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Coustyx Users Manual - Altair Partner Alliance

1. Name Default Type Uniform Velocity w Help Velocity Frequency Dependence Type Constant x Reakx 0 0 Imaginary X 0 0 Real y 0 0 Imaginary Y 0 0 Real 2 0 0 Imaginary Z 0 0 Impedence T Use Impedence Figure 9 16 Edit boundary conditions window Type in the new name Structural Velocity BC Select Structure Velocity from the drop down menu for Type The window in Figure 9 17 will appear Fill the Structure Name with Structmesh_0 or lt Struct mesh name gt For the current model there is no structure interface so leave Structure Interface Name blank Select Choose Default Options as interpolation options for mismatched meshes 9 4 Coustyx MultiDomain Model 309 New Boundary Condition MN gt Structure Velocity BC Interpolation Options for Mismatched Meshes Y Choose Default Options E 0 30480000000000 5 0000000000000 Figure 9 17 Edit structure velocity boundary condition window 310 Tutorial Gear Box Radiation Click OK to save the boundary condition e Create a new rigid boundary condition In the main model menu select Model Boundary Conditions Right click on Boundary Conditions and select New In the New Boundary Condition window type in the new name Rigid BC Select Uniform Normal Velocity from the drop down menu for Type Enter zero constant value
2. Sa Ed SE ents i2 Fill Hole Stop Slning Figure 5 31 Create Skin 130 Pre processing Features e To select a node in the GUI left click on it with the shift key held down Coustyr provides options to create new Triangle or Juadrilateral elements with linear quadratic or cubic interpolation schemes The coordinate nodes for the new element are read by selecting nodes in the GUI For the formation of a new element Coustyr needs the coordinate nodes to be assigned in the proper sequence Figure 5 33 shows the coordinate node connectivi ties for all the element shapes provided by Coustyx The coordinate nodes should be chosen in the same order as required by the node numbering shown in the Figure 5 33 The center nodes in higher order elements are optional and are absent for elements created through this function Once all the coordinate nodes are selected properly an outline of the new element is shown as a preview in the GUI If the element looks OK then create the new element by clicking on the Accept button At any time the selected nodes are deleted by clicking on Clear Node which deletes only the selected node or by clicking on Clear All Nodes which deletes all the nodes Shape The shape of the new element can be chosen to be either Triangle or Quadrilateral from the drop down menu Order The order of the coordinate interpolation used on the new element It can be either of the following three options Linea
3. Uniform Pressure Continuous v po Figure 6 22 Uniform Pressure Continous 6 4 Indirect BE Model BCs 169 New Boundary Condition x Name New BC Type Nonuniform Pressure Continuous Pressure 1 Ejfunction GetPressure in PosnVec 2 AngularFreq SoundSpeed WaveNumber and AmbientDensity are read only variables that can be used here The following is just an example change the formula to suil var PressMagn 12 0 var Press PressMagn exp i WaveNumber PosnVec 2 return Eval Press WOiInh bw OK Cancel Figure 6 23 Non Uniform Pressure Continous The pressure value is set by selecting any of the frequency dependent types Constant Table or Script 6 4 5 Non uniform Pressure Continuous BC This Boundary Condition is applied on elements with non uniform pressure on both sides of the boundary The BC is continuous which implies that the values of pressure at the same point on side 1 p and side 2 p are identical refer to Figure 6 16 for side 1 and side 2 definitions p x p7 x po x where po x is the pressure that varies with position x on the element The pressure is defined in the script by the function GetPressure which takes in the predefined position vector Posn Vec as the argument Other predefined variables such as AngularFreq w SoundSpeed c WaveNumber k 2 and AmbientDensity p c
4. Copy Paste Delete Open Analysis Sequenc Close Edit Help Load Freq Response Data Nastran OP2 File Clear Freq Response Data Nastran Punch File Ansys rst File Load Natural Mode Data Clear Natural Mode Data Figure 5 2 Loading frequency response data into Coustyr model 98 Pre processing Features 100 0000 Hz 130 0000 Hz 160 0000 Hz 180 0924 Hz 190 0000 Hz 220 0000 Hz 250 0000 Hz 280 0000 Hz 310 0000 Hz 338 2615 Hz 340 0000 Hz 370 0000 Hz 400 0000 Hz 430 0000 Hz 454 4722 Hz 460 0000 Hz 484 2651 Hz 490 0000 Hz 506 2977 Hz 520 0000 Hz 550 0000 Hz 580 0000 Hz 609 9999 Hz 640 0000 Hz 669 1083 Hz 670 0000 Hz 699 9999 Hz 729 9999 Hz 759 9999 Hz Figure 5 3 Select frequencies to load dialog box 5 1 Importing FE Data 99 5 1 2 3 Ansys rst File Coustyx can retrieve the frequency response data from ANSYS results file in rst format 5 1 2 4 Ansys rfrq File Coustyx can retrieve the frequency response data from ANSYS results file in rfrq format 5 1 2 5 I DEAS Universal File Coustyx provides translator to retrieve the frequency response data from files in I DEAS Universal file format 5 1 2 6 Abaqus Output File The ABAQUS odb file is the output database file from the ABAQUS FE analysis Currently Coustyz does not provi
5. Table 7 8 IS03745 Coordinates of microphone positions on a sphere 3 Microphone a a position 1 1 0 0 05 2 0 49 0 86 0 15 3 0 48 0 84 0 25 4 0 47 0 81 0 35 5 0 45 0 77 0 45 6 0 84 0 0 55 7 0 38 0 66 0 65 8 0 66 0 0 75 9 0 26 0 46 0 85 10 0 31 0 0 95 11 1 0 0 05 12 0 49 0 86 0 15 13 0 46 0 84 0 25 14 0 47 0 81 0 35 15 0 45 0 77 0 45 16 0 84 0 0 55 17 0 38 0 66 0 65 18 0 66 0 0 75 19 0 26 0 46 0 85 20 0 31 0 0 95 Fixed Positions Choose this option to specify an array of fixed microphone positions associated with equal partial areas distributed over the sphere surface Number of Probe Positions Choose the number of microphones to be 20 or 40 from the drop down menu In general 20 microphone positions are suf ficient However when the source has high directivity increase the number of microphone positions to 40 Table 7 8 lists coordinates of 20 microphone positions The additional 20 point array can be obtained by rotating the original array by 180 about the Z axis Coaxial Circular Paths Figure 7 34 shows coaxial circular paths in parallel planes traversed by a microphone over the top half of the sphere Repeat the same for the bottom half of the sphere with heights chosen symmetrical to the top half paths The paths are selected such that the annular area associated with each path is the same Number of Circular Path
6. where Zo poc is the characteristic impedance of the fluid medium c is sound speed po is ambient density k w c is wave number w is frequency in radians sec and j 1 Note that the amplitude A has dimensions M T whereas the volume velocity V has dimensions ERE The wave equation for a monopole source in frequency domain and its solution is given by V p r k p r jkZoV r R 4 3 cjklr R E ejklr R p r T 4r r R JKZoV TRI 4 4 where p r is sound pressure at position r x y z New Source r ID Type Position Vector X component Y component Z component Source Strength Strength Type Volume Velocity Real 1 0000000000000 Imaginary 0 0 GD ea Figure 4 38 Monopole Position Vector The location R of the monopole source is set by X component Y com ponent and Z component Note that the units should be consistent with the geometry units Source Strength The monopole source strength could be set to be any of the following two types Amplitude A or Volume Velocity V Choose the type from the drop down menu Strength Type Then define the value of the monopole source strength amplitude A or volume velocity V through any of the frequency dependent types Constant Table or Script Note that the units used here should be consistent with the rest of the model inputs 4 5 Acoustic Sources 87 4 5 2 Plane Wave Q x y 2 R xr yr
7. 8 6 15 Function Definition Functions may be defined anywhere using a declaration of the form function IDENTIFIER lt parameterlist gt lt statement gt The identifier IDENTIFIER is the name assigned to the function lt statement gt is a simple or compound statement that forms the body of the function Here lt parameterlist gt is a list 8 6 Statements 279 of zero or more parameter declarations separated by commas Each parameter may be an in parameter an out parameter or an inout parameter Accordingly the parameter declarations are of the form in IDENTIFIER out IDENTIFIER inout IDENTIFIER Here IDENTIFIER is the name of the parameter The value of an in parameter cannot be modified in the body of the function The value of an out variable is initially undefined and must be set in the function body The value of an inout variable is already defined and may also be modified in the function body The return statement is used to transfer control out of a function The return statement can optionally return a value to the calling routine The return statement is of one of the following two forms return return lt exp gt The first form of the return statement returns the value 0 and the second form returns a copy of the expression lt exp gt Example function Factorial in n if n 1 return 1 else I return Eval n Factorial n 1 Out Factorial 4 Out Factorial 5 Output 24 1
8. To hide selected nodes click on Hide To merge coincident nodes among the selected nodes click on Merge Coincident Pn Nodes Merge Coincident Sigma Nodes When a node is mistakenly split this function would be helpful to get back to the original state Left click with shift key held down to select elements and add them to Group 1 Group 2 by clicking on Add to Group 1 Add to Group 2 See Figure 5 44 and Figure 5 45 The elements added to Group 1 are displayed in Red and the elements added to Group 2 are displayed in Blue To delete elements from a Group select the element and click on Delete from Group 1 Delete from Group 2 Note We need to first create two different groups of elements between which common nodes are split After adding elements to Group 1 and Group 2 click on Split All Shared Pn Nodes between Groups Split All Shared Sigma Nodes between Groups to split all shared nodes between Group 1 and Group 2 See Figure 5 46 To split only few selected nodes not all shared nodes between elements belonging to Group 1 and Group 2 first select nodes by left clicking on them while holding down the shift key then click on Split Pn Nodes between Groups Split Sigma Nodes between Groups Only selected nodes are split between Group 1 and Group 2 See Figure 5 47 and Figure 5 48 Note It is important to understand that if a node to be split is shared not only between elements belonging to Group 1 and Group 2 but also between
9. inch pound force second foot pound force second other Length scale factor 1 0000000000000 Mass scale factor 1 0000000000000 Note Model units are presently only used in the computation of sound power levels from ISO standards Modifying model units does not rescale the model oa Lene Figure 4 16 New model dialog box 4 3 Model Setup 53 4 3 1 2 Indirect Model An Indirect model is created to solve the acoustic problem using the Indirect Boundary Integral Formulation The primary variables used in this formulation are pressure jumps Or pressure discontinuities and velocity jumps or velocity discontinuities across the boundary These are also known as double layer potentials u and single layer potentials 0 respectively The single layer potential is the difference between the normal derivative of pressures on positive p and negative p sides of an element that is o P Ph The double layer potential 1 is the difference between the pressures on the positive p and negative p sides of an element that is p p p This formulation solves both the upper and lower sides of the boundary simultaneously For a closed mesh it solves both the exterior and interior domains at once Note that only one mesh is allowed in this model type Table 4 3 shows some of the important differences between MultiDomain and Indirect models Variable Node Concept The concept of Varia
10. 66 Getting Started File Edit Preferences Help Olesa Ble lelole Sale E lt Model E Type lt Indirect gt Version lt 1 00 00 gt Model Description Materials Planes Coord Nod A Elements Rename di Sigma Nod Copy En Mu Nodes Paste w Pn Nodes Delete Boundary CJ Sources Open J Jump Conc Close i Junction Edit AG Sets a Helg E Context Script Bese Analysis Seque Helium Figure 4 24 Selecting Material 4 3 Model Setup 67 4 3 8 4 Sigma Nodes Select Model Indirect BE Mesh Sigma Nodes Use this sub tree member to review Sigma Nodes Sigma Nodes are variable nodes associated with the single layer potential at the location of the node The single layer potential at a point is defined as the difference of the normal derivative of pressures on the positive side p of the element to the negative side p that is o p ph Single layer potential 0 and double layer potential u are the primary acoustic variables in the Indirect BE formulation used for Indirect models The right click menu provides the following options Open Opens the list of all Sigma nodes The table shows the Sigma node ID its location coordinates X Y Z and the Status of the node The Status is determined by the solid angle covered by the node When the solid angle is 47 the status shows On Free Edge Close Closes the opened Sigma nodes window 4 3
11. Air Right click on Air and select Edit Figure 9 38 will appear a Name Air SpeedSound Frequency Dependence Type Real 343 00000000000 Imaginary 0 0 AmbientDensity Frequency Dependence Type Constant gt Value 1 2100000000000 Figure 9 38 Edit material properties e Type in the name of the material as Air e Define SpeedSound as a constant with value 343 m s The unit is consistent with the unit of length m in the structure mesh e Define AmbientDensity as a constant with value 1 21 kg m The unit is consistent with the unit of length m in the structure mesh 330 Tutorial Gear Box Radiation 9 5 1 6 Fill Holes e Open the Coustyx BE mesh from the main model menu by selecting Model Indirect BE Mesh Right click on it and select Open to view the boundary element mesh in the GUL Select the tabbed window Fill Hole from the series of tabs located below the BE mesh Follow the instructions given earlier in Section 9 5 1 4 to display element edges in the mesh Left click on the elements around the edge of a hole while holding the shift key Make sure to select elements with nodes on the hole edge similar to the Figure 9 33 Right click on the mesh while holding down the shift key to view the context menu and select Selected Elements Display Connected Nodes similar to the Figure 9 36 Left click on the displayed nodes while holding the shift key to pick the nodes on the edge of
12. Frequency Dependence Type Constant y realo o Imaginary 0 0 Figure 6 29 Discontinous Uniform Pressure be specified by selecting any of the frequency dependence types Constant Table or Script Figure 6 29 6 4 10 3 Non uniform Pressure This Boundary Condition is applied on the side of the element where pressure varies with position The pressure is defined in the script by the function GetPressure which takes in the predefined position vector Posn Vec as the argument Other predefined variables that can be used in the script are AngularFreq w SoundSpeed c WaveNumber k and AmbientDensity p Figure 6 30 6 4 10 4 Uniform Normal Velocity This Boundary Condition is applied on the side of the element where the normal velocity is uniformly distributed The normal velocity values can be specified by selecting any of the frequency dependence types Constant Table or Script The user should be aware that the normal velocity defined here is in the direction of the element normal Figure 6 16 Figure 6 31 Use Impedance can be used to specify impedance Refer to Section 6 3 for more details Figure 6 31 6 4 10 5 Uniform Velocity This Boundary Condition is applied on the side of the element where the velocity vector is uniformly distributed That is there is no variation of velocity components vz vy vz with position over an element The velocity vector components values can be specified by
13. Note 0 1 2 3 4 5 6 2 is not valid Transfm Matrix 1 2 0 1 o 1 1 07 1 2 1 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 8 6 Statements All simple statements are terminated by a semi colon The statement is not processed until the semicolon is entered A statement does not have to be contained entirely in one line 8 6 1 Declaration Statement The first type of statement is a declaration statement It simply declares one or more vari ables for later use If a variable is used without being formally declared an error is generated Examples var x var X y Z 8 6 2 Expression Statement The second type of statement is an expression followed by a semicolon Set_Surface_Pairs Conformal CrankCase Body InnerSeal OrbitingScroll_Body PressureSurface Friction_Coeff Separation_Tolerance_Conf 1 1 x1 x2 x3 Fixed_Frame 268 Language Syntax l Conformal CrankCase Body OuterSeal OrbitingScroll Body PressureSurface Friction Coeff Separation Tolerance Conf 1 1 x1 x2 x3 Fixed Frame 8 6 3 Assignment Statement The next type of statement is an assignment Symbolic assignment Planet 3 Runout Error 0 001 e1 0 00003 e2 Evaluated assignment Planet 1 Runout Error 0 001 e1 0 00003 e2 8 6 4 Declaration with Assignment A value can be assigned to a variable at the same time that it is being declared var x 1 y z 3 Arrays are allocated using the Di
14. try lt statement1 gt catch lt statement2 gt try lt statementi gt catch IDENTIFIER lt statement2 gt The statement lt statement1 gt is executed during the normal course of execution If while exe cuting this part of code an exception is thrown then control gets transferred to the statement lt statement2 gt The exception may be thrown anywhere inside lt statement1 gt or even inside functions called by it These exceptions are thrown by the throw statement which takes one of the following two forms throw throw lt exp gt here lt exp gt is any expression Just like in the return statement this expression must not be dependent on any variables not visible to the routine that will catch this thrown exception When this statement is executed control is transferred to the lt statement2 gt part of the inner most try catch statement that encloses this throw statement The IDENTIFIER in the try catch statement is assigned the expression lt exp gt Example function Factorial in n if n lt 0 throw Factorial of negative number attempted if n gt 75 throw Overflow if n 1 return 1 else I return Eval n Factorial n 1 try Out Factorial 4 Factorial 4 Out Factorial 5 Factorial 5 Out Factorial 4 5 Factorial 4 5 catch message Out Eval Error message Output 8 6 Statements 283 Factorial 4 24 Factorial 5 120 Error Factorial
15. 97 Select frequencies to load dialog box o o e 98 Loading natural mode data into Coustyx model o o 100 Select natural frequencies to load dialog box o o 101 Copy the mode data to the frequency response data 102 Alert message displayed before copying mode data to frequency response data 103 EXPOBE MES os a ef a ai di Rd A AAA RA 104 LIST OF FIGURES xiii 5 9 5 10 5 11 5 12 5 13 5 14 5 15 5 16 Df 5 18 5 19 5 20 5 21 5 22 5 23 5 24 5 25 5 26 5 27 5 28 5 29 5 30 5 31 5 32 5 33 5 34 5 35 5 36 5 37 5 38 5 39 5 40 5 41 5 42 5 43 5 44 5 47 5 48 Damping ratios edit dialog box s s so varar dd bakke AG ke awd 105 Select modes by frequency range o rar eee reese 106 Edit selected modal damping ratios using Frequency dependent values 107 Edit selected modal damping ratios using Rayleigh damping coefficients 108 Apply nodal force and moment lt s i s s cas e s e doe a a a a e p a a a e a A 108 Perform modal superposition 2 ss 4s ae kaka d d bee ee nee b de 110 Participating modes selection s sa 8 84 4 88 4 Ska SE RR 111 Coishr GUIs FIL Holes ssa oy RS EEG OE EE a we SS SG Ge 112 Fill Hole Parameters 44 2 2444444446646 Seta dundee Paes 113 Display Connected Nodes sa vev s eosa eee BRR ee We eee ee 114 Press Skin Create Skin to check for incompatible elements
16. Contact us to renew your expired license Click on the Copy License Information button to copy the information if you need to send us your license details Press OK to install the license key and exit the window or press Cancel to discard changes before exiting the window Figure 2 5 2 3 License Key Installation Install License Key HA Computer ID 0021708A7C31705F22AA Use Network Dongle Server Host Name lt Unavailable Server Name gt Find Dongle Dongle ID lt Unavailable Dongle ID gt License Key 185b286b 185b286b 185b286b 185c28694e5b7c3a 1d0a7e3a4609726c430a253a 150a In order to get a License Key copy the Computer ID and email it to sales ansol com The License Key will be e mailed back to you If you skip this step for now you can install License Key later using the Install License Key icon Coustyx will not run unless a valid License Key has been installed Figure 2 3 Install License Key window Installing Coustyx Install License Key mn License Key License Features Computer ID 0021708A7C31705F22AA Use Network Dongle Server Host Name lt Unavallable Server Name gt Find Dongle Dongle ID Sentinel USB E5608EF2531F12634832 3 Nov 2009 License Key 185b286b 185b 286b 185b286b 185 28694e 5b7c3a 1d0a7e3a4609726c430a253a 150a In order to get a License Key copy the Computer ID and email it to sales ansol c
17. Elements Sigma Nodes Mu Nodes Pn Nodes E Boundary Conditions E Default Boundary Conditions s E ee Rename Sources z E CJ Jump Conditions 24 Paste E Zero Jump Junction Constraint __ PAE a Sets Open Context Script Close 9 Analysis Sequences Edit Help Figure 6 5 New Boundary Condition 152 Boundary Conditions 6 3 1 Dummy BC This Boundary Condition is applied on elements which have no interaction with the fluid medium They don t contribute to the acoustic radiation Figure 6 6 For example Dummy BC could be used on elements lying on a ground plane as these elements don t interact with the fluid medium File Edit Preferences Help oela Er Model E Type lt MultiDomain gt LE Version lt 1 33 00 gt 3 Model Description E lt Structures structmesh2 Materials Planes Interfaces Boundary Conditions 13 Default New Boundary Condition xj E Hole 1 BC 5 Hole 2 BC Name New Dummy BC 3 Direct BE Meshes ro FE Meshes Test Dummy 7 Help n structmesh2 E Domains 3 Context Script Analysis Sequences Figure 6 6 Dummy Boundary Condition 6 3 2 Interface BC This Boundary Condition is applied on the boundary of an interface between two domains in a MultiDomain model Physical details of the interface are provided in the Model Interfaces Figure 6 7 6 3 2 1 Interface Name Defines the name of the acoustic interface Figure
18. Fill the Structure Name with Structmesh 0 or lt Struct mesh name gt For the current model there is no structure interface so leave Structure Interface Name blank Select Choose Default Options as interpolation options for mismatched meshes Click OK to save the boundary condition e Create a new rigid boundary condition In the main model menu select Model Boundary Conditions Right click on Boundary Conditions and select New In the New Boundary Condition window type in the new name Rigid BC 332 Tutorial Gear Box Radiation New Boundary Condition Structure Velocity BC Type Structure Velocity Continuous Structure Info Structure Name Structmesh 0 Structure Interface Name Interpolation Options for Mismatched Meshes Y Choose Default Options User Options Ca coma Figure 9 41 Edit structure velocity boundary condition window Select Uniform Normal Velocity Continuous from the drop down menu for Type Enter zero constant values for the real and imaginary values of the normal velocity Click OK to save the boundary condition 9 5 1 8 Apply Boundary Conditions The boundary conditions defined earlier are applied to the elements in the Coustyx BE mesh before running acoustic analysis e Apply structure velocity boundary condition to all the elements in the Coustyx BE model Select Model Indirect BE Mesh Rig
19. Select Model Domains lt Domain Name gt Direct BE Meshes lt Direct BE Mesh Name gt Xfm Matrix This defines a 4x4 coordinate transformation matrix The current location of the mesh in the domain is obtained by applying the transformation to all the coordinates of the BE mesh The default transformation matrix is a unit matrix which places the BE mesh at its original position The transformation matrix is given by Ry Ria Rig Ax Ra Roo Ro Ay Ra R32 R33 Az 0 o 0 1 4 3 Model Setup 73 File Edit Preferences Help Hell Hele skje E Model E Type lt MultiDomain gt version lt 2 00 00 gt Model Description Structures Materials CJ Planes CJ Interfaces Boundary Conditions Y Direct BE Meshes FE Meshes B C Domains E C7 AD 1 E Type Direct BE gt E Material lt Air gt Boundedness lt Bounded gt C Direct BE Meshes Rename E Chief Points iy E Context Script erd O Analysis Sequences Delete Open Close Edit Boundedness Unbounded e Bounded Figure 4 28 Choosing Boundedness 74 Getting Started where the first 3x3 entries are for rotation transformation Ax Ay Az are the translations in x y and z directions Note that the above transformation matrix is a general matrix that can be applied to an absolute vector s such as position vector or to a relative vector n such as normal and velocity vector These vectors are represented in Cou
20. Set Path Add Folder after opening Matlab 7 2 2 2 Import From File The sensor coordinates can be imported from an ASCII file with components separated by commas tabs or spaces The file must contain three columns representing X Y and Z coordinates of a sensor Figure 7 21 Each new sensor is added to a new row Import Options window opens up after the selection of the file with the following options Whether to replace the table or append the data to it The imported data from the file can be used to either replace the current table or append to the existing table by the selection of one of the options Replace or Append Figure 7 21 Scale factor All the values in the ASCII file are multiplied by the Scale factor before being read into the table Figure 7 21 This is specifically useful when the imported file has different units compared to Coustyx model A unit conversion factor should be used as the Scale factor to convert these values For example when the coordinates in the ASCII file are in m and the Coustyz units are in mm a Scale factor of 10 is entered to convert the 216 Analysis Sequences Analysis Sequence Name Analysis Sequence Description Solver Controls Frequency Ranges Outputs Script Binary Results Sensors IGlass Sensors Y Create an Ascii Sensors File File Name sensors dat Browse Sensor Coordinates Import from file Figure 7 20 Sensor out
21. Undo Redo Cut Copy Paste Select all Match braces Search Previous Search Previous Selected Undo the last action Redo the last action Cut the selected text Copy the selected text Paste the text in clipboard Select the entire text in a script Match opening and closing braces in a script Do backward search for the word typed in the search text box Search criteria include Case sensitivity search Case Whole word search Word and Regular expression search RegExp Do backward search for the word selected in the script Search criteria include Case sensitivity search Case Whole word search Word and Regular expression search RegExp 4 1 Main Menu Features Table 4 1 continued Menu Items Description Search Next Search Next Selected Do forward search for the word typed in the search text box Search criteria include Case sensitivity search Case Whole word search Word and Regular expression search RegExp Do forward search for the word selected in the script Search criteria include Case sensitivity search Case Whole word search Word and Regular expression search RegExp Search Search Page Browse through multi page window to view First Previous Next and Last pages Analysis Run Run the selected Analysis Sequence Abort Abort the current analysis run Preferences Common Figure 4 2 Show splash screen on start up Show log messages V
22. tions Refer to Section 6 4 for a detailed discussion on different types of boundary conditions available for an Indirect model The user defines the boundary conditions as separate entities which are named uniquely and these are applied over BE elements directly or through sets group of elements before running the analysis refer to Section 6 5 2 e Define a New Boundary Condition Right click on Boundary Conditions and se lect New and proceed with entering new parameters information Click OK to accept Figure 4 25 e Edit an Existing Boundary Condition Select Boundary Conditions lt Boundary Condition Name gt Right click on lt Boundary Condition Name gt and select Edit Pro ceed with editing the parameters Click OK to accept 4 3 8 8 Sources Select Model Indirect BE Mesh Sources This is used to include acoustic sources in the model Available acoustic sources in Coustyx are Monopole Dipole Quadrupole Plane Wave Cylindrical and User Defined Refer to Section 4 5 for detailed discussion on how to define an acoustic source To add a new acoustic source right click on Sources and select New Figure 4 26 The right click menu items Edit and Delete are used to edit and delete selected sources 4 3 8 9 Jump Conditions Select Model Indirect BE Mesh Jump Conditions The Jump conditions in the Indirect model can be reviewed here Right click and select Open to see the list of Mu nodes and their jumps in
23. x n Uno x n 6 4 9 Structure Velocity Continuous BC Structure Velocity BC is the most common Boundary Condition in the industry This can be loaded from frequency response analysis of the structure FEA done externally Refer to Section 5 1 2 for details on how to load frequency response data Figure 6 27 172 Boundary Conditions New Boundary Condition sen Name Structure Velocity BC Type Structure Velocity Continuous y Helo Structure Info Structure Name Structmesh_0 X Structure Interface Name Interpolation Options for Mismatched Meshes E Choose Default Options User Options Number of Interpolatina Points 4 Maximum Search Distance 0 30480000000000 Y Terminate Search if Percentage Weight of Farthest Point is lt 5 0000000000000 Ce Les Figure 6 27 Structure Velocity Continous 6 4 9 1 Structure Name Select the structure name from which the BCs are applied Figure 6 27 6 4 9 2 Structure Interface Name Select the structure interface from which the BCs are applied A structure interface is a group of faces of FEA elements in contact with the fluid medium Each structure interface is uniquely identified by the structural mesh ID element ID and the local face number on the element If this field is left blank the structure velocity is applied directly from the structure Figure 6 27 6 4 9 3 Interpolation Options for Mismatched Meshes Refer to Section 6 2
24. 1 Co 1 theta 0 71 1 1 theta 0 73 6 A tx theta 0 72 2 1 theta 0 74 24 1 C000 5 t 1 71 1 0 25 t 1 72 2 0 375 t 1 73 6 Scope of returned values When a function returns an expression the expression should not be dependent on any variable that is not visible to the calling routine function g var n 1 return Eval n function f var n 1 return n Out Eval g This is OK Out Eval This will generate an error the variable n is not visible here Functions may be defined in a separate file The name of the file should be the same as that of the function with the extension clx Example Contents of file hex clx function hex in x var Table 0 1 2 3 4 5 16 7 gE ge MAN BU EN p EN F if x lt 0 throw Invalid input to hex routine if x int x 0 throw non integer input to hex routine if x lt 16 I return Eval Table x 1 else I var ni int x 16 var n2 x 16 n1 return Eval hex n1 hex n2 Input to Coustyz Out hex 3 Out hex 13 Out hex 6876 282 Language Syntax Output 3 D 1ADC 8 6 16 try catch and throw Statements The try catch and throw statements form a exception handling mechanism They offer an alternative to goto statements when trying to gracefully recover from an error try catch statement is of one of the two following forms
25. 116 Select all Bad Elements s can ha a a SG ee eG Sw eee 117 Add Bad Elements to a Set 2 2 0 0 ee 118 Display Set of Bad Elements o 264 0205 4 444 bb eee ee dd ee ad oe 119 Display Connected Nodes of Selected Element oo 120 Display Connected Elements of Selected Node o 120 Mesh with free edges shown in blue color 2 0 0 0 0 a 123 Create Seams ocdi dadas sia aa A a 124 Select Elements for Creating a Seam 126 Display Connected Nodes for Selected Elements o 127 Choose Nodes for Creating Seams eee eee eee 128 Accept Sean 2 24 420 one ae ba wade ea eae se GAS ke Sed 128 Create OKIE amaia ote BE AA RE ee ne Sele a 129 Create new element window vr rn knr eee eee 130 New elements coordinate node connectivity 2 arv vr vr kr kr kran 131 Stitch Seam Dialog Panel va og sage s saka Sess aa Se ae GE wee 132 Select Elements si 0 606 rest es SANE SEA SAA ee seen 133 Display Connected Nodes for Elements o 134 FE E EE be he 134 SEND eee BG kl he GA ER GSE Gs AR EE 135 Transparent elements shown for inspection before Stitching Seams 135 Complete Stitched Seam 41 st sann eee bbe bee GS SG ee GAs 136 Delete element window 0000 0 knr ee 136 Merge Nodes window csat s eg aaie mau aiana a ee 137 Split Pn Nodes Split Sigma Nodes window showing duplicat
26. Clicense Key 495f7c694c5129371b0228334e027c344f002d331f037c334b57736143072537150 In order to get a License Key copy the Computer ID and email it to sales amp ansol com The License Key will be e mailed back to you If you skip this step for now you can install License Key later using the Install License Key icon Coustyx will not run unless valid License Key has been installed Figure 2 8 Steps to install a network dongle 14 Installing Coustyx OK to install the license key and exit the window or press Cancel to discard changes before exiting the window Figure 2 5 2 3 1 4 If you are using a Demo Model If you are using a demo model posted on our web site you do not need to install a license key The demo models have embedded license keys which are valid only for those models Any changes to the model will make the license key invalid 2 3 2 Use Altair GridWorks License Coustyx has partnered with Altair to enable users run Coustyx under Altair s GridWorks License Management ALM system For more information on GridWorks License Management system contact your local Altair software distributor or visit http www altair com Under this licensing system a predetermined number of tokens also called GridWorksUnits GWUs will be drawn from the Altair License server each time Coustyx is invoked These GWUs are returned to the server once the user exists Coustyx The number of GWUs drawn
27. Figure 5 6 Copy the mode data to the frequency response data 5 2 Exporting Mesh 5 3 Forced Response Analysis using Modal Superposition 103 Alert i Es This action will clear any existing frequency response data to copy A current mode data Do you want to proceed Figure 5 7 Alert message displayed before copying mode data to frequency response data Coustyx provides option to export a structure mesh or a boundary element mesh to a Nastran bulk data format To export a mesh Right click on the lt Structure Mesh Name gt or lt Boundary Element Mesh Name gt and select Export Nastran Bulk Data bdf File see Figure 5 8 5 3 Forced Response Analysis using Modal Superposition Select Model Structures lt Structure Mesh Name gt The frequency response data which is applied as the structure velocity boundary condition could either be imported from an external finite element forced response analysis see Sec tion 5 1 2 or could be directly computed within Coustyx for the case when the natural modes of the structure are already available Coustyx uses modal superposition method to compute the forced response analysis Follow the steps below to compute the forced response using Coustyx e Load natural mode data Load natural modes computed from any external finite el ement modal analysis Note Make sure the modes are ortho normalized with respect to the finite element mass matrix e Modify modal dam
28. Figure 7 40 Specify the value of L2 such that it satisfies the definition L2 12 2d where 12 is the reference box dimension in Y direction and d is the measurement distance The recommended value for d 1m L3 Length of the parallelepiped in Z direction Figure 7 40 Specify the value of L3 such N1 N2 N3 that it satisfies the definition L3 13 d where 13 is the reference box dimension in Z direction and d is the measurement distance The recommended value for d 1 m Number of subdivisions in X direction Figure 7 40 Select the value of N1 such that the length of the rectangular partial area formed by these subdivisions satisfies the criterion El lt 3d where Ll is the length of parallelepiped in X direction and d is the measurement distance Refer Figure 7 37 The microphone positions are in the center of each partial area and at each corner of the partial area excluding the corners intruding into reflecting planes Number of subdivisions in Y direction Figure 7 40 Select the value of N2 such that the length of the rectangular partial area formed by these subdivisions satisfies the criterion F lt 3d where L2 is the length of parallelepiped in Y direction and d is the measurement distance Refer Figure 7 37 The microphone positions are in the center of each partial area and at each corner of the partial area excluding the corners intruding into reflecting planes Number of subdivisions in Z direc
29. Hz Damping Ratio 0 000 gt lt Natural Frequency 3036 3101 Hz Damping Ratio 0 000 gt lt Natural Frequency 3127 1084 Hz Damping Ratio 0 000 gt Mathes Eramianru 2157 6427 fiz Namnina Dstin NAN CRMC KKK KKK KKK CS Figure 5 15 Participating modes selection 112 5 4 Fill Hole Pre processing Features The Fill Hole tabbed window is located at the bottom pane of the Mesh Viewer window Figure 5 16 Coustyz uses an Optimized Delaunay Triangulation Method to fill holes The parameters used are shown in Figure 5 17 First we will explain each of the parameters in the Figure 5 17 and then discuss the procedure to fill a hole Figure 5 16 2 Structmesh 0 C selected Coord Nodes Cy Selected Elements 3 Fil Hole lt skin E stitch Seams E Delete Elements 3 Element Orientation Delaunay Triangulation Optimization Parameters Fill Parameters 7 Maximum Number of Iterations 3600 4 Element Type LINEAR Minimum Triangle Vertex Angle 30 a New Set Name Hoe Maximum Triangle Area Ratio 15 Fill Hole Figure 5 16 Coustyx GUI Fill Hole 5 4 1 Delaunay Triangulation Optimization Parameters 5 4 Fill Hole 113 C Selected Coord Nodes Selected Elements Fill Hole S Skin EJ Delete Elements EJ Element Orientation Delaunay Triangulation Optimization Parameters Fill Parameters Element Type LINEAR v Maximum Number of Iteration
30. Install License Key window by clicking on the icon found in the Start menu Start All Pro grams Coustyx32 or Coustyx64 InstallLicenseKey Choose the license scheme Use Na tive License From the tabbed window License Key select the option Use Network Dongle Figure 2 8 Enter the Server IP Address or Server Name in the Server Host Name box and click on Find Dongle to look for the network dongle When the local computer finds a network dongle the Dongle ID will be updated The license key will have already been sent to you with the dongle or by email Copy and paste the license key into the License Key box You can verify the features licensed under this key from the tabbed window License Features Figure 2 6 If the license key is invalid or expired appropriate information is highlighted Figure 2 7 Contact us to renew your expired license Click on the Copy License Information button to copy the information if you need to send us your license details Press OK to install the key on to the network dongle and exit the window or press Cancel to discard changes before exiting the window Figure 2 5 Step 3 Register Server Name Make sure you register the server name on local computers that run Coustyx Open Install License Key window by clicking on the icon found in the Start menu Start All Programs Coustyx32 or Coustyx64 InstallLicenseKey Choose the license scheme o
31. New Boundary Condition s Name New BC Type Structure Velocity v Help Structure Info Structure Name Structmesh 0 X Structure Interface Name Interpolation Options for Mismatched Meshes E Choose Default Options User Options Number of Interpolating Points 4 Maximum Search Distance 0 30480000000000 V Terminate Search if Percentage Weight of Farthest Point is lt 5 0000000000000 Impedence Z Use Impedence a Gen Figure 6 13 Structure Velocity BC 6 3 8 1 Structure Name Select the structure name from which the Boundary Conditions are applied Figure 6 13 6 3 8 2 Structure Interface Name Select the structure interface from which the Boundary Conditions are applied structure interface is a group of faces of FEA elements in contact with the fluid medium Each structure interface is uniquely identified by the structural mesh id element id and the local face number on the element If this field is left blank the structure velocity is applied directly from the structure Figure 6 13 6 3 8 3 Interpolation Options for Mismatched Meshes Refer to Section 6 2 6 3 8 4 Use Impedance When this option is enabled the impedance Z relates the pressure p at the surface of the acoustic material to the particle normal velocity Uni and the structure velocity Un walt Refer Section 6 1 for the definition of impedance implemented in Coustyx The impedance 160 Boundary Conditions New
