nodes and how the nodes are connected The macros listed in Table 3 2 1 and Table 3 2 2 can be used to return the real Cartesian coordinates of the cell node at the cell corner in SI units The variables are available in both the pressure based and the density based solver Definitions for these macros can be found in metric h The argument Node node for each of the variables defines a node Node Position Table 3 2 1 Macros for Node Coordinates Defined in metric h Macro Argument Types Returns NODE_X node Node node real x coordinate of node NODE_Y node Node node real y coordinate of node NODE_Z node Node node real z coordinate of node Number of Nodes in a Face F_NNODES The macro F_NNODES shown in Table 3 2 2 returns the integer number of nodes associated with a face Table 3 2 2 Macro for Number of Nodes Defined in mem h Macro Argument Types Returns F_NNODES f t face_t f
302. ed inlet_x_velocity Fluent Inc September 11 2006 5 2 Compile a UDF Using the GUI il Note that compiled UDFs are displayed in FLUENT panels with the associated UDF library name using the identifier For exam ple a compiled UDF named inlet_x_velocity that is associated with a shared library named libudf will appear in FLUENT panels as inlet_x_velocity libudf This visually distinguishes UDFs that are compiled from those that are interpreted Once the compiled UDF s become visible and selectable in graphics panels in FLUENT they can be hooked to your model See Chapter 6 Hooking UDFs to FLUENT for details You can use the UDF Library Manager panel to unload the shared library if desired See Section 5 5 Load and Unload Libraries Using the UDF Library Manager Panel for details 10 Write the case file if you want the compiled function s in the shared library to be saved with the case The functions will be loaded automatically into FLUENT whenever the case is subsequently read If you do not want the shared library saved with your case file then you must remember to load it into FLUENT using the Compiled UDFs panel or the UDF Library Manager panel in subsequent sessions Fluent Inc September 11 2006 5 9 Compiling UDFs 5 3 Compile a UDF Using the TUI The first step in compiling a UDF source file using the text user interface TUI involves setting up the directory structure where the shared compiled libr
303. ed rates If the Replace with UDF Rate checkbox is checked for a given NO formation pathway in the NOx Model panel then the FLUENT calculated rate for that NO pathway will not be used and it will instead be replaced by the NO rate you have defined in your UDF When you hook a NO rate UDF to the graphical interface without checking the Replace with UDF Rate box for a particular pathway then the user NO rate will be added to the internally calculated rate for the source term calculation il Note that a single UDF is used to define the different rates for the four NO pathways thermal NO prompt NO fuel NO and N2O intermediate pathway That is a NO rate UDF can contain up to four separate rate functions that are concatenated in a single source file which you hook to FLUENT Usage DEFINE_NOX_RATE name c t Pollut Pollut_Par NOx Argument Type Description symbol name UDF name cell_t c Cell index Thread t Pointer to cell thread on which the NO rate is to be applied Pollut Cell Pollut Pointer to the data structure that contains the common data at each cell Pollut Parameter Pollut Par Pointer to the data structure that contains auxiliary data NOx Parameter NOx Pointer to the data structure that contains data specific to the NO model Function returns void 2 48 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros There are six arguments to DEFINE_NOX_RATE name c t Pollut Pollut_Par and NO
304. ed so that all computers on the cluster can see this directory To share the directory that the case data and compiled UDF reside in using the Windows Explorer right click on the directory choose Sharing from the menu click Share this folder and then click OK If you forget to enable the sharing option for the directory using the Win dows Explorer then FLUENT will hang when you try to load the library in the Compiled UDFs panel See Section 5 6 Common Errors When Building and Loading a UDF Library for a list of errors you can encounter that are specific to Windows parallel 5 28 Fluent Inc September 11 2006 Chapter 6 Hooking UDFs to FLUENT Once you have interpreted or compiled your UDF using the methods described in Chap ters 4 and 5 respectively you are ready to hook the function to FLUENT using a graphic interface panel Once hooked the function will be utilized in your FLUENT model De tails about hooking a UDF to FLUENT can be found in the following sections Note that these sections relate to corresponding sections in Chapter 2 DEFINE Macros e Section 6 1 Hooking General Purpose UDF s e Section 6 2 Hooking Model Specific UDFs e Section 6 3 Hooking Multiphase UDFs e Section 6 4 Hooking Discrete Phase Model DPM UDFs e Section 6 5 Hooking Dynamic Mesh UDFs e Section 6 6 Hooking User Defined Scalar UDS Transport Equation UDFs e Section 6 7 Common Errors While Hooking a UDF to FLUENT 6 1 Hooking Ge
305. el boundary condition e g Velocity Inlet Fluent Inc September 11 2006 2 27 DEFINE Macros 2 28 Table 2 3 2 Quick Reference Guide for Model Specific DEFINE Functions Continued Function DEFINE Macro Panel Activated In velocity at a boundary pressure at a boundary temperature at a boundary mass flux at a boundary target mass flow rate for pressure outlet turbulence kinetic energy turbulence dissipation rate specific dissipation rate porosity viscous resistance inertial resistance porous resistance direction vector user defined scalar boundary value internal emissivity wall thermal conditions heat flux heat generation rate temperature heat transfer coefficient external emissivity external radiation and free stream temperature wall radiation internal emissivity irradiation wall momentum shear stress x y z components swirl component moving wall velocity components roughness height roughness constant wall species mass fractions wall user defined scalar boundary value wall discrete phase boundary value wall functions DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE
306. elocity in stateO of particle for i 0 i lt idim i p gt state0 V i p gt state Vlil return PATH_ACTIVE return PATH_ABORT J Fluent Inc September 11 2006 2 1 43 DEFINE Macros Example 2 This example shows how to use DEFINE_DPM_BC for a wall impingement model The function must be executed as a compiled UDF include udf h include dpm h include surf h include random h define a user defined dpm boundary condition routine bc_reflect name p the tracked particle t the touched face thread f the touched face f_normal normal vector of touched face dim dimension of the problem 2 in 2d and 2d axi swirl 3 in 3d return is the status of the particle see enumeration of Path_Status in dpm h define V_CROSS a b r DEFINE_ Cr 0 a 1 b 2 b 1 a 2 r 1 a 2 b 0 bo 2 a 0 r 2 a 0 b 1 Cb 0 a 1 DPM_BC bc_wall_jet p thread f f_normal dim Routine implementing the Naber and Reitz Wall impingement model SAE 880107 real real real real real real real 2 144 normal 3 tan_1 3 tan_2 3 l rel_vel 3 face_vel 3 alpha beta phi cp sp rel_dot_n vmag vnew dum Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros real weber_in weber_out int i idim din cxboolean moving SV_ALLOCATED_P thread SV_WA
307. els only See the example below for details Fluent Inc September 11 2006 2 79 DEFINE Macros For Multiphase Flows e surface tension coefficient VOF model e cavitation parameters including surface tension coefficient and vaporization pres sure Mixture cavitation models e heat transfer coefficient Mixture model e particle or droplet diameter Mixture model e speed of sound function Mixture cavitation models e density as a function of pressure for compressible liquid flows only Mixture cavitation models e granular temperature and viscosity Mixture Eulerian models e granular bulk viscosity Eulerian model e granular conductivity Eulerian model e frictional pressure and viscosity Eulerian model e frictional modulus Eulerian model e elasticity modulus Eulerian model e radial distribution Eulerian model e solids pressure Eulerian Mixture models e diameter Eulerian Mixture models Usage DEFINE_PROPERTY name c t Argument Type Description symbol name UDF name cellt c Cell index Thread t Pointer to cell thread on which the property function is to be applied Function returns real 2 80 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros There are three arguments to DEFINE_PROPERTY name c and t You supply name the name of the UDF c and t are variables that are passed by the FLUENT solver to your UDF Your UDF will need to compute the real pro
308. er file Fluent Inc September 11 2006 3 1 Introduction Each function behind a macro either outputs a value to the solver as an argument or returns a value that is then available for assignment in your UDF Input arguments belong to the following FLUENT data types Node node pointer to a node cell t c cell identifier facet f face identifier Thread t pointer to a thread Thread pt pointer to an array of phase threads Below is an example of a UDF that utilizes two data acess macros C_T and C_CENTROID and two looping macros begin end_c_loop_all and thread_loop_c C_CENTROID outputs a value to the solver as an argument which is then operated on in the UDF and C_T returns a value that is then available for assignment in the UDF Two looping macros are used to set the cell temperature of each cell in every thread in the computational domain begin end_c_loop_all is used to loop over all the cells in a cell thread to get the cell centroid and set the cell temperature and thread_loop_c allows this loop to be repeated over all cell threads in the domain C_CENTROID has three arguments xc c and t Cell identifier c and cell thread pointer t are input arguments and the argument array xc the cell centroid is output as an argument to the solver and used in the UDF in a conditional test C_T is used to set the cell temperature to the value of 400 or 300 depending on the outcome of the conditional test It is passed the cell
309. er to your UDF Your UDF will need to return the real value for the temperature Prandtl number to the solver Fluent Inc September 11 2006 2 63 DEFINE Macros Example Specifying a Constant Temperature Prandtl Number include udf h DEFINE_PRANDTL_T user_pr_t c t real pr_t pr_t 0 85 return pr_t J Hooking a Prandtl Number UDF to FLUENT After the UDF that you have defined using DEFINE_PRANDTL_T is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user_pr_t will become visible and selectable in the Viscous Model panel in FLUENT See Sec tion 6 2 12 Hooking DEFINE_PRANDTL UDFs for details DEFINE_PRANDTL_T_WALL Description You can use DEFINE PRANDTL T WALL to specify Prandtl numbers for thermal wall func tions Usage DEFINE_PRANDTL_T_WALL name c t Argument Type Description symbol name UDF name cell_t c Index that identifies the cell on which the Prandtl number function is to be applied Thread t Pointer to cell thread Function returns real 2 64 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros There are three arguments to DEFINE_PRANDTL_T_WALL name c and t You supply name the name of the UDF c and t are variables that are passed by the FLUENT solver to your UDF Your UDF will need to return the real value for the thermal wall fu
310. er to your UDF The new position after projection to the geometry defining the zone is returned to FLUENT by overwriting the position array Example The following UDF named parabola is executed as a compiled UDF 2 200 Fluent Inc September 11 2006 2 6 Dynamic Mesh DEFINE Macros DCO OO COO ORO I AIA A Ak defining parabola through points 0 1 1 2 5 4 1 1 BEA IIII k a a kkk include udf h DEFINE_GEOM parabola domain dt position set y x 2 x 1 position 1 position 0 position 0 position 0 1 Hooking a Dynamic Mesh Geometry UDF to FLUENT After the UDF that you have defined using DEFINE GEOM is interpreted or compiled see Chapter 5 Compiling UDFs for details the name of the argument that you supplied as the first DEFINE macro argument will become visible in the Dynamic Zones panel in FLUENT See Section 6 5 2 Hooking DEFINE_GEOM UDFs for details on how to hook your DEFINE_GEOM UDF to FLUENT Fluent Inc September 11 2006 2 201 DEFINE Macros 2 6 3 DEFINE_GRID_MOTION Description By default FLUENT updates the node positions on a dynamic zone by applying the solid body motion equation This implies that there is no relative motion between the nodes on the dynamic zone However if you need to control the motion of each node independently then you can use DEFINE_GRID_MOTION UDF A grid motion UDF can for example update the position of each node based on th
311. erms that appear in Equations 8 2 10 and 8 2 11 are a result of the evaluation of the gradient of incident radiation in Equation 8 2 8 In FLUENT the component of a gradient of a scalar directed normal to a cell boundary face VG n is estimated as the sum of primary and secondary components The primary component represents the gradient in the direction defined by the cell centroids and the secondary component is in the direction along the face separating the two cells From this information the face normal component can be determined The secondary component of the gradient can be found using the Fluent macro BOUNDARY_SECONDARY_GRADIENT_SOURCE The use of this macro first requires that cell geometry information be defined which can be readily obtained by the use of a second macro BOUNDARY_FACE_GEOMETRY see Sec tion 3 2 5 Boundary Face Geometry BOUNDARY_FACE_GEOMETRY You will see these macros called in the UDF that defines the wall boundary condition for G To complete the implementation of the P1 model the radiation energy equation must be coupled with the thermal energy equation This is accomplished by modifying the source term and wall boundary condition of the energy equation Consider first how the energy equation source term must be modified The gradient of the incident radiation is proportional to the radiative heat flux A local increase or decrease in the radiative heat flux is attributable to a local decrease or increase in
312. error occurs because the other computer s on the cluster cannot see the UDF through the network To remedy this you will need to 1 modify the environment variables on the computer where the compiled UDF case and data files reside and 2 share the directory where the files reside See Section 5 2 Compile a UDF Using the GUI for details on file sharing or contact FLUENT installation support for additional assistance There are instances when FLUENT can hang when trying to read a compiled UDF using network parallel as a result of a network communicator problem Contact FLUENT installation support for details You may receive an error message when you invoke the command nmake if you have the wrong compiler installed or if you have not launched the Visual Studio Command Prompt prior to building the UDF See Section 5 1 2 Compilers and Section 5 2 Compile a UDF Using the GUI for details or contact FLUENT installation support for further assistance Fluent Inc September 11 2006 5 27 Compiling UDFs 5 7 Special Considerations for Parallel FLUENT If you are running serial or parallel FLUENT on a Windows system then you must have Microsoft Visual Studio installed on your machine and have launched FLUENT from the Visual Studio console window in order to compile UDF s in your model Also note that if you have compiled a UDF while running FLUENT on a Windows parallel network you must share the directory where the UDF is locat
313. ers This is how I put a comment in my C program that spans more than one line Do not include a DEFINE macro name e g DEFINE PROFILE within a comment in your source code This will cause a compilation error A3 C Data Types in FLUENT The UDF interpreter in FLUENT supports the following standard C data types int integer number long integer number of increased range float floating point real number double double precision floating point real number char single byte of memory enough to hold a character Note that in FLUENT real is a typedef that switches between float for single precision arithmetic and double for double precision arithmetic Since the interpreter makes this assignment automatically it is good programming practice to use the real typedef when declaring all float and double data type variables in your UDF A 2 Fluent Inc September 11 2006 A 4 Constants A 4 Constants Constants are absolute values that are used in expressions and need to be defined in your C program using define Simple constants are decimal integers e g 0 1 2 Constants that contain decimal points or the letter e are taken as floating point constants As a convention constants are typically declared using all capitals For example you may set the ID of a zone or define constants YMIN and YMAX as shown below define WALL_ID 5 define YMIN 0 0 define YMAX 0 4064 A 5 Variables A variable or object is a
314. ersus compiled 1 6 interpreting 4 3 limitations 1 3 programming language 1 1 purpose 1 3 single phase vs multiphase 1 17 source files compiled 1 6 interpreted 1 6 tutorial 8 1 DS diffusivity UDFs 2 34 DS flux UDFs 2 215 DS source term UDFs 2 210 DS transport equation UDFs 2 209 DS transport equations 1 3 diffusivity UDFs 2 34 DS UDFs anisotropic diffusivity 2 211 diffusion coefficient 2 209 examples 8 43 flux 2 210 2 215 postprocessing example 8 43 source terms 2 210 unsteady 2 210 unsteady term 2 219 UNIVERSAL_GAS_CONSTANT 2 53 2 55 2 101 2 103 2 112 3 76 Index 15 Index UNIX systems directory structure 5 11 shared library 5 15 unstable simulations 3 12 unsteady term UDFs 2 219 unsteady UDFs 2 210 Use Contributed CPP 4 5 8 8 user defined data types A 8 User Defined Function Hooks panel 6 2 6 5 6 7 6 9 6 12 6 15 6 16 6 19 6 21 6 23 6 25 6 27 6 42 6 44 6 46 6 67 User Defined Functions panel 6 32 6 35 6 49 6 52 6 64 User Defined Memory panel 6 14 user defined memory 2 21 2 154 6 14 user defined memory variable example 3 43 for cells 3 43 for faces 3 42 user defined scalar transport equations examples 2 209 8 43 source term UDF 2 93 user defined scalar variable example 3 43 for cells 3 39 for faces 3 39 User Defined Scalars panel 6 81 6 82 user_nt udf 5 10 5 13 utilities dimension 3 63 vector 3 63 vapor pressure UD
315. es primary and secondary phases s primary and secondary phases s mixture mixture Fluid mass source momentum source energy source turbulence dissipation rate source turbulence kinetic energy source user defined scalar source velocity temperature DEFINE_ SOURCE DEFINE_ SOURCE DEFINE SOURCE DEFINE SOURCE DEFINE SOURCE DEFINE SOURCE DEFINE PROFILE DEFINE PROFILE primary and secondary phase s primary and secondary phase s primary and secondary phase s primary and secondary phase s primary and secondary phase s mixture primary and secondary phase s primary and secondary phase s Fluent Inc September 11 2006 C 19 Quick Reference Guide for Multiphase DEFINE Macros Table C 6 2 DEFINE Macro Usage for the Eulerian Model Per Phase Tur bulence Flow Variable Macro Phase Specified On Fluid turbulence kinetic energy turbulence dissipation rate granular flux granular temperature porosity viscous resistance inertial resistance user defined scalar DEFINE_PROFILE DEFINE PROFILE DEFINE_PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE primary and secondary phase s primary and secondary phase s secondary phase s secondary phase s mixture primary and secondary phase s primary and secondary phase s mixture Wall species boundary condition shear stress components moving veloc
316. es From Non FLUENT Sources SOURCES Put the names of your UDF C files here They will be calling the functions in the User Objects FLUENT_INC the path to your release directory USER_OBJECTS the precompiled object file s that you want to build a shared library for e g myobject1 o Use a space delimiter to specify multiple object files e g myobjecti o myobject2 0 An excerpt from a sample makefile is shown below fro rr rr re makefile for user defined functions fro rr rr Pas S SS SS Pr re et cn tm re enr User modifiable section HS SOURCES udf_sourcei c FLUENT_INC path Fluent Inc Precompiled User Object files for example o files from f sources USER_OBJECTS myobjecti o myobject2 0 fas a Sa SS Sea Se ee See Build targets do not modify below this line RE ee 4 In your library directory e g libudf execute the Makefile by typing a command that begins with make and includes the architecture of the machine you will run FLUENT on which you identified in a previous step e g ultra make FLUENT_ARCH ultra Fluent Inc September 11 2006 5 23 Compiling UDFs The following messages will be displayed linking to src makefile in ultra 2d building library in ultra 2d linking to src makefile in ultra 3d building library in ultra 3d 5 5 Load and Unload Libraries Using the UDF Library Manager Panel You can use the UDF Library Manager panel to
317. es to be added together temp C_T c c_thread end_c_loop c c_thread Looping Over Faces in a Face Thread begin end_f_loop You can use begin_f_loop and end_f_loop when you want to loop over all faces in a given face thread It contains a begin and end loop statement and performs operation s on each face in the face thread as defined between the braces This loop is usually nested within thread_loop_f when you want to loop over all faces in all face threads in a domain face_t f Thread f_thread begin_f_loop f f_thread loops over faces in a face thread end_f_loop f f_thread Fluent Inc September 11 2006 3 51 Additional Macros for Writing UDFs Example Loop over faces in a face thread to get the information stored on faces begin_f_loop f f_thread F_T gets face temperature The will cause all of the face temperatures to be added together temp F_T f f_thread end_f_loop f f_thread Looping Over Faces of a Cell c face loop The following looping function loops over all faces of a given cell It consists of a single loop statement followed by the action to be taken in braces cell_t c Thread t face_t f Thread tf int n c_face_loop c t n loops over all faces of a cell f C_FACE c t n tf C_FACE_THREAD c t n The argument n is the local face index number The local face index number is used in the C_FACE mac
318. essure and surface tension coefficient cavitation parameters that are defined using DEFINE PROPERTY See Section 2 3 14 DEFINE PROPERTY UDFs for details Table 2 4 2 DEFINE EXCHANGE PROPERTY Variables Mixture Model Eulerian Model net heat transfer rate drag exchange drag coefficient coefficient lift coefficient Usage DEFINE EXCHANGE PROPERTY name c mixture thread second_ column phase index first _column phase_index Note that all of the arguments to a DEFINE macro must be placed on the same line in your source code Splitting the DEFINE statement onto several lines will result in a compilation error 2 1 22 Fluent Inc September 11 2006 2 4 Multiphase DEF INE Macros Argument Type Description symbol name UDF name cell_t c Cell index Thread mixture_thread Pointer to the mixture level thread int second_column_phase_index Identifier that corresponds to the pair of phases in your multiphase flow that you are specifying a slip velocity for The identifiers correspond to the phases you select in the Phase Interaction panel in the graphical user interface An index of 0 corresponds to the primary phase and is incremented by one for each secondary phase int first column phase index See int second_column_phase_index Function returns real There are five arguments to DEFINE EXCHANGE PROPERTY name c mixture thread second column phase index and first column phase index You supply name th
319. eta0 gamma0 Gsource Ibw real Ew epsilon_w 2 2 epsilon_w Thread t0 thread gt t0 Do nothing if areas aren t computed yet or not next to fluid if Data_Valid_P FLUID_THREAD_P t0 return Fluent Inc September 11 2006 8 49 Examples begin_f_loop f thread cell_t c0 F_CO f thread BOUNDARY_FACE_GEOMETRY f thread A ds es A_by_es dr0 At NV_MAG A if NULLP T_STORAGE_R_NV tO SV_UDSI_G P1 Gsource 0 if gradient not stored yet else BOUNDARY_SECONDARY_GRADIENT_SOURCE Gsource SV_UDSI_G P1 dG es A_by_es 1 gammaO C_UDSI_DIFF c0 t0 P1 alphaO A_by_es ds beta0 Gsource alpha0 aterm alphaO0 gamma0 At Ibw SIGMA_SBC pow WALL_TEMP_OUTER f thread 4 M_PI Specify the radiative heat flux F_PROFILE f thread position aterm Ew Ew aterm 4 M_PI Ibw C_UDSI c0 t0 P1 betaO end_f_loop f thread DEFINE_HEAT_FLUX heat_flux f t c0 tO cid cir real Ew epsilon_w 2 2 epsilon_w cir 0 Ew F_UDSI f t P1 cir 3 4 0 Ew SIGMA_SBC 8 50 Fluent Inc September 11 2006 Appendix A A 1 C Programming Basics This chapter contains an overview of C programming basics for UDFs e Section A 1 e Section A 2 e Section A 3 e Section A 4 e Section A 5 e Section A 6 e Section A 7 e Section A 8 e Section A 9 e Section A 10 e Section A 11 e Section A 12 e Section A 13 e Section A 1
320. etic energy and dissipation rate respectively for a 2D fully developed duct flow Three separate UDFs named x velocity k profile and dissip profile are defined These functions are concatenated in a single C source file and can be interpreted or compiled in FLUENT The 1 7th power law is used to specify the x velocity component Ve Vr fi eM x Vx free 5 A fully developed profile occurs when 6 is one half the duct height In this example the mean x velocity is prescribed and the peak free stream velocity is determined by averaging across the channel The turbulent kinetic energy is assumed to vary linearly from a near wall value of to a free stream value of king 0 002u2 oo The dissipation rate is given by CB KA where the mixing length is the minimum of y and 0 0850 is the von Karman constant 0 41 Fluent Inc September 11 2006 2 69 DEFINE Macros The friction velocity and wall shear take the forms Ur VTw P FPu ee 2 Tw The friction factor is estimated from the Blasius equation 1 4 Ufree 0 045 eles PK kkk k ak kk ak ak k ak 2k ak K 3k 3k K K FK 2K K 3K 2K 2K K FK 2K 2K K 2K 2K K FK 3K 2K K FK 2K 2K K FK 2K K FK 3K K K FK 2K 2K FK FK 2K SL LS FK 2K 2K K FK 2K 2K K FK gt K Concatenated UDFs for fully developed turbulent inlet profiles EEEE ooo ooo oo kkk 21 kkk kkk kk kkk kkk kkk include udf h define YMIN 0 0 constants defin
321. f basename f then echo linking to f in d In s f fi done 5 16 Fluent Inc September 11 2006 5 3 Compile a UDF Using the TUI echo echo building library in d make k gt makelog 2 gt amp 1 cat makelog DN done linking to myudf c in 1nx86 2d building library in 1nx86 2d make 1 Entering directory udf_names c Generating udf_names make 2 Entering directory profile c make libudf so Compiling udf_names o Compiling profile o Linking libudf so make 2 Leaving directory udf_names c make 1 Leaving directory profile c You can also see the log file in the working directory for compilation history Done Fluent Inc September 11 2006 5 17 Compiling UDFs 5 3 3 Load the UDF Library You can load the shared library you compiled and built using the TUI from the Compiled UDFs panel or the UDF Library Manager panel Follow the procedure outlined in Step 9 of Section 5 2 Compile a UDF Using the GUI or in Section 5 5 Load and Unload Libraries Using the UDF Library Manager Panel respectively 5 4 Link Precompiled Object Files From Non FLUENT Sources FLUENT allows you to build a shared library for precompiled object file s that are derived from external sources using the text user interface TUI option For example you can link precompiled objects derived from FORTRAN sources 0 objects from f
322. f User Defined Memory on Faces mem h Macro Argument Types Usage F_UDMI f t i face_t f Thread t int i stores the face value of a user defined memory with index i There are three arguments to F_UDMI f t and i f is the face identifier t is a pointer to the face thread and i is an integer index that identifies the memory location where data is to be stored An index i of 0 corresponds to user defined memory location 0 or User Memory 0 Example Compute face temperature and store in user defined memory begin_f_loop f t temp F_T f t F_UDMI f t 0 temp tmin tmax tmin end_f_loop f t See Section 2 5 4 DEFINE DPM EROSION for another example of F_UDMI usage 3 42 Fluent Inc September 11 2006 3 2 Data Access Macros C_UDMI You can use C_UDMI to access or store the value of the user defined memory in a cell C_UDMI can be used to allocate up to 500 memory locations in order to store and retrieve the values of cell field variables computed by UDFs Table 3 2 38 These stored values can then be used for postprocessing for example or by other UDFs See Section 3 2 9 Ex ample UDF that Utilizes UDM and UDS Variables for an example of C_UDMI usage Table 3 2 38 Storage of User Defined Memory in Cells mem h Macro Argument Types Usage C_UDMI c t i cell_t c Thread t int i stores the cell value of a user defined memory with index i
323. f a time step or the end of an iteration This is done automatically when you select the steady or unsteady time method in your FLUENT model Usage DEFINE_EXECUTE_AT_END name Argument Type Description symbol name UDF name Function returns void There is only one argument to DEFINE EXECUTE AT END name You supply name the name of the UDF Unlike DEFINE_ADJUST DEFINE_EXECUTE_AT_END is not passed a do main pointer Therefore if your function requires access to a domain pointer then you will need to use the utility Get_Domain ID to explicitly obtain it see Section 3 2 6 Do main Pointer Get_Domain and the example below If your UDF requires access to a phase domain pointer in a multiphase solution then it will need to pass the appropriate phase ID to Get_Domain in order to obtain it Example The following UDF named execute_at_end integrates the turbulent dissipation over the entire domain using DEFINE_EXECUTE_AT_END and prints it to the console window at the end of the current iteration or time step It can be executed as an interpreted or compiled UDF in FLUENT Fluent Inc September 11 2006 2 9 DEFINE Macros pLa oo kkk kkk kkk kk kkk kkk kkk k kkk UDF for integrating turbulent dissipation and printing it to console window at the end of the current iteration or time step EEEE ooo OK DH DH A A 21 1 21 21 21 21 DH DH ED DH D OO include udf h DEFINE_EXECUTE_AT_END execute_at_end Domain d T
324. f you have previously interpreted or compiled a DEFINE_DIFFUSIVITY UDF then the User Defined Functions panel will open allowing you to hook your UDF to FLU ENT Othewise you will get an error Fluent Inc September 11 2006 6 17 Hooking UDFs to FLUENT 2 You have two options available for hooking diffusion coefficient UDF s to UDS equa tions You can either specify a UDF on a per UDS basis or you can hook a single diffusivity UDF that will apply to all scalar equations In the Materials panel choose either defined per uds or user defined from the drop down list for UDS Diffusivity Figure 6 2 4 and select the desired UDF Materials Name Material Type Order Materials By air fluid Name b Chemical Formula Fluent Fluid Materials Chemical Formula P fair Fluent Database Mixture User Defined Database none Cp j kg k constant Edit f 666 43 Properties Thermal Conductivity wim lconstant e Edit 0 0242 Viscosity kg m s constant Edit Fermes UDS Diffusivity kg m s ge fined per uds v Edit Change Create Delete Close Help Figure 6 2 4 The Materials Panel See Section 2 3 3 DEFINE DIFFUSIVITY for details about defining DEFINE_DIFFUSIVITY UDFs and the User s Guide for general information about UDS diffusivity 6 18 Fluent Inc September 11 2006 6 2 Hooking Model Specific UDFs 6 2 4 Hooking DEFINE_DOM_DIFFUSE_REFLECTIVITY
325. f you select the Replace with UDF Rate option in the SOx Model panel It is assumed that the release of fuel sulphur from fuel is proportional to the rate of release of volatiles and all sulphur is in the form of SO2 when released to the gas phase The reversible reaction for SO2 SO3 is given below SO O SO 02 2 3 8 with forward and reverse rates of reaction in the Arrhenius form ky 1 2 39765 575 RT ky 1 0e T 1e 10464 625 RT The O atom concentration in the gas phase is computed using the partial equilibrium assumption which states oeg 36 64705e 27123 0 RT D Here all units are in m gmol J sec The function so2_so3_rate is used to compute the forward and reverse rates for both SO and SOs The rate of release of SO from volatiles is given by r_volatile x Y s_volatile x fuels_so2_frac x 1000 MWs x V Sso volatile Fluent Inc September 11 2006 2 97 DEFINE Macros where r_volatile is the rate of release of volatiles Y s_volatile is the mass fraction of sulphur species in volatiles and fwels_so2_frac is the mass fraction of fuel S that converts to SO MWs is the molecular weight of sulphur and V is the cell volume Note that the reverse rate is divided by the respective species mass frac tion This practice is different from that used in prior versions of FLUENT where the actual reverse rate was stored without division by pollutant mass fraction See Section 3 2 7 SO Macros fo
326. faces are grouped into zones that typically define the physical components of the model e g inlets outlets walls fluid regions A face will bound either one or two cells depending on whether it is a boundary face or an interior face A domain is a data structure in FLUENT that is used to store information about a collection of node face threads and cell threads in a mesh node cell center simple 3D grid Figure 1 7 1 Grid Components Fluent Inc September 11 2006 1 9 Overview node grid point node thread grouping of nodes edge boundary of a face 3D face boundary of a cell 2D or 3D face thread grouping of faces cell control volume into which domain is broken up cell center location where cell data is stored cell thread grouping of cells domain a grouping of node face and cell threads 1 8 Data Types in FLUENT In addition to standard C language data types such as real int etc that can be used to define data in your UDF there are FLUENT specific data types that are associated with solver data These data types represent the computational units for a grid Figure 1 7 1 Variables that are defined using these data types are typically supplied as arguments to DEFINE macros as well as to other special functions that access FLUENT solver data Some of the more commonly used FLUENT data types are Node face_t cell_t Thread Domain Node is a structure data type that stores data associated with
327. file e g udfexample c at runtime The process involves a visit to the Interpreted UDFs panel where you can interpret all of the functions in a source file e g udfexample c in a single step Once a source file is interpreted you can write the case file and the names and contents of the interpreted function s will be stored in the case In this way the function s will be automatically interpreted whenever the case file is subsequently read Once interpreted either manually through the Interpreted UDFs panel or automatically upon reading a case file all of the interpreted UDFs that are contained within a source file will become visible and selectable in graphical user interface panel s in FLUENT Inside FLUENT the source code is compiled into an intermediate architecture independent machine code using a C preprocessor This machine code then executes on an internal emulator or interpreter when the UDF is invoked This extra layer of code incurs a performance penalty but allows an interpreted UDF to be shared effortlessly between different architectures operating systems and FLUENT versions If execution speed does become an issue an interpreted UDF can always be run in compiled mode without modification Fluent Inc September 11 2006 4 1 Interpreting UDFs 4 1 1 Location of the uaf h File UDFs are defined using DEFINE macros see Chapter 2 DEFINE Macros and the defi nitions for DEFINE macros are included in udf h he
328. fine Dynamic Mesh Zones Dynamic Mesh Zones Zone Names Dynamic Zones axis Type C Stationary Rigid Body C Deforming User Defined Motion Attributes Geometry Definition Meshing Options Mesh Motion UDF beam libudf i Draw Delete Update Close Help Figure 6 5 3 Dynamic Mesh Zones Select User Defined under Type in the Dynamic Mesh Zones panel Figure 6 5 3 and click on the Motion Attributes tab Choose the function name e g beam from the Mesh Motion UDF drop down list Click Create then Close See Section 2 6 3 DEFINE_GRID_MOTION for details about DEFINE_GRID_MOTION functions Fluent Inc September 11 2006 6 75 Hooking UDFs to FLUENT 6 76 6 5 4 Hooking DEFINE_SDOF_PROPERTIES UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_SDOF_PROPERTIES UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Dynamic Mesh Zones panel Figure 6 5 4 in FLUENT To hook the UDF to FLUENT you will first need to enable the Dynamic Mesh model Define Dynamic Mesh Parameters To enable the model select Dynamic Mesh under Model and click OK FA The Dynamic Mesh panel will be accessible only when you choose Unsteady as the time method in the Solver panel Next open the Dynamic Mesh Zones panel Define Dynamic Mesh
329. fine User Defined Scalars User Defined Scalars Number of User Defined Scalars 2 E M Inlet Diffusion User Defined Scalars Options UDS Index Solution Zones All fluid zones Edit Flux Function mass flow rate Figure 6 6 3 The User Defined Scalars Panel To hook the UDF to FLUENT first specify the Number of User Defined Scalars e g 2 in the User Defined Scalars panel Figure 6 6 3 As you enter the number of user defined scalars the panel will expand to show the Flux Function settings Next for each scalar you have defined increment the UDS Index and choose the Zone Type e g all fluid zones select the function e g my uds flux from the Flux Function drop down list and click OK Fluent Inc September 11 2006 6 81 Hooking UDFs to FLUENT 6 6 3 Hooking DEFINE_UDS_UNSTEADY UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_UDS_UNSTEADY UDF the name of the argument that you sup plied as the first DEFINE macro argument e g my_uds_unsteady will become visible and selectable in the User Defined Scalars panel Figure 6 6 4 in FLUENT Define User Defined Scalars User Defined Scalars Number of User Defined Scalars 2 M Inlet Diffusion UDS Index User Defined Scalars Options Solution Zones all fluid zones v li Flux Function mass tlow rate v Unsteady Function my_u
330. fine DEFINE_HFAT_FLUX name f t cO t0 cid cir void name face_t f Thread t cell_t c0 Thread t0 real cid real cir define DEFINE_NET_REACTION_RATE name c t particle pressure temp yi rr jac void name cell_t c Thread t Particle particle double pressure double temp double yi double rr B 2 Fluent Inc September 11 2006 B 2 Model Specific DEFINE Macro Definitions double jac define DEFINE_NOX_RATE name c t Pollut Pollut_Par NOx void name cell_t c Thread t Pollut_Cell Pollut Pollut_Parameter Poll_Par NOx_Parameter NOx define DEFINE_PRANDTL_K name c t real name cell_t c Thread t define DEFINE_PRANDTL_D name c t real name cell_t c Thread t define DEFINE_PRANDTL_O name c t real name cell_t c Thread t define DEFINE_PRANDTL_T name c t real name cell_t c Thread t define DEFINE_PRANDTL_T_WALL name c t real name cell_t c Thread t define DEFINE_PROFILE name t i void name Thread t int i define DEFINE_PROPFRTY name c t real name cell_t c Thread t define DEFINE_PR_RATE mame c t r mw ci p sf dif_index cat_index rr void name cell_t c Thread t Reaction r real mw real ci Tracked_Particle p real sf int dif_index int cat_index real rr define DEFINE_SCAT_PHASE_FUNC name c f real name real c real f define DEFINE_SOLAR_INTENSITY name sun_x sun_y sun_z S_hour S_minute real na
331. fined Function Hooks panel in FLUENT See Section 6 4 12 Hooking DEFINE DPM SPRAY COLLIDE UDFs for details on how to hook your DEFINE_DPM_SPRAY_COLLIDE UDF to FLUENT 2 1 84 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros 2 5 13 DEFINE DPM_ SWITCH Description You can use DEFINE DPM SWITCH to modify the criteria for switching between laws The function can be used to control the switching between the user defined particle laws and the default particle laws or between different user defined or default particle laws Usage DEFINE DPM SWITCH name p ci Argument Type Description symbol name UDF name Tracked Particle p Pointer to the Tracked Particle data structure which contains data related to the particle being tracked int ci Variable that indicates if the continuous and discrete phases are coupled equal to 1 if coupled with continuous phase 0 if not coupled Function returns void There are three arguments to DEFINE_DPM_SWITCH name p and ci You supply name the name of the UDF p and ci are variables that are passed by the FLUENT solver to your UDF Pointer p can be used as an argument to the macros defined in Sec tion 3 2 7 DPM Macros to obtain information about particle properties e g injection properties Example The following is an example of a compiled UDF that uses DEFINE_DPM_SWITCH to switch between DPM laws using a criterion The UDF switches to DPM_LAW_USER_1
332. g DEFINE Macros 1 41 Including the udf h Header File in Your Source File The udf h header file contains definitions for DEFINE macros as well as include compiler directives for C library function header files It also includes header files e g mem h for other Fluent supplied macros and functions You must therefore include the udf h file at the beginning of every UDF source code file using the include compiler directive include udf h For example when udf h is included in the source file containing the DEFINE statement from the previous section include udf h DEFINE_PROFILE inlet_x_velocity thread index upon compilation the macro will expand to void inlet_x_velocity Thread thread int index FH You won t need to put a copy of udf h in your local di rectory when you compile your UDF The FLUENT solver automatically reads the udf h file from the Fluent Inc fluent6 x src directory once your UDF is compiled Fluent Inc September 11 2006 1 5 Overview 1 5 Interpreting and Compiling UDFs Source code files containing UDFs can be either interpreted or compiled in FLUENT In both cases the functions are compiled but the way in which the source code is compiled and the code that results from the compilation process is different for the two methods These differences are explained below Compiled UDFs Compiled UDFs are built in the same way that the FLUENT executable itself is built A script
333. g DEFINE_ANISOTROPIC_DIFFUSIVITY UDFs 6 87 60 2 Hooking DEFINE UDS FEUX UDES o ca berote boeg ee po ewh 6 90 6 6 3 Hooking DEFINE UDS UNSTEADY UDFs 6 91 6 7 Common Errors While Hooking a UDF to FLUENT 6 92 7 Parallel Considerations 7 1 T L Overview or Parallel FLUENT 24 4 24 La mu eee pe Ree oo 7 1 7 1 1 Command Transfer and Communication 7 4 7 2 Celle and Faces in a Partitioned Grids 422 mou pa me a mate 7 7 T Paralelizing Your Serial UDP s eor a6 pass OS ek we eR ee 7 11 7 4 Parallelization of Discrete Phase Model DPM UDFs 7 12 to Macros for Parallel VFS so u do Juin ek ede eek Be eo se Haut 7 13 Tol Compiler Direciived 4 Lahaie eh Pe SG eds et ACY ee eS 7 13 7 5 2 Communicating Between the Host and Node Processes 7 16 tous Predicates 2 sis s s eid cdi hadi Shae hee ida 7 18 7 5 4 Global Reduction Macros seau ss EE ee eb a de dad 7 19 Tom LOMME Macros sss si 22 wads 6 4 Sek ba hed og SE NS 7 23 7 5 6 Cell and Face Partition ID Macros 7 30 tot Messe Displaying Macros 4 4 4 aba sante he eS 7 31 7 5 8 Message Passing Macros 7 32 7 5 9 Macros for Exchanging Data Between Compute Nodes 7 36 T6 Limitations of Parallel UDFS cee 24 444 acea 24 4244044 x 7 37 ta Process Ieuan se sice ests iie Re AEE RL ER SOS 7 39 Vill Fluent Inc September 11 2006 CONTENTS To Sorel UDF Pils oe d ew ee SE BER ew Ge ES
334. g DEFINE_INIT UDFs Once you interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs your DEFINE_INIT UDF it is ready to be hooked to FLUENT Note that you can hook multiple initialization UDFs to your model if desired Open the User Defined Function Hooks panel Figure 6 1 8 Define User Defined Function Hooks User Defined Function Hooks Initialization none Edit Adjust none Edit Execute at End none Edit Read Case none Edit Write Case none Edit Read Data none Edit Write Data none Edit Figure 6 1 8 The User Defined Function Hooks Panel Fluent Inc September 11 2006 6 9 Hooking UDFs to FLUENT Click on the Edit button next to Initialization This will open the Initialization Functions panel Figure 6 1 9 Initialization Functions Available Initialization Functions Selected Initialization Functions user_initl libudf user_init2 libudf Add Remove Figure 6 1 9 The Initialization Functions Panel In the Initialization Functions panel from the Available Initialization Functions you have in terpreted or compiled and loaded select the functions you wish to hook to your model and click Add and then OK Click OK in the User Defined Function Hooks panel to apply the settings The number of functions you select will then appear in the User Defined Func tion Hooks panel For example if you select two in