32. Once the skin is created select Skin Create Mesh From Skin to generate a boundary element mesh e To verify the creation of boundary element mesh from the main model menu select Model gt Direct BE Meshes NewMeshCreatedFromSkin Right click on NewMeshCre atedFromSkin and select Open to view the boundary element mesh created from skin ning the FE structure mesh 9 4 1 5 Define Material Properties e In the main model menu select Model Materials Air Right click on Air and select Edit Figure 9 14 will appear Name Air SpeedSound Frequency Dependence Type Constant v Real 343 00000000000 Imaginary 0 0 AmbientDensity Frequency Dependence Type Constant X Value 1 2100000000000 Figure 9 14 Edit material properties e Type in the name of the material as Air e Define SpeedSound as a constant with value 343 m s The unit is consistent with the unit of length m in the structure mesh 9 4 Coustyx MultiDomain Model 307 Define Ambient Density as a constant with value 1 21 kg m The unit is consistent with the unit of length m in the structure mesh 9 4 1 6 Fill Holes Open the Coustyx BE mesh from the main model menu by selecting Model Di rect BE Meshes NewMeshCreatedFromSkin Right click on NewMeshCreat edFromSkin and select Open to view the boundary element mesh in the GUI Select the tabbed window Fill Hole from the series of tabs located below the BE mesh Follow
33. Surface 2 12 Pb Pa p Surface 1 Surface 3 Do e Pc Figure 4 27 Junction constraints 4 3 8 11 Sets Select Model Indirect BE Mesh Sets This sub tree member is used to review or create a new Set and add elements and nodes to it A Set is a group of elements and nodes grouped together for organization and manipulation convenience Refer to Section 4 4 for more details 4 3 9 Domains Select Model Domains This model tree member is present only for MultiDomain models Multiple domains can be defined here Each domain can have a different acoustic medium and is identified with a unique name and type Currently only domains of type Direct BE are allowed A default domain is automatically created when a new MultiDomain model is opened For each domain we need to set the following options with proper care in order to solve the acoustics problem correctly 72 Getting Started 4 3 9 1 Sources Select Model Domains lt Domain Name gt Sources This is used to include acoustic sources in the model Available acoustic sources in Coustyx are Monopole Dipole Quadrupole Plane Wave Cylindrical and User Defined Refer to Section 4 5 for detailed discussion on how to define an acoustic source To add a new acoustic source right click on Sources and select New Figure 4 26 The right click menu items Edit and Delete are used to edit and delete selected sources 4 3 9 2 Boundedness Select M
34. d Bt MBO v 8 E lt 3 Model E Type lt Indirect gt Version lt 1 00 00 gt JE Model Description Units CJ Structures Materials CJ Planes gt Indirect BE Mesh lt 1 gt Context Script S L Analysis Sequences co f Analysis Sequence Analysis Sequence Rename Copy Paste Delete Open Close Edit Help Run Abort Figure 7 4 Abort the analysis run Run will be aborted at the next logical step This may take a few minutes Figure 7 5 Abort message 194 Analysis Sequences selections in the previous tabbed windows Advanced users can directly modify the script to suit their requirements Users should exercise reasonable caution in the selection of the input parameters due to their influence on the solution accuracy and the speed of the analysis 7 1 Inputs Input parameters required to run an analysis are spread over Solver Controls and Fre quency Ranges tabbed windows 7 1 1 Solver Controls The Solver Controls window is shown in Figure 7 6 7 1 1 1 Parallel Processing The bulk of the computations in Coustyr are parallelized on shared memory multi CPU machines To use system resources effectively the user can select the number of CPUs to be available for Coustyz Figure 7 6 Use Maximum Possible Number of CPUs This option can be checked if the user wants Coustyx to choose the number of CPUs Coustyx selects either the maximum CPUs available to the
35. e Please read the user agreement and if you agree to all terms and conditions select I Agree to proceed with the installation e After you have clicked on I Agree the driver will be installed e Click Finish to complete the installation of the dongle device driver 2 3 License Key Installation A valid License Key has to be installed before using the software Open Install License Key window by clicking on the icon found in the Start menu Start All Programs Coustyx32 or Coustyx64 InstallLicenseKey Figure 2 3 shows the Install License Key window You can use any of the two licensing schemes listed in the window Select the option Use Native License when you have a valid license key provided by ANSOL Select Use Altair GridWorks License when you want to use Altair GridWorks License management system 2 3 1 Use Native License Choose this option if you want to use the license key provided by ANSOL 2 3 1 1 If you have a local dongle If you are using a ANSOL dongle attached to your local computer the Install License Key window displays the dongle ID as shown in Figure 2 4 The license key will have already been sent to you with the dongle or by email Copy and paste the license key into the License Key box You can verify the features licensed under this key from the tabbed window License Features Figure 2 6 If the license key is invalid or expired appropriate information is highlighted Figure 2 7
36. ie a DD A AER ES ES 316 9432 sensorsd t 14 cocinar a 316 92430 Power dk s bona saks duk A Bar sind 318 9434 Aglassigl oie ey be ee oe a ae 318 95 Coustye Indirect Model saka s Vet ke See Ree SYS SSS Sra a aa 321 951 Problem Setup aiii bed EEG b e dd ka ESS 321 951 1 Createva New M del 2 64 mansa a Gikk 321 9512 Import FE Structure Mesh o ss csr hb esse EE a 322 9 5 1 3 Load Frequency Response Data 322 9 5 1 4 Generate BE Mesh 0 o e 2000 324 9 5 1 5 Define Material Properties o 329 Table of Contents 9 5 2 9 5 3 dadi6 Bill Holege sk kb bd ashe ee ma 330 9 5 1 7 Define Boundary Conditions 331 9 5 1 8 Apply Boundary Conditions 4 332 Run Acoustic Analysis 4 5 44 0 80446 5488 bebe a a ees 333 Post processing Qutputs s oa eaa asukkaana ee 336 Odio reks dat o 00a ae eee berbere b Te eens 336 532 Sens rsdat 1 nen E a en SEAS SES ARSE DEE RS 337 95 33 POWEIMAE owe ea eee eee eae het eae DE 4 337 DIE BP eee Se EPA DES 337 List of Figures 2 1 2 2 2 3 2 4 2 5 2 6 2T 2 8 29 2 10 3 1 3 2 3 3 3 4 3 5 3 6 3 7 4 1 4 2 4 3 4 4 4 5 4 6 4 7 4 8 4 9 4 10 4 11 4 12 Sele path WOW sce aa gal kat da see ke seeing Windows installer error message 2 1 Install License Key window lt o eee Computer and dong
37. lt Natural Frequency 180 0925 Hz Damping Ratio 0 000 gt lt Natural Frequency 338 2615 Hz Damping Ratio 0 000 gt Natural Frequency 454 4722 Hz Damping Ratio 0 000 gt lt Natural Frequency 484 2651 Hz Damping Ratio 0 000 gt lt Natural Frequency 506 2977 Hz Damping Ratio 0 000 gt lt Natural Frequency 669 1085 Hz Damping Ratio 0 000 gt lt Natural Frequency 890 2686 Hz Damping Ratio 0 000 gt lt Natural Frequency 950 5137 Hz Damping Ratio 0 000 gt lt Natural Frequency 1528 7089 Hz Damping Ratio 0 000 gt lt Natural Frequency 1620 3582 Hz Damping Ratio 0 000 gt lt Natural Frequency 1850 4165 Hz Damping Ratio 0 000 gt lt Natural Frequency 1892 9052 Hz Damping Ratio 0 000 gt lt Natural Frequency 1977 7131 Hz Damping Ratio 0 000 gt lt Natural Frequency 2053 1284 Hz Damping Ratio 0 000 gt lt Natural Frequency 2151 9858 Hz Damping Ratio 0 000 gt lt Natural Frequency 2251 4260 Hz Damping Ratio 0 000 gt lt Natural Frequency 2347 9280 Hz Damping Ratio 0 000 gt lt Natural Frequency 2594 0295 Hz Damping Ratio 0 000 gt lt Natural Frequency 2646 1001 Hz Damping Ratio 0 000 gt lt Natural Frequency 2762 1985 Hz Damping Ratio 0 000 gt lt Natural Frequency 2844 6494 Hz Damping Ratio 0 000 gt lt Natural Frequency 2916 3306 Hz Damping Ratio 0 000 gt lt Natural Frequency 2926 0222 Hz Damping Ratio 0 000 gt lt Natural Frequency 3010 9651
38. number of bands along the main diagonal of the preconditioner matrix are non zero The non zero terms are assembled from the element self influence matrices The con vergence rate is the worst among all the preconditioners However the time taken for each iteration is less than other preconditioners The number of bands to be consid ered while assembling Diagonal preconditioner are specified by the option Number Bands including Diagonal Number Bands including Diagonal This option is enabled only when Diagonal precondi tioner is selected The preconditioner is assembled upto the number of bands specified from the element self influence matrices Figure 7 6 Convergence Criterion GMRES breaks out of the iteration when the error in the solution becomes less than the specified tolerance Coustyx offers the following two choices for the convergence criterion Figure 7 6 Residual This option computes the residue from the solution vector at each iteration It is the most commonly used convergence criterion Figure 7 6 Sound Power This option computes the error between sound powers from two consecu tive iterations and verify if that is less than the specified tolerance The sound power convergence criterion is useful in cases where the sound power converges faster than the field solution Figure 7 6 Residual as a Percentage This option is enabled only when Residual option is selected as the Convergence Criterion Figure 7 6 For a li
39. velocity at a point and is given as follows I z t P z t V z t p x v x cos dp wt cos wt pave 2 cos p wt cos y wt PRO cos p wt y wt cos p y pis cos 2p 2wt pr cos y p x v a 7 cos 2 Pp wt cos r sin 2 p wt sin r cos PEDESE 1 cos 2 p wt EG sin Gp wt Pr x v 2 tpstajuste 1 cos 2 bp wt de primita sin 2 dp wt 7 8 3 The complex exponential representation of sound intensity is given as I x t Re Et 1 exp 2i wt I Re C a C 2 1 cos 2 6 wt isin 2 9 wt 7 9 OC x 1 cos 2 P wt Ci x sin 2 P wt The real part of x is C 2 and represents the mean active intensity The imaginary part of C x is C x represents the amplitude of the reactive intensity C x OC a 10 x Iu iL x Comparing Equation 7 8 with Equation 7 9 we get the expressions for mean active intensity I x and amplitude of reactive intensity as follows 7 10 pr x v 2 p x v x _ 1 2 2 Re p x 0 x 7 11 1 2 Cua HOME POE _ hasta 7 12 7 3 Script 261 where p x pr x ip and 0 x vr x ivi The complex intensity C x is given as Cu p z 0 x 7 13 7 3 Script The window Script shows the script used by Coustyx to run the analysis The s
40. with the applied vibrations for the desired frequencies Note that Coustyx solves both the interior and exterior domains simultaneously for the Indirect Model 9 5 3 Post processing Outputs Coustyx creates the following output files based on the choices made in Outputs tab in Analysis Sequence 9 5 3 1 results dat A binary results file is saved by Coustyx for later use When the model is re run Coustyx directly uses these results if the checksum of the model matches with the checksum in the results file This file can t be interpreted by the user and is only for Coustyx use 9 5 Coustyx Indirect Model 337 9 5 3 2 sensors dat The pressure and particle velocity at the sensor locations are written into this ASCII text file Since we didn t add any sensors to the gearbox housing radiation problem this file is empty 9 5 3 3 power dat This ASCIEtext file contains acoustic power values computed at each analysis frequency Each file has five columns The first column contains analysis frequencies in Hertz The second and third columns contain radiated active sound power and reactive sound power respectively The input power is written to the fourth column All the power units will be consistent with the material properties sound speed and ambient density defined earlier here the unit is Watt The fifth column consists of the radiation efficiency of the gearbox housing The radiated sound power and radiation e
41. 000000 0 000000 0 000000 0 000000 0 000000 0 000000 No of divisions N1 fi No of divisions N2 fi Lo coma Figure 7 24 Quadrilateral Glass field point grid types 7 2 Outputs 221 di Analysis Sequence xj Name analysis Sequence Description Solver Controls Frequency Ranges Outputs Script Binary Results Sensors Glass riGlass IV Create a IGlass File File Namesfiglass igl Browse Field Point Grids Name Type New o Field Mesh Name NewF eldPointGrid Type E cTrianglular Grid Data 0 000000 0 000000 0 000000 0 000000 0 000000 0 000000 0 000000 0 000000 No of divisions N fi Figure 7 25 IGlass Triangle field point grid types 222 Analysis Sequences Annular Disc This option is selected to generate an annular disc grid specified by the position of its center the normal vector to the plane of the disc the inner and outer radii and the number of divisions in the radial and angular directions Figure 7 26 Center The coordinates of the center of the annular disc are set using this option Figure 7 26 Normal The normal to the plane of the annular disc is set using this option Fig ure 7 26 Inner Radius This option sets the inner radius of the annular disc Any value greater than or equal to zero and less than the outer radius is valid Figure 7 26 Outer Radius This option sets the outer
42. 012 821 P22 0 01182 091811 012829 0992812 0 6 4 12 Non uniform Arbitrary BC This Boundary Condition option could be used to define non uniform boundary conditions which do not fall into any of the other BC types Any of the non uniform BC type can be 6 5 Applying BCs 181 expressed in this general form The general transfer relation between pressures and normal velocities on either side of the boundary at any point is given by Equation 6 10 The variables Q11 412 A21 22 011 Pre B21 Baza V1 Y2 can be defined by the function call GetAlphaBetaGamma Figure 6 36 The input arguments position vector Posn Vec and normal vector NormalVec along with other predefined variables such as AngularFreq w SoundSpeed c WaveNumber k AmbientDensity p and reference frame unit vectors el e2 e3 can be used to compute the values The output arguments of this function call include the following variables See Figure 6 37 Figure 6 38 and Figure 6 39 _ 01 12 Bu Bie _ 7 lo eae pe Pal Si ee Name New BC Type Nonuniform Arbitrary y Help Alpha Beta Gamma Script gt 1 Hfunction GetilphaBetaGarma in PosnVec in NormalVec out Alpha out Beta out Gamma 2 AngularFreq SoundSpeed VaveNumber and imbientDensity are predefined read only variables that can be used here Alpha and Beta are 2x2 matrices Gamma is a 2 vector Alpha 1 0 AngularFreg 2 AngularFreg 0 1
43. 2 used by Sullivan and Crocker in their experiments C 6 8 Porosity Define porosity x of the plate or pipe using this option Porosity is defined as the ratio between open surface area and total surface area open surface area X total surface area When x 0 surface is completely closed the acoustic normal velocity vn on both sides of the perforated plate will be equal to the structure velocity vsn On the other hand when x oo open surface the pressure on both sides of an imaginary dividing surface will be equal Figure 6 20 Plate Thickness Define the thickness of the plate or pipe tw using this option Note the units should be consistent with the model length units Hole Diameter Define the diameter of holes dp using this option Note the units should be consistent with the model length units 6 4 3 2 Transfer Impedance Coustyx allows you to define your own transfer impedance models New transfer impedance models are usually derived from experiments or other empirical models Note that the transfer impedance specified here should have no dimensions Make sure the impedance definition is consistent with the e77 convention used in Coustyx see Section 6 1 R jX 6 9 6 4 Indirect BE Model BCs 167 6 4 3 3 Use Structure Velocity Structure velocity can be used by enabling this option Equation 6 7 shows the transfer relation between pressure on both sides of the element pt and p and
44. 4 e Overlapping elements 1 and 2 These ele ments have the same coordinate nodes 1 2 3 and 4 e Delete any one of the overlapping ele ments 5 5 Skin 123 5 5 2 Free Edges in a FE Mesh While in the Skin tabbed window Coustyx displays all the Free Edges in the FE mesh in color Blue Figure 5 25 55 S A SA IM I ass SVO SN SO Accept Seam stop Skinning Create Mesh From Skin Delete Selected Seams Clear Skin Delete Al Seams Create Sk It gate Skin Hell Figure 5 25 Mesh with free edges shown in blue color 5 5 3 Create Seam Seams are demarcation lines which stop the propagation of skin beyond them Listed below are some examples where seams are created to skin only the desired side of a mesh e A seam around a hole edge will avoid skinning through the hole averting the propagation of the skin to the other side of the mesh e Another example where seams are useful is in case of a FE mesh representing a symmetrical geometry In that case the FE mesh doesn t enclose a closed volume and to skin only one side of the mesh we have to specify seams at the mesh edges on the symmetry planes 124 Pre processing Features Type lt Indirect gt Version lt 1 00 00 gt Opening file wait Done Failed to find a from Node with ID 446 to Node with ID 1332 Failed to find a path from Node with ID 446 to
45. 5 7 6 12 T 13 9 21 13 36 18 66 20 78 21 91 23 105 Table 7 2 List of the integration orders and the corresponding quadrature points on quadrilateral elements Note the total number of quadrature points are nptsxnpts Order No of Points n even n 2 1 n odd n 1 2 Use Fixed Integration Order This option is to set fixed number of quadrature points to be used for all elements For a FMM case this option is selected by default The user can t un select this option when Use FMM is already selected Figure 7 6 Integration Order of Triangular Elements This option is active only when Use Fixed Integration Order is selected The user can select the order to which element inte grals are evaluated on triangular elements Table 7 1 shows the list of valid integration orders and the corresponding quadrature points on triangle elements If the user se lects an integration order that is not in the Table 7 1 Coustyx automatically considers the quadrature points belonging to the next highest order Figure 7 6 Integration Order of Quadrilateral Elements This option is active only when Use Fixed Integration Order is selected The user can select the order to which element integrals are evaluated on quadrilateral elements Table 7 2 shows the list of valid integration orders and the corresponding quadrature points on quadrilateral elements Figure 7 6 Variable Order Integration Scheme This option is enabled
46. 6 4 10 Discontinuous BC This Boundary Condition allows the user to apply different types of boundary conditions on each side of the boundary Presently no other commercially available acoustic BEM software provides these options The discontinuous BCs in conventional acoustic softwares are limited to the same boundary condition type known pressure known velocity or known impedance to be specified on both sides of the surface But Coustyr allows different BC types on either side For example pressure can be specified on one side and velocity on the other side This complete decoupling of the boundary conditions allows for greater modeling flexibility for the user 6 4 Indirect BE Model BCs 173 New Boundary Condition xd Name New BC Type Discontinuous y Help m Discontinuous Side 1 side 2 Type Don t Care Help Figure 6 28 Discontinous BC Don t Care Combinations of different types of BCs on each side of the boundary can be applied to overcome the non uniqueness problems which are very common in boundary element methods An example of this would be a determining the exterior sound field on a vibrating surface which encloses a volume At the resonance frequencies of the interior the interior acoustic variables become very large and dominate the values of surface potentials This leads to error in the computation of the exterior field However accurate results for this exterior problem can be obtained
47. 6 7 6 3 2 2 Domain is on the Positive Side of this Interface Defines whether the acoustic domain being solved is on the positive side of the interface or not Figure 6 7 6 3 3 Uniform Pressure BC This Boundary Condition is applied on the element where pressure is uniformly distributed There is no variation of pressure with position over the element However the pressure can 6 3 Multi Domain Model BCs 153 New Boundary Condition Figure 6 7 Interface Boundary Condition New Boundary Condition Uniform Pressure v Help Constant Figure 6 8 Uniform Pressure BC 154 Boundary Conditions be dependent on the frequency The pressure values can be specified by selecting any of the frequency dependence types Constant Table or Script Figure 6 8 6 3 4 Non uniform Pressure BC This Boundary Condition is applied on the element where pressure varies with position The pressure is defined using a script function GetPressure The input argument to this function is a predefined position variable PosnVec The variable Posn Vec reads the coordinates of a point on the element that is PosnVec x y z Other predefined variables that can be used in the script are AngularFreq w frequency in radians sec SoundSpeed c speed of sound in the medium w with the same units as those defined in materials WaveNumber k and AmbientDensity p density of the medium with th
48. AUS 0 MENICE ss as a cece ad ed rd AA Se 61 43 6 Boundary Conditions sov pude 4484 eres k ek d eo ees 61 AS Direct BE Meshes csi ia BRIS GE k bo wie GE 62 Ads Coord Nodesuisss ss eee Ge k g AE sk EG DENG 62 ATS Bleness A AEE ea ee DAR ek ERS dg 63 4913 P NOMS 2424442004455 G4 4240 2 ode ee Ge ed 64 4374 Po Nodeg s skokk se ARE GER k he a Re 64 Ad Constraint Bqudtions rocas ia 64 A 9608 RA 65 A38 Todirect BE Mesh o aeey 45442 48 624 Gre GRE bake ke 65 1581 Material houses aa pa DEG ARADO ODED RS RES 65 4382 Coord Nodes boc ee ee ae kes Pa See Re 65 2983 Elements avse gt PRR RR ee ee SEA aE OSs 65 43824 Sigma Nodes ios sees bd dhe be ee eae an ewe ed 67 42385 Mu Nodes anc cee ore es BO Aw ae GG GS Se Re da 67 CONTENTS v 1386 Pa Nodes 3 24444 eee eee SPEL da sk aa 67 4 3 8 7 Boundary Conditions lt es s s e mm ea 67 ALGO POUCES ecs i s oe aa aa KG BR ea 68 23809 Jomp ondtidHs 00d a see a 68 43 8 10 Junction Constraints s lt se ratati Poe be pa aida 68 ACB Bl SECS aer ke AN a A A ee aa a ode ikek 71 ALSO DOME ser seem bk se EN Frede Se er As ral ADO SOURCES san s el baa ee eee a SE NET SEE EG 72 1302 Boumdedaess 2 44 4 dnc var P be EE dead 72 4393 Material cna ako ba aw he ea ee eS RO eg wR 72 1394 Direct BE Meshes 2222464 ninay a a a eee 72 1395 Chief POWES usina Pale aS a oa raskt kg 74 43 10 Context Script 602 3 sko saa Ger Fed
49. All Displayed Nodes This selects all the nodes that are displayed in the GUI Select All Bad Nodes This selects all the Bad nodes identified by Coustyz This operation is active only when Coustyx finds Bad nodes in the mesh and throws error messages in the log window mentioning the same Bad nodes are those nodes with incorrect solid angles or have some inconsistencies that prevent Coustyx to perform its usual tasks Generally this set is populated if some nodes in the mesh fail the consistency checks done before skinning a FE mesh to get a BE mesh This operation selects all the bad nodes in the mesh Selected Nodes This sub menu lists the operations that are performed on selected nodes Fig ure 4 9 It is activated only when nodes are selected in the GUI Unselect This un selects the selected nodes Display Style The user can pick the display style for nodes Figure 4 10 4 2 Operations on Mesh Viewer Window 43 Node Display Style ES 4 Display Y Apply Resolution level 1 Apply Color Red 0 Green 0 Blue 255 Color Palette Figure 4 10 Nodes Display Style Window Display This option when selected displays the nodes The selected node will be hidden if this option is turned off Apply Resolution level This option controls the resolution of the sphere used to display the node Apply Color The color of the element face displayed can be changed using this option The user can select the color b
50. Analysis Sequence 0 000000 0 000000 0 000000 Figure 7 27 IGlass Box field point grid types 7 2 Outputs 225 ll Analysis Sequence b x analysis Sequence Name Description Solver Controls Frequency Ranges Outputs Script Binary Results Sensors IGlass iGlass IV Create a IGlass File File Name figass ig Browse Field Point Grids Field Mesh Name NewFieldPointGrid m Spherical Grid Data 0 000000 0 000000 center 050000 Radius 1 0000000000000 No of divisions in zenith angle direction fe of divisions in azil jon fe Figure 7 28 IGlass Sphere field point grid types 226 Analysis Sequences Analysis Sequence 1 x Analysis Sequence 1 Figure 7 29 IGlass Structure mesh field point grid types 7 2 Outputs 227 Structure Name The name of the structure mesh to be used as the field point grid This list would be populated only if there are structure meshes in the main model tree member Structures 7 2 3 3 IGlass Outputs e Run acoustic analysis and create an IGlass file e Double click on the IGlass file to open it using IGlass Viewer Figure 9 48 e Click on the Attribs tab on the top left of the viewer e Visualize outputs by selecting any of the acoustic variables listed in the Attribute drop down menu Multi Doma
51. Beta 0 0 1 2 Gamma 2000 AngularFreq 0 m W0 J3J00 gt 0 4 m r OK Cancel Figure 6 36 Sample script for the function GetAlphaBetaGamma 6 5 Applying BCs First the user needs to define boundary conditions and save them using unique names For information on how to define boundary conditions in MultiDomain and Indirect BE models refer to Section 6 3 and Section 6 4 Once the boundary conditions are defined they are applied over elements by any of the following methods 6 5 1 Apply BCs directly to Elements To apply BCs directly to elements follow these steps e Open the BE mesh in the GUI 182 Boundary Conditions Alpha 1 1 Frequency Dependence Script po o o o o Figure 6 37 Alpha Frequency Dependence Script Beta 1 1 Frequency Dependence Script Uniform Arbitrary Beteta beta Gammelt Beta Betazal Somme ox ene Figure 6 38 Beta Frequency Dependence Script 6 5 Applying BCs 183 Gammal 1 Frequency Dependence Script x Ereguency Dependence Type Constant hd Realj0 0 Imaginary 0 0 ca x Name New BC Type Uniform Arbitrary v Help Alpha 1 1 Alpha 1 2 Beta 1 1 Beta 1 2 Gamma 1 Alphaf2101 alphaf212 Beta 21 Beta 21 2 Gammal2 Ce e Figure 6 39 Gamma Frequency Dependence Script For a MultiDomain model right click on Mo
52. Boundary Condition Figure 6 14 Arbitrary Uniform BC 6 3 Multi Domain Model BCs 161 Z is defined by selecting any of the frequency dependent types Constant Table or Script Figure 6 13 6 3 9 Arbitrary Uniform BC This option can be used to define a Uniform Boundary Condition BC that doesn t fall into any of the other BC types Any uniform boundary condition could be expressed in this general form The general equation for this BC is given by where p is the pressure vn is the normal velocity at a point on the element and a 8 y are variables defined by any of the frequency dependent types Constant Table or Script The values of a and y don t vary with position over the element Figure 6 14 New Boundary Condition x Name New BC Type Arbitrary Nonuniform Alpha Beta Gamma Script 1 Ejfunction Get ilphaBetaGamma in PosnVec in NormalVec out Alpha out Be 2 f AngularFreq SoundSpeed WaveNumber and AmbientDensity are predef 3 read only variables that can be used here 4 The following is just an example change the formula to suit your 5 Alpha 1 0 AngularFreq 2 e1 e2 2000 AngularFregq e1 NormalVec 6 Beta AngularFreg 2 7 Gamma 2000 AngularFreq 8 9 Figure 6 15 Arbitrary Non Uniform BC 6 3 10 Arbitrary Non uniform BC This option can be used to define Non uniform Boundary Condition that doesn t fall into any of the other BC ca
53. Boundary Condition is applied on the side of the element if the frequency response data is known from the FEA analysis of the structure Figure 6 34 Refer to Section 5 1 2 for details on how to load frequency response data Structure Name is the name of structure from which the velocity values are loaded Structure Interface Name is the interface group of element faces which is used to apply BC More details on Structure Name and Structure Interface Name are given in Section 6 3 8 1 and Section 6 3 8 2 Refer to Section 6 2 for details about Interpolation Options for Mismatched Meshes Figure 6 34 176 Boundary Conditions New Boundary Condition x Uniform Normal Velocity ha po ooo Figure 6 31 Discontinous Uniform Normal Velocity 6 4 Indirect BE Model BCs 177 New Boundary Condition Figure 6 32 Discontinous Uniform Velocity 178 Boundary Conditions New Boundary Condition 1 Hfunction GetNormalVelocity in PosnVec in Normalve 7 angularFreq SoundSpeed WaveNumber and Ambie read only variables that can be used here The following is just an example change the var VMag 12 0 var Vn VMag e3 NormalVec return Eval Vn angularFreq SoundSpeed VaveNumber and Amb read only variables that can be used here The following is just an examp change th Figure 6 33 Discontinous Non Uniform Normal Velocity 6 4 Indirect BE
54. Coord Nodes to find the following menu options Open Opens the list of all coordinate nodes with their ID s and coordinates in a new window The table rows can be copied to a clip board by right clicking on the rows and selecting Copy Close Closes the window opened by Open menu item 4 3 Model Setup 63 Display All Displays all of the coordinate nodes in the mesh opened in the GUI This menu item is active only for meshes open in the GUI Hide All Hides all the displayed coordinate nodes in the GUI This menu item is active only for meshes open in the GUI Display Style Changes the display style of the coordinate nodes Refer to Section 4 2 3 2 for more details on each of the options in the Display Style dialog window 4 3 7 2 Elements Select Model Direct BE Meshes lt Direct BE Mesh Name gt Elements This sub tree member is used to review the elements of the mesh Right click on Elements to find the following menu options Open Opens the list of all elements with their ID s and connectivity details in a new window The table rows can be copied to a clip board by right clicking on the rows and selecting Copy Close Closes the window opened by Open menu item Display All Displays all the elements in the mesh opened in the GUI This menu item is active only for meshes open in the GUI Hide All Hides all the displayed elements in the GUI This menu item is active only for meshes open in the GUI Display Styl
55. Figure 5 27 Select Elements for Creating a Seam e The propagation of the skin could be stopped at any time by pressing Skin Stop Skinning e The created skin can be cleared by pressing Skin Clear Skin e Once you are satisfied with the skin a new BE mesh can be created using this skin by pressing Skin Create Mesh From Skin button 5 6 New Element This tabbed window is located at the bottom pane of the Mesh Viewer window It is used to fill gaps in the mesh by creating new surface 2D elements This function is especially useful in creating new elements for cases where the functions Fill Hole and Stitch Seams can not be used new element is added by specifying the coordinate node ids and the type of the element to be created Figure 5 32 shows the window to create a new element in a BE mesh e Left click with shift key held down to select elements e Right click with shift key held down and select Operations on Selection Selected Elements Display Connected Nodes e Go to the New Element tab and select the shape and type of the new element e Begin building the new element by selecting nodes Element Coord Node ID show the IDs of the nodes selected in sequence 5 6 New Element 127 Figure 5 28 Display Connected Nodes for Selected Elements 128 Pre processing Features Figure 5 29 Choose Nodes for Creating Seams Figure 5 30 Accept Seam 5 6 New Element 129
56. Figure 7 20 The sensor coordinates could be entered manually or imported from an ASCII file 7 2 Outputs 215 Analysis Sequence Name Analysis Sequence Description Units Solver Controls Frequency Ranges Outputs Script Binary Results Sensors IGlass Sound Power Standards Binary Results Y Create a Binary Results File File Name results dat Browse Figure 7 19 Analysis outputs window The output data is written to a file entitled sensors dat You can modify the output file name by typing in a new name or by selecting an existing file through the Browse button Each row in the output file corresponds to the data at all sensors at one frequency The first column corresponds to the frequency of analysis the second and third correspond to the real and imaginary parts of the field point pressure at the first sensor the fourth and fifth contain the real and imaginary parts of the x component of the velocity vector vz at the first sensor columns six to nine contain velocity components in y vy and z vz directions The data for n sensor is written between columns 8 n 1 2 and 8 n 1 09 Use the matlab utility function ImportSensorData m provided with Coustyx to import the data into matlab workspace You can find this file in the folder InstallDir MatlabFiles To set the folder in the matlab path use gt gt addpath InstallDir MatlabFiles or go to Matlab File
57. Figure 7 6 None This option is selected if the user wants to use GMRES without any preconditioner Selection of this option reduces the memory usage as the preconditioner matrix is not created but results in large number of iterations before the solution converges to the specified tolerance EBE This option selects the Element By Element EBE preconditioner to be used in GMRES The preconditioner matrix is represented as a product of element matrices This helps to store individual element self influence matrices in unassembled form thus reducing the memory usage to O N from O N for Near field preconditioner where N is the number of unknowns The convergence rate that is the number of iterations taken by GMRES to converge to a specified tolerance is in between that of Near field and Diagonal preconditioners Near Field This option selects the Near field preconditioner to be used in GMRES The preconditioner is assembled from the element self influence matrices By far this is the best preconditioner known for its fast convergence rate However it s memory usage increases scales as O N and rapidly with the number of unknowns N This method is suggested if the number of unknowns are small If memory usage is not an issue the user is strongly recommended to use this option for all problems For a large number of unknowns use the EBE method Diagonal This option selects the Diagonal preconditioner where only the terms in certain
58. Menu Features 2 46 65460 64 BERD Oe Ee eee eee ee Ee 29 4 2 Operations on Mesh Viewer Window 00000 ee eee 34 121 GUL Control Panel Wools cocida a Es 34 4 2 2 Rotate Pan amp Selection Operations 2 00 38 4 2 3 Operations on Selection in GUI 004 38 4 2 3 1 Operations on Displayed Elements 38 4 2 3 2 Operations on Displayed Nodes 42 4 2 3 3 Operations on Displayed Faces 0 44 4 2 4 Selected Coord Nodes o 00000 eee ee eee 44 425 Selected Elements occ woe dag ass t ke See se died a 45 406 o pene eee ey Be OE ee ee ee 46 AO A AER E E Eee eS 46 428 New Element 3 brida ds EEE bee 46 ADO BG SCAMS da KS a JD GE ae ah 49 21d Delete Elements emigra 99 44 GE FE DENG 49 42 11 Merge Nodes 230300 Se DEG Ga G SER EEE SE RS 49 4 2 12 Split Pn Nodes Split Sigma Nodes o rn 49 42 13 Element Orientation sica see kg oss ee ku bee as skodde 50 Ea Model Setup socias a a G SE A 2 50 4 3 1 New Model Open Model File o 50 4 3 1 1 MultiDomain Model 1 s e ss 644 psc 44 G4 50 1512 Indirect Model sos onus wee H GE G AG OO AASE EY 53 AS Stuchur s 4 4 4 medidas AE A 56 ASS Whaterale zorra SETTER ee ee G SAKE ORES 56 4331 Speedot Sound cisco ddr ea bes 58 4332 Ambient Density varene dear akter keg Fase Ree a 59 ASA PIES es e 44 eee Te ea eh SPAR A 59
59. Mesh 4a s sdas du ara e H dd 102 5 3 Forced Response Analysis using Modal Superposition 103 531 Load Natural Mode Data s sre qeg tredd ee e 103 532 Modify Modal Dampe sa stas see eee SK SEE ST SEERE 105 533 Apply leads 1 23 30 are PES P ae sea dans 108 5 3 4 Perform Modal Superposition s s a segada ata o e e E 109 vi CONTENTS OAL Fill 5 EEE EE EE a banaa 112 5 4 1 Delaunay Triangulation Optimization Parameters 112 nad Fil Paramevers 2 24 vb as e gel ee SSE De 113 5 4 3 Procedure to Fill Hole nr renn 115 DO EE EE eae ee A 115 5 5 1 Treatment of Bad Elements ce eee ee eens 121 55 2 Free Edees in a FE Mesh ccoo eee bow be ye ee dd age Sag 123 DAS Create SEAM acl cco a ER RA A 123 5 5 3 1 Procedure to Create Seams ss ocs rava vr rv eee 125 bod Create IM a o a Peon RG EE A RR 125 mo New Benet 242444 sager a As 126 o a KER GS RSS god doar EE edb dow AE aes 130 HL Get Parameters oa t soda daa es 6546444 0 eR ea ee aS 130 Dia Proc dure to Stitch CAMS si rs ee Gas Sk a 132 bo Delete Elements 24 4 2 coed weit ae e eee be ee ae ee eS OS 133 59 Merse Nodes s sac see ae PS WR a eG REESE E 137 5 10 Split Pn Nodes Split Sigma Nodes ssa sone o o 0000000004 137 511 Element Orientation n s s sani EERE RE ER ROE Ra G ed dia 139 6 Boundary Conditions 145 6 1 Impedance Definition in Coustyx oe eses asiedad destestar ttt
60. Model BCs 179 Figure 6 34 Structure Velocity 180 Boundary Conditions 6 4 11 Uniform Arbitrary BC This Boundary Condition option could be used to define uniform boundary conditions which don t fall in any of the other BC types This is the most general type of boundary condition possible Any of the uniform BCs can be expressed in this form The user can specify the relation between the pressure and normal velocity on one side of the element to the other side by the following transfer function Figure 6 35 New Boundary Condition x Name New BC Type Uniform Arbitrary vj Help Alpha 1 1 Alpha 1 2 Beta 1 1 Beta 1 2 Gamma 1 Alpha 2 1 Alpha 2 2 Beta 2 1 Beta 2 2 Gamma 2 ne Figure 6 35 Uniform Arbitrary BC ke EE Wea 6 10 Q21 Q22 p Bar Baz Un Y2 where pt and p are pressures on side 1 and side 2 vt and v7 are normal velocity on side 1 and side 2 The variables Q11 12 M21 22 011 Pia Bar Boa Y ya are uniform over the element and are defined by any of the frequency dependent types Constant Table or Script These values do not vary with position over the element All the entries in the coefficient matrices of Equation 6 10 are not independent They should satisfy the following relations for Coustyx to apply the arbitrary BC correctly 011097 012091 40 B11B22 Bia2P21 40 6 11 az 022 811 b12 011
61. NewMeshCreatedFromSkin gt JE Material lt gt e Coord Nodes Elements Sigma Nodes Mu Nodes Pn Nodes mE Boundary Conditions C Sources Esse Jump Conditions J Junction Constre ai i Sets Paste E Context Script Delete i Q Analysis Sequences Open Glose Edit Figure 4 25 Create Boundary Conditions 70 Getting Started File Edit Preferences Help Dela Helje sjel E lt Model Type lt Indirect gt Version lt 1 00 00 gt Model Description a Y Structures gt Structmesh O 7 Materials Q Planes Es 3 p Indirect BE Mesh lt NewMeshCreatedFromSkin gt r Material lt gt j Coord Nodes A Elements Sigma Nodes Mu Nodes Pn Nodes a 20 Boundary Conditions Default hu E Sources al EY Jump Cc Sources 3 Junction O Y Sets Copy E Context Scri pi CJ Analysis Sec Pasta Delete Open Glose Edit Figure 4 26 Create New Source 4 3 Model Setup 71 different subspaces The double layer potentials at this junction are interdependent Figure 4 27 shows a junction constraint with surfaces dividing the space into three regions The nodes p1 u2 H3 represent the value of the double layer density at the same spatial location By definition 111 H2 43 represent the following pressure differences H Pa Pe H2 Pb Pa H3 Pc Pb From the above expressions the constraint equation at the junction is pa pa us 0 4 2
62. This shows whether the selected element lies on a baffle plane or not For a model with baffled planes the acoustic variables include normal derivative of pressures on both sides in addition to the single layer o and double layer u potentials P Nodes Only for MultiDomain BE meshes This displays a list of pressure nodes p nodes used in MultiDomain models 46 Getting Started Pn Nodes Only for MultiDomain BE meshes This displays a list of normal derivative of pressure nodes pn nodes used in MultiDomain models Pn Plus Nodes Used in Indirect BE meshes with baffled elements This displays the normal derivative of pressure on the positive side of an element pn plus in Indirect BE elements Pn Minus Nodes Only for Indirect BE meshes with elements on baffled plane This displays the normal derivative of pressure on the negative side of an element pn minus in Indirect BE elements Sigma Nodes Only for Indirect BE meshes This displays single layer potential 7 nodes used in defining the variable connectivity of the element The single layer potential at a point is defined as the difference between the normal derivative of pressures on the positive p and the negative p sides of an element that is o p p Mu Nodes Only for Indirect BE meshes This displays double layer potential u nodes used in defining the variable connectivity of the element The double layer potential is defined as the difference betw
63. To accurately model the velocity discontinuity along 138 Pre processing Features the common boundary of these adjacent elements you need to have duplicate Pn or Sigma nodes Please be aware that for most other cases such as geometry discontinuities edges cor ners junctions etc Coustyr automatically creates appropriate duplicate nodes during skinning Figure 5 43 shows the window for Split Pn Nodes or Split Sigma Nodes pe Selene 1 Group 1 Delete from Group 1 net rade 1 Add to Group 2 Delete from Group 2 S t Sigma Nodes between Groups spit Al Shared Sigma Nodes between Groupe merge Canodent Sigma Nodes Figure 5 43 Split Pn Nodes Split Sigma Nodes window showing duplicate nodes along edges Note During skinning Coustyr automatically creates duplicate nodes for most common cases such as geometry discontinuities edges corners junctions etc Left click with shift key held down to select elements Click on Display Connected Pn Nodes Display Connected Sigma Nodes to display Pn Nodes Sigma Nodes for all selected elements in a MultiDomain Indirect model Left click with shift key held down to select a displayed node in the GUI To select all dis played nodes click on Select Displayed Pn Nodes Select Displayed Sigma Nodes To unselect selected nodes click on Unselect or left click on a selected node with the shift key held down 5 11 Element Orientation 139
64. View Frequency 9 5 Coustyx Indirect Model 339 View Bodies Attibs a Surface Pressure Plu Surface Pressure Minus Field Point Pressure Figure 9 48 IGlass viewer showing sound pressure distribution on the exterior surface of the housing at 760 Hz Bibliography 1 A Seybert T W Wu and X F Wu Experimental validation of finite element and boundary element methods for predicting structural vibration and radiated noise Technical report NASA Contractor Report 4561 1994
65. a table The table shows the list of Mu node IDs and the magnitude of jumps at these nodes For a node on Free Edge the magnitude of jump will be zero that is y p p 0 as the pressures p and p on either side of the surface are equal at the edge Coustyr automatically generates this list for all Free Edges while skinning the FE structure mesh 4 3 8 10 Junction Constraints Select Model Indirect BE Mesh Junction Constraints The Junction constraints in the Indirect model can be reviewed here Right click and select Open to see the list of constraint equations in a table The table shows the Constraint ID of the equation the left hand side consisting of the Node Type with its ID and the Coefficient the right hand side RHS of the constraint equation The Node Type can be any of the following types Sigma Mu or Pn These constraint equations are automatically generated during the skinning of the FE struc ture mesh These equations typically represent the junction constraints between double layer potentials Mus associated with various acoustic subspaces For example the nodes connecting a two dimensional rib to a mesh are to be associated with junction constraints as they connect 4 3 Model Setup 69 File Edit Preferences Help Olesa Hela Sales E Model Type lt Indirect gt Version lt 1 00 00 gt E Model Description Eg Structures O Structmesh O Materials i Planes Ex Indirect BE Mesh lt
66. and right click to select Elements Display All Figure 5 22 Select a Bad Element by left clicking on it while holding down the shift key To display co ordinate nodes of this element right click with shift key held down and select Operations on Selection Selected Elements Display Connected Nodes Figure 5 23 Select any one of the coordinate nodes of the Bad Element by left clicking on the node while holding down the shift key Then right click and select Operations on Selection Selected Nodes Display Connected Elements to display all the elements connected to that node neighboring elements Figure 5 24 Check how the coordinate connectivity of the Bad Element is not compatible with its neighbors Treat the Bad Element appropriately based on the kind of incompatibility Some of the most common types of Bad Elements found in FE meshes are listed in the Ta ble 5 1 along with valid treatments If required delete the Bad Element or its neighboring elements using the Manipulation Task Function Delete Elements New elements can be created using the Manipulation Task Function New Element 122 Pre processing Features Table 5 1 Some of the common types of Bad Elements and their Treatment Bad Elements Treatment e Incompatible coordinate connectivity be tween elements 3 and 1 2 e Delete elements 1 2 and 3 e Create a new element using the coordi nates 1 2 3 and
67. convention 148 Boundary Conditions A boundary element BE mesh and a structure mesh are said to be mismatched when not all nodes in the BE mesh have a corresponding node in the structure mesh that is coincident by position In such cases nodal velocities at mismatched BE nodes are estimated by interpolating velocities from the nearby structure nodes also referred to as interpolating points Refer to Figure 6 3 For two matching meshes the velocities at structure nodes are directly applied to BE nodes d2 Figure 6 3 Interpolation for mismatched meshes Coustyx employs an inverse distance weighted interpolation method to estimate velocities at the mismatched nodes The inverse of the distance between the BE node and the interpolating point is used as the weight This approach diminishes the effect of far away interpolating points with respect to the nearby points Employing this approach the unknown velocity at a BE node is estimated by computing the weighted average of known velocities at N nearby interpolating points collected from the structure mesh Thus the velocity at a mismatched BE node v S computed from the four interpolating points shown in Figure 6 3 is given by dig pi 28 bjj i Ui T U2 U3 4 U3 _ di d2 d3 d3 v S 1 cd que de a al 6 3 di j da d3 l d4 Various options that control the number of interpolation points and the search criteria are discussed below Figure 6 13 Choose Defau
68. created has slightly mismatched or disjoint meshes In constraint equations pressure P nodes along the demarcating borders of the mismatched meshes are combined together to satisfy the pressure continuity at a point These equations are not required when the model is created from a single 4 3 Model Setup 65 contiguous mesh in which case the pressure continuity among adjacent elements is automatically satisfied by the sharing of common P nodes 4 3 7 6 Sets Select Model Direct BE Meshes lt Direct BE Mesh Name gt Sets This sub tree member is used to review or create a new Set and add elements faces or coordinate nodes to it A Set is a group of elements faces and coordinate nodes grouped together for organization and manipulation convenience Refer to Section 4 4 for more details 4 3 8 Indirect BE Mesh Select Model Indirect BE Mesh This model tree member is present only for Indirect models It consists of one BE mesh generated by skinning a FE structure mesh Refer to Section 5 5 for more details on how to skin a FE mesh to generate a BE mesh To view the Indirect BE mesh in the GUI Right click on Indirect BE Mesh and select Open The mesh in the GUI can be closed by selecting Close The Mesh Manipulation Functions located at the bottom of the GUI are used to manipulate the mesh opened in the GUI Use Selected Coord Nodes to view the coordinates of the selected nodes in the GUI Selected Elements to view det
69. data available for the selected structure an alert window will pop up with the same message e Structure Name This drop down menu lists names of all structures present in the Coustyx model Select the desired structure from the menu Analysis frequencies are extracted from this structure s frequency response data 7 1 2 3 Structure Natural Mode Data Analysis frequencies could be extracted from a structure s natural mode data using this option Figure 7 17 Verify whether the selected structure defined in Structure Name has natural mode data from Model Structures lt Structure Mesh Name gt Natural Mode Data See Section 5 1 3 on how to load natural mode data of a structure to the Coustyr model Press OK to load natural frequencies new dialog box with a list of available natural frequencies from the natural mode data appear See Figure 5 5 Select the frequencies of interest by check ing unchecking a natural frequency or by using any of the buttons Select All Unselect All or Select by Frequency Range If there is no natural mode data available for the selected structure an alert window will pop up with the same message 210 Analysis Sequences En AE Es Source Structure Natural Mode Data v Help Whether to replace the table or append the data to it Replace Structure Info Structure Name v Figure 7 17 Load frequencies from the structure natural mode data e Structure Name This drop down m
70. e564 444448 85 164 64 3 Pertorated BO acs ccna ele ea Bw Bae GG he DB dk d 164 CONTENTS vii 6431 Sullivan and Crocker co occiso Ga Ga 166 0432 Tramster Impedance gt gt sss a a tits a 166 6 433 Use Structure Velocity 44 sabel sees a 167 62434 Uniform Perforated BC o is oc eee Saw Ta SST as 167 6 4 3 5 Non uniform Perforated BC 0 167 6 4 4 Uniform Pressure Continuous BO o a se cesca care oca aiiai o ah 167 6 4 5 Non uniform Pressure Continuous BO ascesa esaa a ayera sa 169 6 4 6 Uniform Normal Velocity Continuous BC oaaae 169 6 4 7 Uniform Velocity Continuous BC rave rv vr kr idas 170 6 4 8 Non uniform Normal Velocity Continuous BC LL rv vr o 171 6 4 9 Structure Velocity Continuous BC o 171 BALL Structure Name lt ociosrcia a a RRA 172 6 4 9 2 Structure Interface Name o vr veka 172 6 4 9 3 Interpolation Options for Mismatched Meshes 172 04 10 Discontinuous BO sa s Y ya cdi A 172 CELLE Drea saca DA ae SR be a AS TE REN 173 64102 Uniform Pressure e av sed d e a e ea den G44 173 6 4 10 3 Non uniform Pressure o rv rv rv i a 174 6 4 10 4 Uniform Normal Velocity 20 eek see a 174 64 105 Uniform Velocity s soo ic oo She SSS SS GSA EG 174 6 4 10 6 Non uniform Normal Velocity o 175 BIN Structure Velocity s ss ssa ae gece a ciento 175 641 Unior Arbitrary BO ay s pe
71. equal partial areas distributed over the hemisphere surface Number of Probe Positions Choose the number of microphones to be 20 or 40 from the drop down menu In general 20 microphone positions are suf ficient However when the source has high directivity increase the number of microphone positions to 40 Table 7 9 lists coordinates of 20 microphone positions The additional 20 point array can be obtained by rotating the original array by 180 about the Z axis Coaxial Circular Paths Figure 7 34 shows coaxial circular paths in parallel planes traversed by a microphone over a reflecting plane The paths are selected such that the annular area associated with each path is the same Number of Circular Paths Traversed by a Probe Enter the number of cir cular paths traversed by a microphone on the hemisphere The least number is five Meridional Arc Traverses Figure 7 42 shows meridional arc traversed by a micro phone The meridional arc is the path traversed along a semicircular arc about a horizontal axis through the center of the source The paths are selected such that the annular area associated with each path is the same 7 2 Outputs 253 Table 7 9 I503745 Coordinates of microphone positions on a hemisphere 3 Microphone position T r z T 1 ANow kw hy 11 12 13 14 15 17 18 19 20 1 0 5 0 5 0 49 0 49 0 96 0 47 0 93 0 45 0 88 0 43 0 41 0 39 0 37 0 69 0 32
72. file to the Frequency Ranges table press OK To discard changes press CANCEL 208 Analysis Sequences Name Analysis Sequence Co Jen Figure 7 14 Load frequencies window Source Whether to e the table or the data to it File File Name Figure 7 15 Load frequencies from a file window 7 1 Inputs 209 e File Name is the full path of the ASCII file used to load analysis frequencies 7 1 2 2 Structure Freq Response Data x Load Frequencies Ex Source Structure Freq Response Data z Help Whether to replace the table or append the data to it Replace z Structure Info Structure Name bd Figure 7 16 Load frequencies from the structure frequency response data Analysis frequencies could be extracted from a structure s frequency response data using this option Figure 7 16 Verify whether the selected structure defined in Structure Name has frequency response data from Model Structures gt lt Structure Mesh Name gt Freq Response Data See Section 5 1 2 on how to load frequency response data of a structure to the Coustyx model Press OK to load frequencies new dialog box with the list of available frequencies from the frequency response data appear See Figure 5 3 Select the frequencies of interest by checking unchecking a frequency or by using any of the buttons Select All Unselect All or Select by Frequency Range If there is no frequency response
73. gearbox housing e Click on the View tab on the top left of the iglass viewer e Press the slider under View Phase to start animation This activates the animation of the wave propagation on the housing surface e To view the results for different frequencies press the slider under View Frequency 9 4 Coustyx MultiDomain Model 319 1e 06 T T T T T 1e 08 1e 10 1e 12 1e 14 Radiated Sound Power Watt 1e 16 Mode 12 10 18 100 200 300 400 500 600 700 800 Frequency Hz 900 1000 Figure 9 25 Sound power from the forced vibration response 1 4 12t 0 8 F Radiation Efficiency 0 4 1 00 200 300 400 500 600 700 800 Frequency Hz 900 1000 Figure 9 26 Radiation efficiency of the gearbox forced vibration 320 Tutorial Gear Box Radiation Contact Pressure Scale Figure 9 27 IGlass viewer showing sound pressure distribution at 760 Hz 9 5 Coustyx Indirect Model 321 9 5 Coustyx Indirect Model Coustyx Indirect model is created by importing the FE mesh The frequency response data from the FEA analysis is loaded into Coustyx and is applied as a structure velocity boundary condition on the gearbox housing The analysis parameters are then set and the acoustic analysis is run to compute radiation predictions 9 5 1 Problem Setup Follow the steps to setup Coustyx model and perform acous
74. model e Fill holes Ability to fill holes based on delaunay triangulation method e Stitch seams Ability to seam stitch gaps between meshes e Create new elements or delete existing ones e Change element orientations e Automatic generation of junction constraint equations jump conditions duplicate acoustic nodes while skinning The main objective of this manual is to provide a comprehensive user s guide on how to run Coustyr for acoustic analysis It describes how to import data files from different programs setup a model define boundary conditions carry out an analysis and retrieve analysis results In Chapter 2 instructions on how to install Coustyx on a windows machine are provided In Chapter 3 we present the unit conventions followed in Coustyz In Chapter 4 we discuss the structure of the Coustyx User Interface and brief descriptions of all the steps required to setup an acoustic model for successfully carrying out an analysis In Chapter 5 we present more detailed discussion on how to generate a Coustyr BE mesh from a FE mesh In Chapter 6 a detailed discussion is provided on how to define and apply boundary condi tions to a MultiDomain or an Indirect Coustyx model In Chapter 7 we provide details on how to set options required to run an analysis and how to retrieve analysis results for post processing Chapter 8 provides the language syntax for writing scripts in Coustyx interpretive language Lastly Chapter 9
75. need not be 164 Boundary Conditions modeled at all because of both the potentials going to zero that is y 0 and 0 However the only exception occurs when the element lies on a Baffle Plane where the normal derivative of pressure is the acoustic variable In this case the user has to keep the element on the baffle plane and apply Transparent BC Figure 6 17 New Boundary Condition Name New BC px Type Transparent Figure 6 17 Transparent BC 6 4 2 Anechoic Termination BC This Boundary Condition is applied on the elements where the pressure p on either side of the boundary and normal velocity vn on either side of the boundary are related by the char acteristic impedance Zo of the fluid medium Refer Section 6 1 for the definition of impedance implemented in Coustyr The relation between pressure and velocity at anechoic termination is given by P Z Z poc 6 6 where po is the mean density of the surrounding medium and c is the speed of sound in the medium Figure 6 18 New Boundary Condition x Name New BC Type Anechoic Termination cm Figure 6 18 Anechoic Termination BC 6 4 3 Perforated BC 6 4 Indirect BE Model BCs 165 Figure 6 19 Perforated Plate New Boundary Condition i 0 New BC Uniform Perforated Perforated Model Type Help Sullivan Crocker Porosity Frequency Dependence Type Constant Value 0 04200000000000 Frequency Dependence T
76. new load right click on Loads and select New A dialog box as shown in Figure 5 13 appears Enter a valid node id and edit the frequency dependent variables Force and Moment Press OK to create a new 5 3 Forced Response Analysis using Modal Superposition 109 load If the node id is not present in the structure mesh or has already been used to define a load Coustyx prompts the user to change the node id Specify the force and moment through any of the frequency dependence types Constant Table or Script Note that the predefined variables Frequency or AngularFreq in the script or table represent analysis frequency To edit an existing load right click on the load in the model tree and select Edit To delete existing loads right click on a load and select Delete or right click on Loads and select Delete All Loads 5 3 4 Perform Modal Superposition Modal superposition method decouples the equations of motion using mode shapes and nat ural frequencies The decoupled system of equations that are solved in Coustyz are given below Note e77 convention is used w A MAu jwATCAu A KAu A f or v Tu jwDiag 2036 u Ou ATF where w is the analysis frequency A a a2 a is the modal matrix with natural modes a M is finite element mass matrix C is the damping matrix K is the stiffness matrix Q Diag w w3 w2 wi is the natural frequency u is the generalized displacement vector f is the
77. normal velocity vn when structure velocity vsn is present Refer to Section 6 4 9 for more details on how to define a structure velocity If this option is disabled structure velocity in the Equation 6 7 is set to zero Figure 6 20 6 4 3 4 Uniform Perforated BC This Boundary Condition is applied over perforated elements with position independent pa rameters Refer to Section 6 4 3 for the transfer relation used to model perforated boundary con dition The values for porosity plate thickness and hole diameter in Sullivan and Crocker model or transfer impedance in Transfer Impedance model are set by selecting any of the frequency dependent types Constant Table or Script Figure 6 20 The option Use Structure Velocity is enabled to define structure velocity used in Equa tion 6 7 Refer to Section 6 4 3 3 for further details 6 4 3 5 Non uniform Perforated BC This Boundary Condition is applied over perforated elements with position dependent pa rameters Refer to Section 6 4 3 for the transfer relation used to model perforated boundary condition The values for porosity plate thickness and hole diameter in Sullivan and Crocker model is set by a call to the function GetSullivanCrockerModelParameters This function ac cepts the predefined position vector Posn Vec as the input argument and outputs Porosity Plate Thickness and Hole Diameter Similarly the value for the transfer impedance in Transfer Impedance model is set by the f
78. of the Spherical Bessel function integer nterms number of terms to be computed All orders from n nti n nterms 1 will be computed complex z argument to the Spherical Bessel function Output complex array result contains jn z 8 10 9 Cylindrical Bessel Function Jn n nterms z result Description Computes Cylindrical Bessel function of integer order n Inputs integer n order of the Cylindrical Bessel function For integer n n can be ve 0 or ve integer nterms number of terms to be computed All orders from n nti n nterms 1 will be computed complex z argument to the Cylindrical Bessel function Output complex array result contains Jn z Jnu n nterms z result Description Computes Cylindrical Bessel function of fractional order n Inputs integer n order of the Cylindrical Bessel function For fractional n n must be ve integer nterms number of terms to be computed All orders from n nti n nterms 1 will be computed complex z argument to the Cylindrical Bessel function Output complex array result contains Jnu z Chapter 9 Tutorial Gear Box Radiation This tutorial is created to outline the steps required to compute radiated noise from a gearbox housing Detailed steps are given on how to create and perform acoustic analysis for Multido main Model and Indirect Model 9 1 Introduction Follow the procedure outlined below for general noise
79. points are found during the search a zero nodal velocity is assigned to the BE node Maximum Search Distance This option sets the maximum distance away from a BE node within which the search for N nearest interpolating points is performed The search for interpolating points is terminated when any of the following criteria is met a N nearest structure nodes are found b maximum search distance from the BE node position is reached c optional when the relative weight in percentage at the farthest point is less than a user defined tolerance If no interpolation points are found during the search a zero nodal velocity is assigned to the BE node Terminate if Percentage Weight of Farthest Point is less than This sets the option to terminate the search when the percentage weight of the farthest point is less than a user defined tolerance tol That is the search is terminated if the following is true 1 100 lt tol D where dy is the distance of the farthest interpolating point from the BE node and Y I is the sum of the weights of all interpolating points This option is specifically useful if the user wants to discard interpolating points that contribute less than a specified tolerance value compared to others even when there are less than N interpolation points or the point lies with in the maximum search distance The search for interpolating points is terminated when any of the following criteria i
80. press the button Compute Forced Response to start the forced response harmonic analysis using modal su perposition The analysis results are stored into the model tree member Freq Response Data This data could later be applied as a structure velocity boundary condition for acoustic analysis 110 Pre processing Features Forced Response from Modal Su NER ITA 1 1 180 092468 338 261536 454 472198 484 265137 434 265137 506 297668 506 297668 0 000000 669 108459 0 000000 890 268616 0 000000 950 513733 0 000000 1528 708862 0 000000 1 1 669 108459 1 1620 358154 0 000000 1 1 1 1 890 268616 950 513733 1528 708862 1620 358154 1850 416504 1892 905151 1977 713135 7 1 4 1 1850 416504 9 000000 1892 905151 0 000000 1977 713135 0 000000 2053 128418 0 000000 1 2053 128418 2151 985840 0 000000 1 2151 985840 2251 426025 0 000000 1 2251 426025 2347 927979 0 000000 1 2347 927979 2594 029541 0 000000 1 2594 029541 2646 100098 0 000000 1 2646 100098 2762 198486 0 000000 1 2762 198486 2844 649414 0 000000 1 2844 649414 7916 330566 n nonnon 1 7916 330566 Figure 5 14 Perform modal superposition 5 3 Forced Response Analysis using Modal Superposition 111 Forced Response from Modal Superposition y l Node Pariapaton Select All Modes Unselect All Modes Select Modes by Frequency Range
81. r 4 2 2 W case _ word jRegExp l Display Style Display All Hide All Set Boundary Condition Select Unselect Add Selection to Set Remove Selection from Set Figure 5 21 Add Bad Elements to a Set 5 5 Skin 119 File Edit Preferences Help Ded Briere E AM Om icael word Regxp l4 2 53 Model Type lt Indirect gt LE Version lt 1 00 00 gt 5 Model Description 2 5 Structures 0 Structmesh 0 i Coord Nodes 9 Elements Y Structmesh_0 1 Structmesh_0 2 E Freq ee i BadElements E Natural Mode D Materials Keams Planes Copy Indirect BE Mesh lt Mesl Paste Context Script Delete 0 Analysis Sequences Open Close Edit Help Replicate Elements Alo CoordNodes Error Incompatible elements ID 13091 and ID 13473 Error Incompatible elements ID 12763 and ID 13483 Error Incompatible elements ID 12806 and ID 13504 Error Incompatible elements ID 13599 and ID 13600 Error Incompatible elements ID 13615 and ID 13616 Error Incompatible elements ID 13620 and ID 13622 Error Incompatible elements ID 13627 and ID 13630 Error Found element connectivity errors in mesh Unable to c Fix the mesh and retry le m t a ul gt Display Style Display All Hide All Set Boundary Condition Select Unselect Add Selection to Set Remove Selection from Set Figure
82. radiation prediction using Coustyx soft ware The two steps involved in the prediction of noise radiated by a gearbox housing are a determination of housing vibration by experiments or analysis here we do finite element anal ysis b prediction of radiated noise based on the vibration using Coustyx boundary element method FEA The Finite Element Analysis FEA is used to build the mesh and to estimate the struc tural vibration which is used as the input velocity for acoustic analysis in Coustyx 1 Build a finite element model of the gearbox housing from the geometry Compute mode shapes and natural frequencies of the structure from FEA modal analysis 2 Estimate the forces transmitted to the gearbox housing through bearings or from other interactions with the components in a gearbox Transform the forces into the frequency domain to obtain force amplitudes as a function of frequency Generally the forces on the gearbox housings are from the gear mesh excitation which are transmitted through the bearings The time domain bearing loads forces and moments can be computed from a Calyx analysis or any other similar analysis The bearing loads can then be transformed into the frequency domain to obtain the bearing load amplitudes as a function of frequency 3 Compute the housing structural response at each frequency of analysis using a FEA software The gearbox housing frequency response is computed by modal superposi tion Coustyx A
83. radius of the annular disc Any value greater than the inner radius is valid Figure 7 26 No of divisions in radial direction The number of divisions in the radial direc tion of the annular disc grid refer to Figure 7 23 No of divisions in circular direction The number of divisions in the circular di rection of the annular disc grid refer to Figure 7 23 Box This option is selected to generate a box grid specified by eight corners and different number of divisions in each direction The coordinates of the eight corners need to be entered in the specific order shown in Figure 7 23 for the box grid Figure 7 27 No of divisions N1 The number of divisions in the direction connecting Corner 1 to Corner 2 refer to Figure 7 23 Figure 7 27 The box grid surface is divided into N1xN2xN3 divisions No of divisions N2 The number of divisions in the direction connecting Corner 1 to Corner 3 refer to Figure 7 23 Figure 7 27 The box grid surface is divided into N1xN2xN3 divisions No of divisions N3 The number of divisions in the direction connecting Corner 1 to Corner 5 refer to Figure 7 23 Figure 7 27 The box grid surface is divided into N1xN2xN3 divisions Sphere This option is selected to generate a sphere grid specified by the position of the center its radius and the number of divisions in 6 and directions Figure 7 28 Center The coordinates of the center of the sphere are set using this o
84. select Clear Freq Response Data on the right click menu Run forced response FE analysis on the structure in the desired frequency range to generate the frequency response data The frequency response data or structure velocity could later be used as a boundary excitation on the BE model which is generated from the structure FE mesh More details on how to define and apply boundary conditions in Coustyx are provided in Chapter 6 The following are the supported frequency response data formats 5 1 2 1 Nastran OP2 File The OP2 Output2 file is a binary output file from the forced response analysis of a FE mesh in NASTRAN It contains the output acceleration velocity or displacement at all the nodes of the FE mesh Coustyr extracts the frequencies and the velocity response at these frequencies from this file Note To create an OP2 file that can be read by Coustyx set the value of the parameter POST in the Nastran Bulk Data to 1 PARAM POST 1 5 1 2 2 Nastran Punch File The NASTRAN punch file also contains the output from the NASTRAN FE analysis similar to the OP2 file but in ASCII format Coustyx extracts the frequencies and the velocity response at these frequencies from this file 5 1 Importing FE Data a s ay Coust File Edit Preferences Help ERAEN 243 Model Type lt MultiDomain gt Version lt 1 00 00 gt Model Description Nicase word JRegep Structmesh 0 Rename
85. selecting any of the frequency dependence types Constant Table or Script 6 4 Indirect BE Model BCs 175 New Boundary Condition GE Name New BC Type Discontinuous Help m Discontinuous Side 1 side 2 Type Nonuniform Pressure y Help Pressure 1 Hfunction GetPressure in PosnVec 2 f f AngularFreq SoundSpeed VaveNumber and AmbientDensity are prede read only variables that can be used here The following is just an example change the formula to suit you var PressMagn 12 0 var Press PressMagn exp i WaveNumber PosnVec 2 return Eval Press enes Figure 6 30 Discontinous Non Uniform Pressure Use Impedance can be used to specify impedance Refer to Section 6 3 6 1 for more details Figure 6 32 6 4 10 6 Non uniform Normal Velocity This Boundary Condition is applied on the side of the element where normal velocity varies with position and normal The normal velocity is defined in the script by the function GetNor mal Velocity which takes in the predefined position vector Posn Vec and normal vector Normal Vec as the arguments Other predefined variables that can be used in the script are AngularFreq w SoundSpeed c WaveNumber k AmbientDensity p and reference frame unit vectors el e2 e3 Figure 6 33 Use Impedance can be used to specify impedance Refer to Section 6 3 7 1 for more details Figure 6 33 6 4 10 7 Structure Velocity This
86. sides are parallel to those of the reference box Click on the Suggest button to auto fill the measurement surface variables in agreement with the standard Verify the input you have entered by clicking on the Check button Coustyx checks to see if the input variables satisfy the standard requirements If the standard requirements are not met a message window pops up to help you make appropriate corrections X Axis Specify the orientation of the X axis here See Figure 7 40 for definition Y Axis Specify the orientation of the Y axis here See Figure 7 40 for definition Corner1 Specify Cornerl of the parallelepiped surface here See Figure 7 40 for definition The parallelepiped is constructed using Cornerl as the starting point and 1 L2 L3 as its dimensions along X Y Z axis respectively 7 2 Outputs 245 Reference box Measurement surface B Corner1 L1 1 d O Microphone positions d Measurement distance Figure 7 40 1503744 Parallelepiped measurement surface with microphone positions for a source placed on the floor against two walls 246 Analysis Sequences L1 Length of the parallelepiped in X direction Figure 7 40 Specify the value of L1 such that it satisfies the definition L1 11 d where l1 is the reference box dimension in X direction and d is the measurement distance The recommended value for d 1m L2 Length of the parallelepiped in Y direction
87. some more elements be longing to neither group then it is split among Group 1 Group 2 and the rest of elements For example let us assume a node is being shared by four elements A B C and D See Figure 5 49 If A is added to Group 1 B to Group 2 C D are not added to any group when the shared node is split Coustyz splits the node into 3 different nodes node 1 for Group 1 Element A node 2 for Group 2 Element B and node 3 for the rest of elements that belong to neither groups Elements C and D See Figure 5 50 5 11 Element Orientation This tabbed window is located at the bottom pane of the Mesh Viewer window It is used to view and or flip the normals of the selected elements in the GUI refer to Figure 5 51 Left click on any element in the GUI with shift key held down to view its orientation To view orientations of all the elements in the GUI right click with shift key held down and select Operation on Selection Select All Displayed Elements Note that green arrow represents the positive side and the red arrow represents the negative side of the element normal Flip Selected Elements This is used to flip the normals of selected elements When an el ement normal is flipped the coordinate connectivity and variable node connectivity are automatically modified to reflect these changes 140 Pre processing Features Figure 5 44 After adding elements to Group 1 Notic
88. split nodes along the common edge of adjacent elements which have different velocity boundary conditions but no duplicate nodes During skinning Coustyx automatically creates duplicate nodes for most other cases such as geometry discontinuities edges corners junctions etc Refer to Section 5 10 for more details 4 2 13 Element Orientation This tabbed window located at the bottom of the Mesh Viewer window is used to view and or flip the normals of the selected elements in the GUI Refer to Section 5 11 for more details 4 3 Model Setup In this section we will briefly discuss the procedure one needs to follow to set up the Coustyx model and run the acoustic analysis We recommend that these steps be followed in the order described below To start using the software open Coustyr from the start menu or from a shortcut on your desktop Coustyz window shows a tree structure named Model at the top most level and several branch members fulfilling specific tasks in building the model or running the analysis The model tree appears at the top left portion of the Coustyx window when a model is open or when a new model is created from the File menu Figure 4 15 shows the structure of the Model tree for MultiDomain and Indirect Coustyx models A brief description on each of the model tree member tasks are provided below 4 3 1 New Model Open Model File To create a new model from the Coustyr Main Menu select File New Model Fig ure 4 16 C
89. the center of each partial area and at each corner of the partial area excluding the corners intruding into reflecting planes N3 Number of subdivisions in Z direction Figure 7 38 Select the value of N3 such that the length of the rectangular partial area formed by these subdivisions satisfies the criterion lt 3d where L3 is the length of parallelepiped in Z direction and d is the measurement distance Refer Figure 7 37 The microphone positions are in the center of each partial area and at each corner of the partial area excluding the corners intruding into reflecting planes Parallelepiped against wall Use this measurement surface when the source under test is placed on a floor against a wall Figure 7 39 shows a parallelepiped measurement sur face whose sides are parallel to those of the reference box Click on the Suggest button to auto fill the measurement surface variables in agreement with the standard Verify the input you have entered by clicking on the Check button Coustyx checks to see if the input variables satisfy the standard requirements If the standard requirements are not met a message window pops up to help you make appropriate corrections X Axis Specify the orientation of the X axis here See Figure 7 39 for definition Y Axis Specify the orientation of the Y axis here See Figure 7 39 for definition Corner1 Specify Cornerl of the parallelepiped surface here See Figure 7 39 for definition The parallelepiped
90. the coordinates in the ASCII file are in m and the Coustyx units are in mm a Scale factor of 1000 is entered to convert the values in the file from m to mm A Scale factor of 1 imports the values as they are 4 4 Sets 77 P Edit Chief Points eS 1 1 0 000000 0 262866 0 425325 2 2 0 425325 0 000000 0 262866 3 3 0 262866 0 425325 0 000000 4 4 0 000000 0 262866 0 425325 a 0 262866 Import Options 0 000000 whether to replace the table or append the data to it 0 425325 Scale factor 1 0000000000000 en Import From file Figure 4 31 Import Chief Points from a File 4 3 10 Context Script Select Model Context Script Coustyx provides the option to define global variables through Context Script These vari ables can then be used in any other scripts such as Boundary Condition Analysis Sequence etc The Context script is executed once at the start of the analysis to compute the global variable values The predefined read only variables that can be used in the Context script are Angular Freq w frequency in radians sec SoundSpeed c speed of sound in the fluid medium with the same units as those defined in materials WaveNumber k AmbientDensity p den sity of the fluid medium with the same units as those defined in materials Right click and select Open to open the Context script for editing select Close to close the window Figure 4 32 4 3 11 Analysis Sequences
91. the real part of impedance R is positive at all frequencies Most acoustic materials and backing combinations are stiffness controlled at low frequency 1 Hence the value of X in Figure 6 2 is large and positive for lower frequencies Also the impedance material absorbs acoustic energy For the sound power to be absorbed by the impedance material the real part of impedance R should be positive This can derived as follows From the definition of impedance in Figure 6 1 the average sound power per unit area absorbed by the impedance material can be reduced to 1 1 1 Power 3Relpvn Re R iX Unive FR vrnil 6 2 where Re stands for real part of and represents the complex conjugate For the sound power to be absorbed the value of R should be positive 6 2 Interpolation Options for Mismatched Meshes Interpolation options are used to apply structure velocities from a structure mesh to a mismatched boundary element mesh Note that these options are available only for bound ary conditions that use Structure Velocity In this section we will learn the kind of velocity interpolation performed for mismatched meshes and the options to control it 6 2 Interpolation Options for Mismatched Meshes 147 an T 0 20200 T Normalized Impedance 100 1000 5000 Frequency Hz Figure 6 2 Specific acoustic impedance Z poc R poc jX poc for a foam of 1 inch thickness measured using e
92. to either replace the current table or append to the existing table by the selection of one of the options Replace or Append Figure 3 6 3 3 Frequency Dependence Type 27 Scale factor All the values in the ASCII file except the first column which is the frequency are multiplied by the Scale factor before being read into the table Figure 3 6 This is specifically useful when the imported file has different units compared to Coustyx model A unit conversion factor should be used as the Scale factor to convert these values For example when the velocities in the ASCII file are in m s and the Coustyx units are in mm s a Scale factor of 10 is entered to convert the values in the file from m s to mm s A Scale factor of 1 imports the values as they are Omega exponent The Omega exponent sets the power of jw which is then multiplied with all the values in the ASCII file except the first column which is the frequency w before being read into the table Figure 3 6 This is useful when the imported values from the file vary from the variable values in the table by a factor of jw For example e Assume that a velocity boundary condition needs to be applied through the Table option But the user has only the displacement data in an ASCII file The Table can still be populated by importing displacement values from the ASCII file and setting the Omega exponent value to 1 That is the velocity values are obtained by multiplying the displacement
93. to load Only these frequencies from the data read are loaded into the model The Natural Mode Data could be loaded in a similar fashion 5 1 Importing FE Data 95 5 1 1 Importing Structure Mesh Select Model Structures Right click on Model Structures and select any of the file format options from Import refer to Figure 5 1 Coustyr has the capability to import FE meshes from the following data formats VEN File Edit View Preferences Help Dae iee amp Ey Modell cyx 3 Type lt MultiDomain gt LE Version lt 1 00 00 gt Model Description ma Structures E Materials a Structures Planes Interfaces Boundary Direct BE C FE Meshe E Domains E Context S Rename Copy Paste Delete Open Analysis Close Edit Help Import gt Abaqus inp File Nastran Bulk Data bdf File Ansys Results rst File Figure 5 1 Importing a finite element structure mesh 5 1 1 1 Abaqus inp files ABAQUS is a commercial FEA software for general purpose non linear finite element analysis used for engineering simulations and analysis The ABAQUS input file is an ASCII file with an extension inp This file contains information about mesh geometry properties of the material boundary conditions and other commands to control output data When imported Coustyx reads only the information regarding the geometry of the model from these files 5 1 1 2 Nastran