335. g model constant Cphi UDFs In the User Defined Function Hooks panel hook the UDF to FLUENT by choosing the function name e g user_cphi from the drop down list for Mixing Model Constant Cphi and click OK See Section 2 3 2 DEFINE_CPHI for details about defining DEFINE_CPHI functions 6 16 Fluent Inc September 11 2006 6 2 Hooking Model Specific UDFs 6 2 3 Hooking DEFINE DIFFUSIVITY UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DIFFUSIVITY UDF the name of the function you supplied as a DEFINE macro argument e g mean_diff_age will become visible and selectable in FLUENT To hook the UDF to FLUENT you will first need to open the Materials panel Define Materials 1 To hook a mass diffusivity UDF for the species tranpsort equations choose user defined from the drop down list for Mass Diffusivity Figure 6 2 3 Materials Name Material Type Order Materials By mixture tenplate mixture Name c 5 Chemical Formula Fluent Mixture Materials Phe ica Foule mixture template Fluent Database Mixture User Defined Database none Y Properties CP GK mixingtaw rai 7 Thermal Conductivity wim constant Edit 8 0454 Viscosity kg m s constant Edit 72e 05 0 Mace Dis 2s PSS ca mean_diff_age libudf Change Create Delete Close Help Figure 6 2 3 The Materials Panel I
336. general purpose DEFINE macros and multiphase specific DEFINE macros that can be used to define UDFs for multiphase model cases 1 10 1 Multiphase specific Data Types In addition to the FLUENT specific data types presented in Section 1 8 Data Types in FLUENT there are special thread and domain data structures that are specific to multiphase UDFs These data types are used to store properties and variables for the mixture of all of the phases as well as for each individual phase when a multiphase model i e Mixture VOF Eulerian is used In a multiphase application the top level domain is referred to as the superdomain Each phase occupies a domain referred to as a subdomain A third domain type the interaction domain is introduced to allow for the definition of phase interaction mechanisms When mixture properties and variables are needed a sum over phases the superdomain is used for those quantities while the subdomain carries the information for individual phases In single phase the concept of a mixture is used to represent the sum over all the species components while in multiphase it represents the sum over all the phases This distinction is important since FLUENT has the capability of handling multiphase multi components where for example a phase can consist of a mixture of species Since solver information is stored in thread data structures threads must be associated with the superdomain as well as with
337. gent of x y tan l x y The function cosh x is the hyperbolic cosine function etc double acos double x returns the arcosine of x double asin double x returns the arcsine of x double atan double x returns the arctangent of x double atan2 double x double y returns the arctangent of x y double cos double x returns the cosine of x double sin double x returns the sine of x double tan double x returns the tangent of x double cosh double x returns the hyperbolic cosine of x double sinh double x returns the hyperbolic sine of x double tanh double x returns the hyperbolic tangent of x A 13 2 Miscellaneous Mathematical Functions The C functions shown on the left below correspond to the mathematical functions shown on the right double sqrt double x yT double pow double x double y x double exp double x e7 double log double x ln x double log10 double x logio x double fabs double x z double ceil double x smallest integer not less than x double floor double x largest integer not greater than x A 14 Fluent Inc September 11 2006 A 13 C Library Functions A 13 3 Standard I O Functions A number of standard input and output I O functions are available in C and in FLU ENT They are listed below All of the functions work on a specified file except for printf which displays information that is specified in the argument of the function The format string argument is
338. gramming Basics A 14 Preprocessor Directives The UDF interpreter supports C preprocessor directives including define and include Macro Substitution Directive Using define When you use the define macro substitution directive the C preprocessor e g cpp performs a simple substitution and expands the occurrence of each argument in macro using the replacement text define macro replacement text For example the macro substitution directive given by define RAD 1 2345 will cause the preprocessor to replace all instances of the variable RAD in your UDF with the number 1 2345 There may be many references to the variable RAD in your function but you only have to define it once in the macro directive the preprocessor does the work of performing the substitution throughout your code In another example define AREA_RECTANGLE X Y X Y all of the references to AREA RECTANGLE X Y in you UDF are replaced by the product of X and Y File Inclusion Directive Using include When you use the include file inclusion directive the C preprocessor replaces the line include filename with the contents of the named file include filename The file you name must reside in your current directory The only exception to this rule is the udf h file which is read automatically by the FLUENT solver For example the file inclusion directive given by include udf h will cause the udf h file to be included with your so
339. h message passing method you are going to use An excerpt from a sample user nt udf file is shown below Replace text in and remove quotes indicates a choice note SRC is defined in the makefile Fluent Inc September 11 2006 5 13 Compiling UDFs 5 14 SOURCES SRC udfexample c VERSION 2d PARALLEL_NODE none 2 In the Visual Studio command prompt window go to each version directory e g libudf ntx86 2d and type nmake C users user_name work_dir libudf ntx86 2d gt nmake The following messages will be displayed Microsoft R Program Maintenance Utility Version 7 10 3077 Copyright C Microsoft Corporation All rights reserved cl c Za DUDF_EXPORTING Ic fluent inc fluent6 3 23 ntx86 2d Ic fluent inc fluent6 3 23 src Ic fluent inc fluent6 3 23 cortex sre Ic fluent inc fluent6 3 23 client sre Ic fluent inc fluent6 3 23 tgrid src Ic fluent inc fluent6 3 23 multiport sre src udfexample c Microsoft R 32 bit C C Standard Compiler Version 13 10 3077 for 80x86 Copyright C Microsoft Corporation 1984 2002 All rights reserved udfexample c Generating udf_names c because of makefile udfexample obj cl c Za DUDF_EXPORTING Ic fluent inc fluent6 3 13 ntx86 2d Ic fluent inc fluent6 3 23 src Ic fluent inc fluent6 3 13 cortex src Ic fluent inc fluent6 3 23 client src Ic fluent inc fluent6 3 23 tgrid src Ic fluent inc fluent6 3 23 multiport src udf_names c
340. han the number of local variables used 6 Keep the Display Assembly Listing option on if you want a listing of assembly lan guage code to appear in your console window when the function interprets This option will be saved in your case file so that when you read the case in a subsequent FLUENT session the assembly code will be automatically displayed 7 Click Interpret to interpret your UDF If the Display Assembly Listing option was chosen then the assembly code will appear in the console window when the UDF is interpreted as shown below x_velocity local pointer thread r0 local int nv r1 local end save local int f r3 push int 0 local pointer x r4 begin data 8 bytes O bytes initialized save pre inc int f r3 pop int b L3 22 restore restore ret v Note that if your compilation is unsuccessful then FLUENT will report an error and you will need to debug your program See Section 4 3 Common Errors Made While Interpreting A Source File for details 8 Click Close when the interpreter has finished 9 Write the case file The interpreted UDF named x velocity will be saved with the case file so that the function will be automatically interpreted whenever the case is subsequently read Fluent Inc September 11 2006 8 9 Examples Compile the Source File You can compile your UDF using the text user interface TUI or the graphical user interface GUI in FLUENT The GUI option for comp
341. have not yet been initialized such as the velocity at interior cells then an error will occur To avoid this kind of error an if else condition can be added to your code If if the data are available the function can be computed in the normal way If the data are not available else then no calculation or a trivial calculation can be performed instead Once the flow field has been initialized the function can be reinvoked so that the correct calculation can be performed FLUID_THREAD_P cxboolean FLUID_THREAD_P t You can use FLUID_THREAD _P to check whether a cell thread is a fluid thread The macro is passed a cell thread pointer t and returns 1 or TRUE if the thread that is passed is a fluid thread and 0 or FALSE if it is not Note that FLUID_THREAD_P t assumes that the thread is a cell thread For example FLUID_THREAD_P t0 returns TRUE if the thread pointer tO passed as an argument represents a fluid thread NULLP amp NNULLP You can use the NULLP and NNULLP functions to check whether storage has been allocated for user defined scalars NULLP returns TRUE if storage is not allocated and NNULLP returns TRUE if storage is allocated Below are some examples of usage NULLP T_STORAGE_R_NV tO SV_UDSI_G p1 NULLP returns TRUE if storage is not allocated for user defined storage variable NNULLP T_STORAGE_R_NV tO SV_UDSI_G p1 NNULLP returns TRUE if storage is allocated for user defined stor
342. he Edit button next to Execute At End This will open the Execute At End Functions panel Figure 6 1 5 Execute at End Functions Available Execute at End Functions Selected Execute at End Functions user_at_end1 libudf user_at_end2 libudf Figure 6 1 5 The Execute At End Functions Panel In the Execute At End Functions panel from the list of available UDFs you have interpreted or compiled and loaded select the functions you wish to hook to your model and click Add and then OK Click OK in the User Defined Function Hooks panel to apply the settings The number of functions you select will then appear in the User Defined Function Hooks panel For example if you select two adjust functions e g user_at_end1 user_at_end2 then the text box for Execute At End in the User Defined Function Hooks panel will display 2 selected See Section 2 2 3 DEFINE EXECUTE AT END for details about defining DEFINE_EXECUTE_AT_END functions Fluent Inc September 11 2006 6 1 Hooking General Purpose UDFs 6 1 4 Hooking DEFINE_EXECUTE_AT_EXIT UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_EXECUTE_AT_EXIT UDF it is ready to be hooked to FLUENT Note that you can hook multiple at exit UDFs to your model if desired Open the User Defined Function Hooks panel Figure 6 1 6 Define User Defined Function Hooks User Defined Functi
343. he ON DEMAND UDF sets the initial values of the UDM locations using udm_offset which is defined in the on loading UDF Note that the on demand UDF must be executed after the solution is initialized to reset the initial values for the UDMs See Sections 3 2 9 and 3 2 9 for more information on reserving and naming UDMs peaa o o kkk k k kkk kk kkk kk kk kkk kkk kkk kk kkk kkk k k k udm_res1 c contains two UDFs an execute on loading UDF that reserves three UDMs for libudf and renames the UDMs to enhance postprocessing and an on demand UDF that sets the initial value of the UDMs BER E DH DH DH EE DO KDE D kk kkk kk kkk kkk kk include udf h define NUM_UDM 3 static int udm_offset UDM_UNRESERVED DEFINE_EXECUTE_ON_LOADING on_loading libname if udm_offset UDM_UNRESERVED udm_offset Reserve_User_Memory_Vars NUM_UDM if udm_offset UDM_UNRESERVED 2 16 Fluent Inc September 11 2006 2 2 General Purpose DEF INE Macros Message nYou need to define up to 4d extra UDMs in GUI and then reload current library s n NUM_UDM libname else Message d UDMs have been reserved by the current library s n NUM_UDM libname Set_User_Memory_Name udm_offset lib1 UDM 0 Set_User_Memory_Name udm_offset 1 lib1 UDM 1 Set_User_Memory_Name udm_offset 2 lib1 UDM 2 Message nUDM Offset for Current Loaded Library 4d udm_offset DEFINE_ON_DEMAND set_udms Domain d Threa
344. he time step variable is then returned to the solver See Section 3 5 Time Dependent Macros for details on CURRENT TIME Fluent Inc September 11 2006 2 7 DEFINE Macros PERC o RIC I I I IOI KK AK AK A ACA A AK KKK KEK A ACA A A A AK KK KK OK UDF that changes the time step value for a time dependent solution BERR DK DH DH EEK I I I I OKI AAA DH A A I kK KK AK DH A A OO HE include udf h DEFINE_DELTAT mydeltat d real time_step real flow_time CURRENT_TIME if flow_time lt 0 5 time_step 0 1 else time_step 0 2 return time_step Hooking an Adaptive Time Step UDF to FLUENT After the UDF that you have defined using DEFINE DELTAT is interpreted Chapter 4 In terpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g mydeltat will become visible and selectable in the Iterate panel in FLUENT See Section 6 1 2 Hooking DEFINE_DELTAT UDFs for details Fluent Inc September 11 2006 2 2 General Purpose DEF INE Macros 2 2 3 DEFINE EXECUTE_AT_END Description DEFINE EXECUTE AT END is a general purpose macro that is executed at the end of an iteration in a steady state run or at the end of a time step in a transient run You can use DEFINE_EXECUTE_AT_END when you want to calculate flow quantities at these particular times Note that you do not have to specify whether your execute at end UDF gets executed at the end o
345. hmidt numbers Usage DEF INE_CPHI name c t Argument Type Description symbol name UDF name cellt c Cell index Thread t Pointer to cell thread Function returns real There are three arguments to DEFINE_CPHI name c and t You supply name the name of the UDF c and t are passed by the FLUENT solver to your UDF Your UDF will need to compute the real value of the mixing constant Cy and return it to the solver Hooking a Mixing Constant UDF to FLUENT After the UDF that you have defined using DEFINE_CPHI is interpreted Chapter 4 In terpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible and selectable in the Users Defined Function Hooks panel in FLUENT whenever the Composition PDF Transport model is enabled See Section 6 2 2 Hooking DEFINE CPHI UDFs for details Fluent Inc September 11 2006 2 33 DEFINE Macros 2 3 3 DEFINE DIFFUSIVITY Description You can use DEFINE DIFFUSIVITY to specify the diffusivity for the species transport equations e g mass diffusivity or for user defined scalar UDS transport equations See Section 8 6 User Defined Scalar UDS Diffusivity in the User s Guide for details about UDS diffusivity Usage DEFINE DIFFUSIVITY name c t i Argument Type Description symbol name UDF name cell tc Cell index Thread t Pointer to cell thread on which the diffusivity function is
346. hread t Integrate dissipation real sum_diss 0 cell_t c d Get_Domain 1 mixture domain if multiphase thread_loop_c t d if FLUID_THREAD_P t begin_c_loop c t sum_diss C_D c t C_VOLUME c t end_c_loop c t printf Volume integral of turbulent dissipation g n sum_diss fflush stdout Hooking an Execute at End UDF to FLUENT After the UDF that you have defined using DEFINE_EXECUTE_AT_END is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g execute_at_end will become visible and selectable in the User Defined Function Hooks panel in FLU ENT Note that you can hook multiple end iteration functions to your model See Sec tion 6 1 3 Hooking DEFINE_EXECUTE_AT_END UDFs for details 2 10 Fluent Inc September 11 2006 2 2 General Purpose DEF INE Macros 2 2 4 DEFINE_EXECUTE_AT_EXIT Description DEFINE EXECUTE AT EXIT is a general purpose macro that can be used to execute a func tion at the end of a FLUENT session Usage DEFINE_EXECUTE_AT_EXIT name Argument Type Description symbol name UDF name Function returns void There is only one argument to DEFINE_EXECUTE_AT_EXIT name You supply name the name of the UDF Hooking an Execute at Exit UDF to FLUENT After the UDF that you have defined using DEFINE_EXECUTE_AT_EXIT is interpreted Cha
347. iderations for Multiphase UDFs 1 17 1 10 1 Multiphase specific Data Types 1 17 2 DEFINE Macros 2 1 2A L O ss as 2 6 8 oe SR ee KG Ee Rte iron nee 2 1 2 2 General Purpose DEFINE Macros 22 54 ia eee be ee ee ee Es 2 2 22 1 DEFINE ADJUST pai e 5 ua es Same le AG sue BSD hae 2 4 22 2 DEPINE DELTAT 2 44 4 La ewe Gog Be dis eae ey wo 2 7 2 2 3 DEFINE EXECUTE AT END 4 2 9 22A DEPINE EXECUTE AT EXIT sa in We ti sueur 2 11 2 2 5 DEFINE EXECUTE FROM GUI 2 12 Fluent Inc September 11 2006 l CONTENTS 2 3 2 2 6 DEFINE EXECUTE ON LOADING aca ace Bae ge a 2 14 DT DEPINE INIT 5 4 saritas 2a Koa shui AR 2 17 2 2 8 DEFINE ON DEMAND o sna rerne Las das p er ks ek 2 19 229 DEFINE RWFILE 2 6 woke eA Bo aR Boe ee Bat ake 2 22 Model Specific DEFINE Macros 2 24 20 DEFINE CHEM STEP 4 be du 6 4 aa cb ha wR 2 29 2 9 2 DEPINE CPHL o aor e ba a ae ee a a E MANN we 2 31 293 DEFINE DIFFUSIVITY coe 4 ou ue bebeu bekon enG 2 32 2 3 4 DEFINE DOM DIFFUSE REFLECTIVITY 2 34 2 3 5 DEFINE DOM SOURGE gt sr 4 ea eh ee ee we E E 2 36 2 3 6 DEFINE_DOM_SPECULAR_REFLECTIVITY 2 38 2 3 7 DEFINE_GRAY_BAND_ABS_COEFF 2 40 2 3 8 DEFINE HEAT FLUX 4 4 5 4 4 a bra ba ba RR mu hu a 2 42 2 3 9 DEFINE NET REACTION RATE 6 sa se ade Lion ne d
348. igned to the compute nodes Since most operations are executed by the serial solver and either the host or compute nodes negated forms of compiler directives are more commonly used Note that the primary purpose of the host is to interpret commands from Cortex and to pass those commands and data to compute node 0 for distribution Since the host does not contain grid data you will need to be careful not to include the host in any calculations that could for example result in a division by zero In this case you will need to direct the compiler to ignore the host when it is performing grid related calculations by wrapping those operations around the if RP_HOST directive For example suppose that your UDF will compute the total area of a face thread and then use that total area to compute a flux If you do not exclude the host from these operations the total area on the host will be zero and a floating point exception will occur when the function attempts to divide by zero to obtain the flux Example if RP_HOST avg_pres total_pres_a total_area if you don t exclude the host this operation will result in a division by zero and error Remember that host has no data so its total will be zero endif You will need to use the if RP_NODE directive when you want to exclude compute nodes from operations for which they do not have data Below is a list of parallel compiler directives and what they do Note that if either RP_HO
349. iling a source file on a UNIX system is discussed below For details about compiling on other platforms e g Windows using the TUI to compile your function or for general questions about compiling UDFs in FLUENT see Chapter 5 Compiling UDFs 1 Make sure that the UDF source file e g udfexample c is in the same directory that contains your case and data file 2 Start FLUENT from your working directory 3 Read or set up your case file 4 Open the Compiled UDFs panel Figure 8 1 6 Define User Defined Functions gt Compiled Compiled UDFs Source Files Header Files udfexample c Add Delete Add Delete Library Name jipudf Build Figure 8 1 6 The Compiled UDFs Panel 5 Click Add under Source Files in the Compiled UDFs panel This will open the Select File panel Figure 8 1 7 8 10 Fluent Inc September 11 2006 8 1 Step By Step UDF Example Select File Look in C2 mywork e a e 2 My Recent Documents we etwork UDF Source File Judfexample c tel aces Files of type UDF Source Files x Cancel Figure 8 1 7 The Select File Panel 6 In the Select File panel under Directories choose the directory path that contains the C source file and then under Files select the desired file e g udfexample c you want to compile Once selected the complete path to the source file will be displayed
350. im P_OPER UNIVERSAL_GAS_CONSTANT T_prim concentration_sat psat_h2o T_sec UNIVERSAL_GAS_CONSTANT T_sec area_density 6 C_VOF c ts diam flux_evap mass_coeff concentration_sat concentration_evap_primary rr area_ density flux_evap Fluent Inc September 11 2006 2 1 31 DEFINE Macros Hooking a Heterogeneous Reaction Rate UDF to FLUENT After the UDF that you have defined using DEFINE_HET_RXN_RATE is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the ar gument that you supplied as the first DEFINE macro argument e g user_evap_condens_react will become visible and selectable under Reaction Rate Function in the Reactions tab of the Phase Interaction panel Note you will first need to specify the Total Number of Reactions greater than 0 See Section 6 3 3 Hooking DEFINE_HET_RXN_RATE UDFs for details 2 1 32 Fluent Inc September 11 2006 2 4 Multiphase DEF INE Macros 2 4 4 DEFINE MASS TRANSFER Description You can use DEFINE MASS TRANSFER when you want to model mass transfer in a multi phase problem The mass transfer rate specified using a DEFINE MASS TRANSFER UDF is used to compute mass momentum energy and species sources for the phases involved in the mass transfer For problems in which species transport is enabled the mass transfer will be from one species in one phase to another species in another phase If one of
351. in the Viscous Model panel and click OK See Section 23 21 DEFINE TURBULENT VISCOSITY for details about DEFINE_TURBULENT_VISCOSITY functions Fluent Inc September 11 2006 6 43 Hooking UDFs to FLUENT 6 2 22 Hooking DEFINE_VR_RATE UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_VR_RATE UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Function Hooks panel Figure 6 2 28 in FLUENT Define User Defined Function Hooks User Defined Function Hooks Initialization one Edit Adjust none Edit Execute at End none Edit Read Case none Edit Write Case none Edit Read Data none Edit Write Data none Edit Execute at Exit none Edit Wall Heat Flux mone Volume Reaction Rate user_vr_rate Cancel Help Figure 6 2 28 The User Defined Function Hooks Panel FA You must turn on the volumetric reactions option before you can hook the UDF by selecting Volumetric under Reactions in the Species Model panel To hook the UDF to FLUENT choose the function name e g user_vr_rate in the Volume Reaction Rate Function drop down list in the User Defined Function Hooks panel and click OK See Section 2 3 22 DEFINE_VR_RATE for details about DEFINE_VR_RATE functions 6 44 Fluent Inc September 11 2006 6 2 Hooking
352. ing Physical Models UDF Numerics Parallel User Defined Functions User Variables Body Force none Number of Scalars 8 Scalar Update melting_index Source none DPM Time Step none OK Injections Cancel Help Figure 6 4 11 The Discrete Phase Model Panel To hook the UDF to FLUENT choose the function name e g melting index in the Scalar Update drop down list under User Defined Functions Figure 6 4 11 and click OK See Section 2 0 10 DEFINE DPM SCALAR UPDATE for details about DEFINE DPM SCALAR UPDATE functions Fluent Inc September 11 2006 6 65 Hooking UDFs to FLUENT 6 4 11 Hooking DEFINE_DPM_SOURCE UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_SOURCE UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Discrete Phase Model panel Figure 6 4 12 in FLUENT Define Models Discrete Phase Discrete Phase Model Interaction Particle Treatment l Interaction with Continuous Phase l Unsteady Particle Tracking Tracking Physical Models UDF Numerics Parallel User Defined Functions User Variables Body Force none Number of Scalars 8 Scalar Update none Source dpm_source DPM Time Step none OK Injections Cancel Help Figure 6 4 12 The Discrete Phase Model Panel To hook the UD
353. ing DEFINE_GRAY_BAND_ABS_COEFF UDFs 6 23 6 2 8 Hooking DEFINE_HEATFLUX UDFs 6 24 6 2 9 Hooking DEFINE_NET_REACTION_RATE UDFs 6 25 6 2 10 Hooking DEFINE NOX RATE UDES 4 2 4 4 44 4 du 64 6 27 GALL Hooking DEFINS PR RATE UDFSs x ew a cee ew Ge des 6 29 6 2 12 Hooking DEFINE PRANDTL UDFs ss 44 4 4 444 4 ax 6 30 6 2 13 Hooking DEFINE PROFILE UDFs 6 31 6 2 14 Hooking DEFINE PROPERTY UDFs2 s res sh 88 ae5ae4 6 36 6 2 15 Hooking DEFINE_SCAT_PHASE_FUNC UDFs 6 38 6 2 16 Hooking DEFINE_SOLAR_INTENSITY UDFs 6 40 6 2 17 Hooking DEFINE SOURCE UDFs pcso ccc Lis oh wees 6 42 6 2 18 Hooking DEFINE SOX RATE UDES eo dor ateg dip eee ax ee eS 6 44 Fluent Inc September 11 2006 CONTENTS 6 219 Hooking DEFINE SRRATE UDES sor 4 5 Lis de wet ee ee eS 6 46 6 2 20 Hooking DEFINE_TURB_PREMIX_SOURCE UDFs 6 47 6 2 21 Hooking DEFINE_TURBULENT_VISCOSITY UDFs 6 48 6222 Hooking DEFINE VAR RATE UDPS 24 e eee ee 4 ma furse s 6 49 6 2 23 Hooking DEFINE_WALL_FUNCTIONS UDFs 6 50 6 3 Hooking Multiphase UDFs 6 51 6 3 1 Hooking DEFINE_CAVITATION_RATE UDFs 6 51 6 3 2 Hooking DEFINE EXCHANGE_PROPERTY UDFs 6 53 6 3 3 Hooking DEFINE HET RXN RATE UDFs 44 4 414 4 anxs 6 55 6 3 4 Hooking DEFINE MASS TRANSFER UDFs 6 56 6 3 5 Hooking DEFINE VECTOR EXCHANGE PROPERT
354. interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_VP_EQUILIB UDF the name of the function you supplied as a DEFINE macro argument e g raoult_vp will become visible and selectable from the Materials panel in FLUENT Before you hook the UDF you ll need to create your particle injections in the Injections panel with the Multicomponent option enabled Define Injections Click Create in the Injections panel to open the Set Injection Properties panel and set up your particle injections Next open the Materials panel Figure 6 4 16 Define Materials Materials Name Material Type Order Materials By particle mixture template particle mixture Name c gt Chemical Formula Fluent Particle Mixture Materials Re nn particle mixture template Fluent Database Mixture User Defined Database none Properties Density kg m3 constant v Edit 1 mll Cp jfkg k mass weighted mixing law v Edit Thermal Conductivity w m k mass weighted mixinglaw Edit Vapor Particle Equilibrium user defined v Edit Change Create Delete Close Help Figure 6 4 16 The Materials Panel 6 70 Fluent Inc September 11 2006 6 5 Hooking Dynamic Mesh UDFs Select your particle mixture material and then choose user defined from the drop down list for Vapor Particle Equilibrium This will open the
355. interpreting and compiling UDFs respectively in FLUENT e Interpreted UDFs are portable to other platforms can all be run as compiled UDFs do not require a C compiler are slower than compiled UDFs are restricted in the use of the C programming language cannot be linked to compiled system or user libraries can access data stored in a FLUENT structure only using a predefined macro see Chapters 3 Fluent Inc September 11 2006 1 7 Overview e Compiled UDFs execute faster than interpreted UDFs are not restricted in the use of the C programming language can call functions written in other languages specifics are system and compiler dependent cannot necessarily be run as interpreted UDFs if they contain certain elements of the C language that the interpreter cannot handle In summary when deciding which type of UDF to use for your FLUENT model e use interpreted UDFs for small straightforward functions e use compiled UDFs for complex functions that have a significant CPU requirement e g a property UDF that is called on a per cell basis every iteration require access to a shared library 1 6 Hooking UDFs to Your FLUENT Model Once your UDF source file is interpreted or compiled the function s contained in the interpreted code or shared library will appear in drop down lists in graphical interface panels ready for you to activate or hook to your CFD model Se
356. ion with Continuous Phase l Unsteady Particle Tracking Tracking Physical Models UDF Numerics Parallel Tracking Parameters Drag Parameters Max Number of Steps Drag Law 566 udt particle drag force l Specify Length Scale Step Length Factor 5 bo OK Injections Cancel Help Figure 6 4 3 The Discrete Phase Model Panel To hook the UDF to FLUENT choose the function name e g particle drag force in the Drag Law drop down list under Drag Parameters Figure 6 4 3 and click OK Note function names listed in the drop down list are preceded by the word udf as in udf particle drag force See Section 2 5 3 DEFINE DPM DRAG for details about DEFINE DPM DRAG functions 6 56 Fluent Inc September 11 2006 6 4 Hooking Discrete Phase Model DPM UDFs 6 4 4 Hooking DEFINE_DPM_EROSION UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_EROSION UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Discrete Phase Model panel Figure 6 4 4 in FLUENT Define Models Discrete Phase Discrete Phase Model Interaction Particle Treatment V Interaction with Continuous Phase Unsteady Particle Tracking Update DPM Sources Every Flow Iteration Number of Continuous Phase 10 Iterations per DPM Iteration Tracking Physical Models UDF Numeric
357. ique integer identifier that is stored as the global variable myid When you use myid in your parallel UDF it will return the integer ID of the current compute node including the host The host process has an ID of node host 999999 and is stored as the global variable node host Compute node 0 has an ID of 0 and is assigned to the global variable node zero Below is a list of global variables in parallel FLUENT Global Variables in Parallel FLUENT int node_zero 0 int node_host 999999 int node_one 1 int node_serial 1000000 int node_last returns the id of the last compute node int compute_node_count returns the number of compute nodes int myid returns the id of the current compute node and host myid is commonly used in conditional if statements in parallel UDF code Below is some sample code that uses the global variable myid In this example the total number of faces in a face thread is first computed by accumulation Then if myid is not compute node 0 the number of faces is passed from all of the compute nodes to compute node 0 using the message passing macro PRF_CSEND_INT See Section 7 5 8 Message Passing Macros for details on PRF_CSEND_INT Example Usage of myid int noface 0 begin_f_loop f tf loops over faces in a face thread and computes number of faces noface end_f_loop f tf Pass the number of faces from node 1 2 to node O Fluent Inc September 11 2
358. irectory make a directory that will store your UDF library e g libudf 2 Make a directory below this called src 3 Put all your UDF source files into this directory e g libudf src 4 Make an architecture directory below the library directory called ntx86 for Intel systems running Windows e g libudf ntx86 5 In the architecture directory e g libudf ntx86 create directories for the FLU ENT versions you want to build for your architecture e g ntx86 2d and ntx86 3d Possible versions are 5 10 Fluent Inc September 11 2006 5 3 Compile a UDF Using the TUI 2d or 3d single precision serial 2D or 3D 2ddp or 3ddp double precision serial 2D or 3D 2d_node and 2d_host single precision parallel 2D 3d_node and 3d_host single precision parallel 3D 2ddp_node and 2ddp host double precision parallel 2D 3ddp_node and 3ddp host double precision parallel 3D Note that you must create two build directories for each parallel version of the solver two for the 3D version two for the 2D double precision version etc regardless of the number of compute nodes 6 Copy user_nt udf from path Fluent Inc fluent6 src user nt udf to all the version subdirectories you have made e g libudf ntx86 3d Note that path is the directory in which you have installed the release directory Fluent Inc and x is replaced by the appropriate number for the release you have e g 3 for fluent6 3 7 Copy makefile nt udf fr
359. is needed when using DPM UDFs in parallel FLUENT with the exception of when you are writing in parallel to a sampling output file In this case you are not allowed to use the C function fprintf Instead new functions are provided to enable the parallel file writing Each node writes its information to separate files which are put together and sorted upon closure of the file by FLUENT The new functions can be used with the same parameter lists as the C function fprintf The sorting of the files in parallel requires the specification of an extended parameter list Information can be placed at the top of the file that will not sorted by using the function par_fprintf_head par_fprintf_head x coordinate y coordinate z coordinate n This function will place the string x coordinate y coordinate z coordinate at the top of the file Information is put on the nodes using the function par_fprintf par_fprintf d d he he e n p gt injection gt try_id p gt part_id P_POS p 0 P_POS p 1 P_POS p 2 Here the additional parameters p gt injection gt try_id and p gt part_id are required for the sorting in parallel The output written to the node specific file of these two parameters will be removed In serial these sorting parameters are not required and the function call is instead the following par_fprintf e he e n P_POS p 0 P_POS p 1 P_POS p 2 An example that utilizes these macros can be found in Section 2 5 8
360. is defined using the DEFINE_PROFILE macro The utility CURRENT_TIME is used to look up the real flow time which is assigned to the variable t See Section 3 5 Time Dependent Macros for details on CURRENT_TIME peaa oao o kkk k kk kkk kkk kk kk kkk kkk kkk kk kkk kkk k k k unsteady c UDF for specifying a transient velocity profile boundary condition BER o ooo ooo o KDE DH HE kkk kkk kk kkk kkk include udf h DEFINE_PROFILE unsteady_velocity thread position face_t f real t CURRENT_TIME begin_f_loop f thread F_PROFILE f thread position 20 5 0 sin 10 t end_f_loop f thread Fluent Inc September 11 2006 8 21 Examples Before you can interpret or compile the UDF you must specify an unsteady flow calcula tion in the Solver panel Then follow the procedure for interpreting source files using the Interpreted UDFs panel Section 4 2 Interpreting a UDF Source File Using the Interpreted UDFs Panel or compiling source files using the Compiled UDFs panel Section 5 2 Com pile a UDF Using the GUI The sinusoidal velocity boundary condition defined by the UDF can now be hooked to the inlet zone for the X Velocity In the Velocity Inlet panel simply select the name of the UDF given in this example with the word udf preceeding it udf unsteady velocity from the drop down list to the right of the X Velocity field Once selected the default value will become grayed out in the X Velocity field Cli
361. ists c1 is undefined for an external face Alternatively if the face is in the interior of the domain then both cO and c1 exist There are two macros F_CO f t and F_C1 f t that can be used to identify cells that are adjacent to a given face thread t F_CO expands to a function that returns the index of a face s neighboring cO cell Figure 3 2 2 while F_C1 returns the cell index for c1 Figure 3 2 2 if it exists Table 3 2 24 Adjacent Cell Index Macros Defined in mem h Macro Argument Types Returns F_CO f t face_t f Thread t cell_t c for cell c0 F_Ci f t face_t f Thread t cell_t c for cell cl See Section 2 7 3 DEFINE_UDS_FLUX for an example UDF that utilizes F_CO 3 22 Fluent Inc September 11 2006 3 2 Data Access Macros Adjacent Cell Thread THREAD_TO THREAD_T1 The cells on either side of a face may or may not belong to the same cell thread Referring to Figure 3 2 2 if a face is on the boundary of a domain then only cO exists c1 is undefined for an external face Alternatively if the face is in the interior of the domain then both cO and c1 exist There are two macros THREAD_TO t and THREAD_T1 t that can be used to identify cell threads that are adjacent to a given face f in a face thread t THREAD_TO expands to a function that returns the cell thread of a given face s adjacent cell c0 and THREAD T1 returns the cell thread for c1 if it exists Table 3 2 25
362. it hits the face in kg s Function returns void There are eight arguments to DEFINE_DPM_EROSION name p t f normal alpha Vmag and mdot You supply name the name of the UDF p t f normal alpha Vmag and mdot are variables that are passed by the FLUENT solver to your UDF Your UDF will need to compute the values for the erosion rate and or accretion rate and store the values at the faces in F_STORAGE_R f t SV_DPMS_EROSION and F STORAGE R t SV_DPMS_ACCRETION respectively Pointer p can be used as an argument to the macros defined in Sec tion 3 2 7 DPM Macros to obtain information about particle properties e g injection properties Fluent Inc September 11 2006 2 1 53 DEFINE Macros Example The following is an example of a compiled UDF that uses DEFINE_DPM_EROSION to extend post processing of wall impacts in a 2D axisymmetric flow It provides additional infor mation on how the local particle deposition rate depends on the diameter and normal velocity of the particles It is based on the assumption that every wall impact leads to more accretion and therefore every trajectory is evaporated at its first wall impact This is done by first setting a DPM user scalar within DEFINE_DPM_EROSION which is then evaluated within DEFINE_DPM_LAW where P_MASS is set to zero User defined mem ory locations UDMLs are used to store and visualize the following e number of wall impacts since UDMLs were reset
363. itialization functions e g user_init1 user_init2 then the text box for Initialization in the User Defined Function Hooks panel will display 2 selected See Section 2 2 7 DEFINE_INIT for details about defining DEFINE_INIT functions 6 10 Fluent Inc September 11 2006 6 1 Hooking General Purpose UDFs 6 1 6 Hooking DEFINE_ON_DEMAND UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_ON_DEMAND UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Execute On Demand panel Figure 6 1 10 in FLUENT Define User Defined Execute On Demand Execute on Demand Execute on Demand update Figure 6 1 10 The Execute On Demand Panel To hook the UDF to FLUENT choose the function name e g update in the Function drop down list in the Execute On Demand panel and click Execute FLUENT will execute the UDF immediately Click Close to close the panel See Section 2 2 8 DEFINE ON DEMAND for details about defining DEFINE ON DEMAND func tions Fluent Inc September 11 2006 6 11 Hooking UDFs to FLUENT 6 1 7 Hooking DEFINE_RW_FILE UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_RW_FILE UDF it is ready to be hooked to FLUENT Note that you can hook multiple read write file UDFs to your model if desired
364. ity components temperature heat flux heat generation rate heat transfer coefficient external emissivity external radiation temperature free stream temperature granular flux granular temperature user defined scalar boundary value discrete phase boundary value DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE DPM_BC phase dependent primary and secondary phase s mixture mixture mixture mixture mixture mixture mixture mixture secondary phase s secondary phase s mixture mixture Material Properties granular diameter granular viscosity granular bulk viscosity granular frictional viscosity granular conductivity granular solids pressure granular radial distribution granular elasticity modulus turbulent viscosity DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE TURBULENT_ VISCOSITY secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s mixture primary and secondary phase s Fluent Inc September 11 2006 C 6 Eulerian Model Per Phase Turbulence Flow Table C 6 3 DEFINE Macro Usage for the Eulerian Model Per Phase Tur
365. ivity UDFs are defined using the DEFINE_DIFFUSIVITY macro Section 2 3 3 DEFINE DIFFUSIVITY and anistropic coefficients UDFs are defined using DEFINE ANISOTROPIC DIFFFUSIVITY Section 2 7 2 DEFINE ANISOTROPIC DIFFUSIVITY Additional pre defined macros that you can use when coding UDS functions are provided in Section 3 2 8 User Defined Scalar UDS Transport Equation Macros Fluent Inc September 11 2006 2 209 DEFINE Macros Flux UDFs For each of the N scalar equations you have specified in your FLUENT model using the User Defined Scalars panel you can supply a unique user defined function or UDF for the advective flux term Recall that FLUENT computes the flux in the UDS equation UDS Flux UDFs are defined using the DEFINE UDS FLUX macro Section 2 7 3 DEFINE_UDS_FLUX Additional pre defined macros that you can use when coding scalar flux UDFs are provided in Section 3 2 8 User Defined Scalar UDS Trans port Equation Macros Unsteady UDFs For each of the N scalar equations you have specified in your FLUENT model using the User Defined Scalars panel you can supply a unique UDF for the unsteady function Recall that FLUENT computes the unsteady term in the UDS equation Scalar Unsteady UDFs are defined using the DEFINE_UDS_UNSTEADY macro Section 2 7 4 DEFINE_UDS_UNSTEADY Additional pre defined macros that you can use when coding scalar unsteady UDFs are provided in Section 3 2 8 User Defined Scalar UDS Transport E
366. ix A e must have an include statement for the udf h file Section 1 4 1 Including the udf h Header File in Your Source File e must be defined using DEFINE macros supplied by Fluent Inc Chapter 2 DEFINE Macros e utilize predfined macros and functions supplied by Fluent Inc to acccess FLUENT solver data and perform other tasks Chapter 3 Additional Macros for Writing UDFs e are executed as interpreted or compiled functions Chapter 4 Interpreting UDFs and Chapter 5 Compiling UDFs e are hooked to a FLUENT solver using a graphical user interface panel Chap ter 6 Hooking UDFs to FLUENT e use and return values specified in SI units Fluent Inc September 11 2006 1 2 Why Use UDFs 1 2 Why Use UDFs UDFs allow you to customize FLUENT to fit your particular modeling needs UDFs can be used for a variety of applications some examples of which are listed below e Customization of boundary conditions material property definitions surface and volume reaction rates source terms in FLUENT transport equations source terms in user defined scalar UDS transport equations diffusivity functions etc e Adjustment of computed values on a once per iteration basis e Initialization of a solution e Asynchronous on demand execution of a UDF e Execution at the end of an iteration upon exit from FLUENT or upon loading of a compiled UDF library e Post processing enhancement e Enhancement of existing FLUEN
367. k kak ak ak ak ak 2k 2k aK ak OR K 2K 2K K ak 2K 2K OR RR 2K 2K K FK 2K A 3K K K a 2k FK 2k 2K 2k FK 2k 2k K 2k 2 2k K 2k K 2k K 2k gt K UDF that models a custom law for evaporation swelling of particles EEEE ooo OO DH kkk kkk kkk A 2A kkk kkk include udf h DEFINE_DPM_LAW Evapor_Swelling_Law p ci real swelling_coeff 1 1 first call standard evaporation routine to calculate the mass and heat transfer VaporizationLaw p compute new particle diameter and density P_DIAM p P_INIT_DIAM p 1 swelling coeff 1 P_INIT_MASS p P_MASS p DPM_VOLATILE_FRACTION p P_INIT_MASS p P_RHO p P_MASS p 3 14159 P_DIAM p P_DIAM p P_DIAM p 6 P_RHO p MAX O 1 MIN 1e5 P_RHO p J Hooking a Custom DPM Law to FLUENT After the UDF that you have defined using DEFINE_DPM_LAW is interpreted Chapter 4 In terpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible in the Custom Laws panel in FLUENT See Section 6 4 7 Hooking DEFINE DPM LAW UDFs for details on how to hook your DEFINE DPM LAW UDF to FLUENT Fluent Inc September 11 2006 2 1 67 DEFINE Macros 2 5 8 DEFINE_DPM_OUTPUT Description You can use DEFINE_DPM_OUTPUT to modify what is written to the sampling device output This function allows access to the variables that are written as a particle passes through a sampler
368. k kkk k kk k kK k OR IRR IR 2k Kk KKK K 2k 2 2k 2 2k K 2k 2k 2 LC 2k 6 2k KKK include udf h DEFINE_ON_DEMAND on_demand_calc Domain d declare domain pointer since it is not passed as an argument to the DEFINE macro real tavg 0 real tmax 0 real tmin 0 real temp volume vol_tot Thread t cell_t c d Get_Domain 1 Get the domain using Fluent utility Loop over all cell threads in the domain thread_loop_c t d Compute max min volume averaged temperature Loop over all cells begin_c_loop c t volume C_VOLUME c t get cell volume temp C_T c t get cell temperature if temp lt tmin tmin 0 tmin temp if temp gt tmax tmax 0 tmax temp vol_tot volume tavg temp volume end_c_loop c t tavg vol_tot printf n Tmin g Tmax g Tavg g n tmin tmax tavg 2 22 Fluent Inc September 11 2006 2 2 General Purpose DEF INE Macros Compute temperature function and store in user defined memory location index 0 begin_c_loop c t temp C_T c t C_UDMI c t 0 temp tmin tmax tmin end_c_loop c t Get Domain is a macro that retrieves the pointer to a domain It is necessary to get the domain pointer using this macro since it is not explicitly passed as an argument to DEFINE_ON_DEMAND The function named on_demand_calc does not take any explicit arguments Withi