94. varies with the number of CPU cores utilized To use this license scheme make sure your computer is connected to a server running the Altair License manager and the value of the environment variable LM_LICENSE_FILE or ALTAIR LM LICENSE FILE is set to 77880servername or portnumber servername Contact your network administrator to find the port number and the server name on which Altair License man ager is running Now open Install License Key window by clicking on the icon found in the Start menu Start All Programs Coustyx32 or Coustyx64 InstallLicenseKey Choose the license scheme Use Altair GridWorks License Press the Test button to check the connec tion to the license server and the number of available GridWorksUnits Figure 2 9 Press OK to install the license and exit the window or press Cancel to discard changes before exiting the window 2 3 3 Modify Path Environment Variable Coustyz allows you to append the installation folder path to your computer s Path environment variable This helps avoid having to specify the full path name of the folder containing the executable every time you call Coustyx exe from the command prompt Figure 2 10 2 4 Running Coustyx After installation you can start using Coustyr by opening the program from the Start menu Start All Programs Coustyx32 or Coustyx64 Coustyx You can also run Coustyx from the command prompt 2 4 1 Running from the Command DOS Pro
95. view perpendicular to the Y axis show the view perpendicular to the Z axis turn the reference axis off or on zoom into the mesh zoom out of the mesh fit the mesh in the window rotate the mesh up by 90 rotate the mesh down by 90 move and rotate the mesh This is the default GUI mouse cursor style 7 la el a PP a rotate the mesh to the left by 90 rotate the mesh CCW by 909 rotate the mesh CW by 90 rotate the mesh up in increments specified in Preferences menu rotate the mesh down in in crements specified in Preferences menu rotate the mesh to the right in in crements specified in Preferences menu rotate the mesh to the left in in crements specified in Preferences menu rotate the mesh CCW in in crements specified in Preferences menu rotate the mesh CW in incre ments specified in Preferences menu perform operations on the selec tion on the mesh This cursor style is obtained by holding shaft key while the cursor is in the GUI 36 Getting Started 3D Viewer Feature angle deg 15 000000000000 Incremental rotation angle deqg 1 3 Ea Timer for rotation msec 5 E Zoom Increment 0 05000000000000 Show element edges by default Element resolution level by default 1 ES ad 2 Relative size of nodes 2 E Show shadows Use Fast draw mode coral Figure 4 3 Preferences dialog box 3D Viewer parameters Figure 4 4 Definition of fe
96. zr Figure 4 39 Description of a plane wave acoustic source A plane wave source is defined by a location R x Yr zr an amplitude A and a direction of propagation n A has the same dimensions as pressure Figure 4 39 Figure 4 40 The pressure p due to a plane wave at any point Q z y z is TI 4 4 5 r Y Yr eo Z E Position Vector The location R of the plane wave source is set by X component Y com ponent and Z component Note that the units should be consistent with the geometry units Source Strength Set the amplitude A of the plane wave through any of the frequency depen dent types Constant Table or Script Note that the units used here should be consistent with the rest of the model inputs Direction Vector The plane wave propagation direction n is set by X component Y com ponent and Z component 4 5 3 Cylindrical A cylindrical wave source is defined by a location R 2 Yr 2r an amplitude A and its axial direction of propagation n Figure 4 41 Figure 4 42 The wave equation for a cylindrical wave propagating in z direction is 88 Getting Started Position Vector X component Y component Z component Source Strength Frequency Dependence Type Real 1 0000000000000 Direction Vector X component Y component Z component 0 0 0 0 1 0000000000000 Figure 4 40 Plane Wave Q x y z A E A A Mia y AN nr R yr zr Figure 4 41 Description o
97. 0 5 5 0 425325 6 6 0 262866 7 7 0 000000 8 10 0 000000 9 11 0 425325 10 12 0 262866 new C Import from file Figure 4 30 Chief Points Edit Dialog Box X The z coordinate of a Chief Point Y The y coordinate of a Chief Point Z The z coordinate of a Chief Point 0 262866 0 000000 0 425325 0 262866 0 000000 0 425325 0 262866 0 262866 0 000000 0 425325 0 425325 0 262866 0 000000 0 425325 0 262866 0 000000 0 425325 0 425325 0 262866 0 000000 Import From File Chief Points can be imported from an ASCII file with components sepa rated by commas tabs or spaces The file must contain four columns with Id and X Y and Z coordinates of a Chief Point Figure 4 31 Each new Chief Point is added to a new row Import Options window opens up after the selection of the file with the following options Whether to replace the table or append the data to it The imported data from the file can be used to either replace the current table or append to the existing table by the selection of one of the options Replace or Append Figure 4 31 Scale factor The X Y Z coordinates of Chief Points in the ASCII file are multiplied by the Scale factor before being read into the table Figure 4 31 This is specifically useful when the imported file has different units compared to Coustyr model unit conversion factor should be used as the Scale factor to convert these values For example when
98. 0 57 0 24 0 38 0 11 0 025 0 075 0 125 0 175 0 225 0 275 0 325 0 375 0 425 0 475 0 525 0 575 0 625 0 675 0 725 0 775 0 825 0 875 0 925 0 975 254 Analysis Sequences Number of Probe Traverses Enter the number of microphone traverses at equal increments of azimuth angle around the source Figure 7 42 The least number of microphone traverses is eight Spiral Path This method uses a traverse along one meridional path and simultane ously traverses the microphone through an integral number of circular paths thus forming a spiral path around the vertical axis of measurement surface Figure 7 43 shows spiral path traversed by a microphone The least number of circular turns that shall be completed by the microphone is five Number of Circular Paths Traversed by a Probe Enter the number of com plete circular turns traversed by a microphone to form the spiral path Fig ure 7 43 The least number is five The sound power level Lw from 1503745 standard is computed as follows Lu Lpf 10 logio dB C C2 0 B 313 15 Bo 273 15 6 B 296 15 C2 15 logio E msn id C 10log 0 dB where S is the area of the measurement surface in square meters Sy 1 m B is the barometric pressure during measurements in Pascals Bo is the reference barometric pressure 1 01325 x 10 Pa is the air temperature during measurement in degrees Celsius La f is the weighted surface sound pres
99. 145 6 2 Interpolation Options for Mismatched Meshes 0 146 63 Multi Domain Model BCS sus ea aa ee ee RS 149 BSL Dummy BC a aa ca denea aaia ieee AAA 152 6 3 2 Inmteriace BC 2424 ob 4448 eed oS ee eed Deke eae as 152 6321 Interface Names sanser sake eR ee ae RS 152 6 3 2 2 Domain is on the Positive Side of this Interface 152 6 3 3 Uniform Pressure BC ee es 152 6 3 4 Non uniform Pressure BC ee e 154 6 3 5 Uniform Normal Velocity BG sex o arasa asthe eee aban dees 154 BSS Use lmpedante 00 ware eae Sa eb ke oO eee AR 156 6 3 6 Unttorm Velocity BO 2 4 vass aa gage Geek ARA 156 6861 Use Impedance orae eean b de 4540 oe 4a deeds 157 6 3 7 Non uniform Normal Velocity BC gt sa coc da Leausa traat dada 157 Ges Use Impedance jada ske coe g a a a GE ee KES AG 157 6 3 0 Structure Velocity BG oe o as TTS d aaa aoa SKE KER 157 6381 Structure Name 20 564545 44424 45 0 48 44a ce ds 159 6 3 8 2 Structure Interface Name rv rv ce eee ee 159 6 3 8 3 Interpolation Options for Mismatched Meshes 159 0382 Use impedance e 0 4a 6 dad iue ee oe a baa aw ed ees 159 G30 Arbitrary Unior BO ss 4644445 46 eo OS pee he Eee eee 161 6 3 10 Arbitrary Non unitorm BO ass eae Gikk ee kOe we RN 161 62 Indirect BE Model BOS 2 2 2 0 Ge a eee Ph eb ee SR TE BRS 162 64 1 Transparent BO corsa a Soe a RR ee ee SHEARS SEERE 163 6 42 Ane choie Termination BG ecos 24 dad
100. 2 is the reference box dimension in Y direction and d is the measurement distance The recommended value for d 1m L3 Length of the parallelepiped in Z direction Figure 7 38 Specify the value of L3 such that it satisfies the definition L3 13 d where 13 is the reference box dimension in Z direction and d is the measurement distance The recommended value for d 1m N1 Number of subdivisions in X direction Figure 7 38 Select the value of N1 such that the length of the rectangular partial area formed by these subdivisions satisfies the criterion lt 3d where L1 is the length of parallelepiped in X direction and d is the measurement distance Refer Figure 7 37 The microphone positions are in the center of each partial area and at each corner of the partial area excluding the corners intruding into reflecting planes N2 Number of subdivisions in Y direction Figure 7 38 Select the value of N2 such that the length of the rectangular partial area formed by these subdivisions satisfies the 242 Analysis Sequences Reference box Measurement surface L1 1 2d O Microphone positions d Measurement distance Figure 7 38 IS03744 Parallelepiped measurement surface with microphone positions 7 2 Outputs 243 criterion i lt 3d where L2 is the length of parallelepiped in Y direction and d is the measurement distance Refer Figure 7 37 The microphone positions are in
101. 20 Example function Binary in n if n 1 return i else if n 0 return 0 else var ni int n 2 var n2 n 2 n1 return Eval Binary n1 Binary n2 280 Language Syntax Out Binary 3 Out Binary 13 Out Binary 6876 Output 11 1101 1101011011100 Like variables a function once declared inside a compound statement is visible to all subse quent statements inside that compound statement It is not visible to statements outside that compound statement Example Sample routine to expand the function f into its Taylor series of order n in variable x about its current value function Taylor in f in x in n define a local function function Factorial in n if n 1 return 1 else I return Eval n Factorial n 1 The first term of the series var lastder Subst f var TaylorSeries f for var i 1 i lt n i i 1 I Obtain the ith order derivative of f wrt x lastder TotalDiff Subst lastder Subst x If this derivative is non zero at the current value of x if Eval lastder 0 TaylorSeries Subst TaylorSeries Eval lastder Subst x Eval x Eval i Factorial i return Subst TaylorSeries var theta 0 Out Taylor sin theta theta 2 Out Taylor sin theta theta 4 Out Taylor cos theta theta 4 8 6 Statements 281 var t 1 Out Taylor t 0 5 t 3 Output o 1 Ctheta 0 71
102. 3 4 3 0 1 3 92 200 10 9 2 0 2 63 250 8 6 1 3 0 1 59 315 6 6 0 8 0 0 81 400 4 8 0 5 0 0 36 500 3 2 0 3 0 0 28 630 1 9 0 1 0 0 46 800 0 8 0 0 0 61 1000 0 0 0 0 1250 0 6 0 0 1 92 1600 1 0 0 1 5 05 2000 1 2 0 1 0 2 7 95 2500 1 3 0 2 0 3 10 32 3150 1 2 0 4 0 5 11 54 4000 1 0 7 0 8 11 1 5000 0 5 1 2 1 3 9 61 6300 0 1 1 9 2 7 63 8000 1 1 2 9 3 5 46 10000 2 5 4 3 4 4 3 44 12500 4 3 6 1 6 2 1 43 16000 6 6 8 4 8 5 0 77 20000 9 3 11 1 11 2 2 74 234 Analysis Sequences Analysis Sequence Description Units Solver Controls Frequency Ranges Outputs Binary Results Sensors IGlass Sound Power Standards Sound Power Create Sound Power File File Name soundpower from standards dat Method 150 3744 1994 Standard 1503744 1503744 Specifications Measurement Surface Hemisphere Grid Data Suggest Check 1 000000 0 000000 0 000000 0 000000 m Radius 3 4641016151378 Microphone Array Fixed Positions Probe Positions Number of Probe Positions Figure 7 32 IS03744 sound power standard window 7 2 Outputs 235 Measurement surface Reference box O Key microphone positions Center Figure 7 33 1503744 Microphone array on the hemisphere 236 Analysis Sequences Table 7 6 IS03744 Coordinates of key microphone positions 1 10 and additional microphone positio
103. 5 22 Display Set of Bad Elements 120 Pre processing Features Operations on Selection Unselect All Select All Displayed Elements Select All Bad Elements Selected Elements Unselect Select All Displayed Nodes pepe DES Select All Bad Nodes BEE Selected Nodes Select Elements Connected Through CoordNodes Hide Set Boundary Condition gt Stop Skinning I Create Mesh From Skin Add to Set gt ams Remove from Set AAA Figure 5 23 Display Connected Nodes of Selected Element Operations on Selection Unselect All Select All Displayed Elements Select All Bad Elements Selected Elements gt Select All Displayed Modes Select All Bad Nodes C Selected Coord nodes selected Nodes gt Unselect Accept Seam Stop Skinning Create Mesh From Skin Display Style Delete Selected Seams Clear Skin Display Saias eee Delete All Seams Add to Set gt Remove from Set gt Figure 5 24 Display Connected Elements of Selected Node 5 5 Skin 121 5 5 1 Treatment of Bad Elements Coustyr performs consistency checks before skinning the FE mesh Press Skin Create Skin button to start these checks If there are no inconsistencies in the FE structure mesh then Coustyx proceeds with the skinning process However when the FE mesh has elements with bad coordinate connectivity Coustyx throws error messages in the log
104. 8 5 Mu Nodes Select Model Indirect BE Mesh Mu Nodes Use this sub tree member to review Mu Nodes Mu Nodes are variable nodes associated with double layer potential 1 at the location of the node The double layer potential at a point is defined as the difference of the pressure on the positive side pt of the element to the pressure on the negative side p7 that is u pt p Single layer potential 0 and double layer potential u are the primary acoustic variables in the Indirect BE formulation used for Indirect models The right click menu provides the following options Open Opens the list of all Mu nodes The table shows the Mu node ID its location coordinates X Y Z and the Status of the node The Status is determined by the solid angle covered by the node When the solid angle is 47 the status shows On Free Edge Close Closes the opened Mu nodes window 4 3 8 6 Pn Nodes Select Model Indirect BE Mesh Pn Nodes This sub tree member is used to review the normal derivative of pressure Pn nodes defined on a Baffled plane 4 3 8 7 Boundary Conditions Select Model Indirect BE Mesh Boundary Conditions The boundary conditions to be imposed on the Indirect model are defined here Bound ary conditions are applied in terms of the surface sound pressure particle velocity acoustic 68 Getting Started impedance Coustyx has a user friendly interface to define a wide variety of boundary condi
105. 9y 9 8 9 9 9 10 9 11 9 12 9 13 9 14 9 15 9 16 9 17 9 18 5 19 9 20 9 21 9 22 9 23 9 24 9 25 9 26 9 27 9 28 Coaxial circular paths in parallel planes for microphone traverses over a reflecting DIANE nus o E Rs A ass A Budde ace 237 I503744 Microphone array on the quadrant o o 239 1503744 Microphone array on the octant o o 240 1503744 Procedure for fixing microphone positions on a parallelepiped measure Men eUI aa os as si Mee dada A a BR Ge 241 1503744 Parallelepiped measurement surface with microphone positions 242 1503744 Parallelepiped measurement surface with microphone positions for a source placed on the floor against a wall 0 o 244 1503744 Parallelepiped measurement surface with microphone positions for a source placed on the floor against two walls o 245 ISO3745 sound power standard window 0000 eee eee ee 248 1503745 Meridional paths for a moving microphone 250 1503745 Spiral path for a moving microphone 251 ISO9614 1 sound power standard window e e eee ues 255 IS09614 1 Parallelepiped measurement surface with probe positions 257 Analysis CDi coros sra bees Poo ELE RR hER EEE Ed 262 Detail of the NASA Lewis gearbox 2 2 2 0 0 0002 eee eee eee 293 FE model of the NASA Lewis gearbox e 294 Surface norma
106. All Hide All 17 35 01 No of bits on Dept 17 35 02 No of bits on Depth buffer 16 17 57 20 No of bits on Depth buffer 16 17 57 20 No of bits on Depth buffer 16 Select Unselect Add Selection to Set Remove Selection from Set Figure 4 35 Menu options for coordinate nodes in a Set 4 4 Sets 83 Display Style Changes the display style of the coordinate nodes in the Set Refer to Section 4 2 3 2 for more details on each of the options in the Display Style dialog window Display All Displays all the coordinate nodes of the Set in the GUI Hide All Hides all the displayed coordinate nodes of the Set in the GUI Select Selects all the coordinate nodes of the Set in the GUI Unselect Unselects coordinate nodes of the Set in the GUI Add Selection to Set Adds selected coordinate nodes to the current Set Remove Selection from Set Removes the selected coordinate nodes from the current Set Faces Right click on lt Set Name gt and select Faces to find the following sub menu options Note that all the options are disabled when the mesh is not open in the GUI Figure 4 36 QF Sets Y Hole 1 OE FE Meshes Hole 2 E Domains Context Script Rename H Analysis Sequence Copy Paste Delete Open Close Edit Help Replicate Elements CoordNodes I Log Faces gt Select 17 35 01 No of bits on Depth 17 35 02 No of bits on Depth buffer 16 Unselect 17 57 20 No of bits on Dep
107. BCs Single sided BCs Double sided BCs Transfer BCs Perforated BCs are all implemented 4 Interpreter support to help users define custom analysis sequences Coustyx provides the ability to execute scripts in a special programming language For example scripts can be written to define a complicated boundary condition or to compute transmission loss for mufflers 5 Parallel implementation of the code on shared memory multi CPU computers allows effi cient usage of system resources 6 Numerous pre processing tools provided in Coustyx cut down the time taken to setup an acoustic problem The user can directly build Coustyr BE model from FE structure mesh instead of using a third party software for converting FE meshes to BE meshes very user friendly Graphical User Interface GUI is developed to assist in setting up the acoustic problem by creating and manipulating boundary element models building the model and running the analysis It incorporates visualization tools and dialog boxes to query and modify any parameter associated with a model Availability of wide variety of pre processing tools in Coustyx make the model setup simple and easy Some of the important pre processing features are listed below e Import options Ability to import FEA mesh and data from any of the three FEA programs NASTRAN ABAQUS and ANSYS and Universal file format e Skinning Ability to skin a finite element mesh to obtain surface mesh for Coustyr BE
108. Bulk Data bdf files The NASTRAN bulk data format bdf is widely used in the industry and can be generated 96 Pre processing Features from a large number of commercially available FE mesh generators The bdf file contains information about the geometry of the mesh which is extracted by Coustyz 5 1 1 3 Ansys Results rst files ANSYS is another commercially available FE modeling package used widely for engineering simulations The ANSYS rst files are binary files containing information about the nodes and elements of the FE model along with the results Coustyx extracts the geometry of the mesh from these files 5 1 1 4 IDEAS Universal unv files IDEAS Universal file formats are widely used in structural dynamics noise and vibrations community Coustyx provides translator to extract geometry information of a mesh from these files 5 1 2 Loading Frequency Response Data Select Model Structures lt Structure Mesh Name gt Right click on lt Structure Mesh Name gt and select the frequency response data from any of the file format options through Load Freq Response Data refer to Figure 5 2 If the data is read successfully a new dialog box with a list of frequencies available in the data appears See Figure 5 3 The user can select what frequencies to load into the model Use Select All Unselect All or Select by Frequency Range buttons to choose the frequencies of interest To clear the data already uploaded
109. But it can also be defined as a frequency dependent complex value c c jci to introduce damping in the system The variation with frequency is simulated by defining the speed of sound to be a frequency dependent type Table or Script Note that for a decaying wave the imaginary part of the speed of sound should always be negative that is c lt 0 Refer to Figure 4 21 This is due to the adoption of the following convention in Coustyz P Re pe where Re stands for real part of P is the time harmonic pressure wave p is the complex amplitude of the sound pressure w is the frequency of fluctuation and j V 1 Consider a point source in a medium with the speed of sound c c jci The outgoing wave has the form p poet je JM where k w c jci is the wave number R w c c is purely real po is real If c lt 0 the pressure p is bounded with an exponential decay in the amplitude as shown Figure 4 21 where as for c gt 0 the pressure p exponentially grows which is physically improbable Note that the units used for speed of sound along with the units for ambient density determine Coustyx model units For more information on the unit conventions followed in Coustyx refer 4 3 Model Setup 59 Real Pressure Real Pressure 1 1 1 1 E 1 1 1 1 N 0 2 4 6 8 10 0 2 4 6 8 10 x x a Decaying bounded pressure with c lt 0 b Unbounded pressure with c gt 0 Figu
110. Coustyx User s Manual Advanced Numerical Solutions Hilliard OH November 4 2009 Contents List of Figures List of Tables Preface 1 Introduction 2 Installing Coustyx 2 1 Software Installation gt aa 24 aa ORR Bee Peete 2 1 1 License Agreement ceras S KR EG ke 2 1 2 Select Installation Folder 243 Conte stalai chute A a AA 2 2 Dongle Device Driver Installation 2 3 License Key Installation avs 20 v sa s see da Zo Use Native License ezo ins TASK SKE AAA 2 3 1 1 If you have a local dongle 2 3 1 2 If you have a network dongle 2 3 1 3 If you are using Coustyz without a dongle 2 3 1 4 If you are using a Demo Model 2 3 2 Use Altair GridWorks License o o 2 3 3 Modify Path Environment Variable 24 RBuniing COS xe aa a h a a b a oe Saa 2 4 1 Running from the Command DOS Prompt 3 Conventions in Coustyx 3 1 Time Dependence 2 44 64 46 ss Sk RA ME EEE AEG EE EN E 3 21 Model Units vas e Se ausra d a ai SG GE bb adie 3 3 Frequency Dependence Type o a duos Constant vaa aa AA 3 02 Table qian aie ee Soe be BSR RE A sek DD A Jodl lreporttrom Wiles ss 4 22h seek mae a xix xxi NDADADARBRA RA ER Ren ee eK Dw 14 iv CONTENTS 39 22 Import Options circuit do 26 Ba OCDE o s A 27 4 Getting Started 29 4 1 Main
111. Coustyx builds system matrices and the linear system of equations are solved either by an iterative method GMRES or by a direct method LU decomposition The user can select either of these solution methods from the drop down menu GMRES This option solves the linear system of equations by the iterative method Generalized Minimum Residual Method GMRES Figure 7 10 Direct This option solves the linear system of equations by LU decomposition 7 1 1 5 GMRES The contents of this panel are activated only when GMRES is selected as the Solution Method Coustyr uses GMRES as the default iterative solver when Use FMM option is selected The linear system of equations are solved by the iterative method Generalized Minimum Residual Method GMRES Figure 7 6 Preconditioner Type Preconditioners are used in iterative solvers to improve spectral prop erties of the system matrices for faster convergence Coustyr implements three precondi 7 1 Inputs 199 Analysis Sequence me x Analysis Sequence Figure 7 9 Solution Method FMM 200 Analysis Sequences Analysis Sequence zs Excitation Vector sl Figure 7 10 GMRES 7 1 Inputs 201 Analysis Sequence Figure 7 11 Direct Solution Method 202 Analysis Sequences tioners which can be selected based on the user requirements for reducing memory usage faster convergence parallel processing etc
112. Description Solver Controls Frequency Ranges Outputs Script Start Hz Delta Hz No Freqs End Hz 100 000000 15 000000 61 1000 000000 Tara Figure 9 24 Set analysis frequencies 9 4 3 3 power dat This ASCIEtext file contains acoustic power values computed at each analysis frequency Each file has five columns The first column contains analysis frequencies in Hertz The second and third columns contain radiated active sound power and reactive sound power respectively The input power is written to the fourth column All the power units will be consistent with the material properties sound speed and ambient density defined earlier here the unit is Watt The fifth column consists of the radiation efficiency of the gearbox housing The radiated sound power and radiation efficiency are plotted against the analysis frequency in Figure 9 25 and Figure 9 26 using matlab plot command The sound power radiated Fig ure 9 25 has peaks corresponding to the structural vibration modes that have a non zero net volume velocity 9 4 3 4 iglass igl IGlass files are post processing data files created by Coustyx to visualize the acoustic analysis results Refer to Figure 9 27 e Double click on iglass igl file to open it e Click on the Attribs tab on the top left of the iglass viewer e Select Attribs Attribute Pressure to view the pressure distribution on the surface of the
113. Elements Set Boundary Condition Rigid BC as shown in Figure 9 43 Repeat the above for other holes as well 9 5 2 Run Acoustic Analysis Coustyx analysis parameters are set in Analysis Sequences which are then Run to solve the acoustics radiation problem e Select Model Analysis Sequences and right click to create a new analysis sequence by selecting New e Select Solver Controls tab to set solver parameters Refer to Figure 9 44 Ensure the default solver options are satisfactory Set Initial Guess Previous Solution from the drop down menu 334 Tutorial Gear Box Radiation File Edit Preferences Help 2 3 Model Type Indirect gt Version lt 1 00 00 gt Model Description CJ Structures Materials Planes Indirect BE Mesh lt Mesh gt Material lt Air gt Coord Nodes 2 Boundary Conditions Y Sources CJ Jump Conditions 2 Junction Constraints Hole I Rename Context Script Copy Y Analysis Sequ Paste Delete Open Close Edit Help Replicate Elements Display Style CaordNodes gt Display All Hide All _ Set Boundary Condition rl Rigid BC i Select Structure Velocity BC Unselect Add Selection to Set Remove Selection from Set Figure 9 43 Apply boundary conditions through sets 9 5 Coustyx Indirect Model 335 Name Analysis Sequence FMM Use FMM 7 Precomp
114. Figure 9 34 Pick the option Show Edges and click OK 326 Tutorial Gear Box Radiation Display Show Faces Transparent Show Edges Display Nodes ag Apply Resolution level Apply Color Red 20 Green 200 Blue 255 ES Gs Figure 9 34 Element Display Style Window 9 5 Coustyx Indirect Model 327 To unselect all the elements right click on the mesh again while holding down the shift key and select Unselect All e Create seams at the hole edges to avoid skinning the interior surface of the gearbox housing Select the tabbed window Skin from the series of tabs located below the structure mesh Move the cursor to the structure mesh in GUI Left click on the elements around the edge of a hole while holding the shift key Make sure to select elements with nodes on the hole edge as shown in Figure 9 35 Figure 9 35 Select elements for creating a seam Right click on the mesh while holding down the shift key to view the context menu and select Selected Elements Display Connected Nodes as shown in Figure 9 36 Left click on the displayed nodes while holding the shift key to pick the nodes to be part of the seam Make sure to pick nodes in a specific direction Pick the nodes until you see a circular seam following the edge of the hole as shown in Figure 9 37 From the tabbed windows located below the structure mesh select Skin Accep
115. Holes 1 Right click on Holes 1 and select Elements Set Boundary Condition Rigid BC as shown in Figure 9 19 Repeat the above for other holes as well 9 4 Coustyx MultiDomain Model 311 Operations on Selection Unselect All Select All Displayed Elements Unselect Selected Elements Display Style Display Connected Nodes Select Elements Connected Through CoordNodes Hide Set Boundary Condition Add to Set Structural Velocity BC Remove from Set Figure 9 18 Apply boundary conditions through selected elements 9 4 1 9 Domains e Specify the type of acoustic problem by selecting Model Domains Domain1 or lt Domain Name gt Boundedness The radiation from a gearbox housing is an exterior or unbounded acoustic problem Right click on Boundedness and select Boundedness Unbounded as shown in Figure 9 20 e Choose the fluid medium around the gearbox housing by selecting Model Domains gt Domaini or lt Domain Name gt Material Right click on Material and select Material Air e To set the side of the mesh on which the domain is you need to first check the direction of mesh normals Open Coustyx BE mesh in the GUI Select Model Direct BE Meshes gt NewMeshesCreatedFromSkin and right click on NewMeshesCreatedFromSkin and select Open Move the cursor to the BE mesh in GUI Right click on the mesh while holding down the shift key to view the context
116. ID 1332 ald to find a path from Node with ID 446 to Node with ID 1332 54 Failed to find a path from Node with ID 446 to Node with ID 1332 56 Failed to find a path from Node with ID 446 to Node with ID 1332 Figure 4 13 Create Skin 4 2 Operations on Mesh Viewer Window 49 4 2 9 Stitch Seams This tabbed window located at the bottom of the Mesh Viewer window is used to fill gaps between disjoint parts of a mesh FE or BE by generating new triangle elements between two seams Figure 4 14 The seams are created by selecting coordinate nodes More details on how to create and stitch seams are discussed in Section 5 7 Figure 4 14 Stitch Seams 4 2 10 Delete Elements This tabbed window located at the bottom of the Mesh Viewer window is used to delete selected elements in the GUI by pressing the Delete Selected Elements button Coustyr provides options to remove unshared coordinate nodes and unshared variable nodes of the deleted element Refer to Section 5 8 for more details 4 2 11 Merge Nodes This tabbed window located at the bottom of the Mesh Viewer window is used to merge selected nodes with all coincident nodes in the GUI Refer to Section 5 9 for more details 4 2 12 Split Pn Nodes Split Sigma Nodes This tabbed window located at the bottom of the Mesh Viewer window is used to split selected Pn or Sigma nodes in a MultiDomain BE mesh or Indirect BE mesh Use this 50 Getting Started function only to
117. In addition to this Coustyx also allows discontinuous boundary conditions with different types on each side of the el ement boundary For example pressure can be specified on one side while specifying velocity on the other side The capability to completely decouple the two sides of a bound ary using different types of BCs provide Coustyx users with greater modeling flexibility unknown in any of today s commercially available acoustic BE programs The discontinuous boundary conditions could be effectively used to eliminate Non uniqueness in the boundary integral solution at Irregular frequencies in meshes which enclose a vol ume Irregular frequencies are related to the eigen frequencies of the interior problem In 6 4 Indirect BE Model BCs 163 Indirect BEM exterior and interior problems are connected and solved at the same time Hence at Irregular frequencies exterior solutions are contaminated by unbounded interior solutions The user can employ discontinuous boundary conditions to decouple the exterior and interior problems As in most cases if the user is interested in the radiation problem alone the interior side of the boundary could be assigned a zero boundary excitation to suppress the interior excitation Refer to Ambarisha et al 2 for more details For example consider a pulsating sphere mesh which encloses a volume and one is interested in the acoustic radiation problem At the eigen frequencies of the interior the unbo
118. Load frequencies from the structure natural mode data 210 Load center frequencies of an octave band rv ee eee eee 213 Analysis outputs window e ec s o ia 0 w ai a a de b ee 215 Sensor Output Window saoe s 44 8 oA AK a a aaa Gee 216 Import Sensor Coordinates from a File 217 IGlass outp t WINdOWs s s s s ssa a n Aada a S eaa Gear et kA 218 IGlass field point grid types Quadrilateral Triangle Annular Disc Box and Spheres p ad eaa dado a aea t a aa ae h ue da a a e gaad 219 Quadrilateral IGlass field point grid types 220 IGlass Triangle field point grid types o aaa 221 IGlass Annular Disc field point grid types o e ren 223 IGlass Box field point grid types arr rn akk e ean 224 IGlass Sphere field point grid types o t ad mata 225 IGlass Structure mesh field point grid types o o 226 IGlass viewer showing sound pressure distribution on the exterior surface of a Housing v a s sa aa Gao ey dr A bade de 228 Relative response plots for different weighting filters 231 IS03744 sound power standard window 2 arr vr arr vr a a eee 234 IS03744 Microphone array on the hemisphere vr rv vr rv 235 xvi LIST OF FIGURES 7 34 7 35 7 36 7 37 7 38 7 39 7 41 7 42 7 43 7 44 7 45 7 46 9 1 92 9 3 9 4 9 5 9 6
119. Musicmatch NaturalSoft NetWaiting PE Explorer Roxio Creator DE SafeNet Sentinel SmartFTP Client Spyware Doctor Startup TextAloud TortoiseSVN Unlocker WebEx WinZip XEmacs Acrobat Distiller 5 0 Figure 2 10 Set path variable P E P EP REP o EI E WEDT R P E AR ER IE E M Path InstalllicenseKey G Prefyx Uninstall Coustyx Set 2 4 Running Coustyx 17 See Section 2 3 3 Figure 2 10 Coustyx accepts the command line arguments explained below These command line arguments may appear in any sequence e model ModelFileName specifies the name of the model file There should be no space between the and ModelFileName The ModelFileName is a cyx file If there are spaces in the ModelFileName it should be enclosed within This file contains infor mation about the Coustyx model It also can contain analysis sequences which are invoked to run the model e analysissequence AnalysisSequenceN ame specifies the name of the analysis sequence to be used to run the analysis The AnalysisSequenceName is defined inside the model specified by Model FileName If there are spaces in the AnalysisSequenceN ame it should be enclosed within This contains details on how to run an analysis the solution method to be used etc It is always used in conjunction with argument model Model FileName e nthreads NumberThreads specifies the number of threads to be used to run the analysis For a
120. Node with ID 1332 Failed to find a path from Node with ID 446 to Node with ID 1332 Failed to find a path Fram Node with ID 446 to Node with 1D 1332 Failed to find a path from Node with ID 446 to Node with ID 1332 Figure 5 26 Create Seams 5 5 Skin 125 5 5 3 1 Procedure to Create Seams Follow the steps below to create a seam Select a few of the elements through which the seam is supposed to pass through To select an element in the GUI Left click on the element with the shift key held down Figure 5 27 To display coordinate nodes of selected elements right click with shift key held down and select Operations on Selection Selected Elements Display Connected Nodes Figure 5 28 Choose the nodes in the path of the seam to be created To select a node Left click on the node with the shift key held down Note You should only select nodes on the corners of the elements not mid side nodes Once three or more nodes are selected the seam connecting these nodes is drawn if Coustyx finds a valid path Seams are constructed based on the shortest path identified by Coustyx while connecting all the selected nodes It may appear that a seam is not being drawn if Coustyr cannot find a closed path However as more nodes are selected in a valid closed path the seam will be drawn Only the last selected node can be unselected without disturbing the rest of the node list in the seam If a node from the seam is arb
121. Note that all the options are disabled when the mesh is not open in the GUI Figure 4 35 80 Getting Started File Edit View Preferences Help De ua Boo 447 aa A 1 5 Type lt MultiDomain gt Version lt 1 33 00 gt Model Description Structures Materials H Boundary Conditions ay Direct BE Meshes i o NewMeshCreatedFromSkin i 9 Coord Nodes a Elements P Nodes AQ Pn Nodes i CJ Constraint Equations 5 4 Sets FE Meshes Sets Domains Aa Rename EI Analysis Se Copy Paste Delete Open Close Edit Help New Figure 4 33 Creating a new set a group of elements and nodes 4 4 Sets 81 Hole 2 Y Domains 4 Context Script 3 Analysis Sequence Copy Rename Paste Delete Open Close Edit Help Replicate Elements gt Display Style CoordNodes Display All Gites Faces gt Hide All 17 35 01 No of bits on Depth rro 17 87 20 No of bts on Depth buffer 16 Set Boundary Condor d 17 57 20 No of bits on Depth buffer 16 Ge Unselect Add Selection to Set Remove Selection from Set Figure 4 34 Menu options for elements in a Set 82 Getting Started Hole 2 E Rename Context Script 1 3 Analysis Sequen Copy Paste Delete Open Close Edit Help Replicate Elements CoordNodes Faces gt Display Style Display
122. Select Model Analysis Sequences Analysis Sequences is a model tree member which is used to set the options such as frequency range solution methods etc required to run an analysis New analysis sequence is created by right clicking and selecting the menu item New Multiple Analysis Sequences can be created by repeating this action Refer to Chapter 7 for a detailed discussion on selection of various parameters for the analysis Once the Coustyx model setup is completed run the acoustic analysis by right clicking on the desired sequence Model Analysis Sequences lt Analysis Sequence Name gt and selecting Run The analysis results are stored in the output files referred in lt Analysis Sequence Name gt 4 4 Sets 78 Getting Started File Edit Preferences Help Helal elkel elral el Ey Model Type lt MultiDomain gt E Version lt 2 00 00 gt Model Description CJ Structures Materials Planes CJ Interfaces Boundary Conditions SJ Direct BE Meshes 103 NewMeshCreatedFromSkin Coord Nodes 2 Elements Q Prev D1 amp Next i P Nodes Pn Nodes E Constraint Equations 5 Y Sets Hole_1 Hole_2 PSHELL1 FE Meshes Domains AD 1 5 Type lt Direct BE gt Sources E Boundedness lt Bounded gt 2 Material lt Air gt Direct BE Meshes Ey NewMeshCreatedFromSkin E Xfm Matrix E Side of Mesh on which Domain is lt Negative gt E Boundary Condition Mappi
123. Selection ta Set Remove Selection from Set Figure 6 43 Applying boundary conditions through sets 188 Boundary Conditions e Apply BC through sets Select the set for a MultiDomain model from Model Direct BE Meshes lt Direct BE Mesh gt Sets lt Set Name gt Select the set for an Indirect model from Model Indirect BE Mesh Sets lt Set Name gt Apply BC to all the elements in the Set through the Set by right clicking on lt Set Name gt and selecting Elements Set Boundary Condition lt Boundary Condition Name gt Figure 6 43 Bibliography 1 A D Pierce Acoustics An introduction to its physical principles and applications Acous tical Society of America 1991 Pages 107 113 2 V K Ambarisha R Gunda and S M Vijayakar A new indirect formulation to address the non uniqueness problem in acoustic bem INCE conference proceedings 116 2007 Pages 1046 1055 3 J W Sullivan and M J Crocker Analysis of concentric tube resonators having unpartitioned cavities Journal of Acoustic Society of America 64 207 215 1978 Chapter 7 Analysis Sequences Coustyr allows users to specify set of parameters and commands required to run an analysis through model tree member Analysis Sequences Typical set of parameters include type of analysis solution accuracy analysis frequency types of outputs sensor locations etc Multiple analysis sequences could be saved through this opti
124. The normal vector that is used is that of the interface elements The interface is defined by a geometry mesh and certain types of boundary conditions such as perforated or arbitrary BCs 4 3 6 Boundary Conditions Select Model Boundary Conditions The boundary conditions to be imposed on the model are defined here Boundary conditions are the acoustic physical constraints such as sound pressure particle velocity acoustic impedance 62 Getting Started that are applied on the surface Coustyx provides options to define a wide variety of boundary conditions in a user friendly way Refer to Section 6 3 for a detailed discussion on different types of boundary conditions The user defines the boundary conditions as separate entities which are named uniquely here These boundary conditions are applied later to BE elements directly or through sets group of elements before running the analysis refer to Section 6 5 2 e Define a New Boundary Condition Right click on Boundary Conditions and select New and proceed with entering new parameters information Click OK to accept e Edit an Existing Boundary Condition Select Boundary Conditions lt Boundary Condition Name gt Right click on lt Boundary Condition Name gt and select Edit Pro ceed with editing the parameters Click OK to accept 4 3 7 Direct BE Meshes Select Model Direct BE Meshes This model tree member is present only for MultiDomain models It consists of