369. kefile An excerpt from a sample makefile is shown below for re makefile for user defined functions for rr re fr rr rr re User modifiable section Fluent Inc September 11 2006 5 15 Compiling UDFs SOURCES udfexamplel c FLUENT_INC path Fluent Inc Precompiled User Object files for example o files from f sources USER_OBJECTS Build targets do not modify below this line 3 In your library directory e g Libudf execute the Makefile by typing a command that begins with make and includes the architecture of the machine you will run FLUENT on which you identified in a previous step For example for the Linux 1nx86 architecture type make FLUENT_ARCH 1nx86 FLUENT will build a shared library for each version you created a directory for Section 5 3 1 Set Up the Directory Structure and will display messages about the compile build process on the console window You can view the compilation history in the log file that is saved in your working directory For example when compiling building a shared library for a source file named profile c and a UDF library named libudf on a Linux architecture the console messages may include the following Working for d in 1nx86 23 do CN cd d for f in src ch src makefile do if
370. kk kk kkk k kkk Custom turbulent viscosity functions for each phase and the mixture in a two phase multiphase flow EEEE o DH DH DH EEE DO HD A A kK 1 21 DK kkk D kkk kk kkk kkk include udf h DEFINE_TURBULENT_VISCOSITY mu_t_ke_mixture c t real mu_t real rho C_R c t real k C_K c t r al d C_D c t real cmu M_keCmu mu_t rhoxcmuxkxk d return mu_t DEFINE_TURBULENT_VISCOSITY mu_t_ke_1 c t Thread tm lookup_thread_by_id DOMAIN_SUPER_DOMAIN THREAD_DOMAIN t t gt id CACHE_T_SV_R density t SV_DENSITY CACHE_T_SV_R mu_t t SV_MU_T CACHE_T_SV_R density_m tm SV_DENSITY CACHE_T_SV_R mu_t_m tm SV_MU_T return density c density_m c mu_t_m c DEFINE_TURBULENT_VISCOSITY mu_t_ke_2 c t Thread tm lookup_thread_by_id DOMAIN_SUPER_DOMAIN THREAD_DOMAIN t t gt id CACHE_T_SV_R density t SV_DENSITY CACHE_T_SV_R mu_t t SV_MU_T CACHE_T_SV_R density_m tm SV_DENSITY CACHE_T_SV_R mu_t_m tm SV_MU_T return density c density_m c mu_t_m c Fluent Inc September 11 2006 2 109 DEFINE Macros Hooking a Turbulent Viscosity UDF to FLUENT After the UDF that you have defined using DEFINE_TURBULENT_VISCOSITY is interpreted Chapter 4 Interpreting UDF s or compiled Chapter 5 Compiling UDFs the function name s that you specified in the DEFINE macro argument s for example user_mu_t for single phase or mu_t_ke mixture mu_t_ke_1
371. l Logicals Macro Action PRF_GLOR1 x TRUE when variable x is TRUE for any of the compute nodes PRF_GLOR x N work TRUE when any of the elements in variable array x is TRUE PRF_GLAND1 x TRUE when variable x is TRUE for all compute nodes PRF_GLAND x N iwork TRUE when every element in variable array x is TRUE Global Synchronization PRF_GSYNC can be used when you want to globally synchronize compute nodes before proceeding with the next operation When you insert a PRF_GSYNC macro in your UDF no commands beyond it will execute until the preceding commands in the source code have been completed on all of the compute nodes Synchronization may also be useful when debugging your function 7 5 5 Looping Macros There are three types of cell looping macros that are available for parallel coding one that loops over interior cells only exterior cells only and both interior and exterior cells Looping Over Cells A partitioned grid in parallel FLUENT is made up of interior cells and exterior cells see Figure 7 2 1 There is a set of cell looping macros you can use to loop over interior cells only exterior cells only or both interior and exterior cells Fluent Inc September 11 2006 7 23 Parallel Considerations Figure 7 5 1 Looping Over Interior Cells in a Partitioned Grid Using begin end_c_loop_int indicated by the green cells Interior Cell Looping Macro The macro begin end c loop int loops over interior cells in
372. l VariaDles accu pure Eo RN Eo sie Ww are A 5 A53 Static Variables op yore 8 ce a de he EO we 48 OS A 7 Fluent Inc September 11 2006 IX CONTENTS A0 User Defined Data Types lt 4 40 lt 4 266 eed ae Da ee aS A 8 AT COR sa po sea us raie SUV RO ee Pd ee ae A 8 A8 Functions os eae we Rw ew ee ESR ER ee A Ee A 8 AD SOONG eae eV WLS MERE E eR Se RI ee ck Ha SS i A 9 GU POES e es ee ee we BE EER ee CR ee aw oe OES A 9 Avil Control Statements i 6 2 Lau Re eRe du Ed eat REM EHS A 11 ATLI af eee cer wk ee ke Se AR Re a A 11 AJI if elseStatement oi e es ee ee NS eS SH GORD A 11 ATIS for Loops gf oe Sk VES Va Ra last dr Rs E A 12 A 12 Common C Operators 4 das eh 60 de ete de de de ae EEE de on A 13 A 12 1 Arithmetic Operators oc cires bo we de de ROK du A 13 AIDE Logical Operators ao se c mor ace EEE SEES Re ER A 13 AT C Library Functions osa c a saras 4 kade ue aS RE AE RE RRS A 14 A131 Trigonometrie P nctionS es lt s koros osor ee ee ai k ehi A 14 A 13 2 Miscellaneous Mathematical Functions A 14 A133 Standard I O Functions o nga 44n 40 ba woes de d s A 15 A 14 Preprocessor Directives A 18 Als Comparison with FORTRAN sai sasoe aane oo ee a sp A 19 B DEFINE Macro Definitions B 1 B 1 General Solver DEFINE Macros B 1 B 2 Model Specific DEFINE Macro Definitions B 2 B 3 Multiphase DEFINE Macros
373. l need to return the real value of the drag force on a particle The value returned to the solver must be dimensionless and represent 18 Cd Re 24 Pointer p can be used as an argument to the macros defined in Sec tion 3 2 7 DPM Macros to obtain information about particle properties e g injection properties Example The following UDF named particle_drag force computes the drag force on a particle and is a variation of the body force UDF presented in Section 2 5 2 DEFINE_DPM_BODY_FORCE The flow is the same but a different curve is used to describe the particle drag DEFINE_DPM_DRAG is called at every particle time step in FLUENT and requires a significant amount of CPU time to execute For this reason the UDF should be executed as a compiled UDF Fluent Inc September 11 2006 2 1 51 DEFINE Macros DECC AAA A o k k kak a k kkk LS UDF for computing particle drag coefficient 18 Cd Re 24 curve as suggested by R Clift J R Grace and M E Weber Bubbles Drops and Particles 1978 BERR RRR kk kia ak a include udf h DEF INE_DPM_DRAG particle_drag_force Re p real w drag_force if Re lt 0 01 drag_force 18 0 return drag_force else if Re lt 20 0 w log10 Re drag_force 18 0 2 367 pow Re 0 82 0 05 w return drag_force else Note suggested valid range 20 lt Re lt 260 drag_force 18 0 3 483 pow Re 0 6305 return drag_force Hooking a
374. lect the UDF source file you want to interpret by either typing the complete path in the Source File Name field or click Browse This will open the Select File panel Figure 4 2 2 Fluent Inc September 11 2006 4 3 Interpreting UDFs Select File Look in CD mywork e ec e 4 My Recent Documents My Network UDF Source File Judfexample c bd Places Files of type UDF Source Files E Cancel Figure 4 2 2 The Select File Panel 6 In the Select File panel highlight the directory path under Directories e g nfs homeserver home clb mywork when running Linux and the desired file e g udfexample c under Files Once highlighted the complete path to the source file will be displayed under Source File s Click OK The Select File panel will close and the complete path to the file you selected e g udfexample c will appear under Source File Name in the Interpreted UDFs panel Figure 4 2 1 FH If you are running FLUENT on a network of Windows machines you may need to type the file s complete path in the Source File Name field instead of using the browser option For example to interpret udfexample c that is located in a shared working directory named mywork you would enter the following lt fileserver gt mywork udfexample c This text goes into the Source File Name field in the Interpreted UDFs panel replacing lt fileserver gt with the name of the computer on which your wo
375. led Object Files From Non FLUENT Sources 5 19 5 4 1 Example Link Precompiled Objects to FLUENT 5 19 5 5 Load and Unload Libraries Using the UDF Library Manager Panel 5 25 5 6 Common Errors When Building and Loading a UDF Library 5 27 5 7 Special Considerations for Parallel FLUENT 5 28 Fluent Inc September 11 2006 V CONTENTS vi 6 Hooking UDFs to FLUENT 6 1 6 1 Hooking General Purpose UDFS 2 44 4 dus 8 durs a eee EES 6 1 6 1 1 Hooking DEFINE ADJUST UDFs 4 due ee we ees 6 2 O12 Hooking DEFINE DELTAT UDES e c x sa ecri se BaP adc 6 4 6 1 3 Hooking DEFINE _EXECUTE _AT_END UDFs 6 6 6 1 4 Hooking DEFINE EXECUTE AT _EXIT UDFs 6 8 6 1 5 Hooking D FINE INIT UDES 4 44 4 Au ve avi isa EY So 6 10 6 1 6 Hooking DEFINE ON _DEMAND UDFs 6054554 6 12 6 1 7 Hooking DEFINE RWFILE UDES 242 2244 6284444 48 4 44 6 13 6 1 8 User Defined Memory Storage 6 15 6 2 Hooking Model Specific UDFs o c si cea ceses ba de don sata 6 15 6 2 1 Hooking DEFINE_CHEM STEP UDFs 6 16 6 2 2 Hooking DEFINE_CPHI UDFS 4 44 44 44 du aus 6 17 6 2 0 Hooking DEFINE DIFFUSIVITY UDFS gt gt 4 4 404 4 ue 6 18 6 2 4 Hooking DEFINE DOM DIFFUSE_REFLECTIVITY UDFs 6 20 6 2 5 Hooking DEFINE DOM SOURCE UDFs 6 21 6 2 6 Hooking DEFINE DOM SPECULAR REFLECTIVITY UDFs 6 22 6 2 7 Hook
376. led UDF The single user defined scalar transport equation for incident radiation G uses a DEFINE DIFFUSIVITY UDF to define I of Equation 8 2 6 and a UDF to define the source term of Equation 8 2 7 The boundary condition for G at the walls is handled by assigning in DEFINE_PROFILE the negative of Equation 8 2 11 as the specified flux A DEFINE_ADJUST UDF is used to instruct FLUENT to check that the proper number of user defined scalars has been defined in the solver Lastly the energy equation must be assigned a source term equal to the negative of that used in the incident radiation equation and the DEFINE HEAT FLUX UDF is used to alter the boundary conditions at the walls for the energy equation In the solver at least one user defined scalar UDS equation must be enabled The scalar diffusivity is assigned in the Materials panel for the scalar equation The scalar source and energy source terms are assigned in the boundary condition panel for the fluid zones The boundary condition for the scalar equation at the walls is assigned in the boundary condition panel for the wall zones The DEFINE_ADJUST and DEFINE_HEAT_FLUX functions are assigned in the User Defined Function Hooks panel Note that the residual monitor for the UDS equation should be reduced from le 3 to le 6 before running the solution If the solution diverges then it may be due to the large source terms In this case the under relaxation factor should be reduced to 0 9
377. lerian Model Laminar Flow Tables C 3 1 C 3 3 list the variables that can be customized using UDFs for the laminar flow Eulerian multiphase model the DEFINE macros that are used to define the UDFs and the phase that the UDF needs to be hooked to for the given variable Fluent Inc September 11 2006 C 7 Quick Reference Guide for Multiphase DEFINE Macros Table C 3 1 DEFINE Macro Usage for the Eulerian Model Laminar Flow Variable Macro Phase Specified On Boundary Conditions Inlet Outlet volume fraction species mass fractions mass flux flow direction components velocity magnitude temperature pressure user defined scalar boundary value discrete phase boundary value DEFINE_PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE DPM BC secondary phase s phase dependent primary and secondary phase s primary and secondary phase s primary and secondary phase s primary and secondary phase s mixture mixture mixture Fluid mass source momentum source energy source species source granular temperature source user defined scalar source velocity temperature DEFINE SOURCE DEFINE SOURCE DEFINE_ SOURCE DEFINE SOURCE DEFINE SOURCE DEFINE SOURCE DEFINE PROFILE DEFINE PROFILE primary and secondary phase s primary and secondary phase s primary and secondary phase s phase dependent seco
378. lie on the partition boundary of a compute node s grid begin end f loop is a face looping macro available in parallel FLUENT that loops over all interior and boundary zone faces in a compute node The macro begin end_f_loop contains a begin and end statement and between these statements operations can be performed on each of the faces of the thread The macro is passed a face index f and face thread pointer tf begin_f_loop f tf end_f_loop f tf FH begin f loop int and begin f loop ext are looping macros that loop around interior and exterior faces in a compute node respectively The int form is equivalent to begin_f_loop_int Although these macros exist they do not have a practical application in UDFs and should not be used Recall that partition boundary faces lie on the boundary between two adjacent compute nodes and are represented on both nodes Therefore there are some computations e g summations when a partition boundary face will get counted twice in a face loop This can be corrected by testing whether the current node is a face s principal compute node inside your face looping macro using PRINCIPAL_FACE_P This is shown in the example below See Section 7 2 Cells and Faces in a Partitioned Grid for details 7 28 Fluent Inc September 11 2006 7 5 Macros for Parallel UDFs Example begin_f_loop f tf each compute node checks whether or not it is the principal compute node with respect to the give
379. llel 7 16 7 17 compiled UDFs 1 2 1 6 building shared library 5 2 example 8 38 8 46 GUI 5 4 restrictions 1 7 Fluent Inc September 11 2006 Index shared library 1 6 Windows parallel network 5 4 5 7 5 28 writing case files 5 9 Compiled UDFs panel 5 2 5 5 8 10 compiler directives 1 5 about 7 13 example 7 14 compiling source files procedure 5 4 using GUI 5 4 compiling UDF source files 5 1 compute nodes 7 4 connectivity macros 3 6 3 8 control statements A 11 cphi UDFs 2 33 cpp 4 5 8 8 CPP Command Name 4 5 8 8 cross product 3 67 CURRENT_TIME 2 7 3 69 8 21 CURRENT_TIMESTEP 3 69 Custom Laws panel 6 61 6 68 data file functions reading and writing 2 24 data structure pointers 1 11 data structures thread 1 9 data types about 1 10 case sensitive 1 10 cell index 1 10 Domain 1 10 face index 1 10 node 1 10 thread 1 10 user defined A 8 Data_Valid_P 2 6 2 197 3 74 debugging your UDF 4 6 DEFINE macros 1 2 1 4 2 1 compilation error 1 4 DPM 2 139 Fluent Inc September 11 2006 dynamic mesh 2 196 format 1 4 general solver 2 2 model specific 2 26 multiphase 1 17 2 117 Eulerian model C 7 C 11 C 14 C 18 Mixture model C 4 VOF model C 1 define A 18 DEFINE ADJUST UDFs defining 2 4 example 8 48 hooking to FLUENT 6 2 DEF INE_ANISOTROPIC_DIFFUSIVITY UDFs defining 2 211 hooking to FLUENT 6 78 DEFINE_CAVITATION_RATE UDFs defining 2 119
380. load and unload multiple shared libraries in FLUENT Load the UDF Library To load a UDF library in FLUENT open the UDF Library Manager panel Figure 5 5 1 Define gt User Defined Functions gt Manage UDF Library Manager UDF Libraries Library Name Load Unload Close Help Figure 5 5 1 The UDF Library Manager Panel 1 In the UDF Library Manager panel type the name of the shared library in the Library Name field and click Load Figure 5 5 1 A message will be displayed on the console window providing a status of the load process For example 5 24 Fluent Inc September 11 2006 5 5 Load and Unload Libraries Using the UDF Library Manager Panel Opening library libudf Library libudf hpux11 2d libudf so opened inlet_x_velocity Done indicates that the shared library named libudf was successfully loaded on an HP machine and contains one UDF named inlet_x_velocity In the UDF Library Manager panel the library name e g libudf will be added under UDF Libraries Repeat this step to load additional libraries Unload the UDF Library To unload a UDF library in FLUENT open the UDF Library Manager panel Figure 5 5 2 Define gt User Defined Functions gt Manage UDF Library Manager UDF Libraries Library Name PO Load Unload Close Help Figure 5 5 2 The UDF Library Manager Panel 1 In the UDF Library
381. log A message will also be reported to the console and log file Error get_udf_function function dpm_timestep libudf has wrong type 28 26 Error Object f Fluent Inc September 11 2006 6 83 Hooking UDFs to FLUENT 6 84 Fluent Inc September 11 2006 Chapter 7 Parallel Considerations This chapter contains an overview of user defined functions UDFs for parallel FLUENT and their usage Details about parallel UDF functionality can be found in the following sections e Section 7 1 Overview of Parallel FLUENT e Section 7 2 Cells and Faces in a Partitioned Grid e Section 7 3 Parallelizing Your Serial UDF e Section 7 4 Parallelization of Discrete Phase Model DPM UDFs e Section 7 5 Macros for Parallel UDFs e Section 7 6 Limitations of Parallel UDFs e Section 7 7 Process Identification e Section 7 8 Parallel UDF Example e Section 7 9 Writing Files in Parallel 7 1 Overview of Parallel FLUENT Fluent Inc s parallel solver computes a solution to a large problem by simultaneously using multiple processes that may be executed on the same machine or on different ma chines in a network It does this by splitting up the computational domain into multiple partitions Figure 7 1 1 and assigning each data partition to a different compute pro cess referred to as a compute node Figure 7 1 2 Each compute node executes the same program on its own data set simultaneously with every other compute node The
382. low boundary UDFs are defined using the DEFINE PROFILE macro Section 2 3 13 DEFINE PROFILE Additional pre defined macros that you can use for coding scalar transport equation UDFs are provided in Section 3 2 8 User Defined Scalar UDS Transport Equation Macros 2 7 2 DEFINE_ANISOTROPIC_DIFFUSIVITY Description You can use DEFINE_ANISOTROPIC_DIFFUSIVITY to specify an anisotropic diffusivity for a user defined scalar UDS tranpsort equation See Section 8 6 2 Anisotropic Diffusion in the User s Guide for details about anisotropic diffusivity material properties in FLUENT Usage DEFINE ANISOTROPIC _DIFFUSIVITY name c t i dmatrix Argument Type Description symbol name UDF name cell t Cell index Thread t Pointer to cell thread on which the anisotropic diffusivity function is to be applied int i Index that identifies the user defined scalar real dmatrix ND ND ND ND Anisotropic diffusivity matrix to be filled in by user Function returns void There are five arguments to DEFINE_ANISOTROPIC_DIFFUSIVITY name c t i and dmatrix You will supply name the name of the UDF c t i and dmatrix are variables that are passed by the FLUENT solver to your UDF Your function will compute the dif fusivity tensor for a single cell and fill dmatrix with it Note that anisotropic diffusivity UDFs are called by FLUENT from within a loop on cell threads Consequently your UDF will not need to loop over cells in a thread since
383. lpha rng_alpha 1 mu mu_t mu pr_d mu_t mutmu_t alpha mu return pr_d DEFINE_SOURCE eps_r_source c t dS eqn 2 60 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros real con source real mu C_MU_L c t real mu_t C_MU_T c t real k C_K c t real d C_D c t real prod C_PRODUCTION c t real s sqrt prod mu mu_t real eta s k d real eta_0 4 38 real term mu_t s s s 1 0 0 012 eta etax eta source term 1 eta eta_0O dSleqn term d return source Hooking a Prandtl Number UDF to FLUENT After the UDF that you have defined using DEFINE PRANDTL K is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user_pr_k will become visible and selectable in the Viscous Model panel in FLUENT See Sec tion 6 2 12 Hooking DEFINE_PRANDTL UDFs for details Fluent Inc September 11 2006 2 61 DEFINE Macros DEF INE_PRANDTL_O Description You can use DEFINE PRANDTL O to specify Prandtl numbers for specific dissipation w in the k w model Usage DEFINE_PRANDTL_O name c t Argument Type Description symbol name UDF name cell_t c Index that identifies the cell on which the Prandtl number function is to be applied Thread t Pointer to cell thread Function returns real There are three arguments to DEFINE
384. lt psat has units of Pascals psat H20_PC exp ans1 return psat i DEFINE_HET_RXN_RATE user_evap_condens_react c t hr mw yi rr rr_t Thread pt THREAD_SUB_THREADS t Thread tp pt 0 Thread ts pt 1 int i real concentration_evap_primary accum 0 mole_frac_evap_prin concentration_sat real T_prim C_T c tp primary phase gas temperature real T_sec C_T c ts secondary phase droplet temperature real diam C_PHASE_DIAMETER c ts secondary phase diameter real D_evap_prim C_DIFF_EFF c tp index_evap_primary 0 7 C_MU_T c tp C_R c tp primary phase species turbulent diffusivity real Re Sc Nu urel urelx urely urelz 0 mass_coeff area_density flux_evap if Data_Valid_P 2 1 30 Fluent Inc September 11 2006 2 4 Multiphase DEF INE Macros urelx C_U c tp C_U c ts urely C_V c tp C_V c ts if RP_3D urelz C_W c tp C_W c ts endif urel sqrt urelx urelx urely urely urelz urelz relative velocity Re urel diam C_R c tp C_MU_L c tp Sc C_MU_L c tp C_R c tp D_evap_prim Nu 2 0 6 pow Re 0 5 pow Sc 0 333 mass_coeff Nu D_evap_prim diam for i 0 i lt MAX_SPE_EQNS_PRIM i accum accum C_YI c tp i mw i prim_index mole_frac_evap_prim C_YI c tp index_evap_primary mwlindex_evap_primary prim_index accum concentration_evap_primary mole_frac_evap_pr
385. lver DEFINE macros incident radiation 8 46 quick reference guide 2 2 include A 18 generic_property 2 84 initialization UDFs 2 19 Get_Domain 1 11 2 9 2 21 3 27 3 54 Injections panel 6 58 6 59 6 70 global reduction macros 7 18 input output functions A 15 gradient vector macros 3 9 interaction domains 1 17 gray band coefficient UDFs 2 42 interior cell looping macro parallel 7 24 Index 8 Fluent Inc September 11 2006 Index interior faces partitioned grid 7 31 INTERIOR_FACE_GEOMETRY 3 23 interpreted UDFs 1 2 1 6 4 1 4 3 C compiler 1 7 C preprocessor 1 6 errors in interpreting source file 4 6 example 8 32 interpreter 1 6 restrictions 1 7 special considerations for parallel 4 7 Windows parallel network 4 3 4 4 writing case files 4 5 Interpreted UDFs panel 4 1 4 3 4 5 8 7 8 8 interpreted vs compiled UDFs 1 7 interpreting source files about 4 3 procedure 4 3 interpreting UDF source files 4 1 irix6 5 5 15 Iterate panel 6 4 8 22 iteration UDFs execute at exit 2 11 k e turbulence model 2 107 k w turbulence model 2 107 laminar flow speed 2 79 LES turbulence model 2 107 log file 4 6 logical operators A 13 looking up a thread pointer 3 25 Lookup_Thread 1 11 Lookup_Thread 1 11 3 25 7 44 looping macros for multiphase applications 3 54 for parallel 7 23 general purpose 3 50 looping over cell threads in domain 3 50 cells in thread 3 51 exterior cells parallel 7 2
386. ly set up in Cortex and assigned a value of 2 by typing the text commands shown in the comments Once a Scheme based variable is set up for the thread ID it can be easily changed to another thread ID from the text interface without the burden of modifying the source code and recompiling the UDF Since the host com municates with Cortex and the nodes are not aware of Scheme variables it is essential to direct the compiler to exclude the nodes from compiling them using if RP_NODE Failure to do this will result in a compile error The surface_thread_id is then passed from the host to compute node 0 using the host_to_node macro Compute node 0 in turn automatically distributes the variable to the other compute nodes The serial and node processes are directed to loop over all faces in the thread associated with the surface thread id using if RP_HOST and compute the total area and total force Since the host does not contain any thread data it will ignore these statements if you do not direct the compiler but it is good programming practice to do so The macro PRINCIPAL_FACE_P is used to ensure that faces at partition boundaries are not counted twice see Section 7 2 Cells and Faces in a Partitioned Grid The nodes display the total area and force on the monitors using the Message utility before the global summation PRF_GRSUM1 Section 7 5 4 Global Reduction Macros is a global summation macro that is used to compute the total area and forc
387. m direction to direction j and return it to the solver Note that the solver computes and stores a scattering matrix for each material by calling this function for each unique pair of discrete ordinates Example In the following example a number of UDFs are concatenated in a single C source file These UDFs implement backward and forward scattering phase functions that are cited by Jendoubi et al 1 The source code can be interpreted or compiled in FLUENT paaa ooo oo o kkk kkk kkk kkk kkk kk kkk LE UDFs that implement backward and forward scattering phase functions as cited by Jendoubi et al EEEE EE ooo ED D D D ED DK HD OK include udf h DEF INE_SCAT_PHASE_FUNC ScatPhiB2 c fsf 2 88 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros real phi 0 fsf 0 phi 1 0 1 2 c 0 25 3 xcxc 1 return phi DEF INE_SCAT_PHASE_FUNC ScatPhiB1 c fsf real phi 0 fsf 0 phi 1 0 0 56524 c 0 29783 0 5 3 c c 1 0 08571 0 5 5 c c c 3 c 0 01003 8 35xckcxcxkc 30 cxc 3 0 00063 8 x 63 cxckckckc 70 xc kcxkc 15 c return phi DEFINE_SCAT_PHASE_FUNC ScatPhiF3 c fsf real phi 0 fsf 0 phi 1 0 1 2 c 0 25 3 xcxc 1 return phi DEF INE_SCAT_PHASE_FUNC ScatPhiF2 c fsf real phi 0 real coeffs 9 1 2 00917 1 56339 0 67407 0 22215 0 04725 0 00671 0 00068 0 00005 real P 9 int i fsf 0 P O 1 P 1 c phi P 0 coeffs
388. macros Section 25T DEFINE_DPM_LAW Section 2 9 1 DEFINE_DPM_BC Section 2 5 6 DEFINE_DPM_INJECTION_INIT Section 2 5 13 DEFINE_DPM_SWITCH and Sec tion 2 5 9 DEFINE_DPM_PROPERTY Table 3 2 26 Macros for Particles at Current Position Defined in dpm h Macro Argument Types Returns P_POS p i Tracked_Particle p int i position i 0 1 2 P_VEL p i Tracked Particle p int i velocity i 0 1 2 P DIAM p Tracked Particle p diameter P_T p Tracked_Particle p temperature P_RHO p Tracked_Particle p density P_MASS p Tracked_Particle p mass P_TIME p Tracked Particle p current particle time P DT p Tracked Particle p time step P_FLOWRATE p Tracked_Particle p flow rate of particles in a stream in kg s see below for details P_LF p Tracked_Particle p liquid fraction wet combusting particles only P_VFF p Tracked Particle p volatile fraction combusting particles only Fluent Inc September 11 2006 3 31 Additional Macros for Writing UDFs P_FLOW_RATE p Each particle in a steady flow calculation represents a stream of many particles that follow the same path The number of particles in this stream that passes a particular point in a second is the strength of the stream P_FLOW RATE returns the strength multiplied by P_MASS p at the current particle position Table 3 2 27 Macros for Particles at Entry to Current Cell Defined in dpm h Macro Argument Types
389. main can be described by an equation that consists of a diffusion and source term The transport equation for incident radiation G is given by Equation 8 2 5 The diffusion coefficient is given by Equation 8 2 6 and the source term is given by Equation 8 2 7 Refer to the equations discussed in Section 13 3 3 P 1 Radiation Model Theory of the User s Guide for more details V VG Sf 0 8 2 5 T 8 2 6 8a 3 C o GES S a 40T G 8 2 7 As shown in Section 13 3 3 P 1 Radiation Model Theory of the User s Guide manual the boundary condition for G at the walls is equal to the negative of the radiative wall heat flux qrw Equation 8 2 8 where is the outward normal vector The radiative wall heat flux can be given by Equation 8 2 9 q TVG 8 2 8 arw TOP a a 40T Gu 8 2 9 This form of the boundary condition is unfortunately specified in terms of the incident radiation at the wall Gw This mixed boundary condition can be avoided by solving first for G using Equations 8 2 8 and 8 2 9 resulting in Equation 8 2 10 Then this expression for G is substituted back into Equation 8 2 9 to give the radiative wall heat flux qrw as Equation 8 2 11 _ AOT Ey 220 Go Bo G k By a 8 2 10 aol p Ey ae ATI lT Go BG 8 2 11 r Top gay T Go AC 8 2 11 8 46 Fluent Inc September 11 2006 8 2 Detailed UDF Examples The additional G9 and Gp t
390. me real sun_x real sun_y real sun_z int S_hour int S_minute define DEFINE_SOURCE name c t dS i real name cell_t c Thread t real dS int i define DEFINE_SOX_RATE name c t Pollut Pollut_Par SOx void name cell_t c Thread t Pollut_Cell Pollut Pollut_Parameter Poll_Par SOx_Parameter SOx define DEFINE_SR_RATE name f t r mw yi rr void name face_t f Thread t Fluent Inc September 11 2006 B 3 DEFINE Macro Definitions Reaction r real mw real yi real rr define DEFINE_TURB_PREMIX_SOURCE name c t turbulent_flame_speed source void name cell_t c Thread t real turbulent_flame_speed real source define DEFINE_TURBULENT_VISCOSITY name c t real name cell_t c Thread t define DEFINE_VR_RATE name c t r mw yi rr rr_t void name cell_t c Thread t Reaction r real mw real yi real rr real rr_t define DEFINE_WALL_FUNCTIONS name f t cO tO wf_ret yPlus Emod real name face_t f Thread t cell_t c0 Thread t0 int wf_ret real yPlus real Emod B 3 Multiphase DEFINE Macros The following definitions for multiphase DEFINE macros see Section 2 4 Multiphase DEFINE Macros are taken from the udf h header file define DEFINE_CAVITATION_RATE name c t p rhoV rhoL vofV p_v cigma f_gas m_dot void name cell_t c Thread t real p real rhoV real rhoL real vofV real p_v real cigma real f_gas real
391. mes will appear in postprocessing panels You can change the default names if you wish using Set_User_Memory_Name as described below Set_User_Memory_Name The default name that appears in the graphical user interface and on plots for user defined memory UDM values in FLUENT e g User Memory 0 can now be changed using the function Set User Memory Name void Set_User_ Memory _Name int i char name i is the index of the memory value and name is a string containing the name you wish to assign It is defined in sg_udms h The Set User Memory Name function should be used only once and is best used in an EXECUTE_ON_LOADING UDF see Section 2 2 6 DEFINE EXECUTE ON LOADING Due to the mechanism used User Memory values cannot be renamed once they have been set so if the name is changed in a UDF for example and the UDF library is reloaded then the old name could remain In this case restart FLUENT and load the library again Fluent Inc September 11 2006 3 41 Additional Macros for Writing UDFs F_UDMI You can use F_UDMI Table 3 2 37 to access or store the value of the user defined memory on a face F_UDMI can be used to allocate up to 500 memory locations in order to store and retrieve the values of face field variables computed by UDFs These stored values can then be used for postprocessing for example or by other UDFs i Note that F_UDMI is available for wall and flow boundary faces only Table 3 2 37 Storage o
392. mod Argument Type Description symbol name UDF name face_t f face index Thread t pointer to cell thread cell_t c0 cell index Thread t0O pointer to face thread int wf_ret wall function index real yPlus y value real Emod wall function E constant Function returns real There are eight arguments to DEFINE_WALL_FUNCTIONS name f t cO t0 wf_ret yPlus and Emod You supply name the name of the UDF f t c0 tO wf_ret yPlus and Emod are variables that are passed by the FLUENT solver to your UDF Your UDF will need to compute the real value of the wall functions U dU and dY for laminar and turbulent regions and return them to the solver Example The following UDF named user_log_law computes U and dU and dY for laminar and turbulent regions using DEFINE_WALL_FUNCTIONS The source code can be interpreted or compiled in FLUENT Fluent Inc September 11 2006 2 1 15 DEFINE Macros peaa oo o kkk kkk kk kkk kk kkk kkk kkk kk User defined wall functions separated into turbulent and laminar regimes peaa ooo o oo kkk kk kkk kkk kkk include udf h DEFINE_WALL_FUNCTIONS user_log_law f t c0 tO wf_ret yPlus Emod real wf_value switch wf_ret case UPLUS_LAM wf_value yPlus break case UPLUS_TRB wf_value log Emod yPlus KAPPA break case DUPLUS_LAM wf_value 1 0 break case DUPLUS_TRB wf_value 1 KAPPAxyPlus break case D2UPLUS_TRB wf_value 1 K
393. n Coef ficients panel for a particular user scalar equation e g uds 0 See Section 6 6 1 Hooking DEFINE_ANISOTROPIC_DIFFUSIVITY UDFs for details 2 214 Fluent Inc September 11 2006 2 7 User Defined Scalar UDS Transport Equation DEFINE Macros 2 7 3 DEFINE_UDS_FLUX Description You can use DEFINE UDS FLUX to customize how the advective flux term is computed in your user defined scalar UDS transport equations See Section 9 3 User Defined Scalar UDS Transport Equations in the User s Guide for details on setting up and solving UDS transport equations Usage DEFINE UDS FLUX name f t i Argument Type Description symbol name UDF name face_t f Face index Thread t Pointer to face thread on which the user defined scalar flux is to be applied int i Index that identifies the user defined scalar for which the flux term is to be set Function returns real There are four arguments to DEFINE_UDS_FLUX name f t and i You supply name the name of the UDF f t and i are variables that are passed by the FLUENT solver to your UDF Your UDF will need to return the real value of the mass flow rate through the given face to the solver The advection term in the differential transport equation has the following most general form V yo 2 7 1 where is the user defined scalar conservation quantity and Y is a vector field In the default advection term w is by default the product of the scalar density
394. n determine a storage variable name from the header file that contains the variable s definition statement For example suppose you want to exchange the cell pressure C_P with an adjacent compute node You can look at the header file that contains the definition of C_P mem h and determine that the storage variable for cell pressure is SVP You will need to pass the storage variable to the exchange macro 7 36 Fluent Inc September 11 2006 7 6 Limitations of Parallel UDFs 7 6 Limitations of Parallel UDFs The macro PRINCIPAL_FACE_P can be used only in compiled UDFs PRF_GRSUM1 and similar global reduction macros Section 7 5 4 Global Reduction Macros cannot be used in DEFINE_SOURCE UDFs in parallel FLUENT As a workaround you can write a DEFINE_ADJUST UDF that calculates a global sum value in the adjust function and then save the variable in user defined memory You can subsequently retrieve the stored variable from user defined memory and use it inside a DEFINE_SOURCE UDF This is demonstrated below In the following example the spark volume is calculated in the DEFINE_ADJUST function and the value is stored in user defined memory using C_UDMI The volume is then retrieved from user defined memory and used in the DEFINE_SOURCE UDF include udf h static real spark_center ND_ND 20e 3 1e 3 static int fluid_chamber_ID 2 DEFINE_ADJUST adjust domain real vol xc ND_ND dis ND_ND radius cell_t c Thre
395. n face and thread if PRINCIPAL_FACE_P f tf face is on the principal compute node so get the area and pressure vectors and compute the total area and pressure for the thread from the magnitudes F_AREA area f tf total_area NV_MAG area total_pres_a NV_MAG area F_P f tf end_f_loop f tf total_area PRF_GRSUM1 total_area total_pres_a PRF_GRSUM1 total_pres_a Fluent Inc September 11 2006 7 29 Parallel Considerations Boundary zone face Node ID Partition ID Partition boundary face Partition ID set to same or different Node ID using Fill macros Interior face Node ID Partition ID Interior cells Exterior cells Node ID Partition ID Node ID and Partition ID different Figure 7 5 4 Partition Ids for Cells and Faces in a Compute Node 7 5 6 Cell and Face Partition ID Macros In general cells and faces have a partition ID that is numbered from 0 to n 1 where n is the number of compute nodes The partition IDs of cells and faces are stored in the variables C_PART and F_PART respectively C_PART c tc stores the integer partition ID of a cell and F_PART f tf stores the integer partition ID of a face Note that myid can be used in conjunction with the partition ID since the partition ID of an exterior cell is the ID of the neighboring compute node Cell Partition IDs For interior cells the partition ID is the same as the compute node ID For exterior cells the
396. n in Figure 1 10 1 The phase_domain_index can be used in UDFs to distinguish between the primary and secondary phase level threads phase_domain_index is always assigned the value of 0 for the primary phase level thread The data structures that are passed to a UDF depend on the multiphase model that is enabled the property or term that is being modified the DEFINE macro that is used and the domain that is to be affected mixture or phase To better understand this consider the differences between the Mixture and Eulerian multiphase models In the Mixture model a single momentum equation is solved for a mixture whose properties are determined from the sum of its phases In the Eulerian model a momentum equation is solved for each phase FLUENT allows you to directly specify a momentum source for the mixture of phases using DEFINE_SOURCE when the mixture model is used but not for the Eulerian model For the latter case you can specify momentum sources for the individual phases Hence the multiphase model as well as the term being modified by the UDF determines which domain or thread is required 1 18 Fluent Inc September 11 2006 1 10 Special Considerations for Multiphase UDFs UDFs that are hooked to the mixture of phases are passed superdomain or mixture level structures while functions that are hooked to a particular phase are passed subdomain or phase level structures DEFINE_ADJUST and DEFINE_INIT UDFs are hardwired t
397. n in conjunction with a heat flux thermal boundary condition In contrast a DEFINE_HEAT_FLUX UDF allows you to modify the way in which the de pendence between the flux entering the domain and the wall and cell temperatures is modeled Fa This function allows you to modify the heat flux at walls adjacent to a solid Note however that for solids since only heat conduction is occurring any extra heat flux that you add in a heat flux UDF can have a detrimental effect on the solution of the energy equation These effects will likely show up in conjugate heat transfer problems To avoid this you will need to make sure that your heat flux UDF excludes the walls adjacent to solids or includes only the necessary walls adjacent to fluid zones Usage DEFINE_HEAT_FLUX name f t c0 t0 cid cir Argument Type Description symbol name UDF name face_t f Index that identifies a wall face Thread t Pointer to wall face thread on which heat flux function is to be applied cell_t cO Cell index that identifies the cell next to the wall Thread t0O Pointer to the adjacent cell s thread real cid Array of fluid side diffusive heat transfer coefficients real cir Array of radiative heat transfer coefficients Function returns void 2 44 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros There are seven arguments to DEFINE_HEAT_FLUX name f t c0 tO cid and cir You supply name the name of the UDF f t c0 an
398. n once depending on the results of your analysis Follow the step by step process in the sections below to see how this is done 8 1 2 Step 1 Define Your Problem The first step in creating a UDF and using it in your FLUENT model involves defining your model equation s Consider the turbine vane illustrated in Figure 8 1 1 An unstructured grid is used to model the flow field surrounding the vane The domain extends from a periodic boundary on the bottom to an identical one on the top a velocity inlet on the left and a pressure outlet on the right DOORS R TAVANA AASS Turbine Vane 1551 cells 2405 faces 893 nodes Grid Figure 8 1 1 The Grid for the Turbine Vane Example Fluent Inc September 11 2006 8 1 Step By Step UDF Example A flow field in which a constant x velocity is applied at the inlet will be compared with one where a parabolic x velocity profile is applied The results of a constant velocity applied field of 20 m s at the inlet are shown in Figures 8 1 2 and 8 1 3 The initial constant velocity field is distorted as the flow moves around the turbine vane 5 98e 01 5 42e 01 4 86e 01 4 30e 01 3 74e 01 3 19e 01 2 63e 01 2 07e 01 1 51e 01 9 54e 00 3 96e 00 Turbine Vane 1551 cells 2405 faces 893 nodes Contours of Velocity Magnitude m s Figure 8 1 2 Velocity Magnitude Contours for a Constant Inlet x Velocity No
399. n order for the Particle Emissivity property to be displayed in the sam ple panel shown above you must enable a radiation model turn on the Particle Radiation Interaction option in the Discrete Phase Model panel and introduce a particle injection in the Injections panel Fluent Inc September 11 2006 6 63 Hooking UDFs to FLUENT 6 64 User Defined Functions fx anthracite emissivi Figure 6 4 10 The User Defined Functions Panel Next choose the function name e g anthracite_emissivity from the list of UDFs dis played in the User Defined Functions panel Figure 6 4 10 and click OK The name of the function will subsequently be displayed under the selected property e g Particle Emissivity in the Materials panel See Section 2 3 14 DEFINE PROPERTY UDFs for details about DEFINE_DPM_PROPERTY func tions Fluent Inc September 11 2006 6 4 Hooking Discrete Phase Model DPM UDFs 6 4 10 Hooking DEFINE_DPM_SCALAR_UPDATE UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_SCALAR_UPDATE UDF the name of the function you sup plied as a DEFINE macro argument will become visible and selectable in the Discrete Phase Model panel Figure 6 4 11 in FLUENT Define Models gt Discrete Phase Discrete Phase Model Interaction Particle Treatment Interaction with Continuous Phase l Unsteady Particle Tracking Track
400. n the Set Injection Properties panel Figure 6 4 6 and choose the function name e g init_bubbles from the Initialization drop down list under User Defined Functions Click OK See Section 2 5 6 DEFINE_DPM_INJECTION_INIT for details about DEFINE_DPM_INJECTION_INIT functions Fluent Inc September 11 2006 6 59 Hooking UDFs to FLUENT Set Injection Properties Injection Name finjection 8 Injection Type single Particle Type Laws Inert C Droplet Combusting C Multicomponent T Custom Material Diameter Distribution Oxidizing Species anthracite linear f vaporating opel ies Devolatilizing opet ies Product Species Point Properties Turbulent Dispersion Wet Combustion Components UDF Multiple Reactions User Defined Functions Initialization init_bubbles HeatMass Transfer none Figure 6 4 6 The Injections Panel 6 60 Fluent Inc September 11 2006 6 4 Hooking Discrete Phase Model DPM UDFs 6 4 7 Hooking DEFINE_DPM_LAW UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_LAW UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Custom Laws panel Figure 6 4 7 in FLUENT To hook the UDF to FLUENT first click Create in the Injec tions panel to open the Set Injection Properties panel Define Injections Next turn on the Custom option unde
401. n the function body the variables that are to be used by the function are defined and initialized first Following the variable declarations a looping macro is used to loop over each cell thread in the domain Within that loop another loop is used to loop over all the cells Within the inner loop the total volume and the minimum maximum and volume averaged temperature are computed These computed values are printed to the FLUENT console Then a second loop over each cell is used to compute the function f T and store it in user defined memory location 0 Refer to Chapter 3 Additional Macros for Writing UDFs for a description of predefined macros such as C_T and begin c loop Hooking an On Demand UDF to FLUENT After the UDF that you have defined using DEFINE ON DEMAND is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFSs the name of the argument that you supplied as the first DEFINE macro argument e g on demand_calc will become visible and selectable in the Execute On Demand panel in FLUENT See Section 6 1 6 Hooking DEFINE_ON_DEMAND UDFs for details Fluent Inc September 11 2006 2 23 DEFINE Macros 2 29 DEFINE_RW_FILE Description DEFINE_RW_FILE is a general purpose macro that you can use to specify customized in formation that is to be written to a case or data file or read from a case or data file You can save and restore custom variables of any data type e g integer real CXBoole
402. n_b Hooking a Discrete Ordinates Model DOM Diffuse Reflectivity UDF to FLUENT After the UDF that you have defined using DEFINE DOM DIFFUSE REFLECTIVITY is in terpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user_dom_diff_ref1 will become visible and selectable in the User Defined Function Hooks panel in FLUENT See Section 6 2 4 Hooking DEFINE_DOM_DIFFUSE_REFLECTIVITY UDFs for details Fluent Inc September 11 2006 2 37 DEFINE Macros 2 3 5 DEFINE DOM SOURCE Description You can use DEFINE DOM SOURCE to modify the emission term first term on the right hand side in Equation 13 3 37 or Equation 13 3 38 of the User s Guide as well as the scattering term second term on the right hand side of either equation in the radiative transport equation for the Discrete Ordinates DO model Usage DEFINE DOM SOURCE name c t ni nb emission in scattering abs coeff scat coeff Argument Type Description symbol name UDF name cellt c Cell index Thread t Pointer to cell thread int ni Direction represented by the solid angle int nb Band number needed for the non gray Discrete Ordinates Model real emission Pointer to emission term in the radiative transport equation Equation 13 3 37 to go to the User s Guide manual real in scattering Pointer to scattering term in the radiative transport eq
403. nc September 11 2006 DEFINE Macro Definitions B 8 Fluent Inc September 11 2006 Appendix C Quick Reference Guide for Multiphase DEF INE Macros This appendix is a reference guide that contains a list of general purpose DEFINE macros Section 2 3 Model Specific DEFINE Macros and multiphase specific DEFINE macros Sec tion 2 4 Multiphase DEFINE Macros that can be used to define multiphase model UDFs See Section 1 10 Special Considerations for Multiphase UDFs for information on special considerations for multiphase UDFs C i VOF Model Tables C 1 1 C 1 2 list the variables that can be customized using UDFs for the VOF multiphase model the DEFINE macros that are used to define the UDFs and the phase that the UDF needs to be hooked to for the given variable Fluent Inc September 11 2006 C 1 Quick Reference Guide for Multiphase DEFINE Macros Table C 1 1 DEFINE Macro Usage for the VOF Model Variable Macro Phase Specified On Boundary Conditions Inlet Outlet volume fraction velocity magnitude pressure temperature mass flux species mass fractions internal emissivity user defined scalar boundary value discrete phase boundary condition DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE secondary phase s mixture mixture mixture primary and secondary phase s phase dependent mixture
404. nce Flow Table C 5 3 DEFINE Macro Usage for the Eulerian Model Dispersed Tur bulence Flow Variable Macro Phase Specified On Other drag coefficient lift coefficient heat transfer coefficient mass transfer coefficient heterogeneous reaction rate DEF INE_EXCHANGE DEFINE EXCHANGE DEFINE PROPERTY DEFINE MASS TRANSFER DEFINE HET RXN RATE phase interaction phase interaction phase interaction phase interaction phase interaction Fluent Inc September 11 2006 C 17 Quick Reference Guide for Multiphase DEFINE Macros C 6 Eulerian Model Per Phase Turbulence Flow Tables C 6 1 C 6 3 list the variables that can be customized using UDFs for the per phase turbulence flow Eulerian multiphase model the DEFINE macros that are used to define the UDFs and the phase that the UDF needs to be hooked to for the given variable C 18 Fluent Inc September 11 2006 C 6 Eulerian Model Per Phase Turbulence Flow Table C 6 1 DEFINE Macro Usage for the Eulerian Model Per Phase Tur bulence Flow Variable Macro Phase Specified On Boundary Conditions Inlet Outlet volume fraction species mass fractions mass flux velocity magnitude temperature pressure user defined scalar boundary value DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE secondary phase s phase dependent primary and secondary phas
405. nction Prandtl number to the solver Example V PLLELLELLELLLLLLLELLELLELLELLLELLELLLLLEL K K K K 2k 2K Kk KK k k k k K K LES ak K Specifying a constant thermal wall function Prandtl number BE ooo k kkk kkk kk include udf h DEFINE_PRANDTL_T_WALL user_pr_t_wall c t real pr_t_wall pr_t_wall 0 85 return pr_t_wall Hooking a Prandtl Number UDF to FLUENT After the UDF that you have defined using DEFINE_PRANDTL_T_WALL is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user pr t wall will become visible and selectable in the Viscous Model panel in FLUENT See Sec tion 6 2 12 Hooking DEFINE_PRANDTL UDFs for details Fluent Inc September 11 2006 2 65 DEFINE Macros 2 3 13 DEFINE PROFILE Description You can use DEFINE PROFILE to define a custom boundary profile that varies as a function of spatial coordinates or time Some of the variables you can customize at a boundary are e velocity pressure temperature turbulence kinetic energy turbulence dissipation rate e mass flux e target mass flow rate as a function of physical flow time e species mass fraction species transport e volume fraction multiphase models e wall thermal conditions temperature heat flux heat generation rate heat transfer coefficients and external emissivity etc e wall roughness conditi
406. nction Hooks Initialization none Edit Adjust hone Edit Execute at End none Edit Read Case none Edit Write Case none Edit Read Data none Edit Write Data none Edit Execute at Exit none Edit Wall Heat Flux mone DO Source mone DO Diffuse Reflectivity none DO Specular Reflectivity Figure 6 2 7 The User Defined Function Hooks Panel The Discrete Ordinates radiation model must be enabled from the Radiation Model panel To hook the UDF to FLUENT choose the function name e g user_dom_spec_ref1 in the DO Specular Reflectivity drop down list in the User Defined Function Hooks panel and click OK See Section 2 3 4 DEFINE DOM DIFFUSE REFLECTIVITY for details about DEFINE DOM SPECULAR REFLECTIVITY functions Fluent Inc September 11 2006 6 21 Hooking UDFs to FLUENT 6 2 7 Hooking DEFINE_GRAY_BAND_ABS_COEFF UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_GRAY_BAND_ABS_COEFF UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Materials panel shown below in FLUENT Define Materials Materials Name Material Type Order Materials By air fluid v Name c c Chemical Formula Fluent Fluid Materials Chemical Formula air s Fluent Database Mixture User Defined Database none 4 Properties Absorption Coefficient
407. nction that computes the maximum of each element of the array x over all the compute nodes uses the array iwork for temporary storage and modifies array x by replacing each element with its resulting global maximum The function does not return a value Example Global Reduction Variable Array Macro real x N iwork N The elements of x are set in the working array here and will have different values on each compute node In this case x 0 could be the maximum cell temperature of all the cells on the compute node x 1 the maximum pressure x 2 the maximum density etc PRF_GRHIGH x N iwork The maximum value for each value over all the compute nodes is found here The elements of x on each compute node now hold the same maximum values over all the compute nodes for temperature pressure density etc 7 20 Fluent Inc September 11 2006 7 5 Macros for Parallel UDFs Global Summations Macros that can be used to compute global sums of variables are identified by the suf fix SUM PRF_GISUM1 and PRF_GISUM compute the global sum of integer variables and integer variable arrays respectively PRF_GRSUM1 x computes the global sum of a real variable x across all compute nodes The global sum is of type float when running a single precision version of FLUENT and type double when running the double precision version Alternatively PRF_GRSUM x N iwork computes the global sum of a float variable array
408. ndary phase s mixture primary and secondary phase s primary and secondary phase s Fluent Inc September 11 2006 C 3 Eulerian Model Laminar Flow Table C 3 2 DEFINE Macro Usage for the Eulerian Model Laminar Flow Variable Macro Phase Specified On Boundary Conditions Fluid species mass fraction granular temperature porosity user defined scalar viscous resistance inertial resistance DEFINE_PROFILE DEFINE_PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE phase dependent secondary phase s mixture mixture primary and secondary phase s primary and secondary phase s Wall species boundary condition shear stress components moving velocity components temperature heat flux heat generation rate heat transfer coefficient external emissivity external radiation temperature free stream temperature user defined scalar boundary value discrete phase boundary value DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE DPM_BC phase dependent primary and secondary phase s mixture mixture mixture mixture mixture mixture mixture mixture mixture mixture Material Properties granular diameter granular solids pressure granular radial distribution granular elasticity modulus granular viscosity granular
409. ndary value discrete phase boundary condition DEFINE PROFILE DEFINE PROFILE DEFINE_PROFILE DEFINE_PROFILE DEFINE PROFILE DEFINE_PROFILE DEFINE_PROFILE DEFINE PROFILE secondary phase s phase dependent primary and secondary phases primary and secondary phases s primary and secondary phases s mixture mixture mixture Fluid mass source momentum source energy source turbulence dissipation rate source turbulence kinetic energy source user defined scalar source user defined scalar turbulence kinetic energy turbulence dissipation rate DEFINE SOURCE DEFINE_ SOURCE DEF INE_SOURCE DEFINE SOURCE DEFINE SOURCE DEFINE SOURCE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE primary and secondary phase s primary and secondary phase s primary and secondary phase s mixture mixture mixture mixture mixture mixture Fluent Inc September 11 2006 Quick Reference Guide for Multiphase DEFINE Macros Table C 4 2 DEFINE Macro Usage for the Eulerian Model Mixture Turbu lence Flow Variable Macro Phase Specified On Fluid velocity DEFINE_PROFILE primary and secondary phase s temperature DEFINE PROFILE primary and secondary phase s porosity DEFINE_PROFILE mixture user defined scalar viscous resistance inertial resistance DEFINE_PROFILE DEFINE PROFILE DEFINE_PROFILE mixture primary and secondary phase s primary and secondary phase s
410. ne face Interior face Partition boundary face External face Interior face Figure 7 2 2 Partitioned Grid Faces Faces at Partition Boundaries There are three classifications of faces in a partitioned grid interior boundary zone and external Figure 7 2 2 Interior faces have two neighboring cells Interior faces that lie on a partition boundary are referred to as partition boundary faces Boundary zone faces lie on a physical grid boundary and have only one adjacent cell neighbor External faces are non partition boundary faces that belong to exterior cells External faces are generally not used in parallel UDFs and therefore will not be discussed here 7 8 Fluent Inc September 11 2006 7 2 Cells and Faces in a Partitioned Grid Note that each partition boundary face is duplicated on adjacent compute nodes Fig ure 7 1 2 This is necessary so that each compute node can calculate its own face values However this duplication can result in face data being counted twice when UDFs are involved in operations that involve summing data in a thread that contains partition boundary faces For example if your UDF is tasked with summing data over all of the faces in a grid then as each node loops over its faces duplicated partition boundary faces can be counted twice For this reason one compute node in every adjacent set is assigned by FLUENT as the principal compute node with respect to partition bound
411. ne that utilizes C_PROFILE include udf h DEFINE_PROFILE porosity_function t nv cell te begin_c_loop c t C_PROFILE c t nv USER INPUT end_c_loop c t 2 76 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros Example 6 Porous Resistance Direction Vector The following UDF contains profile functions for two porous resistance direction vectors that utilize C_PROFILE These profiles can be hooked to corresponding direction vectors under Porous Zone in the Fluid boundary condition panel Porous Resistance Direction Vector Profile that utilizes C_PROFILE include udf h DEFINE_PROFILE dir1 t nv cell_t c begin_c_loop c t C_PROFILE c t nv USER INPUT end_c_loop c t DEFINE_PROFILE dir2 t nv cell_t c begin_c_loop c t C_PROFILE c t nv USER INPUT2 end_c_loop c t Example 7 Target Mass Flow Rate UDF as a Function of Physical Flow Time For some unsteady problems it is desirable that the target mass flow rate be a function of the physical flow time This boundary condition can be applied using a DEFINE_PROFILE UDF The following UDF named tm_pout2 adjusts the mass flow rate from 1 00kg s to 1 35kg s when the physical time step is greater than 0 2 seconds Once interpreted or compiled you can activate this UDF in the Pressure Outlet boundary condition panel in FLUENT by selecting the Specify target mass flow rate option and then choosing the UDF name from the cor
412. neral Purpose UDFs This section contains methods for hooking general purpose UDFs to FLUENT Gen eral purpose UDFs are those that have been defined using macros described in Sec tion 2 2 General Purpose DEFINE Macros and then interpreted or compiled and loaded using methods described in Chapters 4 or 5 respectively Fluent Inc September 11 2006 6 1 Hooking UDFs to FLUENT 6 1 1 Hooking DEFINE_ADJUST UDFs Once you interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs your DEFINE_ADJUST UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Function Hooks panel Figure 6 1 1 Note that you can hook multiple adjust UDFs to your model if desired Define User Defined Function Hooks User Defined Function Hooks Initialization one Edit Adjust Z gelectea Edit Execute at End none Edit Read Case none Edit Write Case none Edit Read Data none Edit Write Data none Edit Execute at Exit none Edit Figure 6 1 1 The User Defined Function Hooks Panel Fluent Inc September 11 2006 6 1 Hooking General Purpose UDFs Click on Edit next to Adjust to open the Adjust Functions panel Figure 6 1 2 Adjust Functions Available Adjust Functions Selected Adjust Functions user_adjustl user_adjust2 Add Remove OK Cancel Help Figure 6 1 2
413. nergy onvergence Solve Turbulence Equation s Update Properties including User Defined Solve Other Transport Properties Equations as required Figure 1 9 2 Solution Procedure for the Pressure Based Coupled Solver Fluent Inc September 11 2006 Overview User Defined Profile User Defined Init Solve Mass Momentum Energy amp Species onvergence Solve Turbulence Equation s Solve Other Transport Equations as required Update Properties including User Defined Properties Figure 1 9 3 Solution Procedure for the Density Based Solver 1 16 Fluent Inc September 11 2006 1 10 Special Considerations for Multiphase UDFs 1 10 Special Considerations for Multiphase UDFs In many cases the UDF source code that you will write for a single phase flow will be the same as for a multiphase flow For example there will be no differences between the C code for a single phase boundary profile defined using DEFINE_PROFILE and the code for a multiphase profile assuming that the function is accessing data only from the phase level domain that it is hooked to in the graphical user interface If your UDF is not explicitly passed a pointer to the thread or domain structure that it requires you will need to use a special multiphase specific macro e g THREAD_SUB_THREAD to retrieve it This is discussed in Chapter 3 Additional Macros for Writing UDFs See Appendix B for a complete list of
414. net_reaction_rate assumes that the net volumetric reaction rate is the expression Rnet 1 Nspe Y 2 3 5 where Nspe is the number of species PK kkk k k kk ak ak k ak 2k 2k k ak 2k k K 2k 2k kK k 2k 2K K 3k 2K 2K K 2K 2K K 2K 2K K K k 2K 2K K 2K 2K K K 2K LL FK 2K 2K K 2K LL SES Net Reaction Rate Example UDF EEEE ooo ooo o kkk k kkk include udf h DEFINE_NET_REACTION_RATE user_net_reaction_rate c t particle pressure temp yi rr jac int i for i 0 i lt n_spe i rrli 1 real n_spe yilil Hooking a Net Mass Reaction Rate UDF to FLUENT After the UDF that you have defined using DEFINE_NET_REACTION_RATE is interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user net reaction rate will become visible and selectable for the Net Reaction Rate function in the User Defined Function Hooks panel in FLUENT See Section 6 2 9 Hook ing DEFINE_NET_REACTION_RATE UDFs for details Fluent Inc September 11 2006 2 47 DEFINE Macros 2 3 10 DEFINE_NOX_RATE Description You can use the DEFINE_NOX_RATE to specify a custom NO rate for thermal NO prompt NO fuel NO and N2O intermediate pathways that can either replace the internally calculated NO rate in the source term equation or be added to the FLUENT rate The default functionality is to add user defined rates to the FLUENT calculat
415. ng Options Motion UDF Profile piston libudf Center of Gravity Location __ _ Center of Gravity Orientation x in fo Theta_Z deg 8 Y fin 6 a Create Draw Delete Update Close Help Figure 6 5 1 The Dynamic Mesh Zones Panel Select Rigid Body under Type in the Dynamic Mesh Zones panel Figure 6 5 1 and click on the Motion Attributes tab Finally choose the function name e g piston from the Motion UDF Profile drop down list and click Create then Close See Section 2 6 1 DEFINE_CG_MOTION for details about DEFINE CG MOTION functions 6 72 Fluent Inc September 11 2006 6 5 Hooking Dynamic Mesh UDFs 6 5 2 Hooking DEFINE_GEOM UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_GEOM UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Dynamic Mesh Zones panel Fig ure 6 5 2 To hook the UDF to FLUENT you will first need to enable the Dynamic Mesh model Define Dynamic Mesh Parameters To enable the model select Dynamic Mesh under Model and click OK FA The Dynamic Mesh panel will be accessible only when you choose Unsteady as the time method in the Solver panel Next open the Dynamic Mesh Zones panel Define Dynamic Mesh Zones Select Deforming under Type in the Dynamic Mesh Zones panel Fig
416. ng Over Exterior Cells in a Partitioned Grid Using begin end_c_loop_ext indicated by the green cells 7 26 Fluent Inc September 11 2006 7 5 Macros for Parallel UDFs Figure 7 5 3 Looping Over Both Interior and Exterior Cells in a Partitioned Grid Using begin end_c_loop Interior and Exterior Cell Looping Macro The macro begin end_c_loop can be used in a serial or parallel UDF In parallel the macro will loop over all interior and exterior cells in a grid partition Figure 7 5 3 Note that in serial this pair of macros is equivalent to the begin end_c_loop_int macros It contains a begin and end statement and between these statements operations can be performed on each of the thread s interior and exterior cells in turn The macro is passed a cell index c and a cell thread pointer tc begin_c_loop c tc end_c_loop c tc Fluent Inc September 11 2006 7 27 Parallel Considerations Example real temp begin_c_loop c tc get cell temperature compute temperature function and store result in user defined memory location index 0 temp C_T c te C_UDMI c tc 0 temp tmin tmax tmin assumes a valid tmax and tmin has already been computed end_c_loop c tc Looping Over Faces For the purpose of discussing parallel FLUENT faces can be categorized into two types interior faces and boundary zone faces Figure 7 2 2 Partition boundary faces are interior faces that
417. ng UDFs to FLUENT 6 2 12 Hooking DEFINE_PRANDTL UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_PRANDTL UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Viscous Model panel Figure 6 2 13 in FLUENT Define Models Viscous Viscous Model Model Model Constants Inviscid Cmu Laminar CCS Spalart Allmaras 1 eqn k epsilon 2 eqn C1 Epsilon k omega 2 eqn 1 44 Reynolds Stress 5 eqn C2 Evsil Epsilon k epsilon Model fi 92 Standard C RNG C Realizable TDR Prandtl Number 1 3 Near Wall Treatment User Defined Functions Standard Wall Functions Turbulent Viscosity C Non Equilibrium Wall Functions none C Enhanced Wall Treatment C User Defined Wall Functions Prandtl Numbers TKE Prandtl Number user_pr_k libudf TDR Prandtl Number none Options l Viscous Heating Energy Prandtl Number none Figure 6 2 13 The Viscous Model Panel xi To hook the UDF to FLUENT choose the function name e g user_pr_k in the TKE Prandtl Number drop down list under User Defined Functions in the panel Viscous Model panel and click OK See Section 2 3 12 DEFINE_PRANDTL UDFs for details about DEFINE_PRANDTL functions 6 28 Fluent Inc September 11 2006 6 2 Hooking Model Specific UDFs 6 2 13 Hooking DEFINE_PROFILE UDFs Once you have inte
418. ng UDFs to FLUENT 6 3 Hooking Multiphase UDFs This section contains methods for hooking UDF s to FLUENT that have been defined using DEFINE macros described in Section 2 4 Multiphase DEFINE Macros and interpreted or compiled using methods described in Chapters 4 or 5 respectively 6 3 1 Hooking DEFINE_CAVITATION_RATE UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE CAVITATION RATE UDF the name of the function you sup plied as a DEFINE macro argument will become visible and selectable in the User Defined Function Hooks panel Figure 6 3 2 in FLUENT Note that cavitation rate UDFs can be applied only to the Mixture multiphase model To hook the UDF to FLUENT you will first need to enable the Mixture model in the Multiphase Model panel Define gt Models gt Multiphase Then in the Mass tab of the Phase Interaction panel Figure 6 3 1 select Cavitation Phase Interaction Drag Lift Collisions Slip Heat Mass Reactions Surface Tension V Cavitation Cavitation Parameters Vaporization Pressure pascal constant vl Edi 2367 8 Surface Tension Coefficient nfm constant vl Egi 6 6717 Non Condensable Gas Mass Fraction constant a 1 5e 65 Figure 6 3 1 The Phase Interaction Panel Next open the User Defined Function Hooks panel Define User Defined Function Hooks 6
419. nge the value of the variable you have defined pres_av thread id to say 7 then you will need to use rpsetvar and issue the follow ing command in the text window rpsetvar pres_av thread id 7 3 6 4 Accessing a Scheme Variable in a UDF Once a new variable is defined on the Scheme side using a text command you will need to bring it over to the solver side to be able to use it in your UDF RP macros are used to access Scheme variables in UDFs and are listed below RP_Get_Real variable name Returns the double value of variable name RP_Get_Integer variable name Returns the integer value of variable name RP_Get_String variable name Returns the char value of variable name RP_Get_Boolean variable name Returns the Boolean value of variable name For example to access the user defined Scheme variable pres_av thread id in your UDF C function you will use RP_Get_Integer You can then assign the variable returned to a local variable you have declared in your UDF e g surface_thread_id as demonstrated below surface_thread_id RP_Get_Integer pres_av thread id 3 72 Fluent Inc September 11 2006 3 7 Input Output Macros 3 7 Input Output Macros Fluent Inc has provided some utilities in addition to the standard C I O functions that you can use to perform input output I O tasks These are listed below and are described in the following sections Message format prints a message to the console
420. nning to iterate Solve Monitors Surface Surface Monitors Surface Monitors LS Name Plot Print Write Every When monitor 1 M M J 1 Time Step Define monitor 2 is i i iteration Define r monitor 3 ja lo ja fi iteration Define jar ronitor 4 F LES f fieran Define a OK Cancel Help Increase the Surface Monitors index to 1 This will enable you to define the parameters of monitor 1 which you could rename if desired in the text entry box under Name Select Plot so that the selected quantity will be plotted as the calculation proceeds Select Print to see the changing values of the selected quantity in the console window Select Write so that the information will be written to a file which will be given the name monitor 1 out If you change the name of the monitor that name will be used as the prefix for the output file Under Every you can choose Iteration Time Step or Flow Time To monitor the result of each time step you should choose the Time Step option By clicking on Define you can specify the quantity to be monitored in the Define Surface Monitor panel 8 24 Fluent Inc September 11 2006 8 2 Detailed UDF Examples Define Surface Monitor Name Report of monitor 1 Velocity Report Type velocity Magnitude Area Weighted Average Y Surfaces Axis Time Step Plot Window D v File Name jmonitor t out
421. nt Inc September 11 2006 2 1 33 DEFINE Macros The arguments from_species_index and to_species_index are relevant for multiphase species transport problems only and only if the respective phase has a mixture material associated with it Example The following UDF named lig_gas_source specifies a simple mass transfer coefficient based on saturation temperature UDF to define a simple mass transfer based on Saturation Temperature The from phase is the gas and the to phase is the liquid phase include udf h DEFINE_MASS_TRANSFER liq_gas_source cell thread from_index from_species_index to_index to_species_index real m_lg real T_SAT 373 15 Thread gas THREAD_SUB_THREAD thread from_index Thread ligq THREAD_SUB_THREAD thread to_index m_lg 0 if C_T cell liq gt T_SAT m_lg 0 1 C_VOF cell 1liq C_R cell 1liq fabs C_T cell 1liq T_SAT T_SAT if m_lg 0 amp amp C_T cell gas lt T_SAT m_lg 0 1 C_VOF cell gas C_R cell gas fabs T_SAT C_T cell gas T_SAT return m_lg 2 1 34 Fluent Inc September 11 2006 2 4 Multiphase DEF INE Macros Hooking a Mass Transfer UDF to FLUENT After the UDF that you have defined using DEFINE_MASS_TRANSFER is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g liq_gas_source will be
422. o data file F DEFINE_RW_FILE reader fp printf Reading UDF data from data file n fscanf fp d amp kount read kount from data file At the top of the listing the integer kount is defined and initialized to zero The first function demo_calc is an ADJUST function that increments the value of kount at each iteration since the ADJUST function is called once per iteration See Sec tion 2 2 1 DEFINE ADJUST for more information about ADJUST functions The second function writer instructs FLUENT to write the current value of kount to the data file when the data file is saved The third function reader instructs FLUENT to read the value of kount from the data file when the data file is read The functions work together as follows If you run your calculation for say 10 iterations kount has been incremented to a value of 10 and save the data file then the current value of kount 10 will be written to your data file If you read the data back into FLUENT and continue the calculation kount will start at a value of 10 and will be incremented at each iteration Note that you can save as many static variables as you want but you must be sure to read them in the same order in which they are written Hooking a Read Write Case or Data File UDF to FLUENT After the UDF that you have defined using DEFINE_RW_FILE is interpreted Chapter 4 In terpreting UDFs or compiled Chapter 5 Compiling UDFSs the name of the argu
423. o first retrieve it using the Get_Domain utility provided by Fluent shown in the example below See Section 3 2 6 Domain Pointer Get_Domain for details on Get_Domain Usage DEFINE_ON_DEMAND name Argument Type Description symbol name UDF name Function returns void There is only one argument to DEFINE_ON_DEMAND name You supply name the name of the UDF Example The following UDF named on_demand_calc computes and prints the minimum maxi mum and average temperatures for the current data field It then computes a tempera ture function P Tmin FT gt Tmax Tmin and stores it in user defined memory location 0 which is allocated as described in Sec tion 3 2 3 Cell Macros Once you hook the on demand UDF as described in Sec tion 6 1 6 Hooking DEFINE_ON_DEMAND UDFs the field values for f T will be available in drop down lists in post processing panels in FLUENT You can select this field by choosing User Memory 0 in the User Defined Memory category If you write a data file after executing the UDF the user defined memory field will be saved to the data file This source code can be interpreted or compiled in FLUENT Fluent Inc September 11 2006 2 21 DEFINE Macros CORO CO OO K FK 2K 2K K 2K 2K 2K FK 3K 2K K FK 2K 2K FK LL A RK K FK 2k K FK 2k 2K K FK 2k UDF to calculate temperature field function and store in user defined memory Also print min max avg temperatures BOO K K k kkk k kkk
424. o name where R denotes real data types I denotes integers and L denotes logicals For example the macro PRF_GISUM finds the summation of integers over the compute nodes Each of the global reduction macros discussed in the following sections has two different versions one takes a single variable argument while the other takes a variable array Macros with a 1 appended to the end of the name take one argument and return a single variable as the global reduction result For example the macro PRF_GIHIGH1 x expands to a function that takes one argument x and computes the maximum of the variable x amongst all of the compute nodes and returns it The result can then be assigned to another variable e g y as shown below Fluent Inc September 11 2006 7 19 Parallel Considerations Example Global Reduction Variable Macro int y int x myid y PRF_GIHIGH1 x y now contains the same number compute_node_count 1 on all the nodes Macros without a 1 suffix on the other hand compute global reduction variable arrays These macros take three arguments x N and iwork where x is an array N is the number of elements in the array and iwork is an array that is of the same type and size as x which is needed for temporary storage Macros of this type are passed an array x and the elements of array x are filled with the new result after returning from the function For example the macro PRF_GIHIGH x N iwork expands to a fu
425. o the mixture level domain Other types of UDFs are hooked to different phase domains For your convenience Appendix B contains a list of multiphase models in FLUENT and the phase on which UDFs are specified for the given variables From this information you can infer which domain structure is passed from the solver to the UDF Fluent Inc September 11 2006 1 19 Overview 1 20 Fluent Inc September 11 2006 Chapter 2 DEFINE Macros This chapter contains descriptions of predefined DEFINE macros that you will use to define your UDF The chapter is organized in the following sections e Section 2 1 Introduction e Section 2 2 General Purpose DEFINE Macros e Section 2 3 Model Specific DEFINE Macros e Section 2 4 Multiphase DEFINE Macros e Section 2 5 Discrete Phase Model DPM DEFINE Macros e Section 2 6 Dynamic Mesh DEFINE Macros e Section 2 7 User Defined Scalar UDS Transport Equation DEFINE Macros 2 1 Introduction DEFINE macros are predefined macros provided by Fluent Inc that must be used to define your UDF A listing and discussion of each DEFINE macros is presented below Refer to Section 1 4 Defining Your UDF Using DEFINE Macros for general information about DEFINE macros Definitions for DEFINE macros are contained within the udf h file For your convenience they are provided in Appendix B For each of the DEFINE macros listed in this chapter a source code example of a UDF that utilizes it is pro
426. o use the compute node ID of the sender when receiving messages For receive messages the argument from is the ID of the sending node buffer is the name of an array of the appropriate type that will be received nelem is the number of elements in the array and tag is the ID of the receiving node The tag convention for receive messages is the from node same as the first argument 7 32 Fluent Inc September 11 2006 7 5 Macros for Parallel UDFs Note that if variables that are to be sent or received are defined in your function as real variables then you can use the message passing macros with the _REAL suffix The compiler will then substitute PRF_CSENT_DOUBLE or PRF_CRECV_DOUBLE if you are running double precision and PRF_CSENT_FLOAT or PRF_CRECV_FLOAT for single precision Because message passing macros are low level macros you will need to make sure that when a message is sent from a node process a corresponding receiving macro appears in the receiving node process Note that your UDF cannot directly send messages from a compute node other than 0 to the host using message passing macros They can send messages indirectly to the host through compute node 0 For example if you want your parallel UDF to send data from all of the compute nodes to the host for postprocessing purposes the data will first have to be passed from each compute node to compute node 0 and then from compute node 0 to the host In the case where
427. oading more than one UDF library into FLUENT raises the pos sibility of user defined scalar UDS clashes To avoid data contention between multiple UDF libraries using the same user defined scalars FLUENT has provided the macro Reserve User Scalar Vars that allows you to reserve scalars prior to use int Reserve_User_Scalar_Vars int num int num is the number of user defined scalars that the library uses The integer returned is the lowest UDS index that the library may use After calling offset Reserve_User_Scalar_Vars int num the library may safely use C_UDSI c t offset to CUDSI c t offsettnum 1 See Section 2 2 6 DEFINE EXECUTE ON LOADING for an example of macro usage Note that there are other methods you can use within UDFs to hardcode the offset to prevent data contention Reserve User Scalar Vars defined in sg_udms h is designed to be called from an EXECUTE_ON_LOADING UDF Section 2 2 6 DEFINE EXECUTE ON LOADING An on loading UDF as its name implies executes as soon as the shared library is loaded into FLUENT The macro can also be called from an INIT or ON DEMAND UDF Once reserved user scalars can be set to unique names for the particular library using Set_User_Memory_Name see below for details on Set_User_Memory_Name Once the number of UDS that are needed by a particular library is set in the GUI and the variables are successfully reserved for the loaded library the other functions in the library can safely use C_U
428. ode and write it out to the file PRF_CRECV_INT node_zero amp size 1 node_zero array real malloc size sizeof real PRF_CRECV_REAL node_zero array size node_zero 7 46 Fluent Inc September 11 2006 7 9 Writing Files in Parallel for i 0 i lt size i fprintf fp g n arraylil free array endif RP_HOST if RP_NODE SERIAL or HOST fclose fp Close the file that was only opened if on SERIAL or HOST Message Done n endif Fluent Inc September 11 2006 7 47 Parallel Considerations 7 48 Fluent Inc September 11 2006 Chapter 8 Examples This chapter provides examples of UDFs that range from simple to complex It begins with a step by step process that takes you through the seven basic steps of programming and using a UDF in FLUENT Some examples for commonly used types of applications are subsequently presented e Section 8 1 Step By Step UDF Example e Section 8 2 Detailed UDF Examples 8 1 Step By Step UDF Example The following 7 step process can be used to code a UDF and use it effectively in your FLUENT model 8 1 1 1 Process Overview Define your problem Section 8 1 2 Step 1 Define Your Problem Create a C source code file Section 8 1 3 Step 2 Create a C Source File Start FLUENT and read in or set up the case file Section 8 1 4 Step 3 Start FLUENT and Read or Set Up the Case File Interpret or compile
429. odel Mixture Turbulence Flow Table C 4 3 DEFINE Macro Usage for the Eulerian Model Mixture Turbu lence Flow Variable Macro Phase Specified On Other drag coefficient lift coefficient heat transfer coefficient mass transfer coefficient heterogeneous reaction rate DEF INE_EXCHANGE DEFINE EXCHANGE DEFINE PROPERTY DEFINE MASS TRANSFER DEFINE HET RXN RATE phase interaction phase interaction phase interaction phase interaction phase interaction Fluent Inc September 11 2006 C 13 Quick Reference Guide for Multiphase DEFINE Macros C 5 Eulerian Model Dispersed Turbulence Flow Tables C 5 1 C 5 3 list the variables that can be customized using UDFs for the dispersed turbulence flow Eulerian multiphase model the DEFINE macros that are used to define the UDFs and the phase that the UDF needs to be hooked to for the given variable C 14 Fluent Inc September 11 2006 C 5 Eulerian Model Dispersed Turbulence Flow Table C 5 1 DEFINE Macro Usage for the Eulerian Model Dispersed Tur bulence Flow Variable Macro Phase Specified On Boundary Conditions Inlet Outlet volume fraction species mass fractions mass flux velocity magnitude temperature pressure user defined scalar boundary value discrete phase boundary condition DEFINE_PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFIN
430. oe p a ras we 2 44 2 310 DEFINE NOX RATE 23 4004 4 aoe e ace GY ae GB ac eee 2 46 291 DEFINE PRARATE 2 4 4 4 aoe KS al e Oa EA Oe a 6 2 50 2 3 12 DEFINE PRANDTL UDFs 2 55 2 9 1 DEFINE PROPILE oo 4 4404 ao era ho oe OR ma ee AO 2 63 2 3 14 DEFINE PROPERTY UDFs 2 76 2 93 15 DEFINE SCAT PHASE FUNG 4 4 4 4 444 45 424 du 4 2 84 2310 DEF INE SOLAR INTENSITY s 224 24 oo ann Sc Se Se rs 2 87 2 93 17 DEFINE SOURCE Des a Set Se Heyy eae Gs ey ii Gei a 2 89 2 9 18 DEFINESODXRATE cc 4 4 4 44 sun 44 Gas m4 Oe oO Ae a 2 92 2 9 19 DEFINE SRRATE sacosa 4 42 den on de mon de a 2 97 2320 DEFINE TURB PREMIX SOURCE 4 0464 8 4 6 ae a4 Sa eas 2 101 2 3 21 DEFINE_TURBULENT_VISCOSITY 2 103 2 9 22 DEFINE VR RATE s 4 4 4 sche Lui we nu a 2 2 107 2 93 29 _D FINE WALL FUNCTIONS Lies his ache has 2 111 Fluent Inc September 11 2006 CONTENTS 24 Multiphase DEFINE Macros 2 2 b nes E wee de eS 2 113 24 1 DEFINE CAVITATION RATE o 2 115 24 2 DEFINE EXCHANGE PROPERTY 144 44 dau ee uen 2 118 24 3 DEFINE HET RAN RATE xe du pa vis d s se da Sue 2 123 2 4 4 DEFINEMASS TRANSFER gt 4 4 ec de de du due de du 2 129 2 4 5 DEFINE VECTOR EXCHANGE PROPERTY 2 132 2 5 Discrete Phase Model DPM DEFINE Macros 2 135 2 5 1 DEFINE DPMOBG o 3
431. oeff real normal 3 int i idim din real NV_VEC x Es 0 3 if RP_2D dim is always 2 in 2D compilation Need special treatment for 2d axisymmetric and swirl flows if rp_axi_swirl real R sqrt p gt state pos 1 p gt state pos 1 p gt state pos 2 p gt state pos 2 if R gt 1 e 20 idim 3 normal 0 f_normal 0 normal 1 f_normal 1 p gt state pos 1 R normal 2 f_normal 1 p gt state pos 2 R else for i 0 i lt idim i 2 1 42 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros normal i f_normal i else endif for i 0 i lt idim i normal i f_ normallil if p gt type DPM_TYPE_INERT alpha M_PI 2 acos MAX 1 MIN 1 NV_DOT normal p gt state V MAX NV_MAG p gt state V DPM_SMALL if NNULLP t amp amp THREAD_TYPE t THREAD_F_WALL F_CENTROID x f t calculate the normal component rescale its magnitude by the coefficient of restitution and subtract the change Compute normal velocity for i 0 i lt idim i vn p gt state V i normal i Subtract off normal velocity for i 0 i lt idim i p gt state V i vn normal i Apply tangential coefficient of restitution for i 0 i lt idim i p gt state V i tan_coeff Add reflected normal velocity for i 0 i lt idim i p gt state V i nor_coeff vn normal i Store new v
432. om path Fluent Inc fluent6 dernieres udf to all the version subdirectories you have made e g libudf ntx86 3d and re name it makefile Note that path is the directory in which you have installed the release directory Fluent Inc and x is replaced by the appropriate number for the release you have UNIX and Linux Systems For compiled UDFs on UNIX systems two Fluent Inc files are required to build your shared UDF library makefile udf and makefile udf2 The file makefile has a user modifiable section that allows you to specify source file parameters The procedure below outlines steps that you need to follow in order to set up the directory structure required for the shared library 1 In your working directory make a directory that will store your UDF library e g libudf Fluent Inc September 11 2006 5 11 Compiling UDFs 2 Copy makefile udf2 from path Fluent Inc fluent6 3 src makef ile udf2 where path is the directory in which you have installed the release directory Fluent Inc and x is replaced by the appropriate number for the release e g 1 for fluent6 2 1 to the library directory e g libudf and name it Makefile 3 In the library directory you just created in Step 1 make a directory that will store your source file and name it src 4 Copy your source file e g myudf c to the source directory src 5 Copy makefile udf from path Fluent Inc fluent6 3 src makefile udf
433. ompiler is designed to look for this file locally in your current directory first If it is not found in your current directory the compiler will look in the src directory automatically In the event that you upgrade your release area but do not remove an old copy of udf h from your working directory you will not be accessing the most recent version of this file REA You should not under any circumstances alter the udf h file There may be instances when will want to include additional header files in the compi lation process Make sure that all header files needed for UDFs are located in the src directory Fluent Inc September 11 2006 5 3 Compiling UDFs 5 1 2 Compilers The graphical and text interface processes for a compiled UDF require the use of a C compiler that is native to the operating system and machine you are running on Most UNIX operating systems provide a C compiler as a standard feature If you are operating on a Windows system you will need to ensure that a Microsft Visual C compiler is installed on your machine before you proceed If you are unsure about compiler require ments for your system please contact FLUENT installation support For Linux machines FLUENT supports any ANSI compliant compiler Obsolete versions of any native compiler may not work properly with com piled UDFs 5 2 Compile a UDF Using the GUI The general procedure for compiling a UDF source file and building a shared library
434. on 2 39 rate of strain 2 79 reaction rate UDFs examples 8 37 heterogeneous 2 127 particle 2 52 species net 2 46 surface 2 101 volumetric 2 111 read write UDFs 2 24 reader 2 24 reconstruction gradient macros 3 9 Reynolds Stress Model macros 3 16 RP macros 3 69 RP_CELL 2 162 2 183 2 185 RP_Get_Integer 3 72 7 43 RP_HOST 7 13 7 41 7 44 RP_NODE 7 13 7 44 RP_THREAD 2 183 2 185 sample problems 8 15 Sample Trajectories panel 6 62 sampling plane output 2 168 scalar transport equation UDF s anisotropic diffusivity 2 211 examples 8 43 flux term 2 215 unsteady term 2 219 scalar transport UDFs diffusion coefficient 2 209 fixed value boundary condition 2 210 flux 2 210 source term example 8 26 source terms 2 210 Index 13 Index unsteady 2 210 wall inflow and outflow boundary con ditions 2 211 scalar update UDFs 2 176 scattering phase UDFs 2 88 Scheme command 3 71 interpreter 3 71 variables 3 71 modifying 3 72 Select File panel 5 5 8 8 8 10 sg_mem h header file 3 16 shared library 1 2 building 5 4 SI units 1 2 six degrees of freedom solver property UDFs 2 205 slip velocity UDFs 2 136 2 137 solar intensity UDFs 2 91 Solid panel 6 39 solidification 8 32 solution process 1 12 density based solver 1 12 pressure based solver 1 12 solver data access using macros 3 2 solver variables accessing 3 1 source files 1 2 4 1 5 5 source term UDF s discre
435. on e g species velocity After the conservation equations properties are updated including PROPERTY UDFs Thus if your model involves the gas law for example the density will be updated at this time using the updated temperature and pressure and or species mass fractions A check for either convergence or additional requested iterations is done and the loop either continues or stops 1 12 Fluent Inc September 11 2006 1 9 UDF Calling Sequence in the Solution Process Pressure Based Coupled Solver The solution process for the pressure based coupled solver Figure 1 9 2 begins with a two step initialization sequence that is executed outside the solution iteration loop This sequence begins by initializing equations to user entered or default values taken from the FLUENT user interface Next PROFILE UDFs are called followed by a call to INIT UDFs Initialization UDFs overwrite initialization values that were previously set The solution iteration loop begins with the execution of ADJUST UDFs Next FLUENT solves the governing equations of continuity and momentum in a coupled fashion which is simultaneously as a set or vector of equations Energy species tranpsort turbulence and other transport equations as required are subsequently solved sequentially and the remaining process is the same as the pressure based segregated solver Density Based Solver As is the case for the other solvers the solution process for the