125. WA SS RR De RARER EOE SES 70 Junction CONSILAINIS 24 24 ge sekkene pA dd eee EME Ee eee ral Choosing Boundedness sara akse Oe ERR ee e ee a 73 Sideyot Mesh on Domain Function oscar ee eRe Se a 75 Chief Points Edit Dialog Box soe es SSK e k SE AAA 76 Import Chief Points from File cuicos 604 644 e440 edad ae ees 77 Content OCDE saka aia a ee eh eee RE ERE OOD eww Se RES 78 Creating a new set a group of elements and nodes 80 Menu options for elements ina Set s co seca Ha eaea ahhaaa eee 81 Menu options for coordinate nodes in a Set 2 arver a 82 Menu options for faces ina Set a acu netee ee 83 Add elements to bete aa il a AA RAS 85 Monopoli 012620 a Sa Seed ee faa se SA 86 Description of a plane wave acoustic source L 2 varer re ras 87 Plane Wave a sa ho sa SJUK Ee RR BRORS FG G Gre Ga Gp R 3 88 Description of a cylindrical wave acoustic source o e 88 Cylindrical aiara aira ee a bol red a a gp AAA 89 An acoustic dipole at R x Yr Zr modeled by two point monopole sources with equal and opposite volume velocities V and V 90 DipGle 64344 SA Bese sa 4 be eed eS Re 91 Quadrupole Dialog Box e cte s eo Sa aa eee s re ed Oe eS 92 User Defined Acoustic Source rv arr rv nn ananas 93 Importing a finite element structure mesh o 95 Loading frequency response data into Coustyx model
126. a AA ae 180 6 4 12 Non uniform Arbitrary BC s a aace e a egaa a E a a a 180 65 Applyim BUs 624 gad agda ad bie ae a a e h aaa ela ws G444 181 6 5 1 Apply BCs directly to Elements aaa aaa vr rn renn 181 6 52 Apply BCs through Sets viral a a 183 7 Analysis Sequences 190 fl TAPUS sopie adone AAA 194 Til Solver Controls sa oe se sd EG BER ada 194 GALL Parallel Processing voss 6 eee Tag STE Sep EEG 194 LIZ Formulation Type 1 ved 44 sed eiid em BAG 194 TELS FMNE cascade ke BO SR RS STE VA GR JG ei 196 11 4 Solution Method ess s recane ska AEG 198 TLL GMRES sama GT FEE ER SSS SEKTER EE 198 LI Integration 41 as 2aa gt redd s He sa Sak Gi 203 fl Frequency Ranges sina ga sere do A ea kok kuk 205 RELE FR vene RO tata A 207 7 1 2 2 Structure Freq Response Data 209 7 1 2 3 Structure Natural Mode Data uad ninia 209 7 1 2 4 Octave Band Center Frequencies 2 ov rav rv 210 7 1 2 5 1 3 Octave Band Center Frequencies 214 7 1 2 6 1 6 Octave Band Center Frequencies 214 7 1 2 7 1 12 Octave Band Center Frequencies 214 7 1 2 8 1 24 Octave Band Center Frequencies 214 viii CONTENTS TA OQUPBUIE soe motricidad a 214 Tal Battery Results s os Bate a ee e ta 214 7 2 1 1 Create a Binary Results File 214 Taa DENSOS 2 s ke SEA Se ea aS Maga G ee a a a Oe 214 7 2 2 1 Create an Asc
127. a list of BE meshes generated by skinning FE structure meshes Refer to Section 5 5 for details on how to skin a FE mesh to generate a BE mesh To open a BE mesh in the GUI expand Direct BE Meshes to find the desired BE Mesh lt Direct BE Mesh Name gt and select the mesh by left clicking on it Then right click and select Open The mesh in the GUI can be closed by selecting Close The Mesh Manipulation Functions located at the bottom of the GUI are used to manipulate the mesh opened in the GUI Use Selected Coord Nodes to view the coordinates of the selected nodes in the GUI Selected Elements to view details of the selected elements in the GUI Fill Hole to fill holes New Element to create a new boundary element Stitch Seams to fill gaps by stitching seams Delete Elements to delete elements from the mesh Merge Nodes to merge coincident nodes in the mesh Split Pn Nodes to split selected Pn nodes to create duplicate nodes along the common edge of elements with discontinuities in velocity boundary conditions Element Orientation to view and flip the element normals Refer to Section 4 2 for more details on the mesh viewer functions and GUI tools used to manipulate the BE mesh Each BE mesh member can be expanded to see the sub tree members mentioned below 4 3 7 1 Coord Nodes Select Model Direct BE Meshes lt Direct BE Mesh Name gt Coord Nodes This sub tree member is used to review the coordinate nodes of the mesh Right click on
128. aLewisGearCasing Status Modified File ModelLcyx Figure 9 31 Structure mesh opened in Coustyx GUI Move the cursor into the GUI window with the structure mesh and observe the cursor change to move cursor style or to the shape of To manipulate the view Use the GUI control panel tools shown in Figure 9 32 to zoom and rotate the model Hold down the left click button and move the mouse to rotate the model in the GUI Hold down the right click button and move the mouse to move the model in the GUI Move and rotate the model to see the holes on one of the side surfaces on the structure 9 5 Coustyx Indirect Model 325 B Structmesh 0 Figure 9 32 Coustyx GUI control panel tools e Display element edges of the structure mesh Move the cursor into the GUI window of the structure mesh Press and hold the shift key to observe the cursor change from move cursor style or shape to an arrow style Right click on the mesh while holding down the shift key to view a pop up context menu shown in Figure 9 33 and select Select All Displayed Elements Operations on Selection Unselect All Select All Displayed Elements Selected Elements Select All Displayed Nodes Selected Nodes Figure 9 33 Select all displayed elements in the GUI Again right click on the mesh while holding down the shift key and select Selected Elements Display Style to view a pop up window shown in
129. acoustic quantities such as acoustic pressure should be in Pascal 1 Pa 1kg m s the particle velocity in m s the sound power in Watts 1 W 1kg m s and the intensity in Watt m Consider another model with mesh geometry in inches Set the model units to inch pound force second inch lbf s Following Table 3 3 the speed of sound should be in inch s and the ambient density should be in Ibf s inch The derived acoustic quantities such as acoustic pressure should be in psi 1 psi 11bf inch the particle velocity in inch s the sound power in lbf inch s and the intensity in lbf inch s As a reference Table 3 4 shows the possible values for acoustic medium properties of air in different unit systems 3 3 Frequency Dependence Type The acoustic variables pressure normal derivative of pressure impedance or material prop erties such as sound speed are complex values which can vary with position normal or frequency 3 3 Frequency Dependence Type 23 The dependence on frequency is categorized into three different types shown below 3 3 1 Constant The Frequency Dependence Type is defined as a Constant when the acoustic variable doesn t vary with frequency The constant real and imaginary values of the variable are entered 3 3 2 Table The Frequency Dependence Type is defined as a Table when the frequency variation of the acoustic variable is given by a table The frequency variation can be enter
130. ails of the selected elements in the GUI Fill Hole to fill holes New Element to create a new boundary element Stitch Seams to fill gaps by stitching seams Delete Elements to delete elements from the mesh Merge Nodes to merge coincident nodes in the mesh Split Sigma Nodes to split selected Sigma nodes to create duplicate nodes along the common edge of elements with discontinuities in velocity boundary conditions Element Orientation to view and flip the element normals Refer to Section 4 2 for more details on the mesh viewer functions and GUI tools used to manipulate the BE mesh The Indirect BE mesh when expanded shows the following sub tree members 4 3 8 1 Material Select Model Indirect BE Mesh Material This sub tree member is used to select the fluid medium on either side of the boundary for acoustic analysis To select Right click and select Material gt lt Material Name gt refer to Figure 4 24 The material defined by the lt Material Name gt is created in Model Materials See Section 4 3 3 on how to create a new material or edit an existing one 4 3 8 2 Coord Nodes Select Model Indirect BE Mesh Coord Nodes This sub tree member is used to review the coordinate nodes of the mesh Refer to Sec tion 4 3 7 1 for more details 4 3 8 3 Elements Select Model Indirect BE Mesh Elements This sub tree member is used to review the elements of the mesh Refer to Section 4 3 7 2 for more details
131. allelepiped measurement surface when there is only one reflecting plane Figure 7 38 shows a parallelepiped measurement surface whose sides are parallel to those of the reference box Click on the Suggest button to auto fill the measurement surface variables in agreement with the standard Verify the input you have entered by clicking on the Check button Coustyx checks to see if the input variables satisfy the standard requirements If the standard requirements are not met a message window pops up to help you make appropriate corrections Figure 7 37 1503744 Procedure for fixing microphone positions on a parallelepiped measure ment surface X Axis Specify the orientation of the X axis here See Figure 7 38 for definition Y Axis Specify the orientation of the Y axis here See Figure 7 38 for definition Corner1 Specify Cornerl of the parallelepiped surface here See Figure 7 38 for definition The parallelepiped is constructed using Cornerl as the starting point and L1 L2 L3 as its dimensions along X Y Z axis respectively L1 Length of the parallelepiped in X direction Figure 7 38 Specify the value of L1 such that it satisfies the definition L1 11 2d where l1 is the reference box dimension in X direction and d is the measurement distance The recommended value for d 1m L2 Length of the parallelepiped in Y direction Figure 7 38 Specify the value of L2 such that it satisfies the definition L2 124 2d where 1
132. an also be used in the script Figure 6 23 6 4 6 Uniform Normal Velocity Continuous BC This Boundary Condition is applied on elements with uniform normal velocity on both sides of the boundary The BC is continuous which implies that the values of normal velocity at the same point on side 1 v F and side 2 v are identical refer to Figure 6 16 for side 1 and side 2 definitions vit Vn Uno where Vno is the uniform normal velocity applied on both sides 170 Boundary Conditions New Boundary Condition Figure 6 24 Uniform Normal Velocity Continous The normal velocity value is set by selecting any of the frequency dependent types Constant Table or Script The user should recognize that the normal velocity defined here is with respect to the element normal Figure 6 24 6 4 7 Uniform Velocity Continuous BC New Boundary Condition Figure 6 25 Uniform Velocity Continous This Boundary Condition is applied on the element with uniform velocity vector on both sides of the boundary The BC is continuous which implies that the velocity at the same point on side 1 v and side 2 v are identical refer to Figure 6 16 for side 1 and side 2 definitions v v Vo where vo is the uniform velocity applied on both sides 6 4 Indirect BE Model BCs 171 The velocity vector components vz Vy vz are uniform over the element and are defined u
133. and Center Frequencies for more details 7 1 2 6 1 6 Octave Band Center Frequencies The center frequencies of two successive bands in a 1 6 octave band have a ratio of 21 91 Refer to Octave Band Center Frequencies for more details 7 1 2 7 1 12 Octave Band Center Frequencies The center frequencies of two successive bands in a 1 12 octave band have a ratio of 21 12 1 Refer to Octave Band Center Frequencies for more details 7 1 2 8 1 24 Octave Band Center Frequencies The center frequencies of two successive bands in a 1 24 octave band have a ratio of 21 21 1 Refer to Octave Band Center Frequencies for more details 7 2 Outputs The Outputs window is shown in Figure 7 19 It consists of options to save the results to a binary file save pressure and velocity at sensor locations to an ASCII file create an Glass file for post processing visualization and options to compute sound power levels from ISO standards 7 2 1 Binary Results 7 2 1 1 Create a Binary Results File This option is selected to save the solution state at the end of each analysis frequency The binary file could later be read using a Coustyx function to recreate the solution state Figure 7 19 7 2 2 Sensors Sensors are field point locations at which pressure and particle velocities are computed 7 2 2 1 Create an Ascii Sensors File This option is selected to save the field point pressure and velocities at sensor locations to an ASCII file sensors dat
134. ane Two different measurement surfaces choices are provided They are Hemisphere and Parallelepiped Grade of Accuracy Specify the grade of accuracy by choosing from the following options in the drop down menu Precision grade Grade 1 Engineering grade Grade 2 and Survey grade Grade 3 This information is used to verify the adequacy of the chosen array of measurement positions and the dimensions of the measurement surface at the end of computations If the measurement surface dimension s or the number of microphone positions are found inadequate appropriate log messages will be displayed Make necessary modifications and redo the sound power level calculations to achieve the required accuracy Hemisphere Refer to Figure 7 33 for the definitions of Center X Axis and Y Axis for a hemisphere surface used in IS09614 1 standard Click on the Suggest button to auto fill the measurement surface variables in agreement with the standard Verify the input you have entered by clicking on the Check button Coustyx checks to see if the input variables satisfy the standard requirements If the standard requirements are not met a message window pops up to help you make appropriate corrections X Axis Specify the orientation of the X axis here See Figure 7 33 for definition Y Axis Specify the orientation of the Y axis here See Figure 7 33 for definition Center Specify the center of the hemisphere surface here Select the coordinates of the
135. ard normal direction pointing into the acoustic material and out of the fluid Figure 6 1 shows the impedance definition followed in Coustyz for a rigid wall case vn wall 0 This definition is consistent with the definition described in Pierce 1 One of the popular methods used to measure impedance Z of a material is the impedance tube method The values of Z are deduced from the standing wave pattern developed when excited by a plane wave in a cylindrical tube impedance tube with acoustic material sample at one end Pierce 1 The time dependence of oscillating quantities in Coustyx follow e77 convention where w is frequency of fluctuation If the user adopts e7 convention during measurements then the impedance value should be appropriately modified before using in Coustyx For example 146 Boundary Conditions Sample Rigid wall gt Incident wave n l Il N ni Figure 6 1 Definition of impedance Note p is the pressure and vn is the particle normal velocity in n direction at the surface of the material impedance value Z R jX adopted from the experimental data with e t convention should be modified to Z R jX to account for the difference in the convention Figure 6 2 shows the normalized impedance values measured for a foam of 1 inch thick ness The values are measured using the e77 convention Observe that the imaginary part of impedance X is positive at sufficiently low frequencies and
136. ased on the shortest path identified by Coustyr while connecting all the selected nodes See Figure 5 37 e Accept the first seam by pressing Stitch Seams Accept Seam 1 e Repeat steps mentioned above to create Seam 2 See Figure 5 38 e To delete a seam select Stitch Seams Delete Seam 1 or Delete Seam 2 5 8 Delete Elements 133 e Once two valid seams are created Coustyz fills up the gap between the seams with trans parent 2 D triangle elements for inspection See Figure 5 39 e Select the type of triangle elements to be filled in the gap Stitch Seams Element Type LINEAR or QUADRATIC e Rename the Set Stitch Seams New Set Name lt Set Name gt e To accept the stitch click on Stitch Seams Stitch Seams See Figure 5 40 Figure 5 35 Select Elements 5 8 Delete Elements This tabbed window is located at the bottom pane of the Mesh Viewer window It could be used to delete selected elements in the Mesh Viewer window refer to Figure 5 41 Coustyx provides options to remove unshared coordinate nodes and unshared variable nodes of the deleted element Delete Unshared Coord Nodes When this option is enabled the unshared coordinate nodes of selected elements are deleted along with the elements Delete Unshared Variable Nodes When this option is enabled the unshared acoustic vari able nodes of selected elements are deleted along with the elements By default this option is enabled as it is nec
137. ata is copied to the Freq Response Data This function is useful when the user wants to perform acoustic analysis over a frequency range with the current mode as the structural velocity excitation A structure velocity boundary condition for the BE mesh is defined by specifying the Structure Name refer 5 1 Importing FE Data 101 Select Natural Frequencies to Load e mesen Select by Frequency Range Select Frequencies Natural Frequency 180 0925 Hz Y Natural Frequency 338 2615 Hz Y Natural Frequency 454 4722 Hz Y Natural Frequency 484 2651 Hz Natural Frequency 506 2977 Hz iv Natural Frequency 669 1085 Hz Y Natural Frequency 890 2686 Hz V Natural Frequency 950 5137 Hz Y Natural Frequency 1528 7089 Hz Y Natural Frequency 1620 3582 Hz iv Natural Frequency 1850 4165 Hz Natural Frequency 1892 9052 Hz W Natural Frequency 1977 7131 Hz V Natural Frequency 2053 1284 Hz Natural Frequency 2151 9858 Hz Natural Frequency 2251 4260 Hz Natural Frequency 2347 9280 Hz __ Natural Frequency 2594 0295 Hz _ Natural Frequency 2646 1001 Hz Natural Frequency 2762 1985 Hz Natural Frequency 2844 6494 Hz Natural Frequency 2916 3306 Hz Natural Frequency 2926 0222 Hz Natural Frequency 3010 9651 Hz Natural Frequency 3036 3101 Hz Natural Frequency 3127 1084 Hz Natural Frequency 3152 6487 Hz Natural Frequency 3205 7666 Hz Natural Frequ
138. ate aco si a aca y sa a a kd eek de RE ee RA 165 Uniform Periorated s e e Sosa ee ee eee wade eet eee SES Se os 165 Non WUnitermPertorated orgia 2 2 a Ae eee eae d dene 168 Uniform Pressure Continous lt 2 44 40 5800 seede 644445454 808 168 Non Uniform Pressure Continous 2 2 2 0 0 000000000004 169 Uniform Normal Velocity Continous oo o 170 Uniform Velocity Continous a A RARA 170 Non Uniform Normal Velocity Continous o e e 171 Structure Velocity Continous fe ee ee eee a 172 Diseontinious BU Don t Care c o8aegacccke Gay waa des eae se 173 Discontinous Uniform Pressure e q cort ossada saa daaag ua eee 174 Discontinous Non Uniform Pressure o eee eee 175 Discontinous Uniform Normal Velocity aa 4 4 42 ne 44 dd Bees 176 Discontinous Uniform Velocity cocos ea ek eR ee ee HSS EES SEG G 177 Discontinous Non Uniform Normal Velocity 000 178 Structure Velocity s a sa see GAS OES BB wn eS eG hes aS dia 179 LIST OF FIGURES XV 6 35 6 36 6 37 6 38 6 39 6 40 6 41 6 42 6 43 Tal 7 2 7 3 7 4 7 5 7 6 sil 7 8 TO 7 10 Tall 7 12 7 13 7 14 7 15 7 16 tA 7 18 ag 7 20 T 21 7 22 7 23 T24 7 25 7 26 7 27 7 28 7 29 7 30 7 31 7 32 7 33 Uniform Arbitrary BC 4 6 peed s k ape lede bad eee dues daad 180 Sample script for the function GetAlphaBetaGamma 181 Alpha Frequency Dependence Scri
139. atement The continue statement is used to jump to the end of the loop in a for while or do while statement Example var 1 function Initialize i 1 function Done return i gt 10 function Increment i i 1 function DoSomething Out Hi Eval i for Initialize Done Increment I if i 5 continue DoSomething Out I m done 8 6 Statements 275 Output Hi Hi Hi Hi Hi Hi Hi Hi Hi I m done OANDFWNHEeE a o 8 6 13 switch Statement The switch statement is used to selectively execute a part of a compound statement It takes the form switch lt exp gt lt compound_stmt gt The simple expression lt exp gt is evaluated first The value of this expression is then compared with the values of expressions in case statements that occur in the compound statement case statement is of the form case lt exp gt lt statement gt If the value matches that of a particular case then execution jumps to the statement part of that case var x 2 switch x 4 case 1 Out One break case 2 Dut Two break case 3 Out Three break Otherwise execution jumps to a default statement which is of the form default lt statement gt var x 4 switch x I case 1 276 Language Syntax Out One break case 2 Dut Two break case 3 Out Three break default Dut Unknown If the exp
140. ature angle between two connected elements Note This definition is applicable only for 2D elements 4 2 Operations on Mesh Viewer Window 37 Figure 4 5 Coustyx with Mesh Viewer Window Figure 4 6 GUI Control Panel Tools 38 Getting Started 4 2 2 Rotate Pan amp Selection Operations When the mouse cursor is moved into the Mesh Viewer window the cursor style changes to To rotate the mesh hold down the left mouse button and drag the mesh with the mouse To pan drag while holding down the right mouse button When the shift key is depressed the cursor style changes to When this cursor style is active the left mouse button may be used to select parts of the mesh The right mouse button will display a pop up context menu which lists operations that may be performed on the selection 4 2 3 Operations on Selection in GUI Below is a brief description of the operations that may be performed on displayed elements nodes or faces in the Mesh Viewer window Figure 4 7 shows the context menu that pops up when you right click any where in the Mesh Viewer window while holding down the shift key 4 2 3 1 Operations on Displayed Elements Unselect All This un selects all the elements in the GUI Select Elements This lists two different options by which one can select displayed elements in the GUI By BC and By Set By BC Select elements belonging to any particular boundary condition from the display
141. ave file in binary format OK Cancel Figure 4 2 Preferences dialog box Common parameters 4 2 Operations on Mesh Viewer Window We can view the Finite Element FE structure mesh or the Boundary Element BE mesh by opening them in a Mesh Viewer window This section describes the user controls and the functions available to manipulate a mesh when it is open in the Mesh Viewer window Note that the Mesh Viewer window appears only when a FE or a BE mesh is opened To open a mesh in the Mesh Viewer window right click on the desired mesh in the model tree and select Open Figure 4 5 shows Coustyx UI with the Mesh Viewer window opened for a BE mesh The Mesh Viewer window is made of two panes the top pane with the Graphical User Interface GUI displays a mesh and the bottom pane with the tabbed windows lists various mesh manipulation tasks 4 2 1 GUI Control Panel Tools The GUI control panel is located on the top left corner of the Mesh Viewer window Fig ure 4 5 Figure 4 6 It has tools to zoom and rotate the model Brief descriptions of these GUI tools are in Table 4 2 Table 4 2 Description of GUI control panel tools Tool Used to Tool Used to iso show an isometric view of the rotate the mesh to the right by mesh 90 4 2 Operations on Mesh Viewer Window 35 Table 4 2 continued Usage Tool Usage CINES NOM E a show the view perpendicular to the X axis show the
142. ble Example var y 1 0 var x 2 y 3 Out x Subst Subst x Output x 2 y 3 Circular definitions could occur in which case evaluation will create a runtime error Exam ple var y var x 2 y 3 y 2 x Out x Eval x Output The variable x has been defined in terms of itself 8 6 7 if Statement An if statement comes in two forms if lt exp gt lt statement gt and if lt exp gt lt statement gt else lt statement gt Here lt exp gt is a Boolean valued expression and lt statement gt is any simple or compound state ment Examples 8 6 Statements 271 if i 10 Out Value 10 Eval val 10 if j gt 2 I x j x j 1l if j gt 2 I x j x j 1 else I x j 1 0 The second form of the if statement can lead to an ambiguity var j 3 if j gt 2 if j 10 Out 0K else Out Not OK The ambiguity is resolved by binding the else part to the innermost if part So the above statement is equivalent to var j 3 if j gt 2 if j 10 Out OK else Out Not OK In such a situation it is recommended that braces be used to explicitly resolve the ambiguity 8 6 8 for Statement The for statement takes the following form for lt assign_decl_exp gt lt exp gt lt assign_exp gt lt statement gt Here lt assign_decl_exp gt is either a simple expression or a declaration with or without an assignment It is executed o
143. ble node is introduced in Indirect model to allow greater flexibility in the modeling of an acoustic problem The concept of Variable node relates the value of a variable u at a geometry node in an Element i to its variable node through a positive or a negative sign Figure 4 17 Each u node in an element is assigned with a positive or a negative sign to allow meshes with adjacent elements oriented inconsistently This adds the flexibility to even handle one sided surfaces such as Mobius strip The sign coefficient for the first element at the node is chosen arbitrarily The sign coefficients for the remaining elements at a geometry node are determined uniquely based on their orientations with respect to the first element Coustyx automatically creates these nodes with appropriate signs when it skins the structure mesh pi Within Element sign coefficient e Variable Node 4 1 This concept is illustrated using Figure 4 18 for two elements element i and element j oriented in opposite directions Local node 4 of element i and local node 1 of element 7 share the same coordinate location Also they share the same variable nodes Hyn and Ovn pi 4 PT PB Hvn Opr Opp _ Opr Opp _ GE On On Oz Oz oye Element j has the opposite orientation as element i since the common edge PQ is traversed in the same sense in both element i and element j 54 Getting Started Variable Node VN sign coefficient 1 Geometry Nod
144. bounded Boundedness lt Unbounded gt Delete Open Close Edit Help Boundedness Figure 9 20 Specifying boundedness of the domain 314 Tutorial Gear Box Radiation the normal Here all the element normals are coming out of the mesh By definition the positive side of the mesh is defined as the side with positive element normals NewMeshcreatedFromskin 45x Gi selected Coord Nodes Y Selected Elements SS Fil Hole EY New Element 53 stitch Seams Delete Elements E Element Orientation Flip Selected Elements Make Mesh Consistent with Selected Element Figure 9 21 Element orientations Since we are interested in the radiation problem the domain is on the positive side of the mesh e Select Model Domains Domain1 or lt Domain Name gt Direct BE Meshes NewMeshesCreatedFromSkin Side of Mesh on which Domain is Right click on Side of Mesh on which Domain is and select Side of Mesh on which Domain is Positive as shown in Figure 9 22 9 4 2 Run Acoustic Analysis Coustyx analysis parameters are set in Analysis Sequences which are then Run to solve the acoustics radiation problem 9 4 Coustyx MultiDomain Model 315 File Edit Preferences Help Del iBOS SR 2 8 Model Type lt MultiDomain gt Version lt 2 00 00 gt Model Description CJ Str
145. bute displays the sound pressure amplitude with phase on the negative side or the minus side of the boundary element mesh and at field point grids Note that the minus side of a boundary element is the side at the trailing end of the element normal refer to Figure 6 16 For field point grids there is no distinction between the positive side plus side and the negative side minus side Hence same values are displayed for Pressure Plus and Pressure Minus Normal Velocity Plus This attribute displays the normal component of the acoustic particle velocity amplitude with phase on the positive side or the plus side of the boundary element mesh surface and at field point meshes For field point grids there is no distinction between the positive side plus side and the negative side minus side Hence same values are displayed for Normal Velocity Plus and Normal Velocity Minus Normal Velocity Minus This attribute displays the normal component of the acoustic particle velocity amplitude with phase on the negative side or the minus side 230 Analysis Sequences of the boundary element mesh surface and at field point meshes For field point grids there is no distinction between the positive side plus side and the negative side minus side Hence same values are displayed for Normal Velocity Plus and Normal Velocity Minus Velocity Plus This attribute displays the acoustic particle velocity vector amplitude with phase on the posi
146. center by projecting the acoustic center of the sound source on the reflecting plane As the location of the acoustic center is frequently not known select the geometric center of the source instead Radius The radius of the hemisphere surface shall be equal to or greater than any of the following e twice the largest source dimension or three times the distance of the acoustic center of the source from the reflecting plane whichever is larger and elm Number of Probes Enter the number of probe positions N to be distributed on the surface of the hemisphere Select N 2n where n is an integer The hemisphere surface is divided into n divisions along direction and 2n divisions along direction Note 6 is the angle made by a point on the hemisphere with the Z axis and is the angle made with X axis by the projection of the point on the X Y plane Probes are placed at the center of each of the partial areas formed with these divisions Parallelepiped Figure 7 45 shows a parallelepiped measurement surface whose sides are par allel to those of the surface of the source Click on the Suggest button to auto fill the measurement surface variables in agreement with the standard Verify the input you have entered by clicking on the Check button Coustyx checks to see if the input variables satisfy the standard requirements If the standard requirements are not met a message window pops up to help you make appropriate corrections 7 2 O
147. ch new frequency is added to a new row 3 3 2 2 Import Options The import options window Figure 3 6 appears after the selection of the ASCII file to be used to import the table This window controls the interpretation of the data from the file New Boundary Condition Eq Name New BC Type Uniform Normal Yelocity v Help ort Options Normal Velocity Frequency Dependg Form of harmonic dependence used in data file exp j Omega time Frequency units Whether to replace the table or append the data to it Scale Factor 1 0000000000000 0 Import from file Omega Exponent Impedence Use Impedence Figure 3 6 Table import options window Form of harmonic dependence used in data file exp j Omega time or e and exp j Omega time or e774 are the two available options where Omega w is the angular frequency in radians s and j y 1 Since Coustyz follows e77 convention the values in the data file are adjusted prior to importing Frequency units The first column of the ASCII file from which the data for the table is imported contains frequency values This frequency could be defined in any one of the fol lowing units Figure 3 6 Appropriate unit conversions are applied based on this selection Available options are Hertz Radians sec RPM Whether to replace the table or append the data to it The imported data from the file can be used
148. computer with dual core CPU you can specify nthreads 2 to use multiple cores to speed up the analysis e command ScriptFileName specifies the name of the Coustyx script file There should be no space between the and Script FileName The Script FileName is a csr file If there are spaces in the Script FileName it should be enclosed within This file contains commands which tell Coustyx from where to read the model and how to run the analysis The model file it reads is a cyx file e workdir WorkingDirectoryName specifies the name of the working directory There should be no space between the and WorkingDirectoryName This argument is op tional If omitted Coustyx will assume that the current directory at the time Coustyz command was started is the working directory The following are the possible ways to run Coustyr from command prompt C users johnsmith gt coustyx model sphere cyx analysissequence Analysis Sequence the file sphere cyx contains the information defining the model configuration and the script Analysis Sequence Analysis Sequence contains commands telling Coustyx how to run the analysis Note that Analysis Sequence is not a separate file but is already defined inside the model Since the workdir argument has not been provided Coustyx uses the directory C users johnsmith as the working directory C users johnsmith gt coustyx command radiation csr the file radiation csr is a Coustyx script file that co
149. coustic radiation problem is then solved using Coustyx by importing the FEA struc ture mesh and loading the structural response for the gearbox housing 9 2 Problem Description 293 1 Build a new Coustyx model by importing the FEA structure mesh 2 Load the frequency response data from the FEA analysis into the Coustyx model This response is used as the velocity boundary condition for the acoustic analysis 3 Set the Coustyx analysis parameters and run acoustic analysis to compute acoustic metrics such as radiated sound power radiation efficiency pressure levels at field points etc at each frequency 9 2 Problem Description The example gearbox housing analyzed in this tutorial is from a gear noise test rig developed at NASA Lewis Research Center 1 The details of the gear box are shown in Figure 9 1 The Figure 9 1 Detail of the NASA Lewis gearbox structure is a rectangular box of overall dimensions 0 2794 m x 0 3048 m x 0 29845 m or 11 inches x 12 inches x 11 75 inches The top plate is made of 1 588 mm or 1 16 inch aluminum and the other five surfaces are made of 12 7 mm or 1 2 inch thick steel Note that all the dimensions considered in this tutorial are in S I units The four corners of the bottom surface are clamped rigidly to the ground The housing supports two shafts through bearings which are mounted on the four holes in the structure To simulate the forces on the gearbox housing transmitted from the gears th
150. cript is gen erated automatically based on the options selected in Solver Controls Frequency Ranges and Outputs windows A sample script is shown in Figure 7 46 Advanced users can directly modify the script to suit their needs Coustyx syntax is presented in Chapter 8 262 Analysis Sequences Analysis Sequence 5317 54 Resolution of field point mesh 55 var FIELD MESH RESOLUTION 56 1 57 Coordinates of field point mesh 58 var FIELD MESH CORNERS 59171 60 Dimensions of field point mesh 61 var FIELD MESH DIMENSIONS 62 1 63 Fjfunction Run 64H try 65 I SetOptionNumThreadsToMax 66 SetOptionUseFMM TRUE 67 i SetOptionFMMPrecomputeNearFieldMatrices TRUE 68 SetOptionFMMNumLevels 6 69 i SetOptionGMRESPreconditioner EBE 70 i SetrOptionGMRESConvergenceCriterion RESIDUAL 71 i SetOptionGMRESMaxResidual 0 00500000000000 72 i SetOpt ionGMRES InitialGuess EXCITATION_VECTOR 73 i SetOptionGMRESNVectorsKrylovS3ubspaceitRestart 1000 74 i SetOptionIntegrationOrderTriangleElem 3 75 i SetOptionIntegrationOrderQuadrilateralElem 3 76 BuildModelDataStructures 77 i var ResultsFile 0pen Binary Output File RESULTS_FILE NAME 78 i var PowerFile Open_Output_File SOUNDPOWER FILE NAME 79 var iGlassFile 0pen Binary Output File IGLASS FILE NAME 80 i GeneratelGlassHeader iGlassFile 81 i var nTotalFreqSteps 11 82 var nRanges 2 83 i Out_Binary Integer iGlassFile Eval nT
151. ctions Syntax 289 8 10 4 Spherical Hankel Function of First Kind hin n nterms z result Description Computes Spherical Hankel function of the first kind and order n n 1 n nterms 1 Inputs integer n order of the Spherical Hankel function integer nterms number of terms to be computed All orders from n nti n nterms 1 will be computed complex z argument to the Spherical Hankel function Output complex array result contains hin z 8 10 5 Spherical Hankel Function of Second Kind h2n n nterms z result Description Computes Spherical Hankel function of the second kind and order n Inputs integer n order of the Spherical Hankel function integer nterms number of terms to be computed All orders from n nti n nterms 1 will be computed complex z argument to the Spherical Hankel function Output complex array result contains h2n z 8 10 6 Cylindrical Hankel Function of First Kind Hin n nterms z result Description Computes Cylindrical Hankel function of first kind integer order n Inputs integer n order of the Cylindrical Hankel function For integer n n can be ve 0 or ve integer nterms number of terms to be computed A11 orders from n n 1 n nterms 1 will be computed complex z argument to the Cylindrical Hankel function Output 290 Language Syntax complex array result contains Hin z Hinu n nterms z result Description Computes Cy
152. dary Condit Direct BE Meshes Paste FE Meshes Delete Context Script C Analysis Sequen Open Close Edit Help Rename Copy Paste Delete Open Close Edit Help Load Freq Response Data Y Nastran OP2 File Clear Freq Response Data Nastran Punch File Ansys rst File Figure 9 6 Load frequency response data into Coustyx 9 4 Coustyx MultiDomain Model 301 e Select the appropriate frequency response data file to be loaded from the browser and click Open 9 4 1 4 Generate BE Mesh e Select Model Structures Structmesh_0 or lt Struct Mesh Name gt e Right click on Structmesh_0 or lt Struct Mesh Name gt and select Open to view the structure mesh in the GUI The structure mesh will appear as shown in Figure 9 7 Model2 File Edit Preferences Help D R tecc SAT E Model E Type MultiDomain gt E Version lt 2 00 00 gt E Model Description EE Structures BD Structmesh_0 C Materials CJ Planes EJ Interfaces 2 Boundary Conditions Y Direct BE Meshes CU FE Meshes C Domains 1 Contest Script EJ Analysis Sequences Flog 09 07 39 Frequency 37 820 0000 Hz 09 0000 Hz Frequency 45 980 0001 Hz Gy Selected Coord Nodes y Selected Elements E Stitch Seams Elements Element Orientation Frequency 46 1000 0000 Hz I sele Is tole E sen E sen l amp Delete fie JE Freque
153. dd b de 77 43 11 Analysis Sequenees ass ed ooo a Pe eee Gi ee RS 77 AA SOUS vs da ania E eee 77 4 4 1 Add elements coordinate nodes or faces toa Set 84 AD Acoustic SOURCES i a ooo pe ee ede eee habe e G Ge 84 ASA Monopole pa sete Soo GE ke Re Oe GA SR ee 84 452 Plane Waver ke oe oe Ge a Be lat need 87 455 Cylindrical a oe sa DOA Bae SES Pare eee ose dee eee 87 AAS Dipole i ed ob ee aoe eR ee be EE bb Gb dekka LED 89 Ass Quadrupole ses id det he ROS OSG SRE EE DRESS RRS 91 455 Ver Demed osuna eee ete ae Se the 93 5 Pre processing Features 94 0 1 Importing PE Datas s ss ss kaka s FEE RA 94 Ll Importing Structure Mesh vas ewa ia omaani el SEE SEE Eg 95 5111 Abagus inp fles 225 000 Saas a KE SEE EG 95 5 1 1 2 Nastran Bulk Data bd filles 2 sea saa bo 95 5 1 1 3 Ansys Results rst files 02200004 96 51 14 EDEAS Universal unv files ias ass saa Aae 96 5 1 2 Loading Frequency Response Data 96 KZT Nastan OPS File s o a as ara ved ba redde oo H dd 96 5122 Nastran Pune File 2 466 2 40 ra KG Oe AGR 96 GL29 Ansyerst Pile pus st sak Gere ee SVENE 99 S24 Ansyetig Pill saa bbe EA SPT FERGER 99 51 25 IDEAS Universal File 2 24 46 bode ke see Badd 99 5 1 2 6 Abagus Output File s s s a a sia aeos Sm eR kikke 99 51 3 Loading Natural Mode Data 22 4 4 422240 a Ra 99 5 1 3 1 Copy to Frequency Response Data 100 5 2 Exporting
154. de a translator for this data format However the user can read the data by converting the ABAQUS output odb file to the NASTRAN Output2 OP2 file format using the ABAQUS command refer 1 abaqus toOutput2 job job name where job name is the name of the ABAQUS output database file and also the name of the newly created NASTRAN OP2 file Note that the results from ABAQUS are written to the NASTRAN OP2 file only when applicable records exist in the ABAQUS output database odb file To ensure the results to be translated are available in an ABAQUS output database file include the following FOUTPUT options in the ABAQUS input file refer 1 OUTPUT FIELD NODE OUTPUT U RF CF ELEMENT OUTPUT S E SF NFORC Other ABAQUS results not specified above are skipped during translation 5 1 3 Loading Natural Mode Data Select Model Structures lt Structure Mesh Name gt Right click on the desired structure mesh lt Structure Mesh Name gt and select Load Natural Mode Data to load the natural modes data from a finite element analysis refer to Figure 5 4 100 Pre processing Features If the data is read successfully a new dialog box with a list of natural frequencies available in the data appears See Figure 5 5 The user can select what natural frequencies to load into the model Use Select All Unselect All or Select by Frequency Range buttons to choose the natural frequencies of interest The imp