436. on 6 2 13 Hooking DEFINE_PROFILE UDFs Section 6 2 17 Hooking DEFINE_SOURCE UDFs and Section 6 2 3 Hooking DEFINE_DIFFUSIVITY UDFs to hook scalar source term profile or isotropic diffusion coefficient UDFs 6 6 1 Hooking DEFINE_ANISOTROPIC_DIFFUSIVITY UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_ANISOTROPIC_DIFFUSIVITY UDF the name of the function you supplied as the first DEFINE macro argument e g cyl_ortho_diff will become visible and selectable in FLUENT To hook the UDF to FLUENT you will first need to open the Materials panel Define Materials 6 78 Fluent Inc September 11 2006 6 6 Hooking User Defined Scalar UDS Transport Equation UDFs Materials Name Material Type Order Materials By air fluid Name 4 Chemical Formula Fluent Fluid Materials _ Chemical F air Fluent Database Mixture User Defined Database none v Cp j kg k constant Edit 1886 43 Thermal Conductivity w m k constant Edit 0 0242 Viscosity kg m s constat Edit 7eome 85 UDS Diffusivity kg m s defined per uds Edit Y Change Create l Delete Close Help Figure 6 6 1 The Materials Panel Choose defined per uds from the drop down list for UDS Diffusivity in the Materials panel Figure 6 6 1 This will open the UDS Diffusion Coefficients panel Figure 6 6 2
437. on Hooks Initialization mone Edit Adjust none Edit Execute at End none Edit Read Case none Edit Write Case none Edit Read Data mone Edit Write Data none Edit Execute at Exit none Figure 6 1 6 The User Defined Function Hooks Panel Click on the Edit button next to Execute At Exit This will open the Execute At Exit Functions panel Figure 6 1 7 In the Execute At Exit Functions panel from the list of Available Execute At End Functions that you have interpreted or compiled and loaded select the functions you wish to hook to your model and click Add and then OK Click OK in the User Defined Function Hooks panel to apply the settings The number of functions you select will then appear in the User Defined Function Hooks panel For example if you select two at exit functions user at exiti user_at_exit2 then the text box for Execute At Exit in the User Defined Function Hooks panel will display 2 selected See Section 2 2 4 DEFINE_EXECUTE_AT_EXIT for details about defining DEFINE_EXECUTE_AT_EXIT functions Fluent Inc September 11 2006 6 7 Hooking UDFs to FLUENT Execute at Exit Functions Available Execute at Exit Functions Selected Execute at Exit Functions user_at_exit libudf user_at_exit2 libudf Add Remove Figure 6 1 7 The Execute At Exit Functions Panel 6 8 Fluent Inc September 11 2006 6 1 Hooking General Purpose UDFs 6 1 5 Hookin
438. ongs to the current partition The convention that is used is that the smaller numbered compute node is assigned as the principal compute node for that face PRINCIPAL_FACE_P returns TRUE if the face is located on its principal compute node The macro can be used as a test condition when you want to perform a global sum on faces and some of the faces are partition boundary faces The macro returns TRUE for the serial process Below is the definition of PRINCIPAL FACE P from para h See Section 7 2 Cells and Faces in a Partitioned Grid for more information about PRINCIPAL_FACE_P predicate definitions from para h header file define PRINCIPAL_FACE_P f t TWO_CELL_FACE_P f t PRINCIPAL_TWO_CELL_FACE_P f t define PRINCIPAL_TWO_CELL_FACE_P f t I_LAM_NODE_MORE_P C_PART F_CO f t THREAD_TO t T_AM_NODE_MORE_P C_PART F_C1 f t THREAD_T1 t 7 5 4 Global Reduction Macros Global reduction operations are those that collect data from all of the compute nodes and reduce the data to a single value or an array of values These include operations such as global summations global maximums and minimums and global logicals These macros begin with the prefix PRF_G and are defined in prf h Global summation macros are identified by the suffix SUM global maximums by HIGH and global minimums by LOW The suffixes AND and OR identify global logicals The variable data types for each macro are identified in the macr
439. ons e wall shear and stress conditions e porosity e porous resistance direction vector e wall adhesion contact angle VOF multiphase model Note that DEFINE_PROFILE allows you to modify only a single value for wall heat flux Single values are used in the explicit source term which FLUENT does not linearize If you want to linearize your source term for wall heat flux and account for conductive and radiative heat transfer separately you will need to use DEFINE_HEAT_FLUX to specify your UDF Some examples of boundary profile UDFs are provided below For an overview of the FLUENT solution process which shows when a DEFINE_PROFILE UDF is called refer to Figures 1 9 1 1 9 2 and 1 9 3 2 66 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros Usage DEFINE _PROFILE name t i Argument Type Description symbol name UDF name Thread t Pointer to thread on which boundary condition is to be applied int i Index that identifies the variable that is to be defined i is set when you hook the UDF with a variable in a boundary condition panel through the graphical user interface This index is subsequently passed to your UDF by the FLUENT solver so that your function knows which variable to operate on Function returns void There are three arguments to DEFINE_PROFILE name t and i You supply name the name of the UDF t and i are variables that are passed by the FLUENT solver to your UDF While DEFINE_PRO
440. onsiderations e Chapter 8 Examples This document provides some basic information about the C programming language Appendix A as it relates to user defined functions in FLUENT and assumes that you are an experienced programmer in C If you are unfamiliar with C please consult a C language reference guide e g 2 3 before you begin the process of writing UDFs and using them in your FLUENT model This document does not imply responsibility on the part of Fluent Inc for the ac curacy or stability of solutions obtained using UDFs that are either user generated or provided by Fluent Inc Support for current license holders will be limited to guidance related to communication between a UDF and the FLUENT solver Other aspects of the UDF development process that include conceptual function design implementation writing C code compilation and debugging of C source code ex ecution of the UDF and function design verification will remain the responsibility of the UDF author UDF compiled libraries are specific to the computer architecture being used and the version of the FLUENT executable being run and must be rebuilt any time FLUENT is upgraded your operating system changes or the job is run on a different type of computer Note that UDFs may need to be updated with new versions of FLUENT Fluent Inc September 11 2006 l About This Document Il Fluent Inc September 11 2006 Chapter 1 Overview This chapter contains
441. ooking to FLUENT 6 68 Index 4 DEF INE_DPM_TIMESTEP UDFs defining 2 190 hooking to FLUENT 6 69 DEF INE_DPM_VP_EQUILIB UDFs defining 2 193 hooking to FLUENT 6 70 DEF INE_EXCHANGE_PROPERTY UDFs defining 2 122 hooking to FLUENT 6 48 DEF INE_EXECUTE_AT_END UDFs defining 2 9 hooking to FLUENT 6 5 DEF INE_EXECUTE_AT_EXIT UDFs defining 2 11 hooking to FLUENT 6 7 DEFINE EXECUTE FROM GUI UDF s defining 2 12 DEF INE_EXECUTE_ON_LOADING UDF s defining 2 15 DEFINE_GEOM UDFs defining 2 200 hooking to FLUENT 6 73 DEF INE_GRAY_BAND_ABS_COEFF UDFs defining 2 42 hooking to FLUENT 6 22 DEFINE_GRID_MOTION UDFs defining 2 202 hooking to FLUENT 6 75 DEF INE_HEAT_FLUX UDFs defining 2 44 example 8 48 hooking to FLUENT 6 23 DEF INE_HET_RXN_RATE UDFs defining 2 127 hooking to FLUENT 6 50 DEFINE_INIT UDFs defining 2 19 hooking to FLUENT 6 9 DEF INE_MASS_TRANSFER UDF s defining 2 133 hooking to FLUENT 6 51 DEF INE_NET_REACTION_RATE UDF s defining 2 46 Fluent Inc September 11 2006 Index hooking to FLUENT 6 24 DEFINE_NOX_RATE UDFs defining 2 48 hooking to FLUENT 6 25 DEFINE_ON_DEMAND UDFs defining 2 21 hooking to FLUENT 6 11 DEFINE_PR_RATE UDFs defining 2 52 hooking to FLUENT 6 27 DEFINE_PRANDTL UDFs defining 2 58 hooking to FLUENT 6 28 DEFINE_PROFILE UDFs defining 2 66 example 8 18 8 48 hooking to FLUENT 6 29 DEFINE PROPERTY UDF s defining 2 79 example 8 32 hooking
442. or details 2 6 Fluent Inc September 11 2006 2 2 General Purpose DEF INE Macros 2 2 2 DEFINE DELTAT Description DEFINE DELTAT is a general purpose macro that you can use to control the size of the time step during the solution of a time dependent problem Note that this macro can be used only if the adaptive time stepping method option has been activated in the Iterate panel in FLUENT Usage DEFINE DELTAT name d Argument Type Description symbol name UDF name Domain d Pointer to domain over which the time stepping control function is to be applied The domain argument provides access to all cell and face threads in the mesh For multiphase flows the pointer that is passed to the function by the solver is the mixture level domain Function returns real There are two arguments to DEFINE_DELTAT name and domain You supply name the name of the UDF domain is passed by the FLUENT solver to your UDF Your UDF will need to compute the real value of the physical time step and return it to the solver Example The following UDF named mydeltat is a simple function that shows how you can use DEFINE_DELTAT to change the value of the time step in a simulation First CURRENT_TIME is used to get the value of the current simulation time which is assigned to the variable flow_time Then for the first 0 5 seconds of the calculation a time step of 0 1 is set A time step of 0 2 is set for the remainder of the simulation T
443. or the surface chemistry model To enable the PDF Transport models select Composition PDF Transport and Volumetric reac tions in the Species Model panel To enable the EDC model select Species Transport and Volumetric reactions in the Species Model panel and choose EDC under Turbulence Chemistry Interaction To hook the UDF to FLUENT choose the function name e g usr net reaction rate in the Net Reaction Rate Function drop down list and click OK See Section 2 3 9 DEFINE NET REACTION RATE for details about DEFINE NET REACTION RATE functions 6 2 10 Hooking DEFINE_NOX_RATE UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_NOX_RATE UDF in FLUENT the function name you supplied in the DEFINE macro argument will become visible and selectable in the drop down list for NOx Rate in the NOx Model panel Figure 6 2 11 Define Models gt Species NOx NOx Model Models Formation Model Parameters Formation Reduction Turbulence Interaction Thermal Prompt Fuel N20 Path Pathways V Thermal NO 0 Model partial equilibrium M Prompt NO OH Model W Fuel NO OH partial equilibrium M N20 Intermediate V Replace with UDF Rate User Defined Functions NOx Rate juser_nox libudf v Figure 6 2 11 The NOx Model Panel Fluent Inc September 11 2006 6 25 Hooking UDFs to FLUENT i Note that
444. os that can be used to send data between the host and the compute nodes host_to_node_type_num and node_to_host_type_num Host to Node Data Transfer To send data from the host process to all the node processes indirectly via compute node 0 we use macros of the form host_to_node_type_num val_1 val_2 val_num where num is the number of variables that will be passed in the argument list and type is the data type of the variables that will be passed The maximum number of variables that can be passed is 7 Arrays and strings can also be passed from host to nodes one at a time as shown in the examples below Examples integer and real variables passed from host to nodes host_to_node_int_1 count host_to_node_real_7 leni len2 widthi width2 breadthi breadth2 vol string and array variables passed from host to nodes char wall_name wall 17 int thread _ids 10 1 29 5 32 18 2 55 21 72 14 host_to_node_string wall_name 8 remember terminating NUL character host_to_node_int thread_ids 10 Note that these host to node communication macros do not need to be protected by compiler directives for parallel UDFs because all of these macros automatically do the following e send the variable value if compiled as the host version e receive and then set the local variable if compiled as a compute node version e do nothing in the serial version The most common use for this set of macro
445. otal_force Does nothing in SERIAL if RP_NODE SERIAL or HOST Message Total Area After Summing f m2 n total_area Message Total Normal Force After Summing f N n total_force Message Average pressure on Surface d is f Pa n surface_thread_id total_force total_area endif RP_NODE 7 42 Fluent Inc September 11 2006 7 8 Parallel UDF Example The function begins by initializing the variables surface_thread_id total_area and total_force for all processes This is done because the variables are used by the serial host and node processes The compute nodes use the variables for computation purposes and the host uses them for message passing and displaying purposes Next the preprocessor is directed to compile thread face and area variables only on the serial and node versions and not the host since faces and threads are only defined in the serial and node versions of FLUENT Note that in general the host will ignore these statements since its face and cell data are zero but it is good programming practice to exclude the host See Section 7 5 Macros for Parallel UDFs for details on compiler directives Next a user defined Scheme variable named pres_av thread id is obtained by the host and serial process using the RP_Get_Integer utility see Section 3 6 Scheme Macros and is assigned to the variable surface_thread_id Note that this user defined Scheme variable was previous
446. ou can make changes with an editor in a separate window Then you can continue to debug and interpret until no errors are reported Remember to save changes to the source code file in the editor window before trying to interpret again One of the more common errors made when interpreting source files is trying to interpret code that contains elements of C that the interpreter does not accommodate For exam ple if you have code that contains a structured reference call which is not supported by the C preprocessor the interpretation will fail and you will get an error message similar to the following Error nfs clblnx home clb fluent udfexample c line 15 structure reference Fluent Inc September 11 2006 4 4 Special Considerations for Parallel FLUENT 4 4 Special Considerations for Parallel FLUENT If you are running the parallel version of FLUENT on a Windows network and you en counter errors when trying to interpret a source file it could be the result of an improper installation of cpp Proper installation of parallel FLUENT for Windows ensures that the FLUENT_INC environment variable is set to the shared directory where FLUENT is installed If the variable is defined locally instead the following error message will be reported when you try to interpret a source file Warning unable to run cpp You will need to see your system administrator to reset the FLUENT_INC environment variable Fluent Inc September 11 200
447. ou have selected a SO rate UDF If you don t check the Replace with UDF Rate box but hook the UDF function to the interface then the UDF rate for that SO formation will be added to the internally calculated rate for the source term calculation 6 40 Fluent Inc September 11 2006 6 2 Hooking Model Specific UDFs Unless specifically defined in your SO rate UDF data and parameter settings will be derived from the settings in the SOx Model panel Therefore it is good practice to make the appropriate settings in the SOx Model panel even though you may use a UDF to replace the default rates with user specified rates There is no computational penalty for doing this because the default rate calculations will be skipped over when the Replace by UDF Rate option is selected See Section 2 3 18 DEFINE_SOX_RATE for details about defining DEFINE_SOX_RATE func tions 6 2 19 Hooking DEFINE SR RATE UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE SR RATE UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Function Hooks panel Figure 6 2 25 in FLUENT Define User Defined Function Hooks User Defined Function Hooks Initialization none Edit Adjust none Edit Execute at End none Edit Read Case none Edit Write Case one Edit Read Data none Edit
448. oundary value species boundary condition DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE DPM BC DEFINE PROFILE mixture mixture mixture mixture mixture mixture mixture mixture mixture mixture mixture secondary phase s secondary phase s mixture mixture phase dependent Material Properties cavitation surface tension coefficient cavitation vaporization pressure particle or droplet diameter granular diameter granular solids pressure granular radial distribution granular elasticity modulus granular viscosity granular temperature DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY phase interaction phase interaction secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s Other slip velocity drag coefficient mass transfer coefficient heterogeneous reaction rate DEFINE VECTOR_ EXCHANGE _ PROPERTY DEFINE EXCHANGE DEFINE MASS TRANSFER DEFINE HET RXN RATE phase interaction phase interaction phase interaction phase interaction Fluent Inc September 11 2006 C 3 Eulerian Model Laminar Flow C 3 Eu
449. over the particle surface Function returns void There are three arguments to DEFINE DPM VP EQUILIB name p and cvap surf You supply the name of your user defined function p is passed by the FLUENT solver to your UDF Your UDF will need to compute the equilibrium vapor concentrations and store the values in cvap_surf Example The following UDF named raoult_vpe computes the equilibrium vapor concentration of a multicomponent particle using hte Raoult law The vapor pressure in the law is proportional to the molar fraction of the condenses material DEFINE_VP_EQUILIB is called several times every particle time step in FLUENT and requires a significant amount of CPU time to execute For this reason the UDF should be executed as a compiled UDF Fluent Inc September 11 2006 2 1 93 DEFINE Macros peaa o kkk k kkk kkk kkk kkk kk kk kkk kk kkk kkk kkk kk kkk k UDF for defining the vapor particle equilibrium for multicomponent particles DO ooo oo k k kkk kkk kk k kkk include udf h include dpm h include surf h DEFINE_DPM_VP_EQUILIB raoult_vpe p cvap_surf int is real molwt MAX_SPEF_EQNS Thread tO RP_THREAD amp p gt cCell cell thread of particle location Material gas_mix THREAD_MATERIAL tO gas mixture material Material cond_mix p gt injection gt material particle mixture material int nc TP_N_COMPONENTS p number of particle components real Tp P_T p
450. ow If you chose not to display the listing and the compilation is successful then the CPP Command Name that was executed will appear on the console If the compilation is unsuccessful then FLUENT will report an error and you will need to debug your program See Sec tion 4 3 Common Errors Made While Interpreting A Source File You can also view the compilation history in the log file that is saved in your working directory 11 Close the Interpreted UDFs panel when the interpreter has finished 12 Write the case file if you want the interpreted function s e g inlet_x_velocity to be saved with the case and automatically interpreted when the case is subse quently read If the Display Assembly Listing option was chosen then the assembly code will appear in the console window Fluent Inc September 11 2006 4 5 Interpreting UDFs 4 3 Common Errors Made While Interpreting A Source File If there are compilation errors when you interpret a UDF source file they will appear in the console window However you may not see all the error messages if they scroll off the screen too quickly For this reason you may want to turn off the Display Assembly Listing option while debugging your UDF You can view the compilation history in the log file that is saved in your working directory If you keep the Interpreted UDFs panel open while you are in the process of debugging your UDF the Interpret button can be used repeatedly since y
451. p return if rp_axi amp amp sg_swirl rp_ke y MAX sqrt SQR p gt state pos 1 SQR p gt state pos 21 DPM_SMALL else Fluent Inc September 11 2006 2 1 69 DEFINE Macros y p gt state pos 1 if PARALLEL par _fprinti fp Ad 4d Le Wf Ef Pf LE He Le Ef he FE n p gt injection gt try_id p gt part_id P_TIME p y p gt state V 0 p gt state V 1 p gt state V 2 P_DIAM p p gt number_in_parcel P_T p P_INIT_DIAM p p gt time_of_birth else par_fprintf fp he Wf Af Af AF he he hf he KE n P_TIME p y p gt state V 0 p gt state V 1 p gt state V 2 P_DIAM p p gt number_in_parcel P_T p P_INIT_DIAM p p gt time_of_birth endif PARALLEL else real flow_time solver_par flow_ time real r x y if header par_fprintf_head fp Timels R m x velocity m s y velocity m s Z velocity m s Drop Diameter m Number of Drops Temperature K Initial Diam m Injection Time s n if NULLP p return p gt state pos 0 p gt state pos 1 sqrt SQR x SQR y tal Il K s lt tou if PARALLEL par_fprintf fp d hd he Wf Af hf hf he he Af he h n p gt injection gt try_id p gt part_id P_TIME p r p gt state V 0 p gt state V 1 p gt state V 2 P_DIAM p p gt number_in_parcel P_T p P_INIT_DIAM p p gt time_of_birth telse par_fprintf fp he Wf Af WE Uf he he AE he AE n P_TIME p r p gt state V 0 p gt s
452. particle Particle particle Pointer to Particle data structure that contains data related to the particle being tracked double pressure Pointer to pressure variable double temp Pointer to temperature variable double yi Pointer to array containing species mass fractions double rr Pointer to array containing net mass reaction rates double jac Pointer to array of Jacobians Function returns void There are nine arguments to DEFINE NET REACTION RATE name c t particle pressure temp yi rr and jac You supply name the name of the UDF The variables c t particle pressure temp yi rr and jac are passed by the FLUENT solver to your UDF and have SI units The outputs of the function are the array of net molar reaction rates rr with units kgmol m s and the Jacobian array jac The Jacobian is only 2 46 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros required for surface chemistry and is the derivative of the surface net reaction rate with respect to the species concentration DEFINE NET REACTION RATE is called for all fluid zones volumetric reactions as well as surface reactions in porous media and for all wall thread zones whenever the Reaction button is enabled in the Boundary Conditions panel and the UDF is hooked to FLUENT in the User Defined Function Hooks panel A DEFINE_NET_REACTION_RATE functions can be executed only as compiled UDFs Example The following UDF named user_
453. pe rp var define pres_av thread id 2 integer f Once set up you can change it to another thread s ID using rpsetvar pres_av thread id 7 Send the ID value to all the nodes host_to_node_int_1 surface_thread_id Does nothing in serial Fluent Inc September 11 2006 7 41 Parallel Considerations if RP_NODE Message nNode d is calculating on thread d n myid surface_thread_id endif RP_NODE if RP_HOST SERIAL or NODE thread is only used on compute processes thread Lookup_Thread domain surface_thread_id begin_f_loop face thread If this is the node to which face officially belongs get the area vector and pressure and increment the total area and total force values for this node if PRINCIPAL_FACE_P face thread Always TRUE in serial version F_AREA area face thread total_area NV_MAG area total_force NV_MAG area F_P face thread end_f_loop face thread Message Total Area Before Summing 7 f n total_area Message Total Normal Force Before Summing f n total_force if RP_NODE Perform node synchronized actions here Does nothing in Serial total_area PRF_GRSUM1 total_area total_force PRF_GRSUM1 total_force endif RP_NODE endif RP_HOST Pass the node s total area and pressure to the Host for averaging node_to_host_real_2 total_area t
454. pecies b in the horizontal section of the duct No reaction takes place in the fluid region although some diffusion of species b out of the porous region is suggested by the wide transition layer between the regions of 100 and 0 species a Fluent Inc September 11 2006 8 41 Examples 1 00e 00 9 00e 01 8 00e 01 7 00e 01 6 00e 01 5 00e 01 4 00e 01 3 00e 01 2 00e 01 1 00e 01 0 00e 00 Contours of Mass fraction of species a Figure 8 2 19 Mass Fraction for species a Governed by a Reaction in a Porous Region 8 42 Fluent Inc September 11 2006 8 2 Detailed UDF Examples 8 2 5 User Defined Scalars This section contains examples of UDFs that can be used to customize user defined scalar UDS transport equations See Section 2 7 User Defined Scalar UDS Transport Equation DEFINE Macros in the UDF Manual for information on how you can define UDFs in FLUENT Refer to Section 9 3 User Defined Scalar UDS Transport Equations of the User s Guide for UDS equation theory and details on how to set up scalar equations Postprocessing Using User Defined Scalars Below is an example of a compiled UDF that computes the gradient of temperature to the fourth power and stores its magnitude in a user defined scalar The computed tem perature gradient can for example be subsequently used to plot contours Although the practical application of this UDF is questionable its purpose here is
455. pecified Value for User Scalar 0 is set to a pressure_profile UDF Note that for interior walls you will need to select Coupled Boundary if the scalars are to be solved on both sides of a two sided wall Note that the Coupled Boundary option will show up only in the drop down list when the scalar is defined in the fluid and solid zones in the User Defined Scalars panel Fluent Inc September 11 2006 6 31 Hooking UDFs to FLUENT In some cases you may wish to exclude diffusion of the scalar at the inlet of your domain You can do this by disabling diffusion of the scalar at the inlet in the User Defined Scalars panel See Section 2 3 13 DEFINE_PROFILE for details about DEFINE_PROFILE functions 6 2 14 Hooking DEFINE_PROPERTY UDFs Material Properties Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your material property UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Functions panel Figure 6 2 18 in FLUENT To hook the UDF to FLUENT you will first need to open the User Defined Functions panel by choosing user defined in the drop down list for the appropriate property e g Viscosity in the Materials panel Figure 6 2 17 Define Materials Next choose the function name e g cell_viscosity from the list of UDFs displayed in the User Defined Functions panel Figure 6 2 18 and cli
456. perty only for a single cell and return it to the solver Note that like source term UDFs property UDFs defined using DEFINE_PROPERTY are called by FLUENT from within a loop on cell threads The solver passes all of the variables needed to allow a DEFINE_PROPERTY UDF to define a custom material since properties are assigned on a cell basis Consequently your UDF will not need to loop over cells in a zone since FLUENT is already doing it Auxiliary Utilities Some commonly used auxiliary utilities for custom property UDFs are described below They are generic property MATERIAL PROPERTY THREAD MATERIAL and mixture_species_loop generic property is a general purpose function that returns the real value for the given property id for the given thread material It is defined in prop h and is used only for species properties The following Property_ID variables are available e PROP_rho density e PROP_mu viscosity e PROP ktc thermal conductivity generic property name c t prop id T Argument Type Description symbol name Function name cell t c Cell index Thread t Pointer to cell thread on which property function is to be applied Property prop Pointer to property array for the thread material that can be obtained through the macro MATERIAL_ PROPERTY m See below Property ID id Property ID of the required property you want to define a custom mixing law for e g PROP_ktc for thermal conductivity See below for list
457. place in memory where you can store a value Every variable has a type e g real a name and a value and may have a storage class identifier static or extern All variables must be declared before they can be used By declaring a variable ahead of time the C compiler knows what kind of storage to allocate for the value Global variables are variables that are defined outside of any single function and are visible to all function s within a UDF source file Global variables can also be used by other functions outside of the source file unless they are declared as static see Section A 5 3 Static Variables Global variables are typically declared at the beginning of a file after preprocessor directives as in include udf h real volume real variable named volume is declared globally DEFINE_ADJUST compute_volume domain code that computes volume of some zone volume Local variables are variables that are used in a single function They are created when the function is called and are destroyed when the function returns unless they are declared as static see Section A 5 3 Static Variables Local variables are declared within the body of a function inside the curly braces In the example below mu_lam and temp are local variables The value of these variables is not preserved once the function returns Fluent Inc September 11 2006 A 3 C Programming Basics DEFINE_PROPERTY cell_viscosity cell
458. pointer The value of domain_id is always 1 for the mixture domain You can obtain the domain_id using the FLUENT graphical user interface much in the same way that you can determine the zone ID from the Boundary Conditions panel Simply go to the Phases panel in FLUENT and select the desired phase The domain_id will then be displayed You will need to hard code this integer ID as an argument to the macro as shown below Fluent Inc September 11 2006 3 27 Additional Macros for Writing UDFs DEFINE_ON_DEMAND my_udf Domain mixture_domain mixture_domain Get_Domain 1 returns mixture domain pointer and assigns to variable Domain subdomain subdomain Get_Domain 2 returns phase with ID 2 domain pointer and assigns to variable Example Below is a UDF named get_coords that prints the thread face centroids for two specified thread IDs The function implements the Get_Domain utility for a single phase applica tion In this example the function Print Thread Face Centroids uses the Lookup Thread function to determine the pointer to a thread and then writes the face centroids of all the faces in a specified thread to a file The Get_Domain 1 function call returns the pointer to the domain or mixture domain in the case of a multiphase application This argument is not passed to DEFINE_ON_DEMAND PK kk k k kk ak ak k ak 2k 2k aK ak 2k K K 3K 2k K 3k 2K 2K K FK 2K K K 2K 2K 2K FK 2K 2K K FK 2K 2K K FK
459. pressure define PSAT_A 0 01 define PSAT_TP 338 15 define C_LOOP 8 define H20_PC 22 089E6 define H20_TC 647 286 user inputs define MAX_SPE_EQNS_PRIM 2 total number of species in primary phase define index_evap_primary 0 evaporating species index in primary phase define prim_index O xindex of primary phase define P_OPER 101325 xoperating pressure equal to GUI valuex xend of user inputs paaa kkk AAR A A k k A k k k kk k kkk k k k k RK kk k k k k k 2k 2k k kkk UDF for specifying an interfacial area density DOBRO 3k 3k 3k ak a 3k ak A aK 2K K K aK K K K K 3K 2K 3K 2K 3K 3K 3K 3K 3K 2K 2K 2K 2K aK 2K K K K 2K kkk i 2k KKK double psat_h2o double tsat Computes saturation pressure of water vapor as function of temperature Equation is taken from THERMODYNAMIC PROPERTIES IN SI by Reynolds 1979 Returns pressure in PASCALS given temperature in KELVIN int i Fluent Inc September 11 2006 2 1 29 DEFINE Macros double vari sumi ansi psat double constants 8 7 4192420 2 97221E 1 1 155286E 1 8 68563E 3 1 094098E 3 4 39993E 3 2 520658E 3 5 218684E 4 vari is an expression that is used in the summation loop vari PSAT_A tsat PSAT_TP Compute summation loop i 0 sumi 0 0 while i lt C_LOOP sumi constants Li pow var1 i i ansi sum1 H20_TC tsat 1 0 compute exponential to determine resu
460. priate boundary face value in memory See Section 3 2 6 Set Boundary Condition Value F_PROFILE for a description of F_PROFILE Note that in the case of porosity pro files you can also utilize C_PROFILE to define those types of functions See the example Fluent Inc September 11 2006 2 67 DEFINE Macros UDFs provided below In multiphase cases a DEFINE PROFILE UDF may be called more than once particularly if the profile is used in a mixture domain thread If this needs to be avoided then add the prefix MP_ to the UDF name The function will then be called only once even if it is used for more than one profile Example 1 Pressure Profile The following UDF named pressure_profile generates a parabolic pressure profile according to the equation 2 11 10 01 10 a Pty i X 0075 Note that this UDF assumes that the grid is generated such that the origin is at the geometric center of the boundary zone to which the UDF is to be applied y is 0 0 at the center of the inlet and extends to 0 0745 at the top and bottom of the inlet The source code can be interpreted or compiled in FLUENT peaa k kk k kk kkk kkk kk kk kkk kk kkk k kk k k k kk kk k kk k kk k k k kk k k k kk k k k K k UDF for specifying steady state parabolic pressure profile boundary profile for a turbine vane KKK ak ak ak ak aK K K K 2K 3K EE EEE EEE 2K 2K 2K 2K 2K EE 3K 3K 3K 3K 3K 3K 2K 2K 2K 2K 2K 3K EE K I Kk kk kk KKK KK include udf h D
461. properties 1 3 material property macros 3 15 material property UDFs general purpose 2 79 MATERIAL_PROP 2 162 2 185 MATERIAL_PROPERTY 2 81 2 84 MATERIAL_TYPE 2 185 Materials panel 6 22 6 32 6 34 6 63 8 33 mathematical functions A 14 mem h header file 3 7 3 8 3 15 Message 2 154 3 73 7 31 7 41 message displaying macros parallel 7 31 message passing parallel 7 4 example 7 33 macros 7 32 MessageO 7 31 metric h header file 3 6 3 7 3 16 3 18 3 19 mixing constant UDF 2 33 mixing law thermal conductivity 2 84 mixture domain pointer 3 61 Mixture model DEFINE macro usage C 4 mixture_species_loop 2 82 model dependent UDFs solar intensity 2 91 model specific DEFINE macros quick reference guide 2 26 Index 10 model specific UDFs gray band coefficient 2 42 hooking to FLUENT 6 14 models h 3 74 MOLECON 3 35 3 37 momentum source term UDF example 8 26 mp_thread_loop_c 3 56 mp_thread loop f 3 57 multicomponent particle heat and mass transfer UDFs 2 159 multiphase DEFINE macros quick reference guide 2 117 multiphase flow getting domain pointer 3 27 Multiphase Model panel 6 46 multiphase models Eulerian property UDFs 2 79 Mixture property UDFs 2 79 VOF property UDFs 2 79 multiphase UDFs cavitation parameters 2 79 cavitation rate 2 119 data structures 1 17 data types 1 17 DEFINE macros 1 17 density compressible liquids 2 79 domains 1 17 drag coefficient 2 122 elasticity mo
462. ptember 11 2006 3 49 Additional Macros for Writing UDFs 3 3 Looping Macros Many UDF tasks require repeated operations to be performed on nodes cells and threads in a computational domain For your convenience Fluent Inc has provided you with a set of predefined macros to accomplish looping tasks For example to define a custom boundary profile function you will need to loop over all the faces in a face thread using begin end_f_loop looping macros For operations where you want to loop over all the faces or cells in a domain you will need to nest a begin end_f_loop or begin end_c_loop inside a thread_loop_f or thread_loop_c respectively The following general looping macros can be used for UDFs in single phase or multiphase models in FLUENT Definitions for these macros are contained in the mem h header file i You should not access a scheme variable using any of the RP_GET_ func tions from inside a cell or face looping macro c loop or f loop This type of communication between the solver and cortex is very time consuming and therefore should be done outside of loops Looping Over Cell Threads in a Domain thread_loop_c You can use thread loop c when you want to loop over all cell threads in a given domain It consists of a single statement followed by the operation s to be performed on all cell threads in the domain enclosed within braces as shown below Note that thread_loop c is similar in implementation to the
463. pter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visi ble and selectable in the User Defined Function Hooks panel in FLUENT Note that you can hook multiple at exit UDFs to your model See Section 6 1 4 Hooking DEFINE_EXECUTE_AT_EXIT UDFs for details Fluent Inc September 11 2006 2 11 DEFINE Macros 2 2 5 DEFINE_EXECUTE_FROM_GUI Description DEFINE_EXECUTE_FROM_GUI is a general purpose macro that you can use to define a UDF which is to be executed from a user defined graphical user interface GUI For example a C function that is defined using DEFINE_EXECUTE_FROM_GUI can be executed whenever a button is clicked in a user defined GUI Custom GUI components panels buttons etc are defined in FLUENT using the Scheme language Usage DEFINE_EXECUTE_FROM_GUI name 1ibname mode Argument Type Description symbol name UDF name char libname name of the UDF library that has been loaded in FLUENT int mode an integer passed from the Scheme program that defines the user defined GUI Function returns void There are three arguments to DEFINE_EXECUTE_FROM_GUI name libname and mode You supply name the name of the UDF The variables libname and mode are passed by the FLUENT solver to your UDF The integer variable mode is passed from the Scheme program which defines the user defined GUI and represent the possible user
464. quation Macros Source Term UDFs For each of the N scalar equations you have specified in your FLUENT model using the User Defined Scalars panel you can supply a unique UDF for each source Recall that FLUENT computes the source term in the UDS equation Scalar source UDFs are defined using the DEFINE_SOURCE macro and must compute the source term Sgp and its derivative at Section 2 3 17 DEFINE SOURCE Additional pre defined macros that you can use when coding scalar source term UDFs are provided in Section 3 2 8 User Defined Scalar UDS Transport Equation Macros Fixed Value Boundary Condition UDFs For each of the N scalar equations you have specified in your FLUENT model using the User Defined Scalars panel you can supply a fixed value profile UDF for fluid boundaries Fixed value UDFs are defined using the DEFINE PROFILE macro See Section 2 3 13 DEFINE PROFILE for details Additional pre defined macros that you can use for coding scalar transport equation UDFs are provided in Section 3 2 8 User Defined Scalar UDS Transport Equation Macros 2 210 Fluent Inc September 11 2006 2 7 User Defined Scalar UDS Transport Equation DEFINE Macros Wall Inflow and Outflow Boundary Condition UDFs For each of the N scalar equations you have specified in your FLUENT model using the User Defined Scalars panel you can supply a specified value or flux UDF for all wall inflow and outflow boundaries Wall inflow and outf
465. r Laws in the Set Injection Properties panel This will open the Custom Laws panel Custom Laws custom law First Law Inactive yy Second Law Inactive ThirdLew Inactive yy Fourth Law macie SS Fifth Law lnacive Sixth Law Detaut Switching Figure 6 4 7 The Custom Laws Panel Finally in the Custom Laws panel Figure 6 4 7 choose the function name e g custom law in the appropriate drop down list located to the left of each of the six particle laws e g First Law and click OK See Section 2 5 7 DEFINE_DPM_LAW for details about DEFINE_DPM_LAW functions Fluent Inc September 11 2006 6 61 Hooking UDFs to FLUENT 6 4 8 Hooking DEFINE_DPM_OUTPUT UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_OUTPUT UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Sample Trajectories panel Figure 6 4 8 in FLUENT Report Discrete Phase gt Sample Sample Trajectories Boundaries Planes Release From Injections atomizer wall injection 0 central_air co flow air default interior outer wall outlet periodic a swirling_air Append Files Accumulate Erosion Accretion Rates User Defined Functions Output dpm_output Start Close Help Figure 6 4 8 The Sample Trajectories Panel To hook the UDF to FLUEN
466. r details about Fluent provided SO macros e g POLLUT_EQN MOLECON ARRH that are used in pollutant rate calculations in this UDF peaa oa oo oo o kkk k k kkk kk kk kkk kkk kkk ES UDF example of User Defined SOx Rate For FLUENT Versions 6 3 or above If used with the replace with udf radio button activated this udf will replace the default fluent SOx rates The flag Pollut_Par gt pollut_io_pdf IN_PDF should always be used for rates other than that from char S so that if requested the contributions will be pdf integrated Any contribution from char must be included within a switch statement of the form Pollut_Par gt pollut_io_pdf OUT_PDF Arguments char sox_func_name UDF name cell_t c Cell index Thread t Pointer to cell thread on which the SOx rate is to be applied Pollut_Cell Pollut Pointer to the data structure that contains common data at each cell Pollut_Parameter Pollut_Par Pointer to the data structure that contains auxiliary data SOx_Parameter SOx Pointer to the data structure that contains data specific to the SOx model BCC A k K 2K A 2K 2K 2K AK 2K k K 2K 2k 2K 2K 2K 2K 2K 2K 2K 2K 2K K K K 2K AK 2K 2K 2K 2K 2K LEE LEZ 2k FK FK 2k FKK 2k LES LLC ak FK 2 2k ok 2 ak k include udf h void so2_so3_rate cell_t c Thread t Pollut_Cell Pollut 2 98 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros Pollut_Parameter Pollut_
467. ral files referring to that variable then it is convenient to include the extern definition in a header h file and include the header file in all of the c files that want to use the external variable Only one c file should have the declaration of the variable without the extern keyword Below is an example that demonstrates the use of a header file il extern can be used only in compiled UDFs Fluent Inc September 11 2006 A 5 C Programming Basics Example Suppose that there is a global variable named volume that is declared in a C source file named filel c include udf h real volume real variable named volume is declared globally DEFINE_ADJUST compute_volume domain code that computes volume of some zone volume If multiple source files want to use volume in their computations then volume can be declared as an external variable in a header file e g extfile h extfile h Header file that contains the external variable declaration for volume extern real volume Now another file named file2 c can declare volume as an external variable by simply including extfile h file2 c include udf h include extfile h header file containing extern declaration is included DEFINE_SOURCE heat_source c t ds eqn code that computes the per unit volume source using the total volume computed in the compute_volume function from filel c real total_source re
468. ramming Below is an example of how the equation derived in Step 1 Equation 8 1 1 can be implemented in a UDF The functionality of the UDF is designated by the leading DEFINE macro Here the DEFINE PROFILE macro is used to indicate to the solver that the code proceeding it will provide profile information at boundaries Other DEFINE macros will be discussed later in this manual See Chapter 2 DEFINE Macros for details about DEFINE macro usage PRR ooo kkk kkk kkk kk kkk kkk A A AK KKK KK OK udfexample c UDF for specifying a steady state velocity profile boundary condition BREA DE DO I ICI I OK OK OK AK AK KR A A 2K 21 DD kkk k k kkk include udf h must be at the beginning of every UDF you write DEFINE_PROFILE x_velocity thread index real x ND_ND this will hold the position vector real y face_t f begin_f_loop f thread loops over all faces in the thread passed in the DEFINE macro argument F_CENTROID x f thread y x 1 F_PROFILE f thread index 20 y y 0745 0745 20 end_f_loop f thread Es Fluent Inc September 11 2006 8 5 Examples The first argument of the DEFINE_PROFILE macro x_velocity is the name of the UDF that you supply The name will appear in the boundary condition panel once the function is interpreted or compiled enabling you to hook the function to your model Note that the UDF name you supply cannot contain a number as the first character The equa