155. del Direct BE Meshes lt Direct BE Mesh Name gt and select Open For an Indirect model right click on Model Indirect BE Mesh and select Open e Select the elements to which the BCs are applied from the mesh in the GUI To select an element Left click on the element with the shift key held down e Apply BC To apply BC on all selected elements in the GUI right click with the shift key held down and select Operations on Selection Selected Elements Set Boundary Condition lt Boundary Condition Name gt Figure 6 40 Note that the boundary condition list is only visible if BCs are defined before hand 6 5 2 Apply BCs through Sets To apply BCs through sets follow these steps e Create a new set For a MultiDomain model right click on Model Direct BE Meshes lt Direct BE Mesh Name gt Sets and select New Figure 6 41 For an Indirect model right click on Model Indirect BE Mesh Sets and select New Figure 6 41 e Add elements to a set Select elements in the GUI which are to be clubbed together to form a set by left clicking on them while holding down the shift key Right click with the shift key held down and select Operations on Selection Se lected Elements Add to Set lt Set Name gt Figure 6 42 Note that the list of sets are only visible if sets are defined before hand 184 Boundary Conditions Figure 6 40 Applying boundary conditions through element
156. del unit for mass is pound mass lb then the mass scale fac tor is 0 45359 Note that lb is international avoirdupois pound and 11b 0 45359 kg Table 3 2 shows mass scale factors for some commonly used mass units 3 2 2 How to choose model units It is very important for the user to clearly understand the units he or she is working with The building block for any Coustyx model is the mesh geometry First identify the units for length in the geometry Use this as the model unit for length Choose any unit for mass The commonly used unit of time is seconds Once the model units for Length Mass and Time are identified all the inputs to the model should be scaled to be consistent with these units Speed of Sound and Ambient Density are two such important inputs that should be scaled correctly before they are input into the model Other inputs such as boundary conditions acoustic source strengths etc should also be scaled correctly The units for all the acoustic metrics derived from the analysis such as pressure velocity power intensity etc depend on the units used to define the Speed of Sound and Ambient Density e Identify the units for length in the mesh geometry Select model units based on this e Scale all model inputs such as speed of sound ambient density boundary condition values acoustic source strengths etc to be consistent with model units e Derived acoustic variables will have units consistent wit
157. des or Faces the second column shows the ID of the component and the third column shows the Data related to the component The data exists only for a face and it represents the face number in the element Close To close the list of contents of a Set opened in a table right click on lt Set Name gt and select Close Replicate To replicate the contents of a Set right click on lt Set Name gt and select Replicate This function performs the tasks Copy and Paste together Elements Right click on lt Set Name gt and select Elements to find the following sub menu options Note that all the options are not enabled when the mesh is not open in the GUI Figure 4 34 Display Style Changes the display style of the elements in the Set Refer to Section 4 2 3 1 for more details on each of the options in the Display Style dialog window Display All Displays all the elements of the Set in the GUI Hide All Hides all the displayed elements of the Set in the GUI Set Boundary Condition Sets the selected boundary condition to all the elements of the Set This option is available only for BE meshes Select Selects all the elements of the Set in the GUI Unselect Unselects elements of the Set in the GUI Add Selection to Set Adds selected elements to the current Set Remove Selection from Set Removes the selected elements from the current Set CoordNodes Right click on lt Set Name gt and select CoordNodes to find the following sub menu options
158. displayed here Selected Faces The face number of the selected face of the element Face 1 refers to the face on the positive side of the element normal and Face 2 refers to the face on the negative side of the normal Type For a BE mesh only two type of elements are considered Triangle and Quadrilateral Coord Conn Type The coordinate connectivity type describes the type of interpolation scheme used to define the geometry on an element This can be linear quadratic or cubic This detail is displayed only for BE meshes Coord Nodes The list of coordinate nodes used to define selected elements Var Conn Type The variable connectivity type describes the interpolation scheme used for acoustic variables on an element The variable connectivity can be linear quadratic or cu bic This detail is displayed only for BE meshes Coustyx allows independent interpolation schemes for coordinates and acoustic variables This increases the flexibility in modeling For example consider a uniformly pulsating sphere modeled for acoustic analysis The sphere geometry should be modeled with quadratic connectivity to accurately model the surface But we don t need to do the same for variable connectivity as the pressure is con stant over a pulsating sphere Hence a simple linear variable connectivity should result in good accuracy This kind of flexibility decreases the analysis run times without reducing the accuracy Baffled Only for Indirect BE meshes
159. dow aaao aa a GUI operations available for selected nodes eee ene Nodes Display Style Window a GUI operations on faces available through the context menu activated by the right mouse button with the shift key held down FI Hess e an a EA KO a a amp Ee se Qe Ae BB Bt CoN I 28 xil LIST OF FIGURES 4 13 4 14 4 15 4 16 4 17 4 18 4 19 4 20 4 21 4 22 4 23 4 24 4 25 4 26 4 27 4 28 4 29 4 30 4 31 4 32 4 33 4 34 4 35 4 36 4 37 4 38 4 39 4 40 4 41 4 42 4 43 4 44 4 45 4 46 5 1 5 2 5 3 5 4 5 5 5 6 Bul 5 8 Great SM Loca idear dra 48 o A 49 Coustyx model tree structure ira aaa a 51 New model dialog B rs sag 4 se SPS ARA AA 52 Variable Nodes in Indirect BEM vr vnr ee 54 Variable Nodes in Indirect BEM ee a a ee a 54 Greate New Materials 222 coed a ee Oe Ee eS OS 57 Edit Material Properties 2294 os a we ae ee eee G b ae PERE 58 Effect of complex speed of sound c cp jci on the pressure variation with distaiice from point SOURCE vass vas BRE ee GM EGG SG a Gee 59 Creating new planes sedes wa se res ye Ce GE REG 60 Descriptions for different types of planes Note arrows represent velocity vectors at those POMS cir cris radiador dara 60 pelecti a Material saa saci suia gima Ge BRO ee dc A 66 Create Boundary C nditions wp we ke ee ae be ee eee ee AM 69 Create New Source saca a eR A
160. e GN O Element i Figure 4 17 Variable Nodes in Indirect BEM O O O 6 2 3 e7 Element j te ey 0 6 5 O O es ez O Figure 4 18 Variable Nodes in Indirect BEM 4 3 Model Setup uj l pB pr Hvn Opr Opp Oz oe Oz The sign coefficient for 1 1 is 1 negative of the sign coefficient for p 4 However the sign coefficient for 0 1 is equal to the sign coefficient for 0 4 This is true in both cases if Element 7 has the same orientation as Element 4 if or Element 7 has the pi 4 Hvn m 1 opposite orientation as Element i Hyn o 4 Oyn o 1 Ovn Table 4 3 Differences between MultiDomain and Indirect models No MultiDomain Indirect 1 Uses Direct Boundary Integral Formu Uses Indirect Boundary Integral For lation mulation 2 Allows several interior domains and Allows only one domain It solves the one exterior domain Each mesh problem on both sides of the bound should enclose a volume ary simultaneously The mesh does not need to enclose a volume 3 Allows multiple meshes in a single Allows only one mesh model 4 Primary variables in the formulation Primary variables in the formulation are pressure p and normal derivative are single layer 7 and double layer of pressure p on the surface u potentials o p ph w p p where is for variables on the posi
161. e 2 of a surface element When selected Coustyx adds Face 1 or Side 1 of selected elements in the GUI to the Set Add Face 2 of Selected Elements to Set This option is available for BE meshes sur face elements only See Figure 6 16 for the description of Side 1 and Side 2 of a surface element When selected Coustyx adds Face 2 or Side 2 of selected elements in the GUI to the Set 4 4 1 Add elements coordinate nodes or faces to a Set Select elements coordinate nodes and faces to be added to a Set from the GUI by left clicking on them while holding down the shift key Right click to see the menu on Operations on Selection To add the selected to a set Selected Elements Selected Nodes or Selected Faces Add to Set lt Set Name gt or Add to New Set Figure 4 37 4 5 Acoustic Sources Acoustic sources can be introduced in addition to BE meshes in Coustyr These acoustic sources have analytical solutions which are incorporated into the BE formulation Coustyr offers the following acoustic wave sources 4 5 1 Monopole A monopole is a spherical wave source which produces spherically symmetric waves in an un bounded space This source is defined by a position vector R x yr zr and amplitude A or volume velocity V Figure 4 38 The monopole amplitude A and the volume velocity V are related as follows A jkZ V 4 5 Acoustic Sources 85 Figure 4 37 Add elements to a set 86 Getting Started
162. e Changes the display style of the elements Refer to Section 4 2 3 1 for more details on each of the options in the Display Style dialog window The Elements sub tree can be expanded to browse through individual elements using Prev and Next or by directly entering the ID of the element The right click menu on the element ID provide these options Display Displays the chosen element Hide Hides the chosen element Select Selects the chosen element Unselect Unselects the chosen element Add to Set Adds the chosen element to a set Refer to Section 4 4 for more details on Sets Remove from Set Removes the chosen element from its current set Set Boundary Condition Sets the selected boundary condition on the chosen element Bound ary condition should already be defined 64 Getting Started 4 3 7 3 P Nodes Select Model Direct BE Meshes lt Direct BE Mesh Name gt P Nodes Use this sub tree member to review P Nodes in the mesh P Nodes are variable nodes associated with pressure at the location of the node pressure p and normal derivative of pressure pn are the primary acoustic variables in Direct BE formulation used for MultiDomain models The right click on P Nodes provides these menu options Open Opens the list of all pressure nodes The table shows the ID of the pressure node location coordinates X Y Z mean normal components mean Nx mean Ny mean Nz and solid angle covered by the Pnode The mean nor
163. e in the GUI Set the speed of the rotation in the GUI Specify the increments at which the zoom takes place in the GUI Show element edges when a structure mesh is opened in the GUI This option sets the order of the coordinate in terpolation used to display the element in the GUI A resolution level 1 displays the element as a linear element Higher resolution levels dis play the element with higher coordinate interpo lations Set level 1 for quick plots Set the relative size of the nodes displayed in the GUI Show shadows while displaying a structure mesh in the GUI 4 1 Main Menu Features 33 Table 4 1 continued Menu Items Description Use fast draw mode Background Color Draw the structure mesh faster while using pan zoom rotate tools in the GUI This mode draws only a wire frame of the mesh in the intermediate steps while using these GUI tools Set the background color of the GUI Help Help Content About Show the user manual for help Show the license information ns Edit Analysis Preferences Help Open Model File Ctrl O New Model Ctrl N Save Model File Ctrl S Save Model File as Ctrl 2 Close Ctrl W Print Setup Print Preview Print Ctrl P Recent Files Properties Figure 4 1 Main menu items 34 Getting Started Preferences i Common 3D Viewer Y Show splash screen on startup Y Show log messages verbosity level 4 E S
164. e nodes along edges Note During skinning Coustyr automatically creates duplicate nodes for most common cases such as geometry discontinuities edges corners junctions etc 138 After adding elements to Group 1 Notice that the elements belonging to Group tare displayed im redi s acs i gn ske ao G Genk E a pda A Gig 140 After adding elements to Group 2 Notice that the elements belonging to Group 2 418 displayed in DIS e ear aene A A ke brede a A E 140 After splitting all shared nodes between Group 1 and Group 2 Notice that the nodes along common edges of elements in Group 1 and Group 2 are split into two 141 Before splitting a selected node between Group 1 and Group 2 141 After splitting a selected node between Group 1 and Group 2 142 xiv LIST OF FIGURES 6 2 6 3 6 4 6 5 6 6 6 7 6 8 6 9 6 10 6 11 6 12 6 13 6 14 6 15 6 16 6 17 6 18 6 19 6 20 6 21 6 22 6 23 6 24 6 25 6 26 6 27 6 28 6 29 6 30 6 31 6 32 6 33 6 34 Before splitting a node shared by Group 1 Element A and Group 2 Element B Note that the node is also shared by Elements C and D that belong to neither Group Lro Grup Dl mies aaa ade eee ee BS 142 After splitting the shared node among Group 1 Element A Group 2 Element B and unselected elements Elements Cand D arr rar ooo oo 142 Element orientations window ever 0 vrak ee ee 143 Definition of impedance Note p is the press
165. e or more nodes to form a unique closed loop on the edge of the hole To select a node Left click on the node with the shift key held down Note You should only select nodes on the corners of the elements not mid side nodes Once a closed loop is identified Coustyz auto fills the hole with outlines of triangle elements for preview Select the type of triangle elements to be filled in the hole Fill Hole Element Type LINEAR or QUADRATIC Rename the Set Fill Hole New Set Name lt Set Name gt Accept the triangulation of the hole by pressing Fill Hole Fill Hole button at the bottom of the window Refer to Figure 5 17 5 5 Skin Coustyx has the ability to skin the 3 D FE structure mesh to create a 2 D surface mesh used for BEA The Manipulation Task Function Skin is located in a tabbed window at the bottom of the Mesh Viewer window refer to Figure 5 26 Coustyz offers the option to specify seams to avoid skinning the unwanted regions of a FE Mesh More details on how to create a seam are given in Section 5 5 3 Once the seams are created the structure mesh can be skinned to obtain surface mesh For structure components with zero thickness such as ribs there is no need to create seams on the edges Coustyz identifies these 2 D elements and creates surface mesh without duplication in the Indirect BE model However ribs cannot be skinned in a MultiDomain model For a MultiDomain model if the skin is allowed to propagate t
166. e same units as those defined in materials Figure 6 9 New Boundary Condition xj Name New BC Type Nonuniform Pressure Pressure 1 Hfunction GetPressure in PosnVec 2 AngularFreq SoundSpeed WaveNumber and imbientDensity are pre read only variables that can be used here f The following is just an example change the formula to suit y var PressMagn 12 0 var Press PressMagn exp i WaveNumber PosnVec 2 return Eval Press vo S e a amp ww Figure 6 9 Non Uniform Pressure BC 6 3 5 Uniform Normal Velocity BC This Boundary Condition is applied on the element where the normal velocity is uniformly distributed There is no variation of normal velocity with position over an element However it can be defined to be dependent on frequency Figure 6 10 The normal velocity values can be specified by selecting any of the frequency dependence types Constant Table or Script The user should be aware that the normal velocity defined here is in the direction of the domain normal Figure 6 4 When Use Impedance option is disabled the Normal Velocity defined in 6 3 Multi Domain Model BCs 155 New Boundary Condition Figure 6 10 Uniform Normal Velocity BC 156 Boundary Conditions this boundary condition BC is considered to be the particle normal velocity vni Figure 6 10 6 3 5 1 Use Impedance When this option is enabled the Normal Velocity defined i
167. e source emits discrete tones The presence of microphones at the same height above the reflecting plane can lead to strong interference effects if the source emits discrete tones Coaxial Circular Paths Figure 7 34 shows coaxial circular paths in parallel planes 7 2 Outputs 237 Table 7 7 1503744 Coordinates of microphone positions for sources emitting discrete tones Microphone a z position 1 0 16 0 96 0 22 2 0 78 0 6 0 2 3 0 78 0 55 0 31 4 0 16 0 9 0 41 5 0 83 0 32 0 45 6 0 83 0 4 0 38 7 0 26 0 65 0 71 8 0 74 0 07 0 67 9 0 26 0 5 0 83 10 0 1 0 1 0 99 Axis of rotation Microphone elevations e Heights of area segments s 4 A Sa dk SN o a y S A F N o N S LIZ a po o gt e A o S x Center Figure 7 34 Coaxial circular paths in parallel planes for microphone traverses over a reflecting plane 238 Analysis Sequences traversed by a microphone over a reflecting plane The paths are selected such that the annular area associated with each path is the same Number of Circular Paths Traversed by a Probe Enter the number of cir cular paths traversed by a microphone The least number is five Quadrant Use quadrant measurement surface when the source under test is in front of a wall Figure 7 35 shows a quadrant measurement surface centered at Center Click on the Sug ge
168. e that the elements belonging to Group 1 are displayed in red Figure 5 45 After adding elements to Group 2 Notice that the elements belonging to Group 2 are displayed in blue 5 11 Element Orientation 141 Figure 5 46 After splitting all shared nodes between Group 1 and Group 2 Notice that the nodes along common edges of elements in Group 1 and Group 2 are split into two Figure 5 47 Before splitting a selected node between Group 1 and Group 2 142 Pre processing Features Figure 5 48 After splitting a selected node between Group 1 and Group 2 Figure 5 49 Before splitting a node shared by Group 1 Element A and Group 2 Element B Note that the node is also shared by Elements C and D that belong to neither Group 1 nor Group 2 Figure 5 50 After splitting the shared node among Group 1 Element A Group 2 Element B and unselected elements Elements C and D 5 11 Element Orientation 143 Make Mesh Consistent with Selected Element This makes all the element normals in the mesh consistent with the normal of the selected element This option is active only when one element is selected For MultiDomain models it is important that all elements are consistently oriented Make Selected Elements Consistent with Each Other This makes selected element nor mals consistent with each other This option is active only when more than one element is se
169. ected faces Add to Set This option allows user to add selected faces to a pre defined Set Refer to Section 4 4 on how to define a Set Remove from Set This option is used to remove selected faces from their current Sets Refer to Section 4 4 for more information on Sets Add to a New Set This option allows user to add selected faces to a new Set new set with a default name New Set or New Set i i is a number is created Refer to Section 4 4 on how to rename the Set 4 2 4 Selected Coord Nodes This tabbed window is part of the bottom pane of the Mesh Viewer window Figure 4 5 This window is read only The window contains a table that shows the id and the coordinates of the 4 2 Operations on Mesh Viewer Window 45 selected nodes in the mesh viewer 4 2 5 Selected Elements This tabbed window is part of the bottom pane of the Mesh Viewer window Figure 4 5 This window is read only The window contains a table that shows properties of the selected elements in the mesh viewer The details presented in the table vary with the type of mesh FE or BE mesh and also vary with the type of the model MultiDomain or Indirect BE model The possible columns in the table are Index The indexes of selected elements An element index can only vary from one to the total number of elements Elem ID The ids of selected elements An element id can be any unique positive number B C The boundary conditions applied on selected elements are
170. ecursively until we reach the lowest level Figure 7 8 shows a cell hierarchy FMM is applied only for far field cells All near field interactions are computed directly A minimum of Level 2 is required to apply FMM to the acoustic problem refer to Figure 7 8 far cells appear only for number of FMM levels gt 3 As a general rule of thumb the number of FMM levels are selected such that the edge length of the cell in the final level is similar to the size of the elements in the boundary element mesh For example consider a cube of size axaxa with a mesh of 30 x 30 elements on each side Select the numberofFMMIevels 6 The size of the cell at the final level is a 32 which is of the same order as the element length a 30 The Levels Suggested in the analysis sequence is computed similarly 7 1 Inputs 197 Analysis Sequence Analysis Sequence A Convergence Criterion Residual M 0 50000000000000 an o0 Excitation Vector E Figure 7 7 Suggested number of FMM levels 198 Analysis Sequences Level 0 Level 1 Level 2 Level 3 Level 4 Legend E Far Cell HE i ea Figure 7 8 Computational cell hierarchy constructed at different FMM levels 7 1 1 4 Solution Method This option is enabled only when the Use FMM is not selected In the Regular method when FMM is not being used
171. ed list Note that this option is available only for boundary element meshes By Set Select elements belonging to any particular set from the displayed list Select All Displayed Elements This selects all the elements that are displayed in the GUI Select All Bad Elements This operation is active only when Coustyx finds bad elements in the mesh and throws error messages in the log window mentioning the same Bad elements are those with bad element connectivities or have other inconsistencies that prevent Coustyx to perform its usual tasks Generally this set is populated if some elements in the mesh fail the consistency checks done before skinning a FE mesh to get a BE mesh This operation selects all the bad elements in the mesh See Table 5 1 for some common types of bad elements Selected Elements This sub menu lists the operations that are performed on selected elements Figure 4 7 It is activated only elements are selected in the GUI Unselect This un selects the selected elements Display Style The user can pick the display style for elements Figure 4 8 Display This option when selected displays the element The selected element will be hidden if this option is turned off Show Faces Display element faces Show Edges Display element edges 4 2 Operations on Mesh Viewer Window 39 Operations on Selection Unselect All Select Elements Select All Displayed Elements Select All Bad Elements Selected Elements Uns
172. ed Modes when pressed opens up a dialog box as shown in Figure 5 11 Select a method from the Specification drop down menu to compute damping ratios for selected modes 5 3 Forced Response Analysis using Modal Superposition 107 Frequency Dependent Damping Ratio Specify the Frequency Dependent Damping Ra tio through any of the frequency dependent types Constant Table or Script See Fig ure 5 11 For example to define a 5 damping ratio for selected modes select the frequency dependence type to be Constant and enter a value of 0 05 You can also specify a Table or a Script to define damping ratios varying with natural frequency For example a natural frequency dependent damping ratio can be defined by a script that returns the following return Eval 0 05 Frequency Note the predefined variables Frequency or Angu larFreq in such scripts or tables represent natural frequencies Press OK to compute damping ratios and edit the table for selected modes Edit Damping Ratios Select All Modes Unselect Al Modes Select Modes by Frequency Range Natural Freq Hz Damping Ratio Mode 1 180 0925 0 000000 Mode 2 338 2615 0 000000 Mode 3 454 4722 0 000000 Edit Selected Modal Damping Ratios Specification Damping Ratio Freguency Dependence Type Value 0 000000 2151 9858 0 000000 2251 4260 0 000000 2347 9280 MER Figure 5 11 Edit selected modal damping
173. ed manually into the table or it can be imported from an ASCII formatted text file with values separated by commas tabs or spaces The values can be copied from the table to the clip board or deleted from the table by selecting the menu options Copy and Delete Rows First select the desired row by left clicking the mouse on the row number and then right click to see the menu Figure 3 3 Figure 3 4 Figure 3 5 Fr New BC 2 Uniform Normal Velocity Continuous Help Dependence Type gt Table IE ABE EA Figure 3 3 Boundary Condition Table 3 3 2 1 Import from File The frequency variation of the variable can be imported from an ASCII file with components separated by commas tabs or spaces The file must contain three columns with the first column 24 Conventions in Coustyx New Boundary Condition x Uniform Normal Velocity Continuous v jm 3 MlM 145 q00000000000 2 0000000000000 3 0000000000000 pen A A eee Figure 3 4 Edit Boundary Condition Table 3 3 Frequency Dependence Type 25 Import Options jexp j Omega time m mw Uniform Normal Velocity Continuous v Ne EE 62 8318530717960 10 0000000000000 2 0000000000000 3 0000000000000 Figure 3 5 Table Boundary Condition example 26 Conventions in Coustyx for the frequency the second for real part of the variable and third for its imaginary part Ea
174. ed to the table or can be loaded into the table by clicking on Load Frequencies button Figure 7 13 More details on various options provided to load frequencies are discussed next Refer to Figure 7 14 e Source is the option type from which frequencies are loaded Frequencies can be loaded from a File Structure Freq Response Data Structure Natural Mode Data Octave Band Center Frequencies 1 3 Octave Band Center Frequencies 1 6 Octave Band Center Fre quencies 1 12 Octave Band Center Frequencies and 1 24 Octave Band Center Frequen cies e Whether to replace the table or append data to it The data from the Source can be used to either replace the current table or append to the existing table with the selection of one of the options Replace or Append respectively 7 1 2 1 File Analysis frequencies could be loaded from an ASCII file using this option Figure 7 15 The components in the file should be separated by commas tabs or spaces Each line in the ASCII file represents one frequency range line may contain at the most three columns the first column represents Start Hz frequency the second represents Delta Hz and the third represents No Freqs If a row contains only one column the value is accepted as the Start frequency and the other values are set to the default values that is Delta 0 0 and No Freqs 1 Click on Browse button to find the desired ASCII file Select the file and click OK To load frequencies from the
175. een the pressures on the positive p and the negative p7 sides of an element that is y pt p Each u node is displayed with a positive or a negative sign These signs are defined to accommodate BE meshes with adjacent elements not oriented consistently Refer to Section 4 3 1 2 for more details 4 2 6 Fill Hole This tabbed window is located at the bottom pane of the Mesh Viewer window This is used to fill holes in both FE and BE meshes Coustyx uses optimized delaunay triangulation method to fill holes with two dimensional triangle elements This method needs a closed path to fill a hole Figure 4 12 A detailed discussion on how to fill holes is provided in Section 5 4 4 2 7 Skin This tabbed window located at the bottom of the Mesh Viewer window is used to generate a 2 D surface mesh BE mesh by skinning the 3 D FE mesh Seams are defined to stop the propagation of skin to unwanted regions of the mesh This function appears only for FE meshes More details on how to skin a structure mesh are discussed in Section 5 5 Figure 4 13 4 2 8 New Element This tabbed window located at the bottom of the Mesh Viewer window is used to fill gaps in the mesh by creating new surface elements This function is especially useful to create new elements for cases where the functions Fill Hole and Stitch Seams can not be used A new element is added by specifying the coordinate node ids and the type of the element to be created Refer to Sec
176. el of the NASA Lewis gearbox The physical properties of the materials used in FEA analysis are given in Table 9 1 9 3 2 Natural Frequencies and Normal Modes The natural frequencies and mode shapes are extracted by solving the FE eigenvalue problem of the gearbox housing The eigenvectors are normalized with respect to the mass matrix to get the structure normal modes Since the top plate is relatively more flexible compared to 9 3 Finite Element Analysis 295 Table 9 1 Physical properties of materials used in FEA Material Elastic Modulus Pa Shear Modulus Pa Poisson s Ratio Density kg m Steel 2 034E 11 7 823E 10 0 3 7850 Aluminum 7 31E 10 2 748E 10 0 33 2700 the remaining five surfaces several free vibration mode shapes of the gearbox housing resemble classic plate modes of the top surface Mode 1 is a 1 1 mode of the top plate Similarly Mode 2 is a 1 2 plate mode Mode 3 is a 2 1 plate mode Mode 4 is a 2 2 plate mode and Mode 5 is a 1 3 plate mode respectively In a m n plate mode m and n represent the number of half wave lengths along the x and y directions respectively Table 9 2 Gearbox natural frequencies from FEA Mode Number Frequency Hz 1 157 2 329 3 366 4 505 5 543 6 647 7 741 8 760 9 789 10 797 11 829 12 907 13 936 14 962 Table 9 2 lists some of the natural frequencies of the gearbox h
177. elect Display Style Display Connected Nodes Select Connected Elements Through Feature Angle Select Elements Connected Through CoordNodes Select Elements Connected Through Variable Nodes Hide Set Boundary Condition gt Select All Displayed Nodes Select All Bad Nodes Selected Nodes Selected Faces gt Oe Add to Set gt Remove from Set gt Add to a New Set Figure 4 7 GUI operations on elements available through the context menu activated by the right mouse button with the shift key held down 40 Getting Started Display 4 Show Faces Show Edges Display Nodes Apply Resolution level Apply Color Red Green Blue ES Gs Transparent l 200 dp 200 dp 255 dp Figure 4 8 Element Display Style Window 4 2 Operations on Mesh Viewer Window 41 Display Nodes This option when selected displays the coordinate nodes of the se lected elements Apply Resolution level This option controls the order of the coordinate interpola tion used to display the element resolution level of one when applied displays the element as a linear element Higher resolution levels display the element with higher coordination interpolations Transparent This option makes the selected element transparent Apply Color The color of the element face displayed can be changed using this option The user can select the color by using the color palette pr
178. ence no ISO 3745 2003 E 4 F J Fahy Sound Intensity Elsevier Applied Science 1989 Page 56 5 A D Pierce Acoustics An introduction to its physical principles and applications Acous tical Society of America 1991 Pages 57 60 Chapter 8 Language Syntax user provides input and instructions to Coustyx through a special programming language This user interaction language consists of comments constants variables function calls arrays expressions and statements 8 1 Comments Single line comments are started by the characters Multiple line comments are started with a and terminated by a x x 2 This is a single line comment x x 2 This is a multiple line comment 8 2 Constants Three type of constants are accepted Numeric Boolean and string constants Numeric constants follow the same conventions as in FORTRAN All constants are treated internally as double precision floating point values regardless of the format in which the user specifies them Some examples of numeric constants are O 1 0 0 123e 20 123 34324 Only two Boolean constants exist TRUE FALSE String constants consist of a sequence of ASCII characters enclosed in double quotes This is a string 8 3 Variables 265 Strings may also contain certain escape sequences This is a tab t and a newline Nn The escape sequences that are available are Ib Backspace t Tab n Newline r Carr
179. encies Help Whether to replace the table or append the data to it Replace z Octave band Frequency Range Lower Limit 10 000000000000 Upper Limit 5000 0000000000 Figure 7 18 Load center frequencies of an octave band Steps to be followed to generate octave band center frequencies e Select one of the 1 N Octave Band Center Frequencies from the Source drop down menu Figure 7 18 e Select one of the options Replace or Append from Whether to replace the table or append data to it drop down menu e Enter the lower and upper frequency limits in text boxes Lower Limit and Upper Limit respectively e Press OK to generate a list of preferred center frequencies for the selected octave band within the upper and lower frequency limits Press CANCEL to discard changes Octave Band frequency range definitions e Lower Limit The lower limit for the selection of octave band center frequencies The frequency defined here should lie between 10Hz 31500Hz Center frequencies generated lie within the upper and lower frequency limits 214 Analysis Sequences e Upper Limit The upper limit for the selection of octave band center frequencies The frequency defined here should lie between 10Hz 31500Hz Center frequencies generated lie within the upper and lower frequency limits 7 1 2 5 1 3 Octave Band Center Frequencies The center frequencies of two successive bands in a 1 3 octave band have a ratio of 21 1 Refer to Octave B
180. ency Figure 5 5 Select natural frequencies to load dialog box 102 Pre processing Features to Section 6 3 8 and Section 6 4 9 Coustyx uses the Freq Response Data of the specified Structure Name as the excitation We can apply natural modes as the structural velocity excita tion by copying the mode data to the frequency response data Note that this action clears any existing frequency response data while copying the selected mode data refer to Figure 5 7 Also note that only one mode could be copied to the frequency response data at a time Once the model setup is completed one can perform acoustic analysis to obtain relative responses at var ious frequencies due to the applied modal excitation Absolute values are irrelevant Radiation efficiency is one of the main results of interest in such an analysis File Edit Preferences Help Dae Bt ers AB A 2 2 case Wod JR E Model 5 Type lt MultiDomain gt J Version lt 1 00 00 gt 5 Model Description ag Structures GO Structmesh_0 i y Coord Nodes LA Elements E Y Sets iE 114 7541 H E 1000 0000 Hz H Materials CJ Planes Y Interfaces 6 07 Boundary Conditions H Direct BE Meshes FE Meshes Domains E Context Script EJ Analysis Sequences g CJ Freq Response Data 53 Natural Mode Data 129 5082 Hz Rename Le apy Paste Delete Open Close Edit Help Copy to Freq Response Data
181. enter frequencies of various fractional octave bands between the frequency limits 1000 10000Hz Table 7 4 Comparison of preferred center frequencies for fractional octave bands between 1000 10000 Hz 1 Octave 1 3 Octave 1 6 Octave 1 12 Octave 1 24 Octave 1000 1000 1000 1000 1000 1030 1060 1060 1090 1120 1120 1120 1150 1180 1180 1220 1250 1250 1250 1250 1280 1320 1320 1360 1400 1400 1400 1450 1500 1500 1550 1600 1600 1600 1600 1650 1700 1700 1750 1800 1800 1800 1850 1900 1900 1950 2000 2000 2000 2000 2000 2060 2120 2120 2180 2240 2240 2240 2300 2360 2360 2430 212 Analysis Sequences Table 7 4 continued 1 Octave 1 3 Octave 1 6 Octave 1 12 Octave 1 24 Octave 2500 2500 2500 2500 2580 2650 2650 2720 2800 2800 2800 2900 3000 3000 3070 3150 3150 3150 3150 3250 3350 3350 3450 3550 3550 3550 3650 3750 3750 3870 4000 4000 4000 4000 4000 4120 4250 4250 4370 4500 4500 4500 4620 4750 4750 4870 5000 5000 5000 5000 5150 5300 5300 5450 5600 5600 5600 5800 6000 6000 6150 6300 6300 6300 6300 6500 6700 6700 6900 7100 7100 7100 7300 7500 7500 7750 8000 8000 8000 8000 8000 7 1 Inputs 213 Table 7 4 continued 1 Octave 1 3 Octave 1 6 Octave 1 12 Octave 1 24 Octave 8250 8500 8500 8750 9000 9000 9000 9250 9500 9500 9750 10000 10000 10000 10000 Load METI Es Source Octave Band Center Frequ
182. enu lists names of all structures present in the Coustyz model Select the desired structure from the menu Analysis frequencies are extracted from this structure s natural mode data 7 1 2 4 Octave Band Center Frequencies The frequency scale for acoustic analysis is usually divided into contiguous proportional fre quency bands The partitioning of a bth band with lower cut off frequency f and upper cut off frequency f is said to be proportional if f f is the same for each band The center frequency fo of such a band is defined as the geometric mean of the upper and lower cut off frequencies that is fo fifz refer 5 The center frequencies of successive bands have the same ratio as the upper and lower cut off frequencies for any band In an octave band the ratio between the upper and lower cut off frequency or two successive band center frequencies is 2 1 that is fo f 2 A 1 3 octave band has fo fi 2 3 For any 1 Nth octave band the ratio of band limits or two successive band center frequencies is given by fa 91 N f Octave band o f 1 3 octave band f2 _ 31 3 2 3 fi 1 6 octave band f2 91 6 fi 1 12 octave band f 91 12 i 7 1 Inputs 211 1 24 octave band fa 91 24 f Hence any proportional or octave band is defined by its center frequency and by N Analysis done at these center frequencies are assumed to be valid over the entire band width Refer to Table 7 4 for comparison of c
183. erbosity Level Enable or disable splash window at the startup of Coustyz Show log messages in the log window This determines how much data that is output while running Coustyx Verbosity levels 0 Fa tal messages only 1 Critical errors or warnings 2 Action notices 3 5 General information Set high verbosity level to display verbose output The verbosity level can only be set when Show log messages is enabled 32 Getting Started Table 4 1 continued Menu Items Description Save file in binary format Enable saving Coustyx model file cyx in com pressed binary file format When unchecked the file is saved in ASCII XML format It is rec ommended to save a large Coustyx model file in the compressed binary file format 3D Viewer Figure 4 3 Feature angle deg Incremental rotation angle deg Time for rotation msec Zoom Increment Show element edges by default Element resolution level by default Relative size of nodes Show shadows Set the feature angle to be used in the GUI Fea ture angle corresponds to the angle between two connected elements as shown in Figure 4 4 The function Select Connected Elements Through Feature Angle is used to select surface features in a mesh The default value for the feature angle is set at 159 But it can be any value between 09 and 180 Note that the definition is applicable only for 2D elements Set the increments of rotation angl
184. erge Nodes Merge Distance e Select the element containing the desired node by left clicking on it while holding down the shift key e Right click with shift key held down and select Operations on Selection Selected Elements Display Connected Nodes e Select the desired node by left clicking on it while holding down the shift key e Press Merge Nodes Merge Selected Coord Nodes with All Coincident Nodes to merge the selected node with all coincident nodes C Selected Coord Nodes La Selected Elements Sy Fill Hole 3 New Element la Stitch Seams 3 Delete Elements Merge Nodes E Eler gt Delete Unshared Coord Nodes Merge Distance 1 000000E 006 Merge Selected Coord Nodes with All Concident Nodes Figure 5 42 Merge Nodes window Delete Unshared Coord Nodes When this option is enabled the unshared coordinate nodes left after the merge are deleted Merge Distance node is considered coincident with the selected node if the distance between the two is less than the merge distance Note that the merge distance units are the same as the FE mesh length units 5 10 Split Pn Nodes Split Sigma Nodes This tabbed window is located at the bottom pane of the Mesh Viewer window It helps user split Pn Nodes or Sigma Nodes in MultiDomain or Indirect models respectively This feature is primarily useful for creating duplicate nodes along the common edge of adjacent elements with different velocity boundary conditions
185. essary to delete unshared acoustic variable nodes to reduce the number of unknowns 134 Pre processing Features Operations on Selection Unselect All Select All Displayed Elements Unselect EE Display Style Select All Displayed Nodes Display Connected Nodes Selected Nodes Select Elements Connected Through CoordNodes Hide Set Boundary Condition Add to Set Remove from Set Figure 5 36 Display Connected Nodes for Elements Figure 5 37 Seam 1 5 8 Delete Elements 135 Figure 5 39 Transparent elements shown for inspection before Stitching Seams 136 Pre processing Features Figure 5 40 Complete Stitched Seam Delete Unshared Coord Nodes Delete Unshared Variable Nodes Figure 5 41 Delete element window 5 9 Merge Nodes 137 5 9 Merge Nodes This tabbed window is located at the bottom pane of the Mesh Viewer window It is used to merge selected nodes with all coincident nodes in the Mesh Viewer window refer to Figure 5 42 Press the button Merge Selected Coord Nodes with All Coincident Nodes to perform this task Note that this button is active only when nodes are selected in the GUI Coustyx also provides option to enter Merge Distance which is used as the maximum distance within which coincident nodes lie The option to remove unshared coordinate nodes is also provided Follow the following instructions to merge coincident nodes e Enter the value for merge distance M
186. estart 1000 Initial Guess Integration Y Use Fixed Integration Order Integration Order for Triangular Elements Integration Order for Quadrilateral Elements variable Order Integration Scheme Medium Figure 7 6 Solver controls window 196 Analysis Sequences 7 1 1 3 FMM The Fast Multipole Method FMM facilitates fast computation of acoustic fields by an ensemble of point sources at a large number of observation points System matrices are not computed instead an iterative solver is used to solve the matrix vector product computed by FMM for each iteration This reduces the memory usage for large problems A Regular method default option when FMM is not chosen can only solve a maximum of 10 000 unknowns on a 2GB machine However FMM is capable of solving much larger problems Acoustic simulations using FMM are 50 times faster at 10 000 unknowns compared to the regular method Use FMM This option is selected when the user wants Coustyx to use Fast Multipole Method FMM for the analysis If this option is un ticked Coustyx uses Regular method to do the analysis In a Regular method Coustyx computes system matrix and solves the linear system of equations for the unknowns Precompute Near Field Matrices This option is enabled only when the option Use FMM is selected If this option is enabled Coustyx computes near field matrices at the beginning of each frequency and
187. f a cylindrical wave acoustic source 4 5 Acoustic Sources 89 V p k p Ad x 27 y yr 4 6 where p is the pressure at a point Q z y z Position Vector The location R of the cylindrical wave source is set by X component Y component and Z component Note that the units should be consistent with the geometry units Source Strength Set the amplitude of the cylindrical wave through any of the frequency dependent types Constant Table or Script Note that the units used here should be consistent with the rest of the model inputs Direction Vector The cylindrical wave axial direction n is set by X component Y com ponent and Z component New Source x Position Vector X component Y component Z component Source Strength Frequency Dependence Type Imaginary 0 0 Direction Vector X component 0 0 Y component 0 0 Z component 1 0000000000000 Ca coma Figure 4 42 Cylindrical 4 5 4 Dipole A dipole source is defined by a location an amplitude A or dipole moment D and the direction of the dipole Figure 4 43 shows an acoustic dipole source at a location R x yr Zr 90 Getting Started Figure 4 43 An acoustic dipole at R z Yr Zr modeled by two point monopole sources with equal and opposite volume velocities V and V modeled by two point monopole sources The direction of the dipole source n is from the monopole sink V to the monopole source V where V i
188. face area S that is w f 1s 7 3 Note that the reactive sound power values in Coustyx are computed at the surface of a structure Input Sound Power The input power for a closed surface S is defined as 1 W spac f vas 7 4 where po is the medium density c is the speed of sound in the medium vm is the particle normal velocity at the structure surface The input sound power is used to estimate the radiation efficiency of a structure Radiation Efficiency Radiation efficiency is a useful measure to understand the radiation characteristics of structures It is defined as the ratio of the radiated active sound power to the input sound power that is Wa Wi g 7 5 260 Analysis Sequences 7 2 5 1 Complex Intensity This section provides a concrete definition of complex sound intensity and the meaning of the real part and imaginary parts The derivation follows Fahy 4 with appropriate modifications to account for our convention for harmonic variation namely exp iwt Let P x t and V x t represent the instantaneous sound pressure and acoustic particle velocity in a certain direction at the location x They are given as P a t Re p x exp id exp iwt p x cos p wt pr x coswt ps 1 sinwt 7 6 V a t Re v x exp id exp iwt v x cos p wt 0 1 coswt u x sinwt 7 7 The instantaneous sound intensity is the product of sound pressure and acoustic particle
189. fficiency are plotted against the analysis frequency in Figure 9 46 and Figure 9 47 using matlab plot command The sound power radiated Fig ure 9 46 has peaks corresponding to the structural vibration modes that have a non zero net volume velocity 1e 06 T T T T T T Mode 12 1e 08 1e 10 te 12 1e 14 Radiated Sound Power Watt 1e 16 1 e 1 8 L L L L L L L L 100 200 300 400 500 600 700 800 900 1000 Frequency Hz Figure 9 46 Sound power from the forced vibration response 9 5 3 4 iglass igl IGlass files are post processing data files created by Coustyx to visualize the acoustic analysis results Refer to Figure 9 48 e Double click on iglass igl file to open it e Click on the Attribs tab on the top left of the iglass viewer 338 Tutorial Gear Box Radiation 5 5 3 08r LU c 2 S ost 3 a 0 4 F 0 2 F 0 ceea i aid fi fi 1 1 1 fi 1 100 200 300 400 500 600 700 800 900 1000 Frequency Hz Figure 9 47 Radiation efficiency of the gearbox forced vibration Select Attribs Attribute Surface Pressure Plus to view the pressure distribu tion on the exterior surface of the gearbox housing Click on the View tab on the top left of the iglass viewer Press the slider under View Phase to start animation This activates the animation of the wave propagation on the housing surface To view the results for different frequencies press the slider under
190. force vector is the modal damping ratio and I is a unit matrix The above decoupled system of equations is solved for the generalized displacements u The physical response displacement x or velocity x is then computed from the generalized displace ment u and modal matrix A as x Au and x jwAu Follow the instructions below to perform forced response harmonic analysis using modal superposition in Coustyz Select Model Structures lt Structure Mesh Name gt Freq Response Data Right click on the model tree member Freq Response Data and select Compute using Modal Superposition Note that this option is active only when Natural Mode Data and Loads are already specified A dialog window as shown in Figure 5 14 appears Enter analysis frequencies using the table in the Frequency Range tabbed window Refer Section 7 1 2 for more details about the frequency range table Select participating modes from the list in the Mode Participation tabbed window See Figure 5 15 There are multiple ways to select modes a check or uncheck the selection box against a mode in the list b use buttons Select All Modes or Unselect All Modes to select or unselect all modes c use the button Select Modes by Frequency Range to select modes lying within a frequency range Set the upper and lower frequency limits and press OK to select modes within the frequency limits Once the analysis frequencies and the participating modes are selected
191. gree 1 and order m not normalized Inputs integer 1 degree integer m1 begin order integer m2 end order double z argument must be in 1 1 Output 288 Language Syntax double array result result contains Plm z for degree 1 and all orders m1 m2 plm l m1 m2 z result Description Computes Associated Legendre functions of degree 1 and order m normalized Inputs integer 1 degree integer m1 begin order integer m2 end order double z argument must be in 1 1 Output double array result result contains plm z for degree 1 and all orders m1 m2 8 10 2 Legendre Polynomials LegendreP maxorder x result Description Computes array of Legendre Polynomials Inputs integer maxorder degree of the Legendre Polynomial All degrees from O maxorder will be computed double x argument to the Legendre Polynomial must be in 1 1 Output double array result result contains Pn z for degrees n in 0 maxorder 8 10 3 Spherical Harmonic Ylm 1 m1 m2 theta phi result Description Computes Spherical Harmonics of degree 1 and order m Inputs integer 1 degree integer m1 begin order integer m2 end order double theta theta in Spherical polar coordinates 0 PI double phi phi in Spherical polar coordinates 0 2 PI any branch is fine Output complex array result result contains Ylm theta phi for degree 1 and all orders m1 m2 8 10 Special Fun
192. h the model units A simple di mensional analysis would be sufficient to derive the units for any derived quantity For example consider a model with mesh geometry in meters Select the model units to be meter kilogram second m kg s As shown in Table 3 3 the speed of sound should 22 Conventions in Coustyx Table 3 3 Variables and Units Model units PU Ed Geometry Speed of Ambient Pressure Particle Sound Power units sound Density Velocity m kg s m m s kg m kg m s m s kg m s3 W Pa mm N s mm mm s N s mm N mm MPa mm s N mm s mW m kgf s m m s kgf s m kgf m m s kgf m s mm kgf s mm mm s kgf s mm kgf mm mm s kgf mm s inch lbf s inch inch s Ibf s inch Ibf inch inch s Ibf inch s ft lbf s ft ft s lbf s ft Ibf ft ft s lbf ft s Table 3 4 Values for acoustic medium properties of air in different units Model units Material Properties Speed of Sound Ambient Density m kg s 343 m s 1 21 kg m mm N s 343000 m s 1 21 x 1071 N s mm m kgf s 343 m s 0 1233857 kgf s m mm kgf s 343000mm s 0 1233857 x 1071 kgf s mm inch Ibf s 13503 94inch s 1 132228 x 1077 Ibf s inch ft lbf s 1125 33 ft s 0 0023478 Ibf s ft be in m s and the ambient density should in kg m The derived
193. he meshes in the model These properties are defined through selecting any of the frequency dependent types Constant Table or Script Any other relevant property is derived from these two e Define a New Material Right click on Materials and select New and proceed with entering new parameters information Click OK to accept See Figure 4 19 and Figure 4 20 e Edit Materials Select Materials gt lt Material Name gt Right click on lt Material Name gt and select Edit Proceed with editing the parameters Click OK to accept Figure 4 20 4 3 Model Setup 57 File Edit Preferences Help oela Hee Slralej E a Model Type lt Indirect gt ke 5 version lt 1 00 00 gt i E Model Description 5 y Structures ee p Structmesh 0 Materials CreatedFromSkin gt Rename Copy Paste Delete z Sign E Mul Open E Pr Ge Edit Help l Context Script i Analysis Sequences Figure 4 19 Create New Material 58 Getting Started New Material i x Name Helium SpeedSound Frequency Dependence Type Constant y Real 450 00000000000 Imaginary 1 0000000000000 AmbientDensity FEE Frequency Dependence Type Constant v value 1 3 one Figure 4 20 Edit Material Properties 4 3 3 1 Speed of Sound The value for the speed of sound c in a fluid medium is defined here For most of the cases the speed of sound is defined as a purely constant real value
194. hoose the model type from the options MultiDomain or Indirect Also choose Model Units from the selection See Section 3 2 2 for more details on model units Press OK to accept selections and create a new model To open an existing model select File Open Model File 4 3 1 1 MultiDomain Model A MultiDomain model is created to solve the acoustic problem using Direct Boundary Inte gral Formulation The primary variables in the direct formulation are pressure p and normal derivative of pressure pn The normal derivative of pressure pn and normal velocity vn at a point are related as follows Pn tPoWUn where po is the ambient density w is the frequency This formulation allows several bounded interior domains and or one unbounded exterior domain It requires all the elements of the BE mesh to be oriented consistently The domain can be either on the positive side of the mesh or on the negative side of the mesh at a time but not both Each boundary element domain can have a different set of material fluid properties Table 4 3 shows some of the important differences between MultiDomain and Indirect models 4 3 Model Setup 51 Figure 4 15 Coustyx model tree structure Getting Started Select Model Type Multidomain Model Indirect Model Select Model Units 9 meter kilogram second SI units O millimeter newton second meter kilogram force second millimeter kilogram force second
195. ht click on it and select Open to view the boundary element mesh in the GUI Right click on the mesh while holding down the shift key to view the context menu and select Select All Displayed Elements Again right click on the mesh while holding down the shift key and select Selected Elements Set Boundary Condition Structure Velocity BC as shown in Figure 9 42 If the boundary condition Structure Velocity BC is inactive it implies that it has already been applied over the selected elements 9 5 Coustyx Indirect Model 333 Operations on Selection Unselect All Select All Displayed Elements Unselect Selected Elements Display Style Display Connected Nodes Select Elements Connected Through CoordNodes Hide Set Boundary Condition Rigid BC Select All Displayed Nodes Selected Nodes Add to Set Structural Velocity BC Remove from Set Figure 9 42 Apply boundary conditions through selected elements e Apply rigid boundary conditions on all the elements created to fill holes Note that we don t have structure velocities for these as they are newly created in Coustyx and not present in the original structure Since the elements filling the holes are conveniently added to sets named Hole_1 Hole_2 and so on we can apply the boundary conditions on them through these sets In the main model menu select Model Indirect BE Mesh Sets Holes 1 Right click on Holes 1 and select
196. i symmetric with respect to the plane Example Con sider a sphere model with axial velocity oscillating sphere The sphere geometry is symmetric and the axial velocity boundary condition is anti symmetric with respect to any plane perpendicular to the axial direction and passing through the center of the sphere Figure 4 23 shows a sphere with the velocity vectors plotted by arrows The size of this problem could be halved by defining an anti symmetry plane and modeling only half of the sphere geometry Ground ground plane is defined when the reflection from the ground needs to be taken into account The ground plane defined in Coustyx is a perfect reflector Baffle Infinite acoustic baffles can be defined by this plane This feature is not imple mented in the current version and will be available in future versions of Coustyx Do not use this feature for now Origin The point through which the plane passes The coordinates of the point are input in X component Y component and Z component Normal Vector The normal vector of the plane is described here The components of the normal vector are input in X component Y component and Z component 4 3 5 Interfaces Select Model Interfaces This model tree member is present only for MultiDomain models An acoustic interface connects two fluid domains It defines the relationship between the acoustic pressure and velocity at coincident points on either side of the separating surface
197. iage return 8 2 1 Built in Constants Some of the built in constants in Coustyz are listed below PI 3 14159265359 i imaginary unit For example a complex number can be represented as 3 4 xi el e2 and e3 are the coordinate directions Origin It is the coordinate origin which must be added to all position vectors For example a position vector is represented as Origin 2 el 3 e245xe3 8 3 Variables Variables are referred to by their names Variable names may be of any length but only the first 128 characters are considered significant The names are case sensitive must begin with an alphabet or and underscore symbol and all the following characters may be alphabets numerals or underscores Examples of valid variable names Transmission_Error Output_Torque Planet 1 All variables must be declared before they can be used few variables are pre defined and do not need to be declared Many of these are Read only which means that their value cannot be changed 8 3 1 Predefined Variables Some of the predefined variables in Coustyz are listed below These variables can be directly used in Coustyz scripts Frequency Analysis frequency in hertz The value could be set by the function call SetFrequency freq AngularFreq Analysis frequency in radians per sec The value could be set by the function call SetAngularFreq afreq 266 Language Syntax SoundSpeed Speed of sound set by material properties Ambien
198. ii Sensors File 214 22 2 Import Prom File ocurridos nados 215 FAN AGUS ai e as ser a Sa LASS Side G 216 7 2 3 1 Create an IGlass File 216 7 2 3 2 Field Point Grids 2 666 0 eee 216 120 39 IGlass Outputs sad oak d kke eee s dad 227 7 2 4 Sound Power Levels from ISO Standards 2 ev ra rv ra kran 230 7 2 4 1 Create a Sound Power File 231 72 42 Weighting Filters o eyy agaaa 231 take ISO IB a a AE RA RR GE ka RS 232 TAAA ISO STID Sie caras isa ee EK NG 247 C240 SO IGEN ocaso AA 254 Lao Sound Power 62 bama te eae dd Ga ag 259 25 0 Complex Intensity o and ap pose 44 amp 2 see aa skoda 260 Kr OCDE a p ae pah NO 261 8 Language Syntax 264 SL Comments s saa sa deg ds Un ek GE R RER a Gr eRe a Ea 264 SD Consta s 2 2 4 44 G Dr ee AE ere ae ae du SE eg 264 821 Built in Constants c ssas Ye STAGE AE G ee EA Ga a a aw GENENE 265 EE 0 EEE eds ee ae 265 8 3 1 Predefined Variables vav rv 0 vr ee ee es 265 8A Fumetion Calls a ei ss re odds bee karse a SA da r yr 266 dy APT SSIONS o 1 sje Peep S TT PIT TREET TEGE HET SEE SETI 266 6 6 DEAEMEN S ociosa dada a sog fed 267 861 Declaration Statement VV AA 267 6 6 2 Expression Statement ela arias AAA 267 8 6 3 Assignment Statement o ss s gt rasa e 268 8 6 4 Declaration with Assignment e 268 865 Compound S
199. ii Sensors File File Name sensors dat Sensor Coordinates Import Options Es whether to replace the table or append the data to it Scale factor 1 0000000000000 Import From file Figure 7 21 Import Sensor Coordinates from a File pressure particle velocity time averaged intensity are some of the acoustic variables com puted at these points Figure 7 23 shows some of the field point grid types and the definition of variables required to generate these grids Field point grids can be added or deleted by pressing the buttons Add or Delete located at the bottom of the IGlass window refer to Figure 7 22 Quadrilateral This option is selected to generate a quadrilateral grid specified by four corners and the number of divisions in each direction The coordinates of the four cor ners need to be entered in a particular order as shown in Figure 7 23 for quadrilateral grid Figure 7 24 No of divisions N1 The number of divisions in the direction connecting Corner 1 to Corner 2 in a quadrilateral grid refer to Figure 7 23 The grid defined by the four corners is divided into N1xN2 divisions No of divisions N2 The number of divisions in the direction connecting Corner 1 to Corner 3 in a quadrilateral grid refer to Figure 7 23 The grid defined by the four corners is divided into N1xN2 divisions Triangle This option is selected to generate a triangle grid specified by three corners and e
200. in Krylov subspace the better are the chances of finding the solution that means faster convergence However a value that is larger than necessary involves excessive work and storage And a value smaller than necessary may lead GMRES to converge slowly or even fail to converge Figure 7 6 Initial Guess GMRES requires an initial guess to start the solver at each frequency The choice of initial guess could determine the rate of convergence Previous Solution This option sets the solution from the previous frequency while run ning a frequency sweep as the initial guess to GMRES For the first frequency it uses the excitation vector This might result in faster convergence when adjacent frequencies have similar solutions Excitation Vector This option selects the excitation vector b from system of equations Ax b as the initial guess to GMRES 7 1 1 6 Integration In Coustyx regular Gauss quadrature method is used to numerically evaluate element ma trices The number of quadrature points are represented by integration order An integration order corresponds to the highest degree of the polynomial that can be integrated over an element with zero error The user can select the integration order for triangle and quadrilateral elements separately Figure 7 6 204 Analysis Sequences Table 7 1 List of valid integration orders and the corresponding quadrature points on triangle elements Order No of points 0 1 2 3 4 6
201. in Model For a Multi Domain model the Attribute drop down menu lists the following outputs Displacement This attribute displays the acoustic particle displacement vector over the surface of the boundary element mesh and at field point grids Surface Normal This attribute displays the surface normals on the boundary element mesh and field point grids Even though this attribute is not an acoustic property it is listed to clarify the normal vectors used to compute Normal Velocity and Normal Sound Intensity For the boundary element mesh in Multi Domain model the surface normal is in the direction of the Domain Normal Note that the Domain Normal always points away from the domain of interest refer to Section 6 3 for definition Surface normals for different types of field point grids provided in Coustyx Fig ure 7 23 are defined below For Quadrilateral and Triangle grids the surface normals point into the surface for the grid coordinates defined in the order shown in Figure 7 23 For Annular Disc grid the surface normal is in the direction of the disc normal For Cube grid the surface normals on all faces of the cube point outward when the grid coordinates are defined in the order shown in Figure 7 23 For Sphere grid the surface normal at any point on the grid points radially away from the center Pressure This attribute displays the sound pressure amplitude with phase on the surface of the boundary element mesh and at field point grid
202. in this Boundary Condition is considered to be the wall velocity Ur wa The impedance Z relates the pressure p at the surface of the acoustic material to the particle normal velocity vni at the surface Refer Section 6 1 for the definition of impedance implemented in Coustyx The impedance is assigned through a script which uses the function call GetImpedence The function takes in the predefined variables PosnVec and NormalVec as the input arguments Other predefined variables such as AngularFreq SoundSpeed etc can also be used to compute impedance Figure 6 33 6 3 8 Structure Velocity BC Structure velocity Boundary Condition is applied when the frequency response data is known from the FEA analysis of the structure Refer to Section 5 1 2 for details on how to load frequency response data Figure 6 13 158 Boundary Conditions New Boundary Condition x Nonuniform Normal velocity ha 1 Fjfunction GetNormalVelocity in PosnVec in NormalVec 2 AngularFreq SoundSpeed WaveNumber and AmbientDensity are 3 4 5 6 T 8 9 read only variables that can be used here The following is just an example change the formula to su var VMag 12 0 var Vn VMag e3 NormalVec return Eval Vn AngularFreq SoundSpeed WaveNumber and imbientDensity read only variables that can be used here Figure 6 12 Non Uniform Normal Velocity BC 6 3 Multi Domain Model BCs 159
203. ind 289 8 10 7 Cylindrical Hankel Function of Second Kidd 290 8 10 8 Spherical Bessel Function a o ss spa dede deda tetee nids 291 8 10 9 Cylindrical Bessel Function lt 4 ssa s aare eae o ae Ala EA Gog GE 291 9 Tutorial Gear Box Radiation 292 OA J troduetione i seas f dd d dessa see dele lete tare VE dd 292 92 Problem Descripti b s 4 248 s n A aa koke 293 93 Finite Element Analysis sa vass bag Pera ae SVEEN 294 98 1 FE Mesh Modeling oc d 22 5 46 ME GR SR GRS Era SEG 294 9 3 2 Natural Frequencies and Normal Modes rav rv re vr ran 294 9 3 3 Forced Response Modal Superposition 295 94 Coustyx MultiDomain Model 042 sak ee Re sy esa a 297 GAL Problem Dep agro PRAERE SEE See wi ARO Gao ee 297 9411 Creates New Model ia cs a maradi paadid 4058 4 44 297 9 4 1 2 Import FE Structure Mesh s caccini sais u a aa a es 297 9 4 1 3 Load Frequency Response Data 297 9 4 1 4 Generate BE Mesh o o E a a 301 9 4 1 5 Define Material Properties o vr rv rare vn 306 J416 Fil Holes seg kn aa tt A RB a Eo ii 307 9 4 1 7 Define Boundary Conditions 0 308 9 4 1 8 Apply Boundary Conditions 310 410 Domains 10 u que tarea dedo HEG 311 942 Run Acoustic Analysis cx edi A eee eS 314 941 3 Post processing Outputs vos Skee ee SEE a ee 316 OSL eesuligilat
204. ing is estimated from the damping ratios damping ratio is a unitless ratio of the damping constant c to the critical damping constant ce Specify 1 for critically damped systems lt 1 for underdamped systems and gt 1 for overdamped systems A non zero modal damping ratio is necessary to restrict infinite responses at natural frequencies The relation between damping matrix C and damping ratios is ATCA Diag 2C w where A is the modal matrix C and w are damping ratio and natural frequency at the it mode Edit Damping Ratios x Select All Modes Unselect All Modes Select Modes by Frequency Range Natural Freq Hz Damping Ratio Selection lt 180 0925 0 000000 Im 338 2615 0 000000 454 4722 0 000000 z 484 2651 0 000000 F 506 2977 0 000000 669 1085 0 000000 390 2686 0 000000 950 5137 0 000000 m 1528 7089 0 000000 Mode 1 o 1620 3582 0 000000 1850 4165 0 000000 1892 9052 0 000000 1977 7131 0 000000 2053 1284 0 000000 2151 9858 0 000000 2251 4260 0 000000 2347 9280 0 000000 lo SAT LATE j m gt Modify Damping Ratios for Selected Modes oc coma Figure 5 9 Damping ratios edit dialog box Follow the instructions below to edit modal damping ratios Select Model Structures lt Structure Mesh Name gt Natural Mode Data Right click on Natural Mode Data and se
205. ipole Method Max No of CPUs allowed Figure 2 6 License Features window 2 3 License Key Installation 11 0 Use Native License Use Altair GridWorks License Key 410271304007703f1108723b430c7339 150b276a455a 7c6a4b0e723e435c256c155c746e435f ID 0021708A7C31705F22AB Expiry Status Invalid Expired Direct Boundary Element Model Indirect Boundary Element Model Acoustic Finite Element Model Structural Coupling Multi domain Model Multipole Method Max No of CPUs allowed Figure 2 7 Invalid or expired License status 12 Installing Coustyx 2 3 1 2 If you have a network dongle If you are using a network dongle follow the steps below to install the license key Step 1 Start the License Server Attach the dongle to your network server Install Sen tinelDongleDeviceDriver exe on the server if it is not done already This automatically starts the Sentinel Key Server service Allow ports 7001 and 7002 to go through the server firewall The status of the license server can be monitored via a web browser using the url http lt Server Internet Protocol IP Address gt 7002 your browser should be java enabled You can monitor the maximum number of seats licenses allowed and the number of seats in use Step 2 Install License Key You can now install the license key from any computer con nected to the server Make sure Coustyx is installed on the computer Open
206. ir and Water at the start of a new model setup Later on material properties can be changed only through Materials model tree member and not by modifying model units Note that editing model units through Units model tree member does not rescale the model 3 2 Units 19 e Model units are also used while computing sound power levels from ISO standards The acoustic variables are converted from model units to S I units before using the empirical relations in ISO standards T Modell cyx File Edit Analysis Preferences Help D BML u E lt Model Type lt MultiDomain gt Version lt 1 02 00 gt Model Description E Stru Units E Matet eae Plane vename Interf Copy Boun Paste Dired Delete FE Me E Doma Open 13 Conte Close Analy Edit Help Figure 3 1 Units model tree member Select Model Units The model units are set at the start of a new model setup Figure 4 16 To edit units later on right click on Units in the model tree and select Edit Figure 3 1 An edit dialog box appears and you can make changes to model units here Figure 3 2 Note that modifying the model units does not rescale the model For convenience six different standard unit systems are predefined meter kilogram second m kg s millimeter newton second mm N s meter kilogram force second m kgf s millimeter kilogram force second mm kgf s inch
207. is constructed using Cornerl as the starting point and L1 L2 L3 as its dimensions along X Y Z axis respectively L1 Length of the parallelepiped in X direction Figure 7 39 Specify the value of L1 such that it satisfies the definition L1 11 d where l1 is the reference box dimension in X direction and d is the measurement distance The recommended value for d 1 m L2 Length of the parallelepiped in Y direction Figure 7 39 Specify the value of L2 such that it satisfies the definition L2 12 2d where 12 is the reference box dimension in Y direction and d is the measurement distance The recommended value for d 1 m L3 Length of the parallelepiped in Z direction Figure 7 39 Specify the value of L3 such that it satisfies the definition L3 13 d where 13 is the reference box dimension in Z direction and d is the measurement distance The recommended value for d 1m N1 Number of subdivisions in X direction Figure 7 39 Select the value of N1 such that the length of the rectangular partial area formed by these subdivisions satisfies the criterion lt 3d where Ll is the length of parallelepiped in X direction and d is the measurement distance Refer Figure 7 37 The microphone positions are in the center of each partial area and at each corner of the partial area excluding the corners intruding into reflecting planes N2 Number of subdivisions in Y direction Figure 7 39 Select the value of N2 such that
208. itrarily unselected there will be problem in finding the correct closed path Figure 5 29 Accept the seam by pressing Skin Accept Seam See Figure 5 30 Delete Selected Seams and Delete All Seams could be used to remove seams already constructed To select a seam for deletion left click on the seam while holding down the shift key 5 5 4 Create Skin Unselect all elements by right clicking on the mesh in the GUI and selecting Operations on Selection Unselect All If necessary form the first seam as described in Section 5 5 3 If the seam is acceptable click on Skin Accept Seam Figure 5 26 Repeat the above process until all the number of necessary seams are created Choose any one face of an element preferably on the side of the acoustic domain you are interested in to start skinning To select an element in the GUI Left click on the element with the shift key held down To ensure skinning is done accurately unselect all elements in the GUI by right clicking with the shift key held down and selecting Operations on Selection Unselect All To start the propagation of skin across the mesh select Skin Create Skin The skin propagation starts from the selected element and covers the entire mesh defined within seams The skin that is going to be used to create the BE mesh is shown in color Red for inspection Check if entire mesh you are interested is covered See Figure 5 31 126 Pre processing Features
209. kin New Elements Stitch Seams Delete Elements Merge Nodes Split Pn Nodes Split Sigma Nodes and Element Orientation These features allow users to fix problems with imported meshes by deleting elements creating new elements filling holes stitching gaps merging coincident nodes flipping element normals etc The imported finite element structure meshes could be skinned to generate surface BE meshes for acoustic analysis 5 1 Importing FE Data The main geometry source for a Coustyx Boundary Element BE model is the Finite Element FE mesh of the structure This section explains the steps involved in importing FE data Coustyx provides translators for most commonly used file formats created by finite element packages NASTRAN ABAQUS ANSYS and I DEAS Universal Files Select Model Structures e To import FE mesh Right click on Structures and select Import Nastran Bulk Data bdf File see Figure 5 1 to import mesh from Nastran bulk data format The FE meshes from other data formats can be imported by selecting Abaqus inp File Ansys Results rst File or IDEAS Universal unv File e To load frequency response data from FE analysis Click on the imported structure lt Structure Mesh Name gt right click on it and select Load Freq Response Data Nastran Punch File see Figure 5 2 The other supported data formats are Nastran OP2 File Ansys rst File Ansys rfrq File IDEAS Universal File Select desired frequencies
210. l from other files The user may put the model through several consistency checks visually inspect it query objects through dialog boxes apply boundary conditions save the model to a file specify analysis parameters run analysis and save the results to a file In this chapter we will discuss the features provided in Coustyx Ul and the procedure to be followed in setting up the acoustic problem and running an analysis 4 1 Main Menu Features A brief description of items in Coustyr UI s main menu bar Figure 4 1 is given below Table 4 1 Description of the main menu bar items in Coustyx UI Menu Items Description File Open Model File New Model Save Model File Save Model File as Close Open an existing Coustyx model cyx files only Create a new MultiDomain or Indirect Coustyx model Save all the changes made to a model Save the model to a new file Close the open model 30 Getting Started Table 4 1 continued Menu Items Description Print Setup Print Preview Print Recent Files Properties Specify print setup properties Active only for scripts Show print preview Active only for scripts Print the selected text Active only for scripts List the most recently visited model files Show the maximum valid frequency for the cur rent acoustic model based on the size of the ele ments in the mesh Edit Vote This menu is active on ly for text in scripts
211. l main menu select Model Structures Structmesh 0 or lt Struct Mesh Name gt e Right click on Structmesh 0 or lt Struct Mesh Name gt and select Load Freq Response Data Nastran Punch File as shown in Figure 9 6 The other valid data formats from which frequency response data can be loaded into Coustyx are Nastran OP2 File and Ansys rst File 298 Tutorial Gear Box Radiation yo Select Model Units 9 meter kilogram second SI units foot pound force second other Lenath scale factor 1 0000000000000 Mass scale factor 1 0000000000000 Note Model units are presently only used Figure 9 4 New Model Selection Window 9 4 Coustyx MultiDomain Model 299 File Edit View Preferences Help Ose eree SR E ModelL cyx i Type lt MultiDomain gt E Version lt 1 00 00 gt Model Description Structures Rename Copy Paste Delete Domains E Context Open iC Analysis Close Edit Help Abaqus inp File Nastran Bulk Data bdf File Ansys Results rst File Figure 9 5 Import a finite element structure mesh 300 Tutorial Gear Box Radiation a Edit View Preferences Help Del Bt Benz SK 23 63 ModelL cyx Type lt MultiDomain gt Version lt 1 00 00 gt Model Description Structures Structmesh 0 Rename Copy CJ Boun
212. l velocity distribution for the first five free vibration modes 296 New Model Selection Window o e o 298 Import a finite element structure mesh 299 Load frequency response data into Coustyx 2 rar arr rv ran 300 Structure mesh opened in Coustyx GUL kr a da Aaaa 301 Coustyx GUI control panel tools o terras ee 302 Select all displayed elements in the GUL o o o oo 302 Element Display Style Window o e e e 303 Select elements for creating a seam o e eee 304 Display connected nodes for creating a seam e rea 305 Pick modes to create a Sed dais PE Ek GK EG and 305 Edit material properties a p g g e ee 306 Fill hole using triangle elements vr vr vr arrene 307 Edit boundary conditions window e e 308 Edit structure velocity boundary condition window 309 Apply boundary conditions through selected elements 311 Apply boundary conditions through sets 22 rar e e e 312 Specifying boundedness of the domain o a 313 Plement Orientations amos aa ok ee ekke E RA 314 Set the side of the mesh on which the domain is 315 Analysis Solver controls 4 pees peed eek QOS sere eden see 317 Set analysis frequeneies vce ek a FJES GE Ee Oe ee HK EG 318 Sound power fro
213. le DS das y AA KARENE EE ES SSS ea aS Steps to install a License Key lt lt wat aia ei rava License Features window socs sv vs ask sk sa SE EE ee Invalid or expired License status o gt a o sosa d soca sagda ee Steps to install a network dongle ee ee ee Use Altair GridWorks License vass k De bekk kasta aa see Set pat Variables ta seres OPS Ta wee Se as des Units model tree member 2 2 vr arr ararra rn rare Edit umits dialog bog ais RARA a Ses Ge Boundary Condition Table gt s siada 268 con bd EEE EG Edit Boundary Condition Table lt se e crin sass rnan carrs Table Boundary Condition example o n ae oao ace ea e ae a a a i E a Table import options window s da s eey pa see aa ee a ei e dd Script to define frequency dependent acoustic variable for the boundary condition Main MENA EMS roar S Preferences dialog box Common parameters oo saoao Preferences dialog box 3D Viewer parameters o aa aaa Definition of feature angle between two connected elements Note This definition is applicable only for 2D elements oa co aa a c dasad damara aeea Coustyx with Mesh Viewer Window Wa a a a a CUL Control Panel Toolse cs a a aa ee RA a AE i GUI operations on elements available through the context menu activated by the right mouse button with the shift key held down o Element Display Style Win
214. lect Edit Damping Ratios A dialog window 106 Pre processing Features shown in Figure 5 9 appears It contains a table that lists modes their natural frequencies damping ratios and selection check boxes The user can modify the damping ratios individually by directly editing the table The damping ratios for a group of selected modes can be edited by pressing the button Modify Damping Ratios for Selected Modes There are multiple ways to select modes in the table for editing a check or uncheck the selection box against a mode in the table b use buttons Select All Modes or Unselect All Modes to select or unselect all modes in the table c use button Select Modes by Frequency Range to select modes lying within a frequency range Figure 5 10 Set the upper and lower frequency limits and press OK to select modes within the frequency limits Edit Damping Ratios _ 3 Select Al Modes Unselect All Modes Natural Freq Hz Damping Ratio Model 180 0925 0 000000 338 2615 0 000000 454 4722 0 000000 484 2651 0 000000 Frequency Range Lower Limit 180 09246826172 Upper Limit 3998 2175292969 Mode13 1977 7131 0 000000 Mode14 2053 1284 0 000000 Mode15 2151 9858 0 000000 Mode16 2251 4260 0 000000 Mode17 2347 9280 0 000000 jP m Figure 5 10 Select modes by frequency range The button Modify Damping Ratios for Select
215. lected Note that this operation is skipped when the group of selected elements have junctions in their midst or when not all the selected elements are connected to one another through coordinate nodes Figure 5 51 Element orientations window Bibliography 1 Abaqus Analysis User s Manual http www simulia com Chapter 6 Boundary Conditions Boundary conditions BCs are used in Coustyx to model reflection absorption or excitation of sound waves from the boundary surfaces Coustyr offers wide variety of boundary conditions for both MultiDomain and Indirect BE models The user defines the boundary conditions as separate entities which are named uniquely These boundary conditions can later be applied to the individual elements directly or collectively through sets group of elements before running the analysis 6 1 Impedance Definition in Coustyx Coustyr supports impedance boundary conditions to simulate the presence of sound absorbing materials Sound pressure p at the surface of the acoustic material Figure 6 1 is related to particle normal velocity Uni as P Uni Un_wall Z 6 1 where Z R jX is the impedance of the acoustic material Rand X are the real and imaginary parts of Z and Un wall is the wall or structure velocity The particle normal velocity vn at any point on the sample surface is the inward normal component of the fluid velocity v at that point that is vj v nj where n is the inw
216. lindrical Hankel function of first kind fractional order n Inputs integer n order of the Cylindrical Hankel function For fractional n n must be ve integer nterms number of terms to be computed All orders from n nti n nterms 1 will be computed complex z argument to the Cylindrical Hankel function Output complex array result contains Hinu z 8 10 7 Cylindrical Hankel Function of Second Kind H2n n nterms z result Description Computes Cylindrical Hankel function of second kind integer order n Inputs integer n order of the Cylindrical Hankel Function For integer n n can be ve 0 or ve integer nterms number of terms to be computed A11 orders from n n 1 n nterms 1 will be computed complex z argument to the Cylindrical Hankel function Output complex array result contains H2n z H2nu n nterms z result Description Computes Cylindrical Hankel function of second kind fractional order n Inputs integer n order of the Cylindrical Hankel Function For fractional n n must be ve integer nterms number of terms to be computed All orders from n nti n nterms 1 will be computed complex z argument to the Cylindrical Hankel function Output complex array result contains H2nu z 8 10 Special Functions Syntax 291 8 10 8 Spherical Bessel Function jn n nterms z result Description Computes Spherical Bessel function of order n Inputs integer n order