469. rce file named udfexample c In general you must compile your function as a compiled UDF if the source code contains structured reference calls or other elements of C that are not handled by the FLUENT interpreter To determine whether you should compile or interpret your UDF see Section 1 5 1 Dif ferences Between Interpreted and Compiled UDFs Fluent Inc September 11 2006 8 1 Step By Step UDF Example Interpret the Source File Follow the procedure below to interpret your source file in FLUENT For more information on interpreting UDFs see Chapter 4 Interpreting UDFs Note that this step does not apply to Windows parallel networks See Section 4 2 Interpreting a UDF Source File Using the Interpreted UDFs Panel for details 1 Open the Interpreted UDFs panel Define gt User Defined Functions Interpreted Fluent Inc September 11 2006 Interpreted UDFs Source File Name nywork udfexample c Browse CPP Command Name cpp Stack Size Display Assembly Listing l Use Contributed CPP Interpret Close Help Figure 8 1 4 The Interpreted UDFs Panel Examples 2 In the Interpreted UDFs panel select the UDF source file by either typing the complete path in the Source File Name field or click Browse to use the browser This will open the Select File panel Figure 8 1 5 Select File Look in O mywork ex Fa
470. rce term can be expressed in general as Equation 2 3 7 where is the dependent variable A is the explicit part of the source term and B is the implicit part Fluent Inc September 11 2006 2 93 DEFINE Macros Sy A B Ce Specifying a value for B in Equation 2 3 7 can enhance the stability of the solution and help convergence rates due to the increase in diagonal terms on the solution matrix FLUENT automatically determines if the value of B that is given by the user will aid stability If it does then FLUENT will define A as S 0S 0 and B as 0S 06 If not the source term is handled explicitly Your UDF will need to compute the real source term only for a single cell and return the value to the solver but you have the choice of setting the implicit term dS eqn to dS d or forcing the explicit solution of the source term by setting it equal to 0 0 Note that like property UDFs source term UDFs defined using DEFINE_SOURCE are called by FLUENT from within a loop on cell threads The solver passes to the DEFINE_SOURCE term UDF all the necessary variables it needs to define a custom source term since source terms are solved on a cell basis Consequently your UDF will not need to loop over cells in the thread since FLUENT is already doing it The units on all source terms are of the form generation rate volume For example a source term for the continuity equation would have units of kg m s Example
471. re the linear velocity is computed from a simple force balance on the body in the x direction such that he f Em dt 2 6 1 to where v is velocity F is the force and m is the mass of the body The velocity at time t is calculated using an explicit Euler formula as Ut vat F m At 2 6 2 Fluent Inc September 11 2006 2 1 97 DEFINE Macros peaa aE oo o kkk k kkk kkk kkk kkk kkk kkk k 1 degree of freedom equation of motion x direction compiled UDF ERA AAA I I I I IKK AK AR ICA A A 2A 1 1 1 1 1 1 1 A A A A KKK kk k kkk k include udf h static real v_prev 0 0 DEFINE_CG_MOTION piston dt vel omega time dtime Thread t face_t f real NV_VEC A real force dv reset velocities NV_S vel 0 0 NV_S omega 0 0 if Data_Valid_P return get the thread pointer for which this motion is defined t DT_THREAD dt compute pressure force on body by looping through all faces force 0 0 begin_f_loop f t F_AREA A f t force F_P f t NV_MAG A end_f_loop f t compute change in velocity i e dv F dt mass velocity update using explicit Euler formula dv dtime force 50 0 v_prev dv Message time f x_vel f force f n time v_prev force set x component of velocity vel 0 v_prev 2 1 98 Fluent Inc September 11 2006 2 6 Dynamic Mesh DEFINE Macros Hooking a Center of Gravity Motion UDF to
472. real vap_rate k molwt gas_index Ap cvap_surf ns cvap_bulk only condensation below vaporization temperature if 0 lt vap_rate amp amp Tp lt vap_temp vap_rate 0 dydt 1 ns vap_rate dzdt gt species gas_index vap_rate dT dt dh dt m Cp dydt 0 hvap gas_index vap_rate mp Cp gas enthalpy source term dzdt gt energy hgas gas_index vap_rate Hooking a DPM Particle Heat and Mass Transfer UDF to FLUENT After the UDF that you have defined using DEFINE_DPM_HEAT_MASS is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g multivap will be come visible in the Set Injection Properties panel in FLUENT See Section 6 4 5 Hooking DEFINE_DPM_HEAT_MASS UDFs for details on how to hook your DEFINE_DPM_HEAT_MASS UDF to FLUENT Fluent Inc September 11 2006 2 1 61 DEFINE Macros 2 5 6 DEFINE_DPM_INJECTION_INIT Description You can use DEFINE DPM INJECTION INIT to initialize a particle s injection properties such as location diameter and velocity Usage DEFINE_DPM_INJECTION_INIT name T Argument Type Description symbol name UDF name Injection I Pointer to the Injection structure which is a container for the particles being created This function is called twice for each Injection before the first DPM iteration and then called
473. responding drop down list Note that the mass flow rate profile is a function of time and only one constant value should be applied to all zone faces at a given time UDF for setting target mass flow rate in pressure outlet at t lt 0 2 sec the target mass flow rate set to 1 00 kg s when t gt 0 2 sec the target mass flow rate will change to 1 35 kg s Fluent Inc September 11 2006 2 77 DEFINE Macros include udf h DEFINE_PROFILE tm_pout2 t nv face _t f real flow_time RP_Get_Real flow time if flow_time lt 0 2 printf Time f sec n flow_time printf Targeted mass flow rate set at 1 0 kg s n begin_f_loop f t F_PROFILE f t nv 1 0 end_f_loop f t else printf Time f sec n flow_time printf Targeted mass flow rate set at 1 35 kg s n begin_f_loop f t F_PROFILE f t nv 1 35 end_f_loop f t J Hooking a Boundary Profile UDF to FLUENT After the UDF that you have defined using DEFINE PROFILE is interpreted Chapter 4 In terpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g vis_res will become visible and selectable in the appropriate boundary condition panel e g the Velocity Inlet panel in FLUENT See Section 6 2 13 Hooking DEFINE PROFILE UDFs for details 2 78 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros
474. riable macro Table 3 5 1 contains a list of solver macros that you can use to access time dependent variables in FLUENT An example of a UDF that uses a solver macro to access a time dependent variable is provided below See Section 2 2 2 DEFINE_DELTAT for another example that utilizes a time dependent macro Table 3 5 1 Solver Macros for Time Dependent Variables Macro Name Returns CURRENT_TIME real current flow time in seconds CURRENT_TIMESTEP real current physical time step size in seconds PREVIOUS_TIME real previous flow time in seconds PREVIOUS 2 TIME real flow time two steps back in time in seconds PREVIOUS_TIMESTEP real previous physical time step size in seconds N_TIME integer number of time steps N_ITER integer number of iterations il You must include the unsteady h header file in your UDF source code when using the PREVIOUS TIME or PREVIOUS 2 TIME macros since it is not included in udf h 3 68 Fluent Inc September 11 2006 3 5 Time Dependent Macros i N_ITER can only be utilized in compiled UDFs Some time dependent variables such as current physical flow time can be accessed directly using a solver macro CURRENT_TIME or indirectly by means of the RP variable macro RP Get Real flow time These two methods are shown below Solver Macro Usage real current_time current_time CURRENT_TIME Equivalent RP Macro Usage real current_time current_time RP_Get_Real flow
475. rial m THREAD_MATERIAL t sp real yi_h2o mw_h2o real r_mix 0 0 if MATERIAL_TYPE m MATERIAL_MIXTURE mixture_species_loop m sp i r_mix C_YI c t i MATERIAL_PROP sp PROP_mwi 2 1 86 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros if 0 strcmp MIXTURE_SPECIE_NAME m i h2o 0 strcmp MIXTURE_SPECIE_NAME m i H20 1 h20 C_YI c t i mw_h2o MATERIAL_PROP sp PROP_mwi return ABS_P C_P c t op_pres yi_h2o mw_h2o r_mix H20_Saturation_Pressure C_T c t define CONDENS 1 0e 4 DEFINE_DPM_LAW condenshumidlaw p coupled real area real mp_dot cell_t c P_CELL p Get Cell and Thread from Thread t P_THREAD p Particle Structure using new macros area 4 0 M_PI P_DIAM p P_DIAM p Note This law only used if Humidity gt 1 0 so mp_dot always positive mp_dot CONDENS sqrt area myHumidity c t 1 0 if mp_dot gt 0 0 P_MASS p P_MASS p mp_dot P_DT p P_DIAM p pow 6 0 P_MASS p P_RHO p M_PI 1 3 P_T p C_T c t Assume condensing particle is in thermal equilibrium with fluid in cell define macro that is not yet standard define C_DPMS_ENERGY c t C_STORAGE_R c t SV_DPMS_ENERGY DEFINE_DPM_SOURCE dpm_source c t S strength p Fluent Inc September 11 2006 2 1 87 DEFINE Macros real mp_dot Material sp P_MATERIAL p mp_dot is the positive ma
476. rking directory mywork and source file udfexample c are located Fluent Inc September 11 2006 4 2 Interpreting a UDF Source File Using the Interpreted UDFs Panel 7 In the Interpreted UDFs panel specify the C preprocessor to be used in the CPP Command Name field You can keep the default cpp or you can select Use Con tributed CPP to use the preprocessor supplied by Fluent Inc If you installed the contrib component from the PrePost CD then by default the cpp preprocessor will appear in the panel For Windows NT users the standard Windows NT installation of the FLUENT product includes the cpp preprocessor For Windows NT systems if you are using the Microsoft compiler then use the command cl E 8 Keep the default Stack Size setting of 10000 unless the number of local variables in your function will cause the stack to overflow In this case set the Stack Size to a number that is greater than the number of local variables used 9 Keep the Display Assembly Listing option on if you want a listing of assembly lan guage code to appear in your console window when the function interprets This option will be saved in your case file so that when you read the case in a subsequent FLUENT session the assembly code will be automatically displayed 10 Click Interpret to interpret your UDF If the compilation is successful and you choose to Display Assembly Listing then the assembler code is printed on the console wind
477. rns C_VOLUME c t cell_t c Thread t real cell volume for 2D or 3D real cell volume 2z for axisymmetric See Section 2 7 4 DEFINE_UDS_UNSTEADY for an example UDF that utilizes C_VOLUME Fluent Inc September 11 2006 3 7 Additional Macros for Writing UDFs Number of Faces C_NFACES and Nodes C_NNODES in a Cell The macro C_NFACES shown in Table 3 2 5 returns the integer number of faces for a given cell C_NNODES also shown in Table 3 2 2 returns the integer number of nodes for a given cell Table 3 2 5 Macros for Number of Node and Faces Defined in mem h Macro Argument Types Returns C_NNODES c t cell_t c Thread t int number of nodes in a cell C_NFACES c t cell_t c Thread t int number of faces in a cell Cell Face Index C_FACE C_FACE expands to return the global face index face_t f for the given cell_t c Thread t and local face index number i Specific faces can be accessed via the integer index i and all faces can be looped over with c_face_loop The macro is defined in mem h Table 3 2 6 Macro for Cell Face Index Defined in mem h Macro Argument Types Returns C_FACE c t i cell t c Thread t int i global face index face t f Cell Face Index C_FACE_THREAD C_FACE_THREAD expands to return the Thread t of the face_t f that is returned by C_FACE see above Specific faces can be accessed via the integer index i and all faces can
478. ro to obtain the global face number e g f C_FACE c t n Another useful macro that is often used in c_face_loop is C_FACE THREAD This macro is used to reference the associated face thread e g tf C_FACE_THREAD c t n Refer to Section 3 8 Miscellaneous Macros for other macros that are associated with c_face_loop 3 52 Fluent Inc September 11 2006 3 3 Looping Macros Looping Over Nodes of a Cell c_node_loop c_node_loop c t n is a function that loops over all nodes of a given cell It consists of a single loop statement followed by the action to be taken in braces Example cell_t c Thread t int n Node node c_node_loop c t n node C_NODE c t n Here n is the local node index number The index number can be used with the C_NODE macro to obtain the global cell node number e g node C_NODE c t n Looping Over Nodes of a Face f node_loop f node loop f t n is a function that loops over all nodes of a given face It consists of a single loop statement followed by the action to be taken in braces Example face_t f Thread t int n Node node f_node_loop f t n node F_NODE f t n Fluent Inc September 11 2006 3 53 Additional Macros for Writing UDFs Here n is the local node index number The index number can be used with the F_NODE macro to obtain the global face node number e g node F_NODE f t n See Section 2 6 3 DEFINE GRID MOTI
479. roducts from more than one phase Unlike DEFINE_VR_RATE a DEFINE_HET_RXN_RATE UDF can be specified differently for different heterogeneous reactions During FLUENT execution the DEFINE_HET_RXN_RATE UDF for each heterogeneous re action that is defined is called in every fluid cell FLUENT will use the reaction rate specified by the UDF to compute production destruction of the species participating in the reaction as well as heat and momentum transfer across phases due to the reaction A heterogeneous reaction is typically used to define reactions involving species of differ ent phases The bulk phase can participate in the reaction if the phase does not have any species i e phase has fluid material instead of mixture material Heterogeneous reactions are defined in the Phase Interaction panel Fluent Inc September 11 2006 2 1 27 DEFINE Macros Usage DEFINE HET RXN RATE name c t r mw yi rr rrt Argument Type Description symbol name UDF name cellt c Cell index Thread t Cell thread mixture level on which heterogeneous reaction rate is to be applied Hetero Reaction r Pointer to data structure that represents the current heterogeneous reaction see sg_mphase h real mw MAX PHASES MAX_SPE_EQNS Matrix of species molecular weights mw i j will give molecular weight of species with ID j in phase with index i For phase which has fluid material the molecular weight can be accessed as mw i 0 real yi MA
480. rofile BOAR I ARIA DH A A A A 11 1 1 21 DH A 2A 211 DO DH DH 2A 2K 2k k kkk kkk include udf h DEFINE_PROFILE pressure_profile t i real x ND_ND this will hold the position vector real y face_t f begin_f_loop f t F_CENTROID x f t y xt F_PROFILE f t i 1 1e5 y y 0745 0745 0 1e5 end_f_loop f t THREAD SHADOW t THREAD_SHADOW returns the face thread that is the shadow of Thread t if it is one of a face face shadow pair that comprise a thin wall It returns NULL if the boundary is not part of a thin wall and is often used in an if statement such as if NULLP ts THREAD_SHADOW t Do things here using the shadow wall thread ts 3 30 Fluent Inc September 11 2006 3 2 Data Access Macros 3 2 7 Model Specific Macros DPM Macros The macros listed in Tables 3 2 26 3 2 31 can be used to return real variables associated with the Discrete Phase Model DPM in SI units They are typically used in DPM UDFs that are described in Section 2 5 Discrete Phase Model DPM DEFINE Macros The variables are available in both the pressure based and the density based solver The macros are defined in the dpm h header file which is included in udf h The variable p indicates a pointer to the Tracked Particle structure Tracked Particle p which gives you the value for the particle at the current position Refer to the following sections for examples of UDFs that utilize some of these
481. roperty Value Density 8000 kg m Viscosity 5 5 x107 kg m s Specific Heat 680 J kg K Thermal Conductivity 30 W m K Fluent Inc September 11 2006 8 27 Examples DRC OO OC OO OR OO RRO 2K FK 2K Ra a 2K 2K 2k 2 2k K 2k 2k 2k 2k 2 2k K K FK UDF that adds momentum source term and derivative to duct flow FO OR KO HRK HRK kk ak 3k 2k 2 ER 2k 2k ak ok 2k 2 ak include udf h define CON 20 0 DEFINE_SOURCE cell_x_source cell thread dS eqn real source if C_T cell thread lt 288 source term source CON C_U cell thread derivative of source term w r t x velocity dS eqn CON else source dS eqn 0 return source To make use of this UDF in FLUENT you will first need to interpret or compile the function and then hook it to FLUENT using the graphical user interface Follow the procedure for interpreting source files using the Interpreted UDFs panel Section 4 2 In terpreting a UDF Source File Using the Interpreted UDFs Panel or compiling source files using the Compiled UDFs panel Section 5 2 Compile a UDF Using the GUI To include source terms in the calculation you will first need to turn on the Source Terms option in the Fluid or Solid panel and click the Source Terms tab This will display the momentum source term parameters in the scrollable window Define Boundary Conditions Next click the Edit button next to the X Momentum source term Thi
482. rpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE PROFILE UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the appropriate boundary condition panel in FLUENT Define Boundary Conditions If for example your UDF defines a velocity inlet boundary condition then to hook it to FLUENT first click on the Momentum tab in the Velocity Inlet panel Figure 6 2 14 and then choose the function name e g x velocity in the appropriate drop down list e g X Velocity and click OK Note that the UDF name that is displayed in the drop down lists is preceded by the word udf e g udf x velocity Velocity Inlet Zone Name velocity inlet Momentum Thermal Radiation Species DPM Multiphase UDS Velocity Specification Method Components Reference Frame Absolute Coordinate System Cartesian K Y z Velocity m s uat x_velocity J Y Velocity m s 1 2 constant X Z Yelocity m s g constant Figure 6 2 14 The Velocity Inlet Panel If you are using your UDF to specify a fixed value in a cell zone you will need to turn on the Fixed Values option in the Fluid or Solid panel and click the Fixed Values tab This will display the fixed values parameters in the scrollable window Next select the name of the UDF in the appropriate drop down list for the value you wish to set See Section 2 3 13 DEFINE PR
483. rview UDFs are defined using DEFINE macros provided by Fluent Inc see Chapter 2 DEFINE Macros They are coded using additional macros and functions also supplied by Fluent Inc that acccess FLUENT solver data and perform other tasks See Chapter 3 Additional Macros for Writing UDFs for details Every UDF must contain the udf h file inclusion directive include udf h at the beginning of the source code file which allows definitions of DEFINE macros and other Fluent provided macros and functions to be included during the compilation process See Section 1 4 1 Including the udf h Header File in Your Source File for details Note that values that are passed to a solver by a UDF or returned by the solver to a UDF are specified in SI units Source files containing UDFs can be either interpreted or compiled in FLUENT For inter preted UDFs source files are interpreted and loaded directly at runtime in a single step process For compiled UDFs the process involves two separate steps A shared object code library is first built and then it is loaded into FLUENT See Chapter 4 Interpreting UDFs and Chapter 5 Compiling UDFs Once interpreted or compiled UDFs will be come visible and selectable in FLUENT graphics panels and can be hooked to a solver by choosing the function name in the appropriate panel This process is described in Chapter 6 Hooking UDFs to FLUENT In summary UDFs e are written in the C programming language Append
484. s Figure 8 2 17 Streamlines for the 2D Duct with a Porous Region The flow pattern is further substantiated by the vector plot shown in Figure 8 2 18 The flow in the porous region is considerably slower than that in the open region The source code rate c that contains the UDF used to model the reaction taking place in the porous region is shown below The function named vol_reac_rate is defined on a cell for a given species mass fraction using DEFINE VR RATE The UDF performs a test to check for the porous region and only applies the reaction rate equation to the porous region The macro FLUID_THREAD_P t is used to determine if a cell thread is a fluid rather than a solid thread The variable THREAD_VAR t fluid porous is used to check if a fluid cell thread is a porous region 8 38 Fluent Inc September 11 2006 8 2 Detailed UDF Examples 2 34e 01 2 10e 01 1 87e 01 1 64e 01 1 40e 01 y 1 17e 01 yy 9 38e 02 7 05e 02 4 72e 02 as RL LI 2 39e 02 LPS 242 me Loose 5 73e 04 Sea Velocity Vectors Colored By Velocity Magnitude m s Figure 8 2 18 Velocity Vectors for the 2D Duct with a Porous Region Fluent Inc September 11 2006 8 39 Examples K k 2k kk ak ak k OC OO OR OO 2K K FK 3K 2K K FK 2K 2K K FK 2K I EL FK 2K 2K aK 2k 22k 2K 2K LL 2K K 2k ak rate c Compiled UDF for specifying a reaction rate in a porous medium
485. s Density kg m3 constant Edit 2250 CP UKE constat ru 000 48 Thermal Conductivity w m k constant Edit 0 0242 Viscosity kg m s y ser defined ce11_viscosity EJ Change Create Delete Close Help Once you select this option the User Defined Functions panel opens from which you can select the appropriate function name In this example only one option is available but in other examples you may have several functions from which to choose Recall that if you need to compile more than one interpreted UDF the functions can be concatenated in a single source file prior to compiling 8 34 Fluent Inc September 11 2006 8 2 Detailed UDF Examples User Defined Functions The results of this model are similar to those obtained in Section 8 2 2 Adding a Mo mentum Source to a Duct Flow Figure 8 2 13 shows the viscosity field resulting from the application of the user defined function The viscosity varies rapidly over a narrow spatial band from a constant value of 0 0055 to 1 0 kg m s The velocity field Figure 8 2 14 demonstrates that the liquid slows down in response to the increased viscosity as expected In this model there is a large mushy region in which the motion of the fluid gradually decreases This is in contrast to the first model in which a momentum source was applied and a more abrupt change in the fluid motion was observed 1 00e 00 9 01e 01 8 01e
486. s Parallel User Defined Functions User Variables Body Force none Number of Scalars ee 4j Erosion Accretion dpm_acer libudt Scalar Update none st Source none DPM Time Step none OK Injections Cancel Help Figure 6 4 4 The Discrete Phase Model Panel To hook the UDF to FLUENT enable the Interaction with Continuous Phase option under Interaction Figure 6 4 4 and then turn on Erosion Accretion under Option Finally choose the function name e g dpm_accr in the Erosion Accretion drop down list under User Defined Functions and click OK See Section 2 5 4 DEFINE DPM EROSION for details about DEFINE DPM EROSION functions Fluent Inc September 11 2006 6 57 Hooking UDFs to FLUENT 6 58 6 4 5 Hooking DEFINE_DPM_HEAT_MASS UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_HEAT_MASS UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Set Injection Prop erties panel Figure 6 4 5 in FLUENT Before you hook the UDF you ll need to create your particle injections in the Injections panel Define Injections Set Injection Properties Injection Name finjection 8 Injection Type single Particle Type Laws C Inert C Droplet C Combusting Multicomponent Custom Material Diameter Distribution Oxidizing Species particle mixture templat
487. s the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Function Hooks panel Figure 6 2 6 in FLUENT i The Discrete Ordinates radiation model must be enabled Define User Defined Function Hooks User Defined Function Hooks Initialization none Edit Adjust none Edit Execute at End none Edit Read Case none Edit Write Case none Edit Read Data none Edit Write Data none Edit Execute at Exit none Edit Wall Heat Flux mone DO Source DO Diffuse Reflectivity mone DO Specular Reflectivity mone Figure 6 2 6 The User Defined Function Hooks Panel To hook the UDF to FLUENT choose the function name e g user_dom_source in the DO Source drop down list in the User Defined Function Hooks panel and click OK See Section 2 3 5 DEFINE DOM SOURCE for details about DEFINE DOM SOURCE functions 6 20 Fluent Inc September 11 2006 6 2 Hooking Model Specific UDFs 6 2 6 Hooking DEFINE_DOM_SPECULAR_REFLECTIVITY UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DOM_SPECULAR_REFLECTIVITY UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Function Hooks panel Figure 6 2 7 in FLUENT Define User Defined Function Hooks User Defined Fu
488. s are the lines of code that are to be executed if the condition is met If the condition is not met then the statements following else are executed Fluent Inc September 11 2006 A 11 C Programming Basics Example if x lt 0 y x 50 else X X y x 25 The equivalent FORTRAN code is shown below for comparison IF X LT 0 THEN Y X 50 ELSE X X Y X 25 ENDIF A 11 3 for Loops for loops are control statements that are a basic looping construct in C They are anal ogous to do loops in FORTRAN The format of a for loop is for begin end increment statements where begin is the expression that is executed at the beginning of the loop end is the logical expression that tests for loop termination and increment is the expression that is executed at the end of the loop iteration usually incrementing a counter Example Print integers 1 10 and their squares int i j n 10 for i 1 i lt n i j i i printf d d n i j A 12 Fluent Inc September 11 2006 A 12 Common C Operators The equivalent FORTRAN code is shown below for comparison INTEGER I J N 10 DO I 1 10 J I I WRITE I J ENDDO A 12 Common C Operators Operators are internal C functions that when they are applied to values produce a result Common types of C operators are arithmetic and logical A 12 1 Arithmetic Operators Some common arithmetic operators
489. s or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible in the Materials panel in FLUENT See Section 6 4 9 Hooking DEFINE DPM PROPERTY UDFs for details on how to hook your DEFINE_DPM_PROPERTY UDF to FLUENT Fluent Inc September 11 2006 2 1 75 DEFINE Macros 2 5 10 DEFINE_DPM_SCALAR_UPDATE Description You can use DEFINE DPM SCALAR UPDATE to update scalar quantities every time a parti cle position is updated The function allows particle related variables to be updated or integrated over the life of the particle Particle values can be stored in an array associ ated with the Tracked_Particle accessed with the macro P_USER_REAL p i Values calculated and stored in the array can be used to color the particle trajectory During FLUENT execution the DEFINE DPM SCALAR UPDATE function is called at the start of particle integration when initialize is equal to 1 and then after each time step for the particle trajectory integration Usage DEFINE DPM SCALAR _UPDATE name c t initialize p Argument Type Description symbol name UDF name cell tc Index that identifies the cell that the particle is currently in Thread t Pointer to the thread the particle is currently in int initialize Variable that has a value of 1 when the function is called at the start of the particle integration and 0 thereafter Tracked_Particle p Pointer to the Tracke
490. s subthreads THREADS_SUB_ THREADS has one argument mixture_thread Thread mixture_thread Thread pt initialize pt pt THREAD_SUB_THREADS mixture_thread mixture_thread is a pointer to a mixture level thread which can represent a cell thread or a face thread It is automatically passed to your UDF by the FLUENT solver when you use a DEFINE macro that contains a variable thread argument e g DEFINE PROFILE and the function is hooked to the mixture Otherwise if the mixture thread pointer is not explicitly passed to your UDF then you will need to use another method to retrieve it For example you can use the Lookup_Thread utility macro see Section 3 2 6 Thread Pointer for Zone ID Lookup_Thread pti an element in the array is a pointer to the corresponding phase level thread for the ith phase where i is the phase_domain_index You can use pt i as an argument to some cell variable macros when you want to retrieve specific phase information at a cell For example C_R c pt i can be used to return the density of the ith phase fluid at cell c The pointer pt i can also be retrieved using THREAD SUB THREAD discussed in Section 3 3 2 Phase Level Thread Pointer THREAD SUB THREAD using i as an argument The phase_domain_index can be retrieved using the PHASE DOMAIN_ INDEX macro See Section 3 3 2 Phase Domain Index PHASE_DOMAIN_INDEX for details Mixture Domain Pointer DOMAIN_SUPER DOMAIN You can use DOMAIN
491. s a pointer array pt that identifies the corre sponding phase level threads The pointer to the cell thread for the ith phase is pt i where i is the phase domain index pt i can be used as an argument to macros re quiring the phase level thread pointer phase domain index can be retrieved using the PHASE_DOMAIN_INDEX macro See Section 3 3 2 Phase Domain Index PHASE_DOMAIN_INDEX for details 3 56 Fluent Inc September 11 2006 3 3 Looping Macros Thread pt Thread cell_threads Domain mixture_domain mp_thread_loop_c cell_threads mixture_domain pt The variable arguments to mp_thread_loop_c are cell_threads mixture_domain and pt cell_threads is a pointer to the cell threads and mixture_domain is a pointer to the mixture level domain pt is an array pointer whose elements contain pointers to phase level threads mixture domain is automatically passed to your UDF by the FLUENT solver when you use a DEFINE macro that contains a domain variable argument e g DEFINE_ADJUST and your UDF is hooked to the mixture If mixture_domain is not explicitly passed to your UDF you will need to use another utility macro to retrieve it e g Get_Domain 1 described in Section 3 2 6 Domain Pointer Get Domain Note that the values for pt and cell_threads are set within the looping function mp_thread_loop_c is typically used along with begin_c_loop begin_c_loop loops over cells in a cell thread When begin_c_loop is neste
492. s a thread pointer it will have to declare the variable locally and then obtain it using the special macro Lookup_Thread An exception to this is if your UDF needs a thread pointer to loop over all of the cell threads or all the face threads in a domain using thread_c_loop c t or thread_f_loop f t respectively and the DEFINE macro isn t passed it Since the UDF will be looping over all threads in the domain you won t need to use Lookup_Thread to get the thread pointer to pass it to the looping macro you ll just need to declare the thread pointer and cell or face ID locally before calling the loop See Section 2 2 1 DEFINE_ADJUST for an example As another example if you are using DEFINE_ON_DEMAND which isn t passed any pointer argument to execute an asynchronous UDF and your UDF needs a domain pointer then the function will need to declare the domain variable locally and obtain it us ing Get Domain See Section 2 2 8 DEFINE_ON_DEMAND for an example Refer to Sec tion 3 2 6 Special Macros for details Fluent Inc September 11 2006 1 11 Overview 1 9 UDF Calling Sequence in the Solution Process UDFs are called at predetermined times in the FLUENT solution process However they can also be executed asynchronously or on demand using a DEFINE_ON_DEMAND UDF If a DEFINE_EXECUTE_AT_END UDF is utilized then FLUENT calls the function at the end of an iteration A DEFINE_EXECUTE_AT_EXIT is called at the end of a FLUE
493. s also stored The diffusive flux D across a face f of a scalar is given by D T V 3 2 2 where I is the diffusion coefficient at the face In FLUENT s unstructured solver the gradient along the face normal direction may be approximated by evaluating gradients along the directions that connect cell centroids and along a direction confined within the plane of the face Given this D may be approximated as o AA D 2T ET ye Vos de Vos 3 2 3 f a dae a where the first term on the right hand side represents the primary gradient directed along the vector and the second term represents the cross diffusion term In this equation A is the area normal vector of face f directed from cell cO to c1 ds is the distance between the cell centroids and is the unit normal vector in this direction Vo is the average of the gradients at the two adjacent cells For boundary faces the variable is the gradient of the c0 cell This is shown in Figure 3 2 2 below Fluent Inc September 11 2006 3 21 Additional Macros for Writing UDFs Cell c1 Cell or Face Centroid A Nodes Face f Cell c0 b NT Figure 3 2 2 Adjacent Cells c0 and c1 with Vector and Gradient Definitions Adjacent Cell Index F_CO F_C1 The cells on either side of a face may or may not belong to the same cell thread Referring to Figure 3 2 2 if a face is on the boundary of a domain then only cO ex
494. s initialized to reset the initial values for the UDMs Fluent Inc September 11 2006 3 45 Additional Macros for Writing UDFs The following describes the process of reserving five UDMs for two libraries named libudf and libudf2 1 In the User Defined Memory panel specify 5 for the Number of User Defined Memory Locations 2 In the Compiled UDFs panel build the compiled library named libudf for udm_res1 c and load the library 3 Build the compiled library for udm res2 c named libudf2 and load the library 4 Initialize the solution 5 Execute the on demand UDFs for libudf and libudf2 in the Execute On Demand panel 6 Iterate the solution 7 Postprocess the results peaa kk kkk kk kkk kkk kkk k k k kkk kkk k k k k k k kk k k k k k k kk kk k k k kkk kkk 4 2k udm_res1 c contains two UDFs an execute on loading UDF that reserves three UDMs for libudf and renames the UDMs to enhance postprocessing and an on demand UDF that sets the initial value of the UDMs EEEE ooo ooo o k kkk DH kk kkk kkk kk kkk include udf h define NUM_UDM 3 static int udm_offset UDM_UNRESERVED DEFINE_EXECUTE_ON_LOADING on_loading libname if udm_offset UDM_UNRESERVED udm_offset Reserve_User_Memory_Vars NUM_UDM if udm_offset UDM_UNRESERVED Message nYou need to define up to 4d extra UDMs in GUI and then reload current library s n NUM_UDM libname else Message d UDMs have been reserved by the current
495. s is to pass parameters or boundary conditions from the host to the nodes processes See the example UDF in Section 7 8 Parallel UDF Example for a demonstration of usage 7 16 Fluent Inc September 11 2006 7 5 Macros for Parallel UDFs Node to Host Data Transfer To send data from compute node 0 to the host process we use macros of the form node_to_host_type_num val_1 val_2 val_num where num is the number of variables that will be passed in the argument list and type is the data type of the variables that will be passed The maximum number of variables that can be passed is 7 Arrays and strings can also be passed from host to nodes one at a time as shown in the examples below Note that unlike the host_to_node macros which pass data from the host process to all of the compute nodes indirectly via compute node 0 node_to_host macros pass data only from compute node 0 to the host Examples integer and real variables passed from compute node 0 to host node_to_host_int_1 count node_to_host_real_7 leni len2 widthi width2 breadthi breadth2 vol string and array variables passed from compute node 0 to host char string int string_length real vel ND_ND node_to_host_string string string_length node_to_host_real vel ND_ND node_to_host macros do not need to be protected by compiler directives e g if RP_NODE since they automatically do the following e send the varia
496. s predefined macros that you can use when defining your user defined function UDF e Section 3 1 Introduction e Section 3 2 Data Access Macros e Section 3 3 Looping Macros e Section 3 4 Vector and Dimension Macros e Section 3 5 Time Dependent Macros e Section 3 6 Scheme Macros e Section 3 7 Input Output Macros e Section 3 8 Miscellaneous Macros Fluent Inc September 11 2006 3 1 Additional Macros for Writing UDFs 3 1 Introduction FLUENT provides numerous C types functions and preprocessor macros to facilitate the programming of UDFs and the use of CFD objects as defined inside FLUENT The previous chapter presented DEFINE macros that you must use to define your UDF with This chapter presents predefined functions implemented as macros in the code that are supplied by Fluent Inc that you will use to code your UDF These macros allow you to access data in a FLUENT solver such as cell variables e g cell temperature centroid face variables e g face temperature area or connectivity variables e g adjacent cell thread and index that your UDF can use in a computation A special set of macros commonly used in UDFs is provided that return such values as the thread ID pointer an internal FLUENT structure when passed the Zone ID the number assigned to a zone in a boundary conditions panel Another special macro F_PROFILE enables your UDF to set a boundary condition value in the solver Other types of m
497. s the cavitation mass transfer rates between the liquid and vapor phase depending on fluid pressure xp turbulence kinetic energy C_K c t and the liquid vaporization pressure p_v In general the existence of turbulence enhances cavitation In this example the tur bulence effect is taken into account by increasing the cavitation pressure by 0 195 CR c t CK c t The pressure p vapor that determines whether cavitation occurs increases from p_v to p_v 0 195 C_R c t C_K c t When the absolute fluid pressure ABS_P is lower than p_vapor then liquid evaporates to vapor Re When it is greater than p_vapor vapor condenses to liquid Re The evaporation rate is calculated by If ABS_P lt p_vapor then c_evap rhoV c sqrt 2 0 3 0 rhoL c ABS p_vapor ABS_P plcl The condensation rate is If ABS_P gt p_vapor then c_con rhoL c sqrt 2 0 3 0 rhoL c ABS p_vapor ABS_P plcl where c_evap and c_con are model coefficients 2 1 20 Fluent Inc September 11 2006 2 4 Multiphase DEF INE Macros PE k k kkk kkk kk kkk kkk k k kkk kk k kk kk k k k k kk k k k kk ak k 2k 2k k k AK ACA A A A k 2k k K kk k k 2K UDF that is an example of a cavitation model different from default Can be interpreted or compiled EEEE ooo ooe A A A 111 21 21 KDE DO DH DH DO include udf h define c_evap 1 0 define c_con 0 1 DEFINE_CAVITATION_RATE user_cav_rate c t p rhoV rhoL mafV p_v cigma f_gas m
498. s the first DEFINE macro argument e g user_dom_source will become visible and selectable in the User Defined Function Hooks panel in FLUENT Note that you can hook multiple discrete ordinate source term functions to your model See Section 6 2 5 Hooking DEFINE_DOM_SOURCE UDFs for details Fluent Inc September 11 2006 2 39 DEFINE Macros 2 3 6 DEFINE_DOM_SPECULAR_REFLECTIVITY Description You can use DEFINE DOM SPECULAR REFLECTIVITY to modify the inter facial reflectivity of specularly reflecting semi transparent walls You may wish to do this if the reflectivity is dependent on other conditions that the standard boundary condition doesn t allow for See Section 13 3 6 Specular Semi Transparent Walls in the User s Guide for more information During FLUENT execution the same UDF is called for all the faces of the semi transparent wall for each of the directions Usage DEFINE DOM SPECULAR REFLECTIVITY name f t nband n_a n b ray_direction en internal reflection specular reflectivity specular transmissivity Note that all of the arguments to a DEFINE macro need to be placed on the same line in your source code Splitting the DEFINE statement onto several lines will result in a compilation error Argument Type Description symbol name UDF name face_t f Face index Thread t Pointer to face thread on which the specular reflectivity function is to be applied int nband Band number needed for non gray Discrete Ordin
499. s will open the X Momentum Sources panel where you will select the number of terms you wish to model Figure 6 2 23 Increment the Number of Momentum sources counter to 1 and then choose the function namefor the UDF in this example udf cell_x_source from the drop down list Note that the UDF name that is displayed in the drop down lists is preceeded by the word udf Click OK to accept the new boundary condition and close the panel 8 28 Fluent Inc September 11 2006 8 2 Detailed UDF Examples The X Momentum parameter in the Fluid panel will now display 1 source Click OK to close the Fluid panel and fix the new momentum source term for the solution calculation X Momentum n m3 sources 1 udt unsteady _velocit Figure 8 2 8 The Fluid Panel Once the solution has converged you can view contours of static temperature to see the cooling effects of the wall on the liquid metal as it moves through the duct Figure 8 2 10 Contours of velocity magnitude Figure 8 2 11 show that the liquid in the cool region near the wall has indeed come to rest to simulate solidification taking place The solidification is further illustrated by line contours of stream function Figure 8 2 12 To more accurately predict the freezing of a liquid in this manner an energy source term would be needed as would a more accurate value for the constant appearing in Equation 8 2 1 Fluent Inc September 11 2006 8 29 Examples Zone N
500. se thread_s THREAD_SUB_THREAD mix_thread f_col solid phase find phase velocities and properties x_vel_g C_U cell thread_g y_vel_g C_V cell thread_g x_vel_s C_U cell thread_s y_vel_s C_V cell thread_s slip_x x_vel_g x_vel_s slip_y y_vel_g y_vel_s rho_g C_R cell thread_g rho_s C_R cell thread_s mu_g C_MU_L cell thread_g compute slip abs_v sqrt slip_x slip_x slip_y slip_y compute Reynold s number reyp rho_g abs_v diam2 mu_g compute particle relaxation time taup rho_s diam2 diam2 18 mu_g void_g C_VOF cell thread_g gas vol frac compute drag and return drag coeff k_g_s 2 1 24 Fluent Inc September 11 2006 2 4 Multiphase DEF INE Macros afac pow void_g 4 14 if void_g lt 0 85 bfac 0 281632 pow void_g 1 28 else bfac pow void_g 9 076960 vfac 0 5 afac 0 06 reyptsqrt 0 0036 reyp reypt0 12 reyp 2 bfac afac t afac afac fdrgs void_g pow 0 63 sqrt reyp vfact4 8 sqrt vfac vfac 2 24 0 k_g_s 1 void_g rho_s fdrgs taup return k_g_s Example 2 Heat Transfer The following UDF named heat udf specifies a coefficient that when multiplied by the temperature difference between the dispersed and continuous phases is equal to the net rate of heat transfer per unit volume include udf h define PR_NUMBER cp mu k cp mu k define IP_HEAT
501. se if the mixture thread pointer is not explicitly passed to your UDF then you will need to use the Lookup_Thread utility macro to retrieve it see Section 3 2 6 Thread Pointer for Zone ID Lookup_Thread phase_domain_index is an index of subdomain pointers It is an integer that starts with O for the primary phase and is incremented by one for each secondary phase phase domain index is automatically passed to your UDF by the FLUENT solver when you use a DEFINE macro that contains a phase domain index argument DEFINE EXCHANGE PROPERTY DEFINE VECTOR EXCHANGE PROPERTY and your UDF is hooked to a specific interaction phase See Section 2 4 2 DEFINE EXCHANGE PROPERTY for an example UDF Otherwise you will need to hard code the integer value of phase domain index to the THREAD SUB THREAD macro If your multiphase model has only two phases defined then phase_domain_index is 0 for the primary phase and 1 for the secondary phase However if you have more than one secondary phase defined for your multiphase model you will need to use the PHASE_DOMAIN_INDEX utility to retrieve the corresponding phase_domain_index for the given domain See Section 3 3 2 Phase Domain Index PHASE_DOMAIN_INDEX for details 3 60 Fluent Inc September 11 2006 3 3 Looping Macros Phase Thread Pointer Array THREAD_SUB_THREAD The THREAD_SUB_THREADS macro can be used to retrieve the pointer array pt whose elements contain pointers to phase level thread
502. sources to FLUENT for use by a UDF The procedures for doing this on a UNIX Linux and Windows system is described below Windows Systems 1 Follow the procedure for setting up the directory structure described in Section Section 5 3 1 Set Up the Directory Structure 2 Copy your precompiled object files e g myobjectl obj myobject2 obj to all of the architecture version directories you created in Step 1 e g ntx86 2d ntx86 3d i The object files should be compiled using similar flags to those used by Fluent e g c Za 3 Using a text editor edit the user_nt udf files in each architecture version directory 5 4 1 Example Link Precompiled Objects to FLUENT The following example demonstrates the linking of a FORTRAN object file test o to FLUENT for use in a UDF named test_use c This particular UDF is not a practical application but has rather been designed to demonstrate the functionality It uses data from a FORTRAN derived object file to display parameters that are passed to the C function named fort_test This on demand UDF when executed from the User Defined Function Hooks panel displays the values of the FORTRAN parameters and the com mon block and common complex numbers that are computed by the UDF using the FORTRAN parameters 5 18 Fluent Inc September 11 2006 5 4 Link Precompiled Object Files From Non FLUENT Sources A Note that the names of the functions and data structures have been changed from th
503. ss source momentum source energy source turbulence kinetic energy source turbulence dissipation rate source granular temperature source user scalar source species source species mass fractions velocity temperature turbulence kinetic energy turbulence dissipation rate porosity granular temperature DEFINE_ SOURCE DEFINE SOURCE DEFINE SOURCE DEFINE SOURCE DEFINE SOURCE DEFINE SOURCE DEFINE_ SOURCE DEFINE SOURCE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE primary and secondary phase s mixture mixture mixture mixture secondary phase s mixture phase dependent phase dependent mixture mixture mixture mixture mixture secondary phase s Fluent Inc September 11 2006 Quick Reference Guide for Multiphase DEFINE Macros Table C 2 2 DEFINE Macro Usage for the Mixture Model Variable Macro Phase Specified On Fluid continued viscous resistance inertial resistance DEFINE PROFILE DEFINE PROFILE primary and secondary phase s primary and secondary phase s Wall roughness height roughness constant internal emissivity shear stress components moving velocity components heat flux heat generation rate heat transfer coefficient external emissivity external radiation temperature free stream temperature granular flux granular temperature user scalar boundary value discrete phase b
504. ss source to the continuous phase Difference in mass between entry and exit from cell multiplied by strength Number of particles s in stream mp_dot P_MASSO p P_MASS p strength C_DPMS_YI c t 0 mp_dot dpm_relax C_DPMS_ENERGY c t mp_dot dpm_relax MATERIAL_PROP sp PROP_Cp C_T c t 298 15 C_DPMS_ENERGY c t mp_dot dpm_relax MATERIAL_PROP sp PROP_latent_heat define UDM_RH O define N_REQ_UDM 1 define CONDENS_LIMIT 1 0e 10 DEFINE_DPM_SWITCH dpm_switch p coupled cell_t c RP_CELL amp p gt cCell Thread t RP_THREAD amp p gt cCell if C_UDMI c t UDM_RH gt 1 0 P_CURRENT_LAW p DPM_LAW_USER_1 else if P_MASS p lt CONDENS_LIMIT P_CURRENT_LAW p DPM_LAW_INITIAL_INERT_HEATING else P_CURRENT_LAW p DPM_LAW_VAPORIZATION DEFINE_ADJUST adj_relhum domain cell_t cell Thread thread 2 188 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros set dpm source underrelaxation dpm_relax Domainvar_Get_Real ROOT_DOMAIN_ID dpm relax if sg_udm lt N_REQ_UDM Message nNot enough user defined memory allocated d required n N_REQ_UDM else real humidity min max min 1e10 max 0 0 thread_loop_c thread domain Check if thread is a Fluid thread and has UDMs set up on it if FLUID_THREAD_P thread amp amp NNULLP THREAD_STORAGE thread SV_UDM_I begin_c_loop cell
505. ssuing the text command solve set expert and then answering yes to the question Keep temporary solver memory from being freed Note that when you do this all of the gradient data is retained but the calculation requires more memory to run You can access a component of a gradient vector by specifying it as an argument in the gradient vector call 0 for the x component 1 for y and 2 for z For example C_T_G c t 10 s returns the x component of the cell temperature gradient vector returns the x component of the temperature gradient vector Table 3 2 9 Macros for Cell Gradients Defined in mem h Macro Argument Types Returns C_R_G c t cell_t c Thread t density gradient vector C_P_G c t cell t c Thread t pressure gradient vector C_UG c t cell_t c Thread t velocity gradient vector CVG c t cell_t c Thread t velocity gradient vector C_W_G c t cell_t c Thread t velocity gradient vector C_T_G c t cellt c Thread t temperature gradient vector C_H_G c t cell t c Thread t enthalpy gradient vector C_NUT_G c t cell t c Thread t turbulent viscosity for Spalart Allmaras gradient vector C_K_G c t cell_t c Thread t turbulent kinetic energy gradient vector CD G c t cell t c Thread t turbulent kinetic energy dissipation rate gradient vector CODEC 6 cell t c Thread t specific dissipation rate gradient vector CYIG c t i cell t c Thread t int i species mass fraction note int i is species in
506. stants specified by K K is defined using the Rate_Const data type and has three elements A B and C The Arrhenius rate is given in the form of R ATP exp C T where T is the temperature Note that the units of K must be in m gmol J s Dynamic Mesh Macros The macros listed in Table 3 2 34 are useful in dynamic mesh UDFs The argument dt is a pointer to the dynamic thread structure These macros are defined in the dynamesh_tools h Table 3 2 34 Macros for Dynamic Mesh Variables Defined in dynamesh_tools h Name Arguments Argument Types Returns DT_THREAD dt Dynamic Thread dt pointer to face thread DT CG dt Dynamic Thread dt center of gravity vector DT_VEL_CG dt Dynamic Thread dt cg velocity vector DT_OMEGA_CG t Dynamic Thread dt angular velocity vector DT_THETA dt Dynamic_Thread dt orientation of body fixed axis vector See Section 2 6 3 DEFINE_GRID_MOTION for an example UDF that utilizes DT_THREAD Fluent Inc September 11 2006 3 37 Additional Macros for Writing UDFs 3 2 8 User Defined Scalar UDS Transport Equation Macros This section contains macros that you can use when defining scalar transport UDFs in FLUENT Note that if you try to use the macros listed below e g F_UDSI C_UDSI before you have specified user defined scalars in your FLUENT model in the User Defined Scalars panel then an error will result Set User Scalar Name FLUENT assigns a defa
507. sure to s filename endif UDF Now does 3 different things depending on SERIAL NODE or HOST if PARALLEL SERIAL begin_c_loop c thread fprintf fp g n C_P c thread Simply write out pressure data end_c_loop c thread endif PARALLEL if RP_NODE Fluent Inc September 11 2006 7 45 Parallel Considerations Each Node loads up its data passing array size THREAD_N_ELEMENTS_INT thread array real malloc size sizeof real begin_c_loop_int c thread array c C_P c thread end_c_loop_int c thread Set pe to destination node If on node_O send data to host Else send to node_0 because compute nodes connect to node_O amp node_O to host pe I_AM_NODE_ZERO_P node_host node_zero PRF_CSEND_INT pe amp size 1 myid PRF_CSEND_REAL pe array size myid free array free array on nodes once data sent node_O now collect data sent by other compute nodes and sends it straight on to the host if I_AM_NODE_ZERO_P compute_node_loop_not_zero pe PRF_CRECV_INT pe amp size 1 pe array real malloc size sizeof real PRF_CRECV_REAL pe array size pe PRF_CSEND_INT node_host amp size 1 myid PRF_CSEND_REAL node_host array size myid free char array endif RP_NODE if RP_HOST compute_node_loop pe only acts as a counter in this loop Receive data sent by each n
508. t 0 There are a number of predicates that allow you to test the identity of the node pro cess in your UDF using the compute node ID A compute node s ID is stored as the global integer variable myid see Section 7 7 Process Identification Each of the macros listed below tests certain conditions of myid for a process For example the predicate I_AM NODE ZERO P compares the value of myid with the compute node 0 ID and returns TRUE when they are the same I_AM NODE_ SAME P n on the other hand compares the compute node ID that is passed in n with myid When the two IDs are the same the function returns TRUE Node ID predicates are often used in conditional if statements in UDFs predicate definitions from para h header file define I_AM_NODE_HOST_P myid node_host define I_AM_NODE_ZERO_P myid node_zero define I_AM_NODE_ONE_P myid node_one define I_AM_NODE_LAST_P myid node_last define I_AM_NODE_SAME_P n myid n define I_AM_NODE_LESS_P n myid lt n define I_AM_NODE_MORE_P n myid gt n HH H H H OF 7 18 Fluent Inc September 11 2006 7 5 Macros for Parallel UDFs Recall that from Section 7 2 Cells and Faces in a Partitioned Grid a face may appear in one or two partitions but in order that summation operations don t count it twice it is officially allocated to only one of the partitions The tests above are used with the neighboring cell s partition ID to determine if it bel
509. t Edit 266 Spectral Fraction V V IR 8 5 Figure 6 2 21 The Radiation Model Panel 6 36 Fluent Inc September 11 2006 6 2 Hooking Model Specific UDFs To hook the UDF to FLUENT first choose user defined from the Direct or Diffuse Solar Ir radiation drop down list under Illumination Parameters in the Radiation Model panel This will open the User Defined Functions panel Select the function name e g user solar intensity from the UDF list in the User Defined Functions panel and click OK The UDF name will appear in the text entry box below the parameter drop down list in the Radiation Model panel Figure 6 2 21 See Section 2 3 16 DEFINE_SOLAR_INTENSITY for details about DEFINE_SOLAR_INTENSITY functions 6 2 17 Hooking DEFINE SOURCE UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE SOURCE UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Fluid or Solid panel in FLUENT To hook the UDF to FLUENT you will first need to turn on the Source Terms option in the Fluid or Solid panel Figure 6 2 22 and click the Source Terms tab This will display the source term parameters mass momentum etc in the scrollable window Define Boundary Conditions Next click the Edit button next to the source term e g Mass you wish to customize Figure 6 2 22 Next click the
510. t plane void name int header FILE fp Tracked_Particle p Thread t Plane plane define DEFINE_DPM_PROPERTY name c t p real name cell_t c Thread t Tracked_Particle p define DEFINE_DPM_SCALAR_UPDATE name c t initialize p void name cell_t c Thread t int initialize Tracked_Particle p define DEFINE_DPM_SOURCE name c t S strength p void name cell_t c Thread t dpms_t S real strength Tracked_Particle p define DEFINE_DPM_SPRAY_COLLIDE name tp p B 6 Fluent Inc September 11 2006 B 6 User Defined Scalar UDS DEFINE Macros void name Tracked_Particle tp Particle p define DEFINE_DPM_SWITCH name p ci void name Tracked_Particle p int ci define DEFINE_DPM_TIMESTEP name p ts real name Tracked_Particle p real ts define DEFINE_DPM_VP_EQUILIB name p cvap_surf void name Tracked_Particle p real cvap_surf B 6 User Defined Scalar UDS DEFINE Macros The following definitions for UDS DEFINE macros see Section 2 7 User Defined Scalar UDS Transport Equation DEFINE Macros are taken from the udf h header file define DEFINE_ANISOTROPIC_DIFFUSIVITY name c t ns dmatrix void name cell_t c Thread t int ns real dmatrix ND_ND ND_ND define DEFINE_UDS_FLUX name f t i real name face_t f Thread t int i define DEFINE_UDS_UNSTEADY name c t i apu su void name cell_t c Thread t int i real apu real su Fluent I
511. t PI dS eqn abs_coeff source abs_coeff 4 SIGMA_SBC pow C_T c t 4 C_UDSI c t P1 return source Fluent Inc September 11 2006 A 7 C Programming Basics A 6 User Defined Data Types C also allows you to create user defined data types using structures and typedef For information about structures in C see 2 An example of a structured list definition is shown below i typedef can only be used for compiled UDFs Example typedef struct list int a real b int c mylist mylist is type structure list mylist x y Z x y z are type structure list A 7 Casting You can convert from one data type to another by casting A cast is denoted by type where the type is int float etc as shown in the following example int x 1 real y 3 14159 int z x int y z 4 A 8 Functions Functions perform tasks Tasks may be useful to other functions defined within the same source code file or they may be used by a function external to the source file A function has a name that you supply and a list of zero or more arguments that are passed to it Note that your function name cannot contain a number in the first couple of characters A function has a body enclosed within curly braces that contains instructions for carrying out the task A function may return a value of a particular type C functions pass data by value Functions either return a value of a particular data type e g
512. t is the source term is modeled as PSe pve 2 3 9 Fluent Inc September 11 2006 2 1 05 DEFINE Macros where c is the mean reaction progress variable p is the density and U is the turbulent flame speed In the UDF example the turbulent flame speed is modeled as U U 1 u U 2 3 10 where U is the laminar flame speed and w is the turbulent fluctuation Note that the par tially premixed combustion model is assumed to be enabled Click see Chapter 17 Mod eling Partially Premixed Combustion to go to the User s Guide manual so that the unburned density and laminar flame speed are available as polynomials See Chap ter 3 Additional Macros for Writing UDFs for details on the NULLP THREAD_STORAGE and SV_VARS macros POR CCC AAO oo RI kkk A A I A KKK KEK kkk A A A kkk kkk UDF that specifies a custom turbulent flame speed and source for the premixed combustion model DO RC A KDE DH 2A 2k KK KK 2 kkk k kkk kkk include udf h include sg_pdf h not included in udf h so must include here DEFINE_TURB_PREMIX_SOURCE turb_flame_src c t turb_flame_speed source real up TRB_VEL_SCAL c t real ut ul grad_c rho_u Xl DV ND_ND ul C_LAM_FLAME_SPEED c t Calculate_unburnt_rho_and_X1 t amp rho_u amp X1 if NNULLP THREAD_STORAGE t SV_PREMIXC_G NV_V DV C_STORAGE_R_NV c t SV_PREMIXC_G grad_c sqrt NV_DOT DV DV ut ul sqrt 1 SQR up ul t
513. tCond Prandtl number real Nu 2 0 0 6 sqrt p gt Re pow Pr 1 3 Nusselt number real h Nu c gt tCond Dp Heat transfer coefficient real dh_dt h c gt temp Tp Ap heat source term dydt 0 dh_dt mp Cp dzdt gt energy dh_dt Material sp mixture_species_loop gas_mix sp ns molwt ns MATERIAL_PROP sp PROP_mwi molecular weight of gas species 2 160 molwt_bulk C_YI cO t0 ns molwt ns average molecular weight prevent division by zero molwt_bulk MAX molwt_bulk DPM_SMALL for ns 0 ns lt nc ns gas species index of vaporization int gas_index TP_COMPONENT_INDEX_I p ns Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros if gas_index gt 0 condensed material Material cond_c MIXTURE_COMPONENT cond_mix ns vaporization temperature real vap_temp MATERIAL_PROP cond_c PROP_vap_temp diffusion coefficient real D MATERIAL_PROP_POLYNOMIAL cond_c PROP_binary_diffusivity c gt temp Schmidt number real Sc c gt mu c gt rho D mass transfer coefficient real k 2 0 6 sqrt p gt Re pow Sc 1 3 D Dp bulk gas concentration real cvap_bulk c gt pressure UNIVERSAL_GAS_CONSTANT c gt temp c gt yilgas_index molwt_bulk solver_par molWeight gas_index vaporization rate
514. ta structure that contains data related to the particle being tracked Pointer to array containing mass fractions of the solid species in the particle char mass at the current time step Diffusion controlled species as defined in the Reactions panel for the current reaction Catalyst species as defined in the Reactions panel for the current reaction Pointer to array containing particle reaction rate kg s Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros There are eleven arguments to DEFINE_PR_RATE name c t r mw ci p sf dif_index cat_index and rr You supply name the name of the UDF c t r mw ci p sf dif_index cat_index and rr are variables that are passed by the FLUENT solver to your UDF Your UDF will need to set the value referenced by the real pointer rr to the particle reaction rate in kg s Note that p is an argument to many particle specific macros defined in Section 3 2 7 DPM Macros and can be used to obtain information about particle properties Also note that the order in which the solid species mass fractions are stored in array sf is the same as the order in which the species are defined in the Selected Solid Species list in the Materials panel which is opened from the Edit Species names option for the Mixture Material DEFINE_PR_RATE is called by FLUENT every time step during the particle tracking cal culation The auxiliary function zbrent_pr_rate is used when there is no analyti
515. table in the Discrete Phase Model panel Figure 6 4 2 in FLUENT Define Models Discrete Phase Discrete Phase Model Interaction Particle Treatment Interaction with Continuous Phase Unsteady Particle Tracking l Update DPM Sources Every Flow Iteration Number of Continuous Phase 16 Iterations per DPM Iteration Tracking Physical Models UDF Numerics Parallel User Defined Functions User Variables Body Force particle _body_force lil Number of Scalars 8 Scalar Update none Source none DPM Time Step none OK Injections Cancel Help Figure 6 4 2 The Discrete Phase Model Panel To hook the UDF to FLUENT choose the function name e g particle body force in the Body Force drop down list under User Defined Functions Figure 6 4 2 and click OK See Section 2 5 2 DEFINE DPM BODY FORCE for details about DEFINE DPM BODY FORCE functions 6 55 Fluent Inc September 11 2006 Hooking UDFs to FLUENT 6 4 3 Hooking DEFINE_DPM_DRAG UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_DRAG UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Discrete Phase Model panel Figure 6 4 3 in FLUENT Define Models gt Discrete Phase Discrete Phase Model Interaction Particle Treatment l Interact
516. tate V 1 p gt state V 2 P_DIAM p p gt number_in_parcel P_T p P_INIT_DIAM p p gt time_of_birth endif PARALLEL endif 2 1 70 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros if REMOVE_PARCELS p gt stream_index 1 endif Hooking a DPM Output UDF to FLUENT After the UDF that you have defined using DEFINE_DPM_OUTPUT is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible in the Sample Trajectories panel in FLUENT See Section 6 4 8 Hooking DEFINE_DPM_OUTPUT UDFs for details on how to hook your DEFINE_DPM_OUTPUT UDF to FLUENT Fluent Inc September 11 2006 2 1 71 DEFINE Macros 2 5 9 DEFINE_DPM_PROPERTY Description You can use DEFINE DPM PROPERTY to specify properties of discrete phase materials For example you can model the following dispersed phase propertieswith this type of UDF e particle emissivity e vapor pressure e vaporization temperature e particle scattering factor e boiling point e particle viscosity e particle surface tension Usage DEFINE_DPM_PROPERTY name c t p Argument Type Description symbol name UDF name cellt c Index that identifies the cell where the particle is located in the given thread Thread t Pointer to the thread where the particle is located Tracked Particle p Pointer to the
517. te Phase Model panel before you can hook the UDF To hook the UDF to FLUENT choose the function name e g udf mean spray in the Spray Collide Function drop down list in the User Defined Function Hooks panel Fig ure 6 4 13 and click OK Fluent Inc September 11 2006 6 67 Hooking UDFs to FLUENT See Section 2 5 12 DEFINE_DPM_SPRAY_COLLIDE for details about DEFINE_DPM_SPRAY_COLLIDE functions 6 4 13 Hooking DEFINE_DPM_SWITCH UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_SWITCH UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Custom Laws panel Figure 6 4 14 in FLUENT To hook the UDF to FLUENT first click Create in the Injec tions panel to open the Set Injection Properties panel Define Injections Next turn on the Custom option under Laws in the Set Injection Properties panel This will open the Custom Laws panel Custom Laws Inert Heating x First Law Inactive Second Law inactive Third Law Inactive Fourth Law Inactive Fifth Law Inactive Sixth Law dpm_switch Switching Figure 6 4 14 The Custom Laws Panel Finally in the Custom Laws panel Figure 6 4 14 choose the function name e g dpm switch from the last drop down list labeled Switching Figure 6 4 14 and click OK See Section 2 5 13 DEFINE DPM SWITCH for details a
518. te Phase Model panel in FLUENT See Section 6 4 10 Hooking DEFINE DPM SCALAR UPDATE UDF for details on how to hook your DEFINE_DPM_SCALAR_UPDATE UDF to FLUENT Fluent Inc September 11 2006 2 1 79 DEFINE Macros 2 5 11 DEFINE_DPM_SOURCE Description You can use DEFINE_DPM_SOURCE to specify particle source terms The function allows access to the accumulated source terms for a particle in a given cell before they are added to the mass momentum and energy exchange terms for coupled DPM calculations Usage DEFINE DPM SOURCE name c t S strength p Argument Type Description symbol name UDF name cellt c Index that identifies the cell that the particle is currently in Thread t Pointer to the thread the particle is currently in dpms_t S Pointer to the source structure dpms_t which contains the source terms for the cell real strength Particle number flow rate in particles second divided by the number of tries if stochastic tracking is used Tracked Particle p Pointer to the Tracked Particle data structure which contains data related to the particle being tracked Function returns void There are six arguments to DEFINE DPM SOURCE name c t S strength and p You supply name the name of the UDF c t S strength and p are variables that are passed by the FLUENT solver to your UDF The modified source terms once computed by the function will be stored in S Pointer p can be used as an argument to the m
519. te ordinates model 2 38 DPM 2 180 example 8 26 for FLUENT transport equations 2 93 premixed combustion model 2 105 source terms 1 3 SOx macros 3 36 SOx rate UDFs 2 96 Spalart Allmaras turbulence model 2 107 species diffusivity UDFs 2 34 species mass fraction 2 31 2 101 species net reaction rate UDFs 2 46 specific dissipation Prandtl number UDFs 2 62 Index 14 specific heat 2 79 specular reflectivity UDFs 2 40 spray collide UDFs 2 182 SQR 2 105 2 108 3 76 storage checking 3 75 sub domain loop 3 54 sub_thread_loop 3 56 subdomains 1 17 subthreads 1 17 superdomains 1 17 superthreads 1 17 Surface Monitors panel 8 24 surface reaction rate 1 3 surface reaction rate UDFs 2 101 switching custom laws for DPM 2 185 Syamlal drag law 2 123 T SAT 2 134 temperature equation diffusion Prandtl number UDFs 2 63 temperature dependent viscosity 8 32 text editor 1 1 thermal conductivity 2 79 thermal wall function Prandtl number UDFs 2 64 Thread data structure 1 10 thread pointer 1 11 3 3 to array of phase threads 3 3 thread storage parallel 7 10 THREAD C0 2 154 THREAD_F_WALL 2 142 THREAD_ID 2 101 2 103 2 162 thread_loop_c 2 9 2 19 2 154 3 50 thread_loop_f 2 154 3 50 THREAD_MATERIAL 2 82 2 84 2 162 2 185 THREAD_SHADOW 3 30 THREAD_STORAGE 2 154 2 185 THREAD SUB_THREAD 2 123 2 125 2 134 2 137 3 60 THREAD_SUB_THREADS 3 61 THREAD_SUPER_THREAD 3
520. temperature DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s Fluent Inc September 11 2006 Quick Reference Guide for Multiphase DEFINE Macros Table C 3 3 DEFINE Macro Usage for the Eulerian Model Laminar Flow Variable Macro Phase Specified On Other drag coefficient lift coefficient heat transfer coefficient mass transfer coefficient heterogeneous reaction rate DEF INE_EXCHANGE DEFINE EXCHANGE DEFINE PROPERTY DEFINE MASS TRANSFER DEFINE HET RXN RATE phase interaction phase interaction phase interaction phase interaction phase interaction C 10 Fluent Inc September 11 2006 C 4 Eulerian Model Mixture Turbulence Flow C 4 Eulerian Model Mixture Turbulence Flow Tables C 4 1 C 4 3 list the variables that can be customized using UDFs for the mixed turbulence flow Eulerian multiphase model the DEFINE macros that are used to define the UDFs and the phase that the UDF needs to be hooked to for the given variable Table C 4 1 DEFINE Macro Usage for the Eulerian Model Mixture Turbu lence Flow Variable Macro Phase Specified On Boundary Conditions Inlet Outlet volume fraction species mass fractions mass flux velocity magnitude temperature pressure user defined scalar bou
521. terval 4 Iterate Apply Close Help Figure 6 1 3 The Iterate Panel To hook the UDF to FLUENT the Unsteady time method must be chosen in the Solver panel You will then need to select Adaptive as the Time Stepping Method in the Iterate panel choose the function name e g mydeltat in the User Defined Time Step drop down list under Adaptive Time Step Parameters and click Apply Note that when you are using the VOF Multiphase Model you will need to select Variable as the Time Stepping Method to hook the time step UDF See Section 2 2 2 DEFINE_DELTAT for details about defining DEFINE_DELTAT functions 6 4 Fluent Inc September 11 2006 6 1 Hooking General Purpose UDFs 6 1 3 Hooking DEFINE_EXECUTE_AT_END UDFs Once you interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs your DEFINE_EXECUTE_AT_END UDF it is ready to be hooked to FLUENT Note that you can hook multiple at end UDFs to your model if desired Open the User Defined Function Hooks panel Figure 6 1 4 Define User Defined Function Hooks User Defined Function Hooks Initialization none Edit Adjust none Edit Execute at End none Edit Read Case none Edit Write Case none Edit Read Data none Edit Write Data none Edit Figure 6 1 4 The User Defined Function Hooks Panel Fluent Inc September 11 2006 6 5 Hooking UDFs to FLUENT Click on t
522. the Materials panel User Defined Functions ScatPhiB2 ScatPhiB1 ScatPhiF3 ScatPhiF2 Scatlso Figure 6 2 20 The User Defined Functions Panel See Section 2 3 15 DEFINE_SCAT_PHASE_FUNC for details about DEFINE_SCAT_PHASE_FUNC functions 6 35 Fluent Inc September 11 2006 Hooking UDFs to FLUENT 6 2 16 Hooking DEFINE_SOLAR_INTENSITY UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_SOLAR_INTENSITY UDF the name of the function you supplied as a DEFINE macro argument you supplied in the argument of the DEFINE macro will become selectable in the Radiation Model panel for Direct Solar Irradiation and Diffuse Solar Irradiation Figure 6 2 21 Define Models Radiation Radiation Model Model Iteration Parameters Off Flow Iterations per Radiation Iteration 419 Rosseland P1 Angular Discretization Non Gray Model C Discrete Transfer DTRM C Surface to Surface S28 Theta Divisions 2 I Number of Bands 8 Discrete Ordinates DO Phi Divisions 2 aj l DO Energy Coupling Theta Pixels f4 z Phi Pixels 4 Solar Load Model Sun Direction Vector Off xig Yio Z 4 Solar Ray Tracing C DO Irradiation M Use Direction Computed from Solar Calculator olar Calculator Ilumination Parameters Direct Solar Irradiation w m2 user defined Edi m v it user_solar_intensity Diffuse Solar Irradiation w m2 constan
523. the UDF name will not appear in the list until the function has been interpreted or compiled and loaded Recall that a single UDF is used to define custom rates for the thermal NO prompt NO fuel NO and N20 NO pathways To replace the internally calculated NO rate with a UDF rate for any of the NO pathways you will first need to choose the UDF name e g user nox from the NOx Rate drop down list click on the desired NO pathway tab Thermal Prompt Fuel N20 Path under Formation Model Parameters check the Replace with UDF Rate box for that pathway and then click Apply Repeat this process until all of the NO pathways are set to the desired state default rate or UDF rate Note that the Replace with UDF Rate checkbox appears only after you have selected a NO rate UDF If you do not check the Replace with UDF Rate box for a particular pathway but hook the UDF function to the interface then the UDF rate for that NO pathway will be added to the internally calculated rate for the source term calculation Unless specifically defined in your NO rate UDF data and parameter settings for each individual NO pathway will be derived from the settings in the NOx Model panel There fore it is good practice to make the appropriate settings in the NOx Model panel even though you may use a UDF to replace the default rates with user specified rates There is no computational penalty for doing this because the default rate calculations will be
524. the cell and Thread that the particle is currently in cell_t c RP_CELL amp tp gt cCell Thread t RP_THREAD amp tp gt cCell Particle index for looping over all particles in the cell Particle pi loop over all particles in the cell to find their mass weighted mean velocity and diameter int i real u_mean 3 0 mass_mean 0 real d_orig tp gt state diam real decay 1 exp t_relax begin_particle_cell_loop pi c t mass_mean pi gt state mass for i 0 1 lt 3 i u_mean i pi gt state Vli pi gt state mass end_particle_cell_loop pi c t relax particle velocity to the mean and diameter to the Fluent Inc September 11 2006 2 1 83 DEFINE Macros initial diameter over the relaxation time scale t_relax if mass_mean gt 0 for i 0 1 lt 3 i u_mean i mass_mean for i 0 i lt 3 i tp gt state V i decay u_mean i tp gt state V i tp gt state diam decay P_INIT_DIAM tp tp gt state diam adjust the number in the droplet parcel to conserve mass tp gt number_in_parcel CUB d_orig tp gt state diam Hooking a DPM Spray Collide UDF to FLUENT After the UDF that you have defined using DEFINE_DPM_SPRAY_COLLIDE is interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible in the User De
525. then hook it to FLUENT using the graphical user interface Follow the procedure for interpreting source files using the Interpreted UDFs panel Section 4 2 In terpreting a UDF Source File Using the Interpreted UDFs Panel or compiling source files using the Compiled UDFs panel Section 5 2 Compile a UDF Using the GUI To hook the UDF to FLUENT as the velocity boundary condition for the zone of choice open the Velocity Inlet panel and click on the Momentum tab Figure 8 2 4 Define Boundary Conditions Velocity Inlet Zone Name velocity inlet 1 Momentum Thermal Radiation Species DPM Multiphase UDS Velocity Specification Method Components Reference Frame Absolute Velocity m s uat inlet_x_velocity YVelocity m s g constant Outflow Gauge Pressure pascal 1691325 constant Figure 8 2 4 The Velocity Inlet Panel In the X Velocity drop down list select udf inlet_ x velocity the name that was given to the function above with udf preceeding it Once selected the default value will become grayed out in the X Velocity field Click OK to accept the new boundary condition and close the panel The user profile will be used in the subsequent solution calculation After the solution is run to convergence a revised velocity field is obtained as shown in Figures 8 2 5 and 8 2 6 The velocity field shows a maximum at the center of the inlet which drops to zero at the edges
526. thread real mu_lam local variable real temp C_T cell thread local variable if temp gt 288 mu_lam 5 5e 3 else if temp gt 286 mu_lam 143 2135 0 49725 temp else mu_lam 1 return mu_lam A 5 1 Declaring Variables A variable declaration begins with the data type e g int followed by the name of one or more variables of the same type that are separated by commas A variable declaration can also contain an initial value and always ends with a semicolon Variable names must begin with a letter in C A name can include letters numbers and the underscore _ character Note that the C preprocessor is case sensitive recognizes uppercase and lowercase letters as being different Below are some examples of variable declarations int n declaring variable n as an integer int il i2 declaring variables il and i2 as integers float tmax 0 tmax is a floating point real number that is initialized to 0 real average_temp 0 0 average_temp is a real number initialized to 0 0 Fluent Inc September 11 2006 A 5 Variables A 5 2 External Variables If you have a global variable that is declared in one source code file but a function in another source file needs to use it then it must be defined in the other source file as an external variable To do this simply precede the variable declaration by the word extern as in extern real volume If there are seve
527. thread humidity myHumidity cell thread min MIN min humidity max MAX max humidity C_UDMI cell thread UDM_RH humidity end_c_loop cell thread Message nRelative Humidity set in udm d range f f n UDM_RH min max end if for enough UDSs and UDMs DEFINE_ON_DEMAND set_relhum adj_relhum Get_Domain 1 J Hooking a DPM Switching UDF to FLUENT After the UDF that you have defined using DEFINE DPM SWITCH is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible in the Custom Laws panel in FLUENT See Section 6 4 13 Hooking DEFINE_DPM_SWITCH UDFs for details on how to hook your DEFINE_DPM_SWITCH UDF to FLUENT Fluent Inc September 11 2006 2 1 89 DEFINE Macros 2 5 14 DEFINE_DPM_TIMESTEP Description You can use DEFINE DPM TIMESTEP to change the time step for DPM particle tracking based on user specified inputs The time step can be prescribed for special applications where a certain time step is needed It can also be limited to values that are required to validate physical models Usage DEFINE_DPM_TIMESTEP name p ts Argument Type Description symbol name UDF name Tracked Particle p Pointer to the Tracked Particle data structure which contains data related to the particle being tracked real ts Time step Function returns real There
528. thread_loop_f macro described below Domain domain Thread c_thread thread_loop_c c_thread domain loops over all cell threads in domain Looping Over Face Threads in a Domain thread_loop_f You can use thread_loop_f when you want to loop over all face threads in a given domain It consists of a single statement followed by the operation s to be performed on all face threads in the domain enclosed within braces as shown below Note that thread loop f is similar in implementation to the thread_loop_c macro described above Thread f_thread Domain domain thread_loop_f f_thread domain loops over all face threads in a domain 3 50 Fluent Inc September 11 2006 3 3 Looping Macros Looping Over Cells in a Cell Thread begin end_c_loop You can use begin_c_loop and end_c_loop when you want to loop over all cells in a given cell thread It contains a begin and end loop statement and performs operation s on each cell in the cell thread as defined between the braces This loop is usually nested within thread_loop_c when you want to loop over all cells in all cell threads in a domain cell_t c Thread c_thread begin_c_loop c c_thread loops over cells in a cell thread end_c_loop c c_thread Example Loop over cells in a thread to get information stored in cells begin_c_loop c c_thread C_T gets cell temperature The will cause all of the cell temperatur
529. tion that is defined by the function will be applied to all cell faces identified by f in the face loop on a given boundary zone identified by thread The thread is defined automatically when you hook the UDF to a particular boundary in the FLUENT graphical user interface The index is defined automatically through the begin f_loop utility In this UDF the begin f_loop macro Section 3 3 Looping Macros is used to loop through all cell faces in the boundary zone For each face the coordinates of the face centroid are accessed by F_CENTROID Section 3 2 4 Face Centroid F_CENTROID The y coordinate y is used in the parabolic profile equation and the returned velocity is assigned to the face through F PROFILE begin f_loop and F_PROFILE Section 3 2 6 Set Boundary Condition Value F_PROFILE are Fluent supplied macros Refer to Chapter 3 Additional Macros for Writing UDFs for details on how to utilize predfined macros and functions supplied by Fluent Inc to acccess FLUENT solver data and perform other tasks 8 1 4 Step 3 Start FLUENT and Read or Set Up the Case File Once you have created the source code for your UDF you are ready to begin the problem setup in FLUENT 1 Start FLUENT from your working directory 2 Read or set up your case file 8 1 5 Step 4 Interpret or Compile the Source File You are now ready to interpret or compile the profile UDF named x_velocity that you created in Step 2 and is contained within the sou
530. tional Macros for Writing UDFs BOUNDARY_FACE_GEOMETRY can be called to retrieve some of the terms needed to evaluate Equations 3 2 1 and 3 2 3 real A ND_ND area normal vector real ds distance between the cell centroid and the face centroid real es ND_ ND unit normal vector in the direction from centroid of cell c0 to the face centroid real A by es value ae real drO ND_ND vector that connects the centroid of cell cO to the face centroid Boundary Face Thread BOUNDARY FACE THREAD BOUNDARY FACE THREAD P t expands to a function that returns TRUE if Thread t is a boundary face thread The macro is defined in threads h which is included in udf h See Section 2 7 3 DEFINE_UDS_FLUX for an example UDF that utilizes BOUNDARY_FACE_THREAD_P 3 24 Fluent Inc September 11 2006 3 2 Data Access Macros 3 2 6 Special Macros The macros listed in this section are special macros that are used often in UDFs Lookup_Thread THREAD_ID Get_Domain F_PROFILE THREAD_SHADOW Thread Pointer for Zone ID Lookup_Thread You can use Lookup_Thread when you want to retrieve the pointer t to the thread that is associated with a given integer zone ID number for a boundary zone The zone_ID that is passed to the macro is the zone number that FLUENT assigns to the boundary and displays in the boundary condition panel e g Fluid Note that this macro does the inverse of THREAD_ID see below There are two arguments to Lookup_
531. to be applied int i Index that identifies the species or user defined scalar Function returns real There are four arguments to DEFINE_DIFFUSIVITY name c and t and i You supply name the name of the UDF c t and i are variables that are passed by the FLUENT solver to your UDF Your UDF will need to compute the diffusivity only for a single cell and return the real value to the solver Note that diffusivity UDFs are called by FLUENT from within a loop on cell threads Consequently your UDF will not need to loop over cells in a thread since FLUENT is doing it outside of the function call 2 34 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros Example The following UDF named mean_age_diff computes the diffusivity for the mean age of air using a user defined scalar Note that the mean age of air calculations do not require that energy radiation or species transport calculations have been performed You will need to set uds 0 0 0 at all inlets and outlets in your model This function can be executed as an interpreted or compiled UDF peaa oo o kkk kkk kkk kkk kk kkk kk kkk kk CLS UDF that computes diffusivity for mean age using a user defined scalar FOR EEEE a a a kk a 3k 2k ER 2k 2k ok ok 2k 2 3k 2k 2k ak ok include udf h DEFINE_DIFFUSIVITY mean_age_diff c t i return C_R c t 2 88e 05 C_MU_EFF c t 0 7 Hooking a Diffusivity UDF to FLUENT After the UDF that you have defined
532. to compute the new velocity of a particle after hitting the wall and then return the status of the particle track as an int after it has hit the wall Fa Pointer p can be used as an argument to the particle specific macros de fined in Section 3 2 7 DPM Macros to obtain information about particle properties Fluent Inc September 11 2006 2 1 41 DEFINE Macros Example 1 This example shows the usage of DEFINE_DPM_BC for a simple reflection at walls It is similar to the reflection method executed by FLUENT except that FLUENT accommodates moving walls The function must be executed as a compiled UDF The function assumes an ideal reflection for the normal velocity component nor_coeff 1 while the tangential component is damped tan_coeff 0 3 First the angle of incidence is computed Next the normal particle velocity with respect to the wall is computed and subtracted from the particles velocity The reflection is complete once the reflected normal velocity is added The new particle velocity has to be stored in stateO to account for the change of particle velocity in the momentum balance for coupled flows The function returns PATH_ACTIVE for inert particles while it stops particles of all other types reflect boundary condition for inert particles include udf h DEFINE_DPM_BC bc_reflect p t f f_normal dim real alpha angle of particle path with face normal real vn 0 real nor_coeff real tan_c
533. to hook your DEFINE GRID MOTION UDF to FLUENT 2 204 Fluent Inc September 11 2006 2 6 Dynamic Mesh DEFINE Macros 2 6 4 DEFINE SDOF PROPERTIES Description You can use DEFINE SDOF PROPERTIES to specify custom properties of moving objects for the six degrees of freedom SDOF solver in FLUENT These include mass moment and products of inertia and external forces and moment properties The properties of an ob ject which can consist of multiple zones can change in time if desired External load forces and moments can either be specified as global coordinates or body coordinates In addi tion you can specify custom transformation matrices using DEFINE_SDOF_PROPERTIES Usage DEFINE_SDOF_PROPERTIES name properties dt time dtime Argument Type Description symbol name UDF name real properties Pointer to the array that stores the SDOF properties Dynamic_Thread dt Pointer to structure that stores the dynamic mesh attributes that you have specified or that are calculated by FLUENT real time Current time real dtime Time step Function returns void There are four arguments to DEFINE SDOF PROPERTIES name properties dt and dtime You provide the name of the UDF properties dt and dtime are variables that are passed by the FLUENT solver to your UDF The property array pointer that is passed to your function allows you to specify values for any of the following SDOF properties SDOF_MASS mass SDOF_IXX
534. to show the method ology of computing gradients of arbitrary quantities that can be used for postprocessing k kk kk CAA k 2k 2k kk k k k K k k K FK 2K 2k k kk k kk k K k K aK a Kk 2 2k LLC 2k K 2k 2k kk 2k LLC LE k KK 2k ak UDF for computing the magnitude of the gradient of T 4 1 PH HER HER HN HER HN RENE HER EH EEEE EEEE include udf h Define which user defined scalars to use enum T4 MAG_GRAD_T4 N_REQUIRED_UDS DEFINE_ADJUST adjust_fcn domain Thread t cell_t c face_t f Make sure there are enough user defined scalars if n_uds lt N_REQUIRED_UDS Internal_Error not enough user defined scalars allocated Fluent Inc September 11 2006 8 43 Examples Fill first UDS with temperature raised to fourth power thread_loop_c t domain if NULL THREAD_STORAGE t SV_UDS_I T4 begin_c_loop c t real T C_T c t C_UDSI c t T4 pow T 4 end_c_loop c t thread_loop_f t domain if NULL THREAD_STORAGE t SV_UDS_I T4 begin_f_loop f t real T 0 if NULL THREAD_STORAGE t SV_T T F_T f t else if NULL THREAD_STORAGE t gt t0 SV_T T C_T F_CO f t t gt t0 F_UDSI f t T4 pow T 4 end_f_loop f t Fill second UDS with magnitude of gradient thread_loop_c t domain if NULL THREAD_STORAGE t SV_UDS_I T4 amp amp NULL T_STORAGE_R_NV t SV_UDSI_G T4 begin_c_loop
535. to your UDF by the FLUENT solver if you are using a DEFINE macro that contains a domain variable argument e g DEFINE_ADJUST and your UDF is hooked to the mixture If mixture_domain is not explicitly passed to your UDF you may use another utility macro to retrieve it e g Get Domain 1 described in Section 3 2 6 Domain Pointer Get_Domain Note that the values for pt and face_threads are set within the looping function mp_thread_loop_f is typically used along with begin_f loop begin_f_loop loops over faces in a face thread When begin f_loop is nested within mp thread loop f you can loop over all faces in all phase face threads within a mixture 3 3 2 Advanced Multiphase Macros For most standard UDFs written for multiphase models e g source term material property profile functions variables that your function needs domain pointers thread pointers etc are passed directly to your UDF as arguments by the solver in the solution process All you need to do is hook the UDF to your model and everything is taken care of For example if your multiphase UDF defines a custom profile for a particular boundary zone using DEFINE PROFILE and is hooked to the appropriate phase or mixture in FLUENT in the relevant boundary condition panel then appropriate phase or mixture variables will be passed to your function by the solver at run time There may however be more complex functions you wish to write that require a variable that is not
536. total area of REACTING_SURFACE faces in contact with cell count is the number of contacting faces and is needed to share the total bubble emission between the faces if count gt 0 if cell is in contact with REACTING_SURFACE P_FLOW_RATE p area MW_H2 STOIC_H2 reaction_rate cell cthread mw yi real count to get correct total flow rate when multiple faces contact the same cell 2 1 64 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros P_DIAM p 1e 3 P_RHO p 1 0 P_MASS p P_RHO p M_PI pow P_DIAM p 3 0 6 0 else P_FLOW_RATE p 0 0 real contact_area cell_t c Thread t int s_id int n int i 0 real area 0 0 A ND_ND n 0 c face_loop c t 1 if THREAD_ID C_FACE_THREAD c t i s_id n F_AREA A C_FACE c t i C_FACE_THREAD c t i area NV_MAG A return area Hooking a DPM Initialization UDF to FLUENT After the UDF that you have defined using DEFINE DPM INJECTION INIT is interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible in the Set Injection Properties panel in FLUENT See Section 6 4 6 Hooking DEFINE DPM INJECTION _INIT UDFs for details on how to hook your DEFINE_DPM_INJECTION_INIT UDF to FLUENT Fluent Inc September 11 2006 2 1 65 DEFINE Macros
537. uation Equation 13 3 38 to go to the User s Guide manual real abs coeff Pointer to absorption coefficient real scat_coeff Pointer to scattering coefficient Function returns void There are nine arguments to DEFINE DOM SOURCE name c ni nb emission in scattering abs coeff and scat coeff You supply name the name of the UDF c ni nb emission in scattering abs coeff and scat coeff are variables that are passed by the FLUENT solver to your UDF DEFINE_DOM_ SOURCE is called by FLUENT for each cell 2 38 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros Example In the following UDF named user_dom_source the emission term present in the radiative transport equation is modified The UDF is called for all the cells and increases the emission term by 5 UDF to alter the emission source term in the DO model include udf h DEFINE_DOM_SOURCE user_dom_source c t ni nb emission in_scattering abs_coeff scat_coeff increased the emission by 5 xemission 1 05 Note that all of the arguments to a DEFINE macro need to be placed on the same line in your source code Splitting the DEFINE statement onto several lines will result in a compilation error Hooking a DOM Source UDF to FLUENT After the UDF that you have defined using DEFINE_DOM_SOURCE is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied a
538. udf user_read2 libudf Figure 6 1 12 The Read Case Functions Panel In the Read Case Functions panel from the Available Read Case Functions you have inter preted or compiled and loaded select the functions you wish to hook to your model and click Add and then OK Click OK in the User Defined Function Hooks panel to apply the settings The number of functions you select will then appear in the User Defined Func tion Hooks panel For example if you select two functions e g user_read1 user_read2 then the text box for Read Case in the User Defined Function Hooks panel will display 2 selected See Section 2 2 9 DEFINE_RW_FILE for details about defining DEFINE_RW_FILE functions Fluent Inc September 11 2006 6 13 Hooking UDFs to FLUENT 6 1 8 User Defined Memory Storage You can store values computed by your UDF in memory so that they can be retrieved later either by a UDF or for postprocessing within FLUENT In order to have access to this memory you will need to allocate memory by spcifying the Number of User Defined Memory Locations in the User Defined Memory panel Figure 6 1 13 Define gt User Defined Memory User Defined Memory Number of User Defined Memory Locations 16 a Figure 6 1 13 The User Defined Memory Panel The macros C_UDMI or F_UDMI can be used in your UDF to access a particular user defined memory location in a cell or face respectively See Sections 3 2 3 and 3 2 4
539. uent Inc September 11 2006 CONTENTS 30 Scheme Macross sates ides ok eee are ER se eRe oS eS 3 71 3 6 1 Defining a Scheme Variable in the Text Interface 3 71 3 6 2 Accessing a Scheme Variable in the Text Interface 3 72 3 6 3 Changing a Scheme Variable to Another Value in the Text Interface 3 72 3 6 4 Accessing a Scheme Variable in a UDF 3 72 ont Japul Cuba Macros ssc cai ra s owe ERE EL ERES RE RES S 3 73 ove Miscellaneous Macros sr we va ha ee REE Se ee OY ws 3 74 4 Interpreting UDFs 4 1 Al Tnyoductiom 264464 6h boa MEN RENE CR ENS OHS OY GSS 4 1 41 1 Locstion dt theudf h File 25 sauge Sauvages 4 2 LL Limitations sushi a Rs Lester Lea es 4 2 4 2 Interpreting a UDF Source File Using the Interpreted UDFs Panel 4 3 4 3 Common Errors Made While Interpreting A Source File 4 5 4 4 Special Considerations for Parallel FLUENT 4 7 5 Compiling UDFs 5 1 gl Introduction s re sso boo be Rede e ee aie ie RE EER 5 2 ZLI Loestiomettheudt b File lt se ksi o de tee ok OY a 5 3 eel Compile e a ed Ba ee Be Bh ee ee oe ee ee 5 4 bo Compile 4 UDF Using the Gul co s cora cs gleo feale n sde ss 5 4 5 3 Compile a UDF Using the TUI 4 4 4 244 x eee sut when 5 11 Sad Set Up the Directory Structure os 4 x siea Da E e ed 5 11 Boe Dold the UDF Library 4 4 1 28 440 pa tai PEPE ss 5 14 pod Load the UDF Library scs 2 44444443444h468 45 5 19 5 4 Link Precompi
540. ult name for every user defined scalar that you allocate in the graphical user interface For example if you specify 2 as the Number of User Defined Scalars then two variables with default names User Scalar 0 and User Scalar 1 will be defined and the variables with these default names will appear in setup and postpro cessing panels You can change the default names if you wish using Set_User_Scalar_Name as described below The default name that appears in the graphical user interface and on plots in FLUENT for user defined scalars e g User Scalar 0 can now be changed using the function Set_User_Scalar_Name void Set_User_Scalar_Name int i char name i is the index of the scalar and name is a string containing the name you wish to assign It is defined in sg_udms h Set_User_Scalar_Name should be used only once and is best used in an EXECUTE_ON_LOADING UDF see Section 2 2 6 DEFINE_EXECUTE_ON_LOADING Due to the mechanism used UDS variables cannot be renamed once they have been set so if the name is changed in a UDF for example and the UDF library is reloaded then the old name could remain In this case restart FLUENT and load the library again 3 38 Fluent Inc September 11 2006 3 2 Data Access Macros F_UDSI You can use F_UDSI when you want to access face variables that are computed for user defined scalar transport equations Table 3 2 35 See Section 3 2 9 Example UDF that Utilizes UDM and UDS Variables for
541. um normal i return PATH_ACTIVE Hooking a DPM Boundary Condition UDF to FLUENT After the UDF that you have defined using DEFINE_DPM_BC is interpreted Chapter 4 In terpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible in the ap propriate boundary condition panel e g the Velocity Inlet panel in FLUENT See Sec tion 6 4 1 Hooking DEFINE_DPM_BC UDF for details on how to hook your DEFINE_DPM_BC UDF to FLUENT 2 1 48 Fluent Inc September 11 2006 2 5 Discrete Phase Model DPM DEFINE Macros 2 5 2 DEFINE_DPM_BODY_FORCE Description You can use DEFINE DPM BODY FORCE to specify a body force other than a gravitational or drag force on the particles Usage DEFINE_DPM_BODY_FORCE name p i Argument Type Description symbol name UDF name Tracked_Particle p Pointer to the Tracked_Particle data structure which contains data related to the particle being tracked int i An index 0 1 or 2 that identifies the Cartesian component of the body force that is to be returned by the function Function returns real There are three arguments to DEFINE DPM BODY FORCE name p and i You supply name the name of the UDF p and i are variables that are passed by the FLUENT solver to your UDF Your UDF will need to return the real value of the acceleration due to the body force in m s to the FLUENT solver Pointer p
542. umerical label for the variable being set within each loop The function begins by declaring variable f as a face_t data type A one dimensional array x and variable y are declared as real data types A looping macro is then used to loop over each face in the zone to create a profile or an array of data Within each loop F_CENTROID outputs the value of the face centroid array x for the face with index f that is on the thread pointed to by thread The y coordinate stored in x 1 is assigned to variable y and is then used to calculate the x velocity This value is then assigned to F PROFILE which uses the integer position passed to it by the solver based on your selection of the UDF as the boundary condition for x velocity in the Velocity Inlet panel to set the x velocity face value in memory PROC AOA ACA AAAI RR kk kkk kk kk kkk kkk kkk kkk kk kk vprofile c UDF for specifying steady state velocity profile boundary condition BER ooo ooo A A 1 1 1 1 21 21 KDE DD HD DO include udf h DEFINE_PROFILE inlet_x_velocity thread position real x ND_ND this will hold the position vector real y face_t f begin_f_loop f thread F_CENTROID x f thread y x 1 F_PROFILE f thread position 20 y y 0745 0745 20 end_f_loop f thread 8 18 Fluent Inc September 11 2006 8 2 Detailed UDF Examples To make use of this UDF in FLUENT you will first need to interpret or compile the function and
543. unction The value of the temperature is checked and based upon the range into which it falls the appropriate value of mu_lam is computed At the end of the function the computed value for mu_lam is returned to the solver 8 32 Fluent Inc September 11 2006 8 2 Detailed UDF Examples paaa oo o k kkk kkk kkk kkk kkk kkk kk UDF for specifying a temperature dependent viscosity property EEEE EE ooo oo DH DH DD ED DH D DORE include udf h DEFINE_PROPERTY cell_viscosity cell thread real mu_lam real temp C_T cell thread if temp gt 288 mu_lam 5 5e 3 else if temp gt 286 mu_lam 143 2135 0 49725 temp else mu_lam 1 return mu_lam This function can be executed as an interpreted or compiled UDF in FLUENT Follow the procedure for interpreting source files using the Interpreted UDFs panel Section 4 2 In terpreting a UDF Source File Using the Interpreted UDFs Panel or compiling source files using the Compiled UDFs panel Section 5 2 Compile a UDF Using the GUI To make use of the user defined property in FLUENT you will use the Materials panel In the drop down list for Viscosity select the user defined option Fluent Inc September 11 2006 8 33 Examples Materials Name Material Type Order Materials By air fluid o Name Chemical Formula Fluent Fluid Materials C Chemical Formula air Fluent Database Mixture User Defined Database none Propertie
544. unction you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Functions panel Figure 6 3 7 in FLUENT To hook the UDF to FLUENT you will first need to open the Phase Interaction panel Figure 6 3 6 by clicking Interactions in the Phases panel Define Phases Phase Interaction Drag Lift Collisions Slip Heat Mass Reactions Surface Tension Slip Velocity m s phase 2 phase 1 user defined f custom_slip El OK Cancel Help Figure 6 3 6 The Phase Interaction Panel Next click on the Slip tab in the Phase Interaction panel and choose user defined in the drop down list for the Slip Velocity This will open the User Defined Functions panel il Slip velocity UDFs apply only to the multiphase Mixture model Finally choose the function name e g custom slip from the list of UDFs displayed in the User Defined Functions panel Figure 6 3 3 and click OK See Section 2 4 5 DEFINE VECTOR EXCHANGE PROPERTY for details about DEFINE VECTOR EXCHANGE PROPERTY functions 6 52 Fluent Inc September 11 2006 6 4 Hooking Discrete Phase Model DPM UDFs User Defined Functions Figure 6 3 7 The User Defined Functions Panel 6 4 Hooking Discrete Phase Model DPM UDFs This section contains methods for hooking UDFs to FLUENT that have been e defined using DEFINE macros described in Section 2 5 Discrete Phase Model DPM DEFINE Macros
545. under Source File s Click OK The Select File panel will close and the file you added will appear in the Source Files list in the Compiled UDFs panel Repeat the previous step to select the Header Files that need to be included in the compilation 7 In the Compiled UDFs panel select the file that is listed under Source Files and type the name of the shared library in the Library Name field or leave the default name libudf Click Build This process will compile the code and will build a shared library in your working directory for the architecture you are running on Fluent Inc September 11 2006 8 11 Examples 8 12 As the compile build process begins a Warning dialog box will appear reminding you that the UDF source file must be in the directory that contains your case and data files i e your working directory If you have an existing library directory e g libudf then you will need to remove it prior to the build to ensure that the latest files are used Click OK to close the dialog box and resume the compile build process The results of the build will be displayed on the console window You can view the compilation history in the log file that is saved in your working directory FA If the compile build is unsuccessful then FLUENT will report an error and you will need to debug your program before continuing See Sec tion 5 6 Common Errors When Building and Loading a UDF Library for a list of common errors
546. urb_flame_speed ut source rho_u ut grad_c 2 1 06 Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros Hooking a Turbulent Premixed Source UDF to FLUENT After the UDF that you have defined using DEFINE_TURB_PREMIX_SOURCE is interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g turb flame src will become visible and selectable in the User Defined Function Hooks panel in FLUENT See Section 6 2 20 Hooking DEFINE_TURB_PREMIX_SOURCE UDFs for details 2 3 21 DEFINE TURBULENT VISCOSITY Description You can use DEFINE TURBULENT VISCOSITY to specify a custom turbulent viscosity func tion for the Spalart Allmaras k e and k w turbulence models for single phase applica tions In addition for 3d versions of FLUENT you can specify a subgrid scale turbulent viscosity UDF for the large eddy simulation model For Eulerian multiphase flows tur bulent viscosity UDFs can be assigned on a per phase basis and or to the mixture depending on the turbulence model See Table 2 3 5 for details Table 2 3 5 Eulerian Multiphase Model and DEFINE_TURBULENT_VISCOSITY UDF Usage Turbulence Model Phase that Turbulent Viscosity UDF Is Specified On k e Mixture mixture primary and secondary phases k e Dispersed primary and secondary phases k e Per Phase primary and secondary phases Usage
547. urce code The FLUENT solver automatically reads the udf h file from the Fluent Inc fluent6 x src directory A 18 Fluent Inc September 11 2006 A 15 Comparison with FORTRAN A 15 Comparison with FORTRAN Many simple C functions are similar to FORTRAN function subroutines as shown in the example below A simple C function An equivalent FORTRAN function int myfunction int x INTEGER FUNCTION MYFUNCTION X int x y Z INTEGER X Y Z y 11 Y 11 Z xXty Z X Y printf z d z WRITE 100 Z return Z MYFUNCTION Z END Fluent Inc September 11 2006 A 19 C Programming Basics A 20 Fluent Inc September 11 2006 Appendix B DEFINE Macro Definitions B 1 General Solver DEFINE Macros The following definitions for general solver DEFINE macros see Section 2 2 General Pur pose DEFINE Macros are taken from the udf h header file define DEFINE_ADJUST name domain void name Domain domain define DEFINE_EXECUTE_AT_END name void name void define DEFINE_EXECUTE_AT_EXIT name void name void define DEFINE_EXECUTE_FROM_GUI name libname mode void name char libname int mode define DEFINE_EXECUTE_ON_LOADING name libname void name char libname define DEFINE_INIT name domain void name Domain domain define DEFINE_ON_DFMAND name void name void define DEFINE_RW_FILE name fp void name FILE fp Fluent Inc September 11 2006 B 1 DEFINE Macro Definitions
548. ure 3 2 1 In other words face area normals always point from cell cO to cell c1 Fluent Inc September 11 2006 3 19 Additional Macros for Writing UDFs Flow Variable Macros for Boundary Faces The macros listed in Table 3 2 20 access flow variables at a boundary face Table 3 2 22 Macros for Boundary Face Flow Variables Defined in mem h Macro Argument Types Returns FU t face t f Thread t u velocity F_V f t face_t f Thread t v velocity F_W f t face_t f Thread t w velocity FT f t face t f Thread t temperature FH f t face t f Thread t enthalpy FK f t face_t f Thread t turbulent kinetic energy FD f t face_t f Thread t turbulent kinetic energy dissipation rate FYI f t i face_t f Thread t int i species mass fraction See Section 2 7 3 DEFINE UDS FLUX for an example UDF that utilizes some of these macros Flow Variable Macros at Interior and Boundary Faces The macros listed in Table 3 2 20 access flow variables at interior faces and boundary faces Table 3 2 23 Macros for Interior and Boundary Face Flow Variables Defined in mem h Macro Argument Types Returns FP f t face t f Thread t pressure F_FLUX f t facet f Thread t mass flow rate through a face F_FLUX can be used to return the real scalar mass flow rate through a given face f ina face thread t The sign of F_FLUX that is computed by the FLUENT solver is positive if the flo
549. ure 6 5 2 and click on the Geometry Definition tab Select user defined in the drop down list under Definition and choose the function name e g plane from the Geometry UDF drop down list Click Create and then Close See Section 2 6 2 DEFINE_GEOM for details about DEFINE_GEOM functions Fluent Inc September 11 2006 6 73 Hooking UDFs to FLUENT Dynamic Mesh Zones Zone Names Dynamic Zones axis Type C Stationary C Rigid Body Deforming C User Defined Motion Attributes Geometry Definition Meshing Options Definition user defined Geometry UDF plane libudt Create Draw Delete Update r Figure 6 5 2 The Dynamic Mesh Zones Panel 6 74 Fluent Inc September 11 2006 6 5 Hooking Dynamic Mesh UDFs 6 5 3 Hooking DEFINE_GRID_MOTION UDFs Once you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_GRID_MOTION UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Dynamic Mesh Zones panel Figure 6 5 3 To hook the UDF to FLUENT you will first need to enable the Dynamic Mesh model Define Dynamic Mesh Parameters Select Dynamic Mesh under Model and click OK i The Dynamic Mesh panel will be accessible only when you choose Unsteady as the time method in the Solver panel Next open the Dynamic Mesh Zones panel De
550. used to define a surface tension coefficient UDF for the multiphase VOF model The following UDF specifies a surface tension coefficient as a quadratic function of temperature The source code can be interpreted or compiled in FLUENT K k 2k OO OC A RO OK 2K 2K A 2K K A FK 2K 2k K 2k 2K 2k FK FKK 2k 2K 2k 2k 2k 2k 2 2k FK 2k 2K 2k ak 2k 2K Surface Tension Coefficient UDF for the multiphase VOF Model BOO AAR I EDEN include udf h DEFINE_PROPERTY sfc c t real T C_T c t return 1 35 0 004 T 5 0e 6 T4T Fa Note that surface tension UDFs for the VOF and Mixture multiphase mod els are both hooked to FLUENT in the Phase Interaction panel but in differ ent ways For the VOF model the function hook is located in the Surface Tension tab in the panel For the Mixture model however the function hook is located in the Mass tab and will become visible upon selecting the Cavitation option Example 4 Density Function for Compressible Liquids Liquid density is not a constant but is instead a function of the pressure field In order to stabilize the pressure solution for compressible flows in FLUENT an extra term related to the speed of sound is needed in the pressure correction equation Consequently when you want to define a custom density function for a compressible flow your model must also include a speed of sound function Although you can direct FLUENT to calculate a speed of sound function by choosing one of the availabl
551. using DEFINE DIFFUSIVITY is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name that you specified in the DEFINE macro argument e g mean_age_diff will become visible and se lectable in the Materials panel in FLUENT See Section 6 2 3 Hooking DEFINE_DIFFUSIVITY UDFs for details Fluent Inc September 11 2006 2 35 DEFINE Macros 2 3 4 DEFINE_DOM_DIFFUSE_REFLECTIVITY Description You can use DEFINE DOM DIFFUSE REFLECTIVITY to modify the inter facial reflectivity computed by FLUENT at diffusely reflecting semi transparent walls based on the refrac tive index values During execution a DEFINE_DOM_DIFFUSE_REFLECTIVITY function is called by FLUENT for each semi transparent wall and also for each band in the case of a non gray Discrete Ordinates Model Therefore the function can be used to modify diffuse reflectivity and diffuse transmissivity values at the interface Usage DEFINE DOM DIFFUSE REFLECTIVITY name t nb n an bdiff ref a diff tran a diff ref bdiff tran b Note that all of the arguments to a DEFINE macro need to be placed on the same line in your source code Splitting the DEFINE statement onto several lines will result in a compilation error Argument Type Description symbol name UDF name Thread t Pointer to the thread on which the discrete ordinate diffusivity function is to be applied int nb Band number needed for the non gray Discrete Ordinates Model real na
552. ute nodes and writes it to the file 6 The host closes the file Since the SERIAL HOST and NODE processes are performing different tasks the example below appears long and utilizes a large number of compiler directives If however as an exercise you make three copies of this example and in each copy delete the unused sections for either the SERIAL HOST or NODE versions then you will see that it is actually quite a simple routine Example Writing Data to a Common File on the Host Process s File System peaa o o kkk k kkk kkk kk kk kkk kkk kk kkk kk kkk LE This function will write pressures and positions for a fluid zone to a file on the host machine EEEE ooo oo D D ED OK HD OK include udf h define FLUID_ID 2 7 44 Fluent Inc September 11 2006 7 9 Writing Files in Parallel DEF INE_ON_DEMAND pressures_to_file Different variables are needed on different nodes if RP_HOST Domain domain Get_Domain 1 Thread thread cell_t c else int i endif if RP_NODE FILE fp NULL char filename press_out txt endif if PARALLEL int size data passing variables real array int pe endif Only Serial and Compute Nodes have data on threads if RP_HOST thread Lookup_Thread domain FLUID_ID endif if RP_NODE SERIAL or HOST if fp fopen filename w NULL Message n Warning Unable to open s for writing n filename else Message nWriting Pres
553. variable arguments to sub_thread_loop are subthread mixture_thread and phase_domain_index subthread is a pointer to the phase thread and mixture_thread is a pointer to the mixture level thread The mixture_thread is automatically passed to your UDF by the FLUENT solver when you use a DEFINE macro that contains a thread variable argument e g DEFINE PROFILE and your UDF is hooked to the mixture If the mixture_thread is not explicitly passed to your UDF you will need to use a utility macro to retrieve it before calling sub_thread_loop phase_domain_index is an index of subdomain pointers that can be retrieved using the PHASE_DOMAIN_INDEX macro See Section 3 3 2 Phase Domain Index PHASE DOMAIN INDEX for details The index be gins at O for the primary phase and is incremented by one for each secondary phase in the mixture Note that subthread and phase_domain_index are initialized within the sub_thread_loop macro definition Looping Over Phase Cell Threads in Mixture mp_thread_loop_c The mp_thread_loop_c macro loops through all cell threads at the mixture level within the mixture domain and provides the pointers of the phase level cell threads asso ciated with each mixture level thread This is nearly identical to the thread_loop_c macro Section 3 3 Looping Over Cell Threads in a Domain thread loop c when applied to the mixture domain The difference is that in addition to stepping through each cell thread the macro also return
554. variable named pres_av thread id in the text interface you can use the scheme command rp var define pres_av thread id 2 integer f Before you define a scheme variable it is often good practice to check that the variable is not already defined You can do this by typing the following command in the text window if not rp var object pres_av thread id rp var define pres_av thread id 2 integer f This command first checks that the variable pres_av thread id is not already defined and then sets it up as an integer with an initial value of 2 Note that the string is allowed in Scheme variable names as in pres av thread id and is a useful way to organize variables so that they do not interfere with each other Fluent Inc September 11 2006 3 71 Additional Macros for Writing UDFs 3 6 2 Accessing a Scheme Variable in the Text Interface Once you define a Scheme variable in the text interface you can access the variable For example if you want to check the current value of the variable e g pres_av thread id on the Scheme side you can type the following command in the text window rpgetvar pres_av thread id i It is recommended that you use rpgetvar when you are retrieving a FLU ENT variable using a scheme command This will ensure that you access the current cached value 3 6 3 Changing a Scheme Variable to Another Value in the Text Interface Alternatively if you want to cha
555. vel domain phase domain_index is an index of subdo main pointers It is an integer that starts with 0 for the primary phase and is incremented by one for each secondary phase Domain subdomain int phase_domain_index PHASE_DOMAIN_INDEX subdomain 3 62 Fluent Inc September 11 2006 3 4 Vector and Dimension Macros 3 4 Vector and Dimension Macros Fluent Inc has provided you with some utilities that you can use in your UDFS to access or manipulate vector quantities in FLUENT and deal with two and three dimensions These utilities are implemented as macros in the code There is a naming convention for vector utility macros V denotes a vector S denotes a scalar and D denotes a sequence of three vector components of which the third is always ignored for a two dimensional calculation The standard order of operations convention of parentheses exponents multiplication division addition and subtraction PEMDAS is not followed in vector functions Instead the underscore _ sign is used to group operands into pairs so that operations are performed on the elements of pairs before they are performed on groups Note that all of the vector utilities in this section have been designed to work correctly in 2D and 3D Consequently you don t need to do any testing to determine this in your UDF 3 4 1 Macros for Dealing with Two and Three Dimensions There are two ways that you can deal with expressions involving two and three
556. very iteration before transport equations are solved For an overview of the FLUENT solution process which shows when a DEFINE ADJUST UDF is called refer to Figures 1 9 1 1 9 2 and 1 9 3 Usage DEFINE_ADJUST name d Argument Type Description symbol name UDF name Domain d Pointer to the domain over which the adjust function is to be applied The domain argument provides access to all cell and face threads in the mesh For multiphase flows the pointer that is passed to the function by the solver is the mixture level domain Function returns void There are two arguments to DEFINE ADJUST name and d You supply name the name of the UDF d is passed by the FLUENT solver to your UDF Fluent Inc September 11 2006 2 2 General Purpose DEF INE Macros Example 1 The following UDF named my_adjust integrates the turbulent dissipation over the entire domain using DEFINE_ADJUST This value is then printed to the console window The UDF is called once every iteration It can be executed as an interpreted or compiled UDF in FLUENT PERO CAAA AA ARR RI I I I OKI RAKE ICA A A A KKK KEK A ACA kkk kkk k kkk UDF for integrating turbulent dissipation and printing it to console window BOAO DH DH DH ED OK I I I CIR AAR DH A A A ED CA ACA A A KKK KK A include udf h DEFINE_ADJUST my_adjust d Thread t Integrate dissipation real sum_diss 0 cell_t c thread_loop_c t d begin_c_loop c t sum_diss
557. vided where available Many of the examples make extensive use of other macros presented in Chapter 3 Additional Macros for Writing UDFs Note that not all of the examples in the chapter are complete functions that can be executed as stand alone UDFs in FLUENT Examples are intended to demonstrate DEFINE macro usage only Special care must be taken for some serial UDFs that will be run in parallel FLUENT See Chapter 7 Parallel Considerations for details Note that all of the arguments to a DEFINE macro need to be placed on the same line in your source code Splitting the DEFINE statement onto several lines will result in a compilation error Fluent Inc September 11 2006 2 1 DEFINE Macros 2 2 General Purpose DEFINE Macros The DEFINE macros presented in this section implement general solver functions that are independent of the model s you are using in FLUENT Table 2 2 1 provides a quick reference guide to these DEFINE macros the functions they are used to define and the panels where they are activated or hooked to FLUENT Definitions of each DEFINE macro are contained in udf h can be found in Appendix B e Section 2 2 1 DEFINE_ADJUST e Section 2 2 2 DEFINE_DELTAT e Section 2 2 3 DEFINE_EXECUTE_AT_END e Section 2 2 4 DEFINE_EXECUTE_AT_EXIT e Section 2 2 5 DEFINE_EXECUTE_FROM_GUI e Section 2 2 6 DEFINE_EXECUTE_ON_LOADING e Section 2 2 7 DEFINE_INIT e Section 2 2 8 DEFINE_ON_DEMAND e Section 2 2 9 DEFI
558. vitation vaporization pressure Mixture particle or droplet diameter Mixture temperature source Eulerian Mixture diameter Eulerian Mixture solids pressure Eulerian Mixture radial distribution Eulerian Mixture elasticity modulus Eulerian Mixture viscosity Eulerian Mixture temperature Eulerian Mixture bulk viscosity Eulerian frictional viscosity Eulerian frictional pressure Eulerian frictional modulus Eulerian granular viscosity Eulerian granular bulk viscosity Eulerian granular conductivity Eulerian DEFINE PROFILE DEFINE PROFILE DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE SOURCE DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY boundary condition Wall boundary condition Phase Interaction Phase Interaction Phase Interaction Phase Interaction Materials boundary condition Secondary Phase Secondary Phase Secondary Phase Secondary Phase Secondary Phase Secondary Phase Secondary Phase Secondary Phase Secondary Phase Secondary Phase Secondary Phase Secondary Phase Secondary Phase Fluent Inc September 11 2006 2 3 Model Specific DEFINE Macros 2 3 1 DEFINE CHEM STEP Description You can use DEFINE CHEM
559. w direction is the same as the face area normal direction as determined by F_AREA see Section 3 2 4 Face Area Vector F_AREA and is negative if the flow direction and 3 20 Fluent Inc September 11 2006 3 2 Data Access Macros the face area normal directions are opposite In other words the flux is positive if the flow is out of the domain and is negative if the flow is in to the domain Note that the sign of the flux that is computed by the solver is opposite to that which is reported in the FLUENT graphical user interface e g Reports gt Fluxes 3 2 5 Connectivity Macros FLUENT provides macros that allow the vectors connecting cell centroids and the vectors connecting cell and face centroids to be readily defined These macros return information that is helpful in evaluating face values of scalars which are generally not stored as well as the diffusive flux of scalars across cell boundaries The geometry and gradients involved with these macros are summarized in Figure 3 2 2 below To better understand the parameters that are returned by these macros it is best to consider how the aforementioned calculations are evaluated Assuming that the gradient of a scalar is available the face value of a scalar can be approximated by f po Vo dr 3 2 1 where dr is the vector that connects the cell centroid with the face centroid The gradient in this case is evaluated at the cell centroid where i
560. w suppose that you want to impose a non uniform x velocity to the turbine vane inlet which is described by the profile 2 Vs 20 20 e 5 8 1 1 where the variable y is 0 0 at the center of the inlet and extends to values of 0 0745 m at the top and bottom Thus the x velocity will be 20 m s at the center of the inlet and 0 at the edges To solve this type of problem you can write a custom profile UDF and apply it to your FLUENT model Fluent Inc September 11 2006 8 3 Examples 6 11e 01 5 52e 01 4 93e 01 4 34e 01 3 75e 01 3 16e 01 2 57e 01 1 98e 01 1 39e 01 7 96e 00 2 05e 00 Turbine Vane 1551 cells 2405 faces 893 nodes Velocity Vectors Colored By Velocity Magnitude m s Figure 8 1 3 Velocity Vectors for a Constant Inlet x Velocity Fluent Inc September 11 2006 8 1 Step By Step UDF Example 8 1 3 Step 2 Create a C Source File Now that you have determined the equation that defines the UDF Equation 8 1 1 you can use any text editor to create a file containing C code that implements the function Save the source code file with a c extension e g udfexample c in your working directory The following UDF source code listing contains a single function only Your source file can contain multiple concatenated functions Refer to Appendix A for basic information on C prog
561. wall function volume reaction rate DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE_SCAT_PHASE FUNC DEFINE SOLAR INTENSITY DEFINE SOURCE DEFINE SOURCE DEFINE SOURCE DEFINE_ SOURCE DEFINE SOURCE DEFINE SOURCE DEFINE SOURCE DEFINE SOURCE DEFINE SR RATE DEFINE SOX RATE DEFINE TURB_PREMIX_ SOURCE DEFINE _TURBULENT_ VISCOSITY DEFINE UDS FLUX DEFINE UDS UNSTEADY DEFINE_WALL_FUNCTIONS DEFINE_VR_RATE Materials Materials Materials Materials Materials Materials Materials Materials Materials Materials Materials Materials Radiation Model boundary condition boundary condition boundary condition boundary condition boundary condition boundary condition boundary condition boundary condition User Defined Function SOx Model User Defined Function Hooks Viscous Model User Defined Scalars User Defined Scalars boundary condition User Defined Function Hooks Fluent Inc September 11 2006 2 29 DEFINE Macros Table 2 3 4 Quick Reference Guide for Model Specific DEFINE Functions MULTIPHASE ONLY Function DEFINE Macro Panel Activated In volume fraction all multiphase models contact angle VOF heat transfer coefficient Eulerian surface tension coefficient VOF cavitation surface tension coefficient Mixture ca
562. where path is the directory in which you have installed the release directory Fluent Inc and x is replaced by the appropriate number for the release e g 1 for fluent6 3 1 to the src directory and name it makefile 6 Identify the architecture name of the machine that you are running from e g ultra This can be done by either typing the command fluent arch in the FLUENT TUI window or running the FLUENT utility program fluent_arch at the command line of a UNIX shell Note that if you are running a 64 bit version of FLUENT the architecture name will have a 64 appended to it e g ultra 64 7 In the library directory e g Libudf use the architecture identifier determined in the previous step to create directories for the FLUENT versions you want to build shared libraries for e g ultra 2d and ultra 3d Possible versions are 2d or 3d single precision serial 2D or 3D 2ddp or 3ddp double precision serial 2D or 3D 2d_node and 2d_host single precision parallel 2D 3d_node and 3d_host single precision parallel 3D 2ddp_node and 2ddp host double precision parallel 2D 3ddp_node and 3ddp host double precision parallel 3D Note that you must create two build directories for each parallel version of the solver two for the 3D version two for the 2D double precision version etc regardless of the number of compute nodes 5 12 Fluent Inc September 11 2006 5 3 Compile a UDF Using the TUI 5 3 2 Build the UDF Library
563. which refers to condenshumidlaw since only one user law has been defined The switching criterion is the local humidity which is computed in the domain using a DEFINE_ON_DEMAND function which again calls the function myHumidity for every cell In the case where the humidity is greater than 1 condensation is computed by applying a simple mass transfer calculation Otherwise one of FLUENT s standard laws for Vaporization or Inert Heating are applied depending on the particle mass The UDF requires one UDML and needs a species called h20 to compute the local humidity Fluent Inc September 11 2006 2 1 85 DEFINE Macros LR HRK HEAR OOO IR HE HR HRK OR KO ER HER a 3 2k a 2k 2k ak 2k 2k Concatenated UDFs for the Discrete Phase Model that includes a usage of DPM_SWITCH DD OK HE HD OK RI EEE DH A A ED 21 kkk KK HD include udf h include dpm h include surf h for macros RP_Cell amp RP_Thread include prop h for function Saturation_Pressure of water static int counter 0 static real dpm_relax 1 0 dpm source relaxation real H20_Saturation_Pressure real T real ratio aTmTp aTmTp 01 T 338 15 ratio 647 286 T 1 7 419242 aTmTp 29721 aTmTp 1155286 aTmTp 8 685635e 3 aTmTp 1 094098e 3 aTmTp 4 39993e 3 aTmTp 2 520658e 3 aTmTp x5 218684e 4 return 22 089e6 exp MIN ratio 35 real myHumidity cell_t c Thread t int i Mate
564. window Error format prints an error message to the console window Message The Message macro is a utility that displays data to the console in a format that you specify int Message char format The first argument in the Message macro is the format string It specifies how the remaining arguments are to be displayed in the console window The format string is defined within quotes The value of the replacement variables that follow the format string will be substituted in the display for all instances of Ztype The character is used to designate the character type Some common format characters are d for integers f for floating point numbers g for double data type and e for floating point numbers in exponential format with e before the exponent Consult a C programming language manual for more details The format string for Message is similar to printf the standard C I O function see Section A 13 3 Standard I O Functions for details In the example below the text Volume integral of turbulent dissipation will be displayed in the console window and the value of the replacement variable sum_diss will be substituted in the message for all instances of g Example Message Volume integral of turbulent dissipation g n sum_diss g represents floating point number in f or e format n denotes a new line FH It is recommended that you use Message instead of printf in compiled UDFs UNIX only
565. x 8 2 4 where X is the mass fraction of species a and K and Ko are constants The 2D planar domain consists of a 90 degree bend The duct is 16 inches wide and approximately 114 inches long A 6 inch thick porous region covers the bottom and right hand wall and the reaction takes place in the porous region only The species in the duct have identical properties The density is 1 0 kg m and the viscosity is 1 72x10 kg m s The outline of the domain is shown in Figure 8 2 16 The porous medium is the region below and to the right of the line that extends from the inlet on the left to the pressure outlet at the top of the domain P Grid Figure 8 2 16 The Outline of the 2D Duct Fluent Inc September 11 2006 8 37 Examples Through the inlet on the left gas that is purely species a enters with an x velocity of 0 1 m s The gas enters both the open region on the top of the porous medium and the porous medium itself where there is an inertial resistance of 5 m in each of the two coordinate directions The laminar flow field Figure 8 2 17 shows that most of the gas is diverted from the porous region into the open region 1 62e 00 1 46e 00 1 30e 00 1 14e 00 9 73e 01 8 11e 01 6 49e 01 4 87e 01 3 24e 01 1 62e 01 l 0 00e 00 Contours of Stream Function kg
566. x You will supply name the name of the UDF c t Pollut Pollut_Par and NOx are variables that are passed by the FLUENT solver to your function A DEFINE_NOX_RATE function does not output a value The calculated NO rates or other pollutant species rates are returned through the Pollut structure as the forward rate Pollut gt fwdrate and reverse rate Pollut gt revrate respectively FH The data contained within the NO structure is specific only to the NOx model Alternatively the Pollut structure contains data at each cell that are useful for all pollutant species e g forward and reverse rates gas phase temperature density The Pollut Par structure contains auxil iary data common to all pollutant species e g equation solved universal gas constant species molecular weights Note that molecular weights ex tracted from the Pollut Par structure i e Pollut Par gt sp IDX i mw has units of kg kg mol The reverse rate calculated by user must be di vided by the respective species mass fraction in order to be consistent with the FLUENT 6 3 implementation prior versions of FLUENT used explicit division by species mass fraction internally Example The following compiled UDF named user_nox exactly reproduces the default FLUENT NO rates for the prompt NO pathway Note that this UDF will replace the FLUENT rate only if you select the Replace with UDF option for the prompt NO pathway in the NO Model panel See Section 3 2
567. y specular_transmissivity real angle cos_theta real PI 3 141592 cos_theta NV_DOT ray_direction en angle acos cos_theta if angle gt 45 amp amp angle lt 60 xspecular_reflectivity 0 3 xspecular_transmissivity 0 7 Hooking a Discrete Ordinate Model DOM Specular Reflectivity UDF to FLUENT After the UDF that you have defined using DEFINE_DOM_SPECULAR_REFLECTIVITY is in terpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user_dom_spec_refl will become visible and selectable in the User Defined Function Hooks panel in FLUENT See Section 6 2 6 Hooking DEFINE_DOM_SPECULAR_REFLECTIVITY UDFs for details Fluent Inc September 11 2006 2 41 DEFINE Macros 2 3 7 DEFINE_GRAY_BAND_ABS_COEFF Description You can use DEFINE_GRAY_BAND_ABS_COEFF to specify a UDF for the gray band absorption coefficient as a function of temperature that can be used with a non gray discrete ordinate model Usage DEFINE GRAY BAND ABS COEFF name c t nb Argument Type Description symbol name UDF name cellt c Cell index Thread t Pointer to cell thread int nb Band number associated with non gray model Function returns real There are four arguments to DEFINE GRAY BAND ABS _COEFF name c t and nb You supply name the name of the UDF The variables c t and nb are passed by the FLUENT
568. you will first need to open the Phase Interaction panel see below by clicking Interactions in the Phases panel Define Phases Phase Interaction Drag Lift Collisions Slip Heat Mass Reactions Surface Tension Drag Coefficient phase 2 phase 1 user defined Edit custom drag 1ibudf i Cancel Help 6 48 Fluent Inc September 11 2006 6 3 Hooking Multiphase UDFs Next click on the appropriate tab e g Drag in the Phase Interaction panel and choose user defined in the drop down list for the corresponding exchange property e g Drag Coefficient that you desire This will open the User Defined Functions panel Make sure that you select Slip Velocity under Mixture Parameters in the Mul tiphase Model panel in order to display the drag coefficient for the Mixture model User Defined Functions custom_drag libudf user_cav_rate Figure 6 3 3 The User Defined Functions Panel Finally choose the function name e g custom_drag from the list of UDFs displayed in the User Defined Functions panel Figure 6 3 3 and click OK The function name e g custom_drag will then be displayed under the user defined function for Drag Coefficient in the Phase Interaction panel See Section 2 4 2 DEFINE EXCHANGE PROPERTY for details about DEFINE EXCHANGE PROPERTY functions Fluent Inc September 11 2006 6 49 Hooking UDFs to FLUENT 6 3 3 Hooking DEFINE_HET_RXN_R
569. ysical property UDF It is executed as an interpreted UDF in FLUENT Solidification via a Temperature Dependent Viscosity UDFs for properties as well as sources are called from within a loop on cells For this reason functions that specify properties are only required to compute the property for a single cell and return the value to the FLUENT solver The UDF in this example generates a variable viscosity profile to simulate solidification and is applied to the same problem that was presented in Section 8 2 2 Adding a Mo mentum Source to a Duct Flow The viscosity in the warm T gt 288 K fluid has a molecular value for the liquid 5 5 x10 kg m s while the viscosity for the cooler re gion T lt 286 K has a much larger value 1 0 kg m s In the intermediate temperature range 286 K lt T lt 288 K the viscosity follows a linear profile Equation 8 2 3 that extends between the two values given above u 143 2135 0 497257 8 2 3 This model is based on the assumption that as the liquid cools and rapidly becomes more viscous its velocity will decrease thereby simulating solidification Here no correction is made for the energy field to include the latent heat of freezing The C source code for the UDF is shown below The function named cell_viscosity is defined on a cell using DEFINE PROPERTY Two real variables are introduced temp the value of C_T cell thread and mu_lam the laminar viscosity computed by the f

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