217. ll Select All Displayed Elements Select All Bad Elements Selected Elements Select All Displayed Nodes Select All Bad Nodes Selected Nodes Ny M k gt C selected Coord Nodes Gy Selected Elements Sy Fil Hole SY Skin Sy New Element Stitch Seams 4 Accept Seam Stop Skinning I Create Mesh From Skin Delete Selected Seams Clear Skin Delete al Seams create Sin Help Figure 5 20 Select all Bad Elements 118 Pre processing Features Feed eee Ded in E Model 15 Type lt Indirect gt Version lt 1 00 00 gt Model Description Structures 2 4 Structmesh_0 Coord Nodes a O Elements a AF Sets i ig BadElements Freq Response E BadElements 5 Natural Mode D Materials anne EJ Planes Copy gt Indirect BE Mesh lt Mes Paste Context Script Delete CJ Analysis Sequences Open Close Edit Help Replicate Elements Ga log CoordNodes Error Error Error Error Error Error Error Error Incompatible elements ID 13091 and ID 13473 Incompatible elements ID 12763 and ID 13483 Incompatible elements ID 12806 and ID 13504 Incompatible elements ID 13599 and ID 13600 Incompatible elements ID 13615 and ID 13616 Incompatible elements ID 13620 and ID 13622 Incompatible elements ID 13627 and ID 13630 Found element connectivity errors in mesh Unable to c Fix the mesh and retry 4 m
218. lt Options Enable this to use default options In the default options the num ber of interpolation points are automatically set to four Coustyx searches for the four nearest interpolating points or structure nodes for a given BE node Then the weighted average of the velocities at these points is computed and applied as the nodal velocity to the BE node Equation 6 3 Weights are obtained from the inverse of the distance between the BE node and the interpolating points The search for interpolating points is terminated only when all the four nearest structure nodes are found or the entire structure mesh is searched which ever happens first If no interpolation points are found during the search a zero nodal velocity is assigned to the BE node 6 3 Multi Domain Model BCs 149 If the user wants to terminate the search sooner than the search over the entire structure mesh or change the number of interpolating points from four then disable this option and set the user options manually Number of Interpolating Points This option sets the number of points N to be used for the velocity interpolation The search for interpolating points is terminated when any of the following criteria is met a N nearest structure nodes are found b maximum search distance from the BE node position is reached c optional when the relative weight in percentage at the farthest point is less than a user defined tolerance If no interpolation
219. luated between Q and R New Source x ID 1 Type Quadrupole gt Position Vector X component 0 0 Y component 0 0 Z component 0 0 Quadrupole Strength Coefficients Strength Type Amplitude v Coeffident Real Imaginary 11000 1 0000000000000 0 0 TH 0 0 0 0 THE 0 0 0 0 TI 0 0 0 0 T 2 2 0 0 0 0 T 2 3 0 0 0 0 TED 0 0 0 0 TE 0 0 0 0 13165 0 0 0 0 Figure 4 45 Quadrupole Dialog Box Position Vector The location R of the quadrupole source is set by X component Y com ponent and Z component Note that the units should be consistent with the geometry units Quadrupole Strength Coefficients The quadrupole strength is set through the tensor com ponents or coefficients These components could be set to be any of the following two types Amplitude T or Quadrupole Moment 7 Choose the type from the drop down menu Strength Type Note that the units used here should be consistent with the rest of the model inputs 4 5 Acoustic Sources 93 4 5 6 User Defined Coustyz offers users the choice to define their own source The User Defined source is defined by the location of the source through Position Vector and the function GetDirectionalResponseAtFieldPoint The relative position of a field point with respect to the source position and the field normal are input to the function through the arguments RelativePosnVec and NormalVec The pressure and the normal derivative of pressure at the field poi
220. ly one reflecting plane Figure 7 33 shows a hemisphere measurement surface centered at Center Click on the Suggest button to auto fill the measurement surface variables in agreement with the stan dard Verify the input you have entered by clicking on the Check button Coustyx checks to see if the input variables satisfy the standard requirements If the standard requirements are not met a message window pops up to help you make appropriate corrections X Axis Specify the orientation of the X axis here See Figure 7 33 for definition Y Axis Specify the orientation of the Y axis here See Figure 7 33 for definition Center Specify the center of the hemisphere surface here Select the coordinates such that the center is in the middle of the reference box and its image in the reflecting plane Radius The radius of the hemisphere surface shall be equal to or greater than twice the characteristic source dimension do and not less than 1m 7 2 Outputs 233 Table 7 5 Relative response levels for various weightings 1 Nominal A weighting B weighting C weighting D weighting Frequency Hz dB dB dB dB 10 70 4 38 2 14 3 26 63 12 5 63 4 33 2 11 2 24 69 16 56 7 28 5 8 5 22 56 20 50 5 24 2 6 2 20 63 25 44 7 20 4 4 4 18 7 31 5 39 4 17 1 3 16 72 40 34 6 14 2 2 14 68 50 30 2 11 6 1 3 12 79 63 26 2 9 3 0 8 10 87 80 22 5 7 4 0 5 8 94 100 19 1 5 6 0 3 7 2 125 16 1 4 2 0 2 5 57 160 1
221. ly reflect the views of the NSF Vijaya Kumar Ambarisha Hilliard OH May 2009 XXII Preface Chapter 1 Introduction Coustyx is a software program developed by Advanced Numerical Solutions ANSOL for the computation of steady state sound fields Coustyx integrates the Fast Multipole Method FMM with Boundary Element BEM formulations to obtain rapid solutions to acoustic field problems The small memory footprint of Coustyx coupled with fast solvers allows simulation of very large problems in acoustics The Boundary Element Method BEM is widely used to predict sound radiation from vi brating mechanical components BEM codes are popular since they involve only surface dis cretization and solve exterior infinite domain problems naturally However conventional BE methods suffer from a major drawback the BEM coefficient matrices are fully populated and frequency dependent This severely limits the size of models that can be built The largest models that can be analyzed presently are limited to about 10 000 unknowns The dimensions of the elements panels are related to the frequency range of interest and thus a limitation on model size restricts the frequency range over which the BE model is useful Presently the usefulness of BEM is restricted to coarse models of small objects such as engine blocks in the low frequency regime In spite of its elegance and power conventional BEM cannot be applied to aircraft interior submari
222. m function var x Dim 20 var x Dim 3 5 8 6 5 Compound Statement A compound statement is formed by enclosing a sequence of zero or more statements in braces Each of these statements may be a simple statement or a compound statement Examples Out Hello Out World var x 1 var y 2 Out x y Out Eval x y 8 6 Statements 269 8 6 6 Symbolic Form and Evaluation of Expressions Expressions are manipulated by Coustyr in symbolic form unless it is explicitly told to evaluate them Example var y 1 0 var x 2 y 3 Out x x Output X Xx Example var y 1 0 var x 2 y 3 Out x Eval x Output x 5 The subsitute function Subst can be used to substitute a variable by the symbolic expression it contains Example var y 1 0 var x y Out x Subst x Output x y Example var y 1 0 var x 2 y 3 Out x Subst x Output x 2 y 3 Evaluation of an expression can also be caused by using the assignment operator instead of the assignment operator In that case evaluation of the expression on the right hand side takes place before it is assigned to variable on the left hand side Example var y 1 0 var x 2 y 3 Out x Subst x 270 Language Syntax Output x 5 Example var y 1 0 var x y Out x Subst Subst x Output x y The Subst function does nothing if its argument is not a simple varia
223. m the forced vibration response 319 Radiation efficiency of the gearbox forced vibration 319 IGlass viewer showing sound pressure distribution at 760 Hz 320 New Model Selection Window 0000 eee eee eee 321 LIST OF FIGURES xvii 9 29 9 30 9 31 9 32 9 33 9 34 9 35 9 36 9 37 9 38 9 39 9 40 9 41 9 42 9 43 9 44 9 45 9 46 9 47 9 48 Import a finite element structure mesh o rv rav kran 322 Load frequency response data into Coustyx 22 vr rv rn a 323 Structure mesh opened in Coustyx GUL rar rv kr kv o 324 Coustyx GUI control panel tools s sv v res See Sew ee He STG ae ee 325 Select all displayed elements in the GUL o o ooo o 325 Element Display Style Window 00 000 eee eee 326 Select elements for creating a seam ren ee ee 327 Display connected nodes for creating a seam o 328 Pick modesto create a Bedis ar A A A a wR we 328 Edit material properties ss t ycr k 44 4006 h E cae e tada Ce 329 Fill hole using triangle elements 330 Edit boundary conditions window lt lt 0 22280 sea a 331 Edit structure velocity boundary condition window 332 Apply boundary conditions through selected elements 333 Apply boundary conditions through sets s s o aoci a soss e renn 334 Analysis s
224. mal components are obtained by averaging the normals at the node on all the elements connected to the node Close Closes the window opened by Open menu item 4 3 7 4 Pn Nodes Select Model Direct BE Meshes lt Direct BE Mesh Name gt Pn Nodes Use this sub tree member to review Pn Nodes in the mesh Pn Nodes are variable nodes associated with normal derivative of pressure pn at the location of the node The normal derivative of pressure pn and normal velocity vn at a point are related as follows Dn tPoWUn where po is the ambient density w is the frequency pressure p and normal derivative of pressure pn are the primary acoustic variables in Direct BE formulation used for MultiDomain models The right click on Pn Nodes provides these menu options Open Opens the list of all Pn nodes The table shows the ID of the Pn node location coordinates X Y Z mean normal components mean Nx mean Ny mean Nz and solid angle covered by the Pn node The mean normal components are obtained by averaging the normals at the node on all the elements connected to the node Close Closes the window opened by Open menu item 4 3 7 5 Constraint Equations Select Model Direct BE Meshes lt Direct BE Mesh Name gt Constraint Equa tions This sub tree member is used to review or create a new set of constraint equations Constraint equations are necessary to correctly setup an acoustic problem when the BE model
225. ments Display Connected Nodes as shown in Figure 9 12 Left click on the displayed nodes while holding the shift key to pick the nodes to be part of the seam Make sure to pick nodes in a specific direction Pick the nodes until you see a circular seam following the edge of the hole as shown in Figure 9 13 From the tabbed windows located below the structure mesh select Skin Accept Seam e Create seams around all the four holes in the gearbox housing following the instructions given above 9 4 Coustyx MultiDomain Model 305 Unselect Display Style Display Connected Nodes Select Elements Connected Through CoordNodes Hide Set Boundary Condition Add to Set Remove from Set Operations on Selection Unselect All Select All Displayed Elements Selected Elements Select All Displayed Nodes Selected Nodes Figure 9 12 Display connected nodes for creating a seam Figure 9 13 Pick nodes to create a seam 306 Tutorial Gear Box Radiation e Right click on the mesh while holding down the shift key and select Unselect All to unselect all elements e Skin the finite element structure mesh to generate a boundary element mesh for Coustyx Left click on any element on the exterior surface of the gearbox housing mesh while holding the shift key Make sure you select only one element From the tabbed windows located below the structure mesh select Skin Create Skin
226. ments here A variable can be declared only once in a compound statement var x 1 var x 2 This will generate an Error Out x Eval x y However it is possible that a variable with the same name might have been declared in an outer context In such a case the variable declared in the innermost context is the only one visible var x 1 var x 2 Dut x is Eval x Output x is 2 278 Language Syntax Variables declared in the initialization part of a for statement will be visible only within the for statement var y Dim 10 for var j 1 j lt 10 j j 1 var k 11 j ylkl j j j 10 This an Error j is not visible here k 1 This is also an Error It is good programming practice to limit the scope of variables to as small a part of the code as possible For example in the following piece of code a programming error will cause an infinite loop that is difficult to debug No error message is generated because there is no syntax error var x1 Dim 10 var x2 Dim 20 var i1 i2 for i1 1 i1 lt 10 i1 i1 1 I x1 i1 1 0 for i2 1 i2 lt 20 i1 i2 1 x2 i2 1 0 But if the scope of the loop variables had been limited as in the following piece of code then the problem would be caught right away and an error message will be generated var x1 Dim 10 var x2 Dim 20 for var i1l 1 i1 lt 10 i1 i1 1 x1 i1 1 0 for var i2 1 i2 lt 20 i1 i2 1 I x2 i2 1 0
227. menu and select Select All Displayed Elements From the tabbed windows located below the mesh select Element Orientation to view the direction of element normals refer to Figure 9 21 The green arrow indicates the positive direction and the red arrow indicates the negative direction of 312 Tutorial Gear Box Radiation File Edit Preferences Help Dodd at Bi E Model Type lt MultiDomain gt Version lt 2 00 00 gt Model Description Cy Structures CJ Materials Y Planes Y Interfaces Boundary Conditions SR Hole I Rename Copy Paste Context Scr C Analysis Sei Delete Open Close Edit Help Replicate Elements Display Style CoordNodes Display All Hide All Set Boundary Condition gt Rigid BC Select Structural Velocity BC E Unselect Add Selection to Set Remove Selection from Set Figure 9 19 Apply boundary conditions through sets 9 4 Coustyx MultiDomain Model 313 File Edit Preferences Help Ce Bs Bo 343 Model Type lt MultiDomain gt Version lt 2 00 00 gt E Model Description 2 Structures CJ Materials Y Interfaces CJ Boundary Conditions a 2 Direct BE Meshes y FE Meshes S E Domains i 5 Domain Type lt Direct BE gt Boundednes Material lt Air gt Direct BE Meshes Chief Points Rename 2 Context Script Copy 2 Analysis Sequences Pide Jn
228. mplemented in Coustyx The impedance Z is defined by selecting any of the frequency dependent types Constant Table or Script 6 3 7 Non uniform Normal Velocity BC This Boundary Condition is applied on the element where normal velocity Note normal velocity is defined with respect to the domain normal Figure 6 4 varies with position and nor mal The normal velocity is defined in the script by the function GetNormal Velocity which takes in the predefined variables Posn Vec and NormalVec as the arguments The variable PosnVec reads the coordinates of a point on the element that is PosnVec x y z The variable Nor mal Vec reads the components of the domain normal vector at a point on the element that is NormalVec nz Ny nz The special vectors el e2 e3 are predefined unit vectors in coordinate directions of the reference frame which can be used in the Coustyx scripts When Use Impedance option is disabled the Normal Velocity defined in this boundary condition BC is considered to be the particle normal velocity vni Figure 6 12 Other predefined variables that can be used in the script are AngularFreq w frequency in radians sec SoundSpeed c speed of sound in the medium with the same units as those defined in materials WaveNumber k and AmbientDensity p density of the medium with the same units as those defined in materials 6 3 7 1 Use Impedance When this option is enabled the Normal Velocity defined
229. mpt Coustyz can be run in interactive mode or in batch mode To run the program interactively type coustyx at the command prompt and press enter In order to avoid entering the full path every time you call the executable we advise you to modify the Path environment variable 2 4 Running Coustyx 15 Install License Key nr 5 Use Native License Use Altair GridWorks License Altair GridWorks License In order to use altair gridworks units set the environment variable LM_LICENSE_FILE or ALTAIR_LM_LICENSE_FILE value to 7788 servername or port servername Click on the test button below to check the connection to the server AA ret A Licensing Scheme Altair GridWorks Units Altair GWU Feature Partner0032 Connecting to server Successfully connected to Altair GridWorks Units License Manager No of GridWorks Units available 15800 Figure 2 9 Use Altair GridWorks License 16 Installing Coustyx temp Default Programs New Office Document Open Office Document Program Updates TextAloud Windows Update WinZip Programs Documents Settings Search Help and Support Run Windows Vista BEES EEEEEEEEEEEEEEEEEEE EB Coustyx32 Microsoft NET Framework SDK v2 0 Microsoft Office Microsoft Office Small Business Tools Microsoft Office Tools Microsoft SOL Server 2005 Microsoft Works MikTeX 2 6 Modem Diagnostic Tool Mozilla Thunderbird
230. n of sine of a number between 1 and 1 The output is in radians Example Asin 0 707107 0 785398 7 4 Acos or acos Obtain the arc cosine inverse function of cosine of a number between 1 and 1 The output is in radians Example Acos 0 707107 0 785398 7 4 Atan or atan Obtain the 2 quadrant arc tangent inverse function of tangent of a number The output is in radians Example Atan 1 0 785398 7 4 atan2 y x Obtain the 4 quadrant arc tangent of the real arguments x and y 7 lt atan2 y x lt T Exp or exp Obtain the exponential of a number Example Exp 1 2 71828 e Ln or ln Obtain logarithm to the base e natural logarithms Example Ln 10 2 30259 Ln exp 1 1 int Obtain the integer value of a number Example int 4 926 4 int 4 926 4 abs Obtain the absolute value of a real number or the magnitude of a complex number Example abs 10 958 10 958 abs 3 4 i 5 mag2 x y Obtains the magnitude v 2 y for real arguments x and y Example mag2 3 4 5 real imag Obtain real and imaginary values of a complex number respectively Example real 3 4 i 3 imag 3 4 i 4 8 10 Special Functions Syntax Given below is the syntax for calling special functions that are available in Coustyx These functions are evaluated numerically Use these functions in Coustyz scripts 8 10 1 Associated Legendre Function Plm l m1 m2 z result Description Computes Associated Legendre functions of de
231. n this Boundary Condition is considered to be the wall velocity Un wa The impedance Z relates the pressure p at the surface of the acoustic material to the particle normal velocity vni at the surface Refer Section 6 1 for the definition of impedance implemented in Coustyr The impedance value is defined by selecting any of the frequency dependent types Constant Table or Script 6 3 6 Uniform Velocity BC This Boundary Condition is applied on the element where the velocity vector is uniformly distributed There is no variation of velocity components Us vy Vz with position over an element However the velocity can be defined to be dependent on frequency The components of the velocity at any point can be specified by selecting any of the frequency dependence types Constant Table or Script Figure 6 11 New Boundary Condition Figure 6 11 Uniform Velocity BC 6 3 Multi Domain Model BCs 157 6 3 6 1 Use Impedance When this option is enabled the velocity defined in this Boundary Condition is considered to be the wall velocity The normal component of the wall velocity Vn wall at a point is computed from the dot product of velocity vector to the domain normal at that point Figure 6 4 The impedance Z relates the pressure p at the surface of the acoustic material to the particle nor mal velocity vn at the surface Refer Section 6 1 for the definition of impedance i
232. nce at the beginning of the for loop lt exp gt is any simple Boolean valued expression It is executed before each iteration If it evaluates to TRUE then the simple or compound statement in lt statement gt is executed otherwise the loop terminates lt assign_exp gt is an expression with or without an assignment It is executed at the end of each iteration It is usually used to increment some counter Example var i x Dim 10 for i 1 i lt 10 i i 1 x i 0 0 272 Language Syntax It is preferable to declare the loop variable inside the for statement as shown below This limits the visibility of the variable to the lt statement gt part of the for statement If this variable is referred to anywhere else in the program an error will be generated var x Dim 10 for var i 1 i lt 10 i i 1 x i 0 0 var i function Initialize i 1 function Done return i gt 10 function Increment i i 1 function DoSomething Out Hi Eval i for Initialize Done Increment DoSomethingO 8 6 9 while Statement The while statement is a simpler alternative to the for statement while lt exp gt lt statement gt lt exp gt is a Boolean valued expression and lt statement gt is a simple or compound statement The expression lt exp gt is evaluated first If its value is TRUE then lt statement gt is executed Otherwise the while statement is terminated This process is repeated u
233. nce between centroids of the elements and L is the average length of the Elemente vane ske aie oe G Sobek RN oe Gia et Gen ca ed 205 Comparison of preferred center frequencies for fractional octave bands between EAS A he Oe Eee a a ee ES 211 Relative response levels for various weightings 1 233 1803744 Coordinates of key microphone positions 1 10 and additional micro phone positions 11 20 on a hemisphere 2 236 1503744 Coordinates of microphone positions for sources emitting discrete tones 237 1803745 Coordinates of microphone positions on a sphere 3 249 1803745 Coordinates of microphone positions on a hemisphere 3 253 Coustyx Language Grammar ou a sa saaa a vr rv knr ee eee 285 Coustyx Language Grammar contd o o 286 Physical properties of materials used in FEA 295 Gearbox natural frequencies from FEA oa a s s coruo a 0000 ee 295 XX LIST OF TABLES Preface Coustyx computer program has been under development for many years and is finally avail able for use by the noise and vibration community This software is developed based on work supported by the National Science Foundation under Grant No 0548629 We would like to thank the National Science Foundation for the support Any opinions findings conclusions or recommendations expressed in this material are those of the author and do not necessari
234. ncy 47 1020 0000 Hz Coord Node Id X Y 2 Frequency 48 1040 0000 Hz a Frequency 49 1060 0000 He Frequency 50 1080 0000 Hz Frequency 51 1100 0000 Hz 39 Done loading frequency response data i 1 i i WorkDir C Users vijay Coustyx trunk Examples Indirect StructureModels NasaLewisGearCasing StatusiModified File Model2 cyx Figure 9 7 Structure mesh opened in Coustyx GUI e Move the cursor into the GUI window with the structure mesh and observe the cursor change to move cursor style or to the shape of To manipulate the view Use the GUI control panel tools shown in Figure 9 8 to zoom and rotate the model Hold down the left click button and move the mouse to rotate the model in the GUI Hold down the right click button and move the mouse to move the model in the GUI Move and rotate the model to see the holes on one of the side surfaces on the structure 302 Tutorial Gear Box Radiation Structmesh 0 Figure 9 8 Coustyx GUI control panel tools e Display element edges of the structure mesh Move the cursor into the GUI window of the structure mesh Press and hold the shift key to observe the cursor change from move cursor style or shape to an arrow style Right click on the mesh while holding down the shift key to view a pop up context menu shown in Figure 9 9 and select Select All Di
235. ne exterior or architectural acoustics problems The Fast Multipole Method FMM is a recent breakthrough which makes it possible to build intricate BEM models of real life systems and perform acoustic simulations efficiently ANSOL has developed new BE formulations which are used in conjunction with iterative solvers from the Krylov family and a new Multilevel Fast Multipole Method MLFMM that facilitates extremely fast matrix vector product computations Thus Coustyx implements this approach to overcome the limitations of traditional BEM and allows to perform fast NVH analysis of large problems in the mid to high frequency regime The main developments in this software are 1 Implementation of a new and improved FMM in conjunction with the BE formulations dramatically reduces the memory requirements of the problem allowing it to handle large problems up to 1 Million unknowns with faster performance 2 A novel BE formulation robust enough to deal with several problems associated with BE formulations such as Thin Shape Breakdown TSB Irregular frequencies or non uniqueness issue ability to model single sided surfaces such as M bius strip handle ex 2 Introduction tremely complex junctions and inconsistent mesh normal orientations Indepedent interpo lation schemes for coordinates and acoustic variables provide greater modeling flexibility 3 The formulation allows Coustyx to deal with wide variety of boundary conditions
236. near system of equations Ax b the 7 1 Inputs 203 residue R as a percentage is given by _ b Aa R T x 100 GMRES keeps running until the percentage error in residue is less than the specified value The smaller the chosen value the better the accuracy of the final solution will be But this increases the analysis run time The selection of this value is based on the user s requirement for the accuracy of the solution to the requirement in speed of the analysis The final solution will have an error in percentage less than the value specified Change in Sound Power as a Percentage This option is enabled only when Sound Power option is selected as the Convergence Criterion Figure 7 6 The change in sound power as a percentage is used as the specified tolerance for the convergence of GMRES Number of Vectors in Krylov Subspace at Restart GMRES approximates the solution by minimizing the residue in an orthonormal basis spanned by vectors in Krylov subspace For every iteration a new vector is added to the Krylov subspace To control storage re quirements in GMRES the maximum number of vectors in Krylov subspace are fixed with this option When GMRES iterations reach this number all the vectors in Krylov subspace are cleared and a new GMRES cycle is restarted using the latest iterate as the initial guess The choice of the maximum number of these vectors is critical in implementing GMRES efficiently The more the number of vectors
237. ng Chief Points Analysis Sequi Context Script Rename Copy Paste Delete Open Close Edit 09 19 48 Opening file 1 Help 09 19 49 Parsing input fiere yxitrunkExamples Indire Figure 4 32 Context Script 4 4 Sets 79 For a MultiDomain BE mesh Select Model Direct BE Meshes lt Direct BE Mesh Name gt Sets For an Indirect BE mesh Select Model Indirect BE Mesh Sets For a structure mesh Select Model Structures lt Structure Name gt Sets A Setis a collection of elements coordinate nodes and faces grouped together for organization and manipulation convenience This sub tree member is used to review or create a new Set and add elements coordinate nodes or faces to it Create a new Set Right click on Sets and select New to create a new Set Figure 6 41 Rename To rename the new Set right click on lt Set Name gt and select Rename Copy To copy contents of a Set right click on lt Set Name gt and select Copy Paste To paste the copied contents of a Set to a new Set right click on lt Set Name gt and select Paste Open To open the list of contents of a Set in a table right click on lt Set Name gt and select Open The table lists the components in the Set The first column shows the Type of the component that is Elements No
238. ns 11 20 on a hemisphere 2 Microphone Z z position 1 0 99 0 0 15 2 0 5 0 86 0 15 3 0 5 0 86 0 15 4 0 45 0 77 0 45 5 0 45 0 77 0 45 6 0 89 0 0 45 7 0 33 0 57 0 75 8 0 66 0 0 75 9 0 33 0 57 0 75 10 0 0 1 11 0 99 0 0 15 12 0 5 0 86 0 15 13 0 5 0 86 0 15 14 0 45 0 77 0 45 15 0 45 0 77 0 45 16 0 89 0 0 45 17 0 33 0 57 0 75 18 0 66 0 0 75 19 0 33 0 57 0 75 20 10 0 0 1 Microphone Array Choose any of the available types of microphone arrays from the drop down menu Figure 7 33 shows a microphone array on the hemisphere Fixed Positions The microphone positions for this option are listed in Table 7 6 Figure 7 33 The key microphone positions are numbered from 1 to 10 and the additional microphones are numbered from 11 to 20 Note that the overhead positions 10 and 20 coincide Number of Probe Positions Choose the number of microphones to be 10 or 19 from the drop down menu The microphones are associated with equal partial areas on the hemisphere surface except for the 10 position when 19 microphones are selected The partial area associated with the 10 position will be twice that of other microphones to account for the omission of 20 position Table 7 6 Fixed Positions for Source Emitting Discrete Tones The microphone positions for this option are listed in Table 7 7 This option is recommended over the earlier option when th
239. nt are output through the arguments P and Pn Figure 4 46 Note that a valid user defined acoustic source should have a pressure field that satisfies the Helmholtz equation exactly New Source 25 A E User Defined Position Vector X component Y component Z component User Defined Source Script 1 E function GetDirectionalResponseAtFieldPoint in RelativePosnVec in NormaiVec out P out Pn AngularFreg SoundSpeed WaveNumber and AmbientDensity are predefined J read only variables that can be used here RelativePosnVec is defined as the position of a field point with respect to the position of the source 1 Sample script to create an equivalent monopole source rno AmbientDensity c SoundSpeed zo rho c k WaveNumber Q 1 0 dx RelativePosnVec 1 dy RelativePosnVec 2 dz RelativePosnVec 3 r dx dx dy dy dz dz 0 5 i rho c Q k 4 PI r exp i k r er RelativePosnVec r Mag i k zo Q 1 i k r 4 PI r 2 exp i k r Pn Mag er NormalVec return 9 Figure 4 46 User Defined Acoustic Source Chapter 5 Pre processing Features Coustyz provides a large set of pre processing tools to manipulate meshes in the model In addition translators for most commonly used data formats are available to import mesh and velocity data The pre processing tools are found at the bottom pane of Mesh Viewer window while a mesh is open in the GUI The features include Fill Hole S
240. ntains functions to read in the model cyx file and other commands on how to run the analysis Since the workdir argument has not been provided Coustyx uses the directory C users johnsmith as the working directory Chapter 3 Conventions in Coustyx In this chapter we will discuss some of the important conventions followed in Coustyz 3 1 Time Dependence The time dependence of oscillating quantities in Coustyx follow a e79 convention where j v 1 For example the time harmonic pressure wave P t in Coustyx is defined as P t Re pe where Re stands for real part of p is the complex amplitude of the sound pressure and w is the frequency of fluctuation 3 2 Units 3 2 1 Model Units The analysis process in Coustyz is independent of the system of units However to assist users in keeping track of units for various physical quantities Coustyx provides an option to choose model units before building a new model Model units are stored in the model for reference only It is the user s responsibility to maintain consistent units among various inputs in the model Figure 4 16 shows the dialog box used to select model units before building a new model The model units specified are stored in the model tree member Units Figure 3 1 Below are two places where the model units are used e Model units are used to setup appropriate material properties speed of sound and ambient density for commonly used materials A
241. ntil lt exp gt evaluates to FALSE var i function Done return i gt 10 function Increment i i 1 function DoSomething Out Hi Eval i 8 6 Statements 273 i 1 while Done DoSomething Increment 3 8 6 10 do while Statement The do while statement is similar to the while statement except that it evaluates its condi tional expression after executing its statement do lt statement gt while lt exp gt First lt statement gt is executed Then the Boolean valued expression in lt exp gt is evaluated If it evaluates to FALSE the do while statement is terminated otherwise the process is repeated Hence the do while statement always executes its body at least once var i function Done Of return i gt 10 function Increment i i 1 function DoSomething Out Hi Eval i i 1 do I DoSomething Increment while Done 8 6 11 break Statement The break statement is used to exit out of the innermost loop in a for while do while or switch statement Example var i function InitializeQ i 1 function Done 274 Language Syntax return i gt 10 function Increment i i 1 function DoSomething Out Hi Eval i for Initialize Done Increment I if i 5 break DoSomething Out I m done Output Hi Hi Hi Hi I m done PONER 8 6 12 continue St
242. o both sides of a 2 D element no surface mesh is generated Use any of the other Manipulation Task Functions to visually inspect the FE mesh fix any inconsistencies etc before skinning 116 Pre processing Features Oem asese A 0 0 Hoeewrlree 4 4 ml Ji SA EY Model Y Structmesh_0 4 bx Type lt Indirect gt i a Version lt 1 00 00 gt E Model Description 3 Structures gt Structmesh 0 Materials Indirect BE Mesh lt Mesh gt Context Script C Analysis Sequences e nsa Ny y ty j Error Incompatible elements ID 13091 and 10 13473 a gt Error I tible elements ID 12763 and ID 13483 Error Incompatible elements ID 12806 and ID 13504 Selected Coord nodes 3 Selected Elements Cy Frio Sn y new Element y sttch Seams Error Incompatible elements ID 13599 and ID 13600 E y Error Incompatible elements ID 13615 and ID 13616 Accept Seam Stop Skinning Create Mesh From Skin Error Incompatible elements ID 13620 and ID 13622 EE 1 a Error Incompatible elements ID 13627 and ID 13630 Delete Selected Seams _ clear skn Error Found element connectivity errors in mesh Unable to c ANTE Fix the mesh and retry create sin te Ski 4 m r Help Figure 5 19 Press Skin Create Skin to check for incompatible elements 5 5 Skin 117 Operations on Selection Unselect A
243. odel Domains lt Domain Name gt Boundedness This is used to set the boundedness of the Domain Right click on Boundedness and select Boundedness Unbounded or Bounded Figure 4 28 If the domain of interest is exterior then set the flag to Unbounded If the domain of interest is interior then set the flag to Bounded Please note that in a MultiDomain model we can have multiple Bounded Domains but only one Unbounded Domain 4 3 9 3 Material Select Model Domains gt lt Domain Name gt Material This sub tree member is used to select the fluid medium present in the domain To select Right click and select Material lt Material Name gt The material defined by the lt Material Name gt is created in Model Materials See Section 4 3 3 on how to create a new material or edit an existing one 4 3 9 4 Direct BE Meshes Select Model Domains lt Domain Name gt Direct BE Meshes Each domain can have multiple BE meshes By default all the meshes available in the Model Direct BE Meshes are included To delete any particular mesh from the domain right click on Model Domains lt Domain Name gt Direct BE Meshes lt Direct BE Mesh Name gt and select Delete To modify the existing mesh in the domain to a different mesh right click and select BE Mesh lt Different Direct BE Mesh Name gt For each Direct BE mesh the following options should be verified before running the analysis
244. odel must be defined with respect to the domain normal e Mesh Normal at a specified point is the surface normal at that point based on the element orientation The element orientation depends on the element coordinate connectivity In Figure 6 4 the element normal is arbitrarily assumed to be pointing inward The direction of mesh normal is irrelevant while defining boundary condition Exterior Problem Sv Sv Ma Sp Sp Nm Interior Problem Sz a Exterior problem b Interior problem Figure 6 4 Definition of domain ng and mesh normals nm Note that domain normal always points away from the domain of interest Mesh normal however can point towards or away from the fluid All boundary conditions in a MultiDomain model are defined with respect to the domain normal For a MultiDomain model the Boundary Conditions are defined at Model Boundary Conditions To create a new Boundary Condition right click on Boundary Conditions and select New Figure 6 5 Below is the description of each of the boundary condition options provided in MultiDomain model 6 3 Multi Domain Model BCs 151 E lt Model Type lt Indirect gt 5 Version lt 1 00 00 gt E Model Description E Structures 2 4 Structmesh 0 Coord Nodes E Elements Q Prev ID 1 KJ Next Y Sets E Freq Response Data Materials i Planes E a Indirect BE Mesh lt NewMeshCreatedFromSkin gt Material lt gt Coord Nodes A
245. of negative number attempted If there is no try catch statement that can catch an exception then the exception will be passed on to Coustyx which will handle it in the same way it handles its internally generated error messages The exception can also be re thrown after being caught tryt Out Factorial 4 Factorial 4 Out Factorial 5 Factorial 5 Out Factorial 4 5 Factorial 4 5 catch message Out Eval Error message throw Subst message 8 6 17 Statement Label Any statement can be assigned a label or IDENTIFIER as follows This label is visible to all statements contained in the compound statement of which this statement is a part Unlike variables and functions this label is also visible to statements preceding the label provided they are contained in the same compound statement IDENTIFIER lt statement gt 8 6 18 Goto Statement A goto statement transfers control to a statement that has been labeled as shown above The goto statement can be used to transfer control to any labeled statement as long as the label is visible However the goto statement cannot be used to transfer control out of a function body goto IDENTIFIER Example var x 1 var y 2 if x 0 goto exitlabel var z 3 exitlabel Out Done Example var x 1 var y 2 284 Language Syntax if x 0 goto exitlabel This is not correct The label exitlabel is not visible from here
246. olver controls o ooo 335 pet analysis frequencies o4 cT w ei d a e ar E a E o oE ee ee eee ee 336 Sound power from the forced vibration response sooo soo a 337 Radiation efficiency of the gearbox forced vibration 338 IGlass viewer showing sound pressure distribution on the exterior surface of the housing at 700 H care aaee brae reg a a aaga aa Se Eee 339 xviii LIST OF FIGURES List of Tables 3 1 3 2 3 3 3 4 4 1 4 2 4 3 5 1 cal Tia 7 3 7 4 7 5 7 6 dd ig 8 1 8 2 9 1 9 2 Length scale factors sosiaa g a a A 21 Mass scale Tactors Lan 4 446 a a ede od be ib MOE S 21 Variablesand Units ro sess nd tama d a AA SG 22 Values for acoustic medium properties of air in different units 22 Description of the main menu bar items in Coustyr l 29 Description of GUI control panel tools o o kr rea 34 Differences between MultiDomain and Indirect models 55 Some of the common types of Bad Elements and their Treatment 122 List of valid integration orders and the corresponding quadrature points on trian Blevelemients 2 kai A a svat Be ee we RD we A A A 204 List of the integration orders and the corresponding quadrature points on quadri lateral elements Note the total number of quadrature points are nptsxnpts 204 Variable integration order used for element matrix computations Note D is the dista
247. om The License Key will be e mailed back to you If you skip this step for now you can install License Key later using the Install License Key icon Coustyx will not run unless valid License Key has been installed Figure 2 4 Computer and dongle IDs 2 3 License Key Installation Install License Key JR 0 Use Native License Use Altair GridWorks License Computer ID 0021708A7C31705F22AA E Use Network Dongle Server Host Name 3md2400xp64 Find Dongle Dongle ID lt Unavailable Dongle ID gt 1 License Key 185b286b185b286b 185b286b 185c28694e 5b 7c3a 1d0a7e3a4609726c430a253a 150A In order to get a License Key copy the Computer ID and email it to sales ansol com The License Key will be e mailed back to you If you skip this step for now you can install License Key later using the Install License Key icon Coustyx will not run unless a valid License Key has been installed Figure 2 5 Steps to install a License Key 10 Installing Coustyx Install License Key JA Use Native License 5 Use Altair GridWorks License Key 185b286b 1850 286b 185b286b 185c28694e5b 7c3a 1d0a7e3a4609726c430a253a150a7438430 ID 000000000000705F22AA License ID Vs Computer Dongle ID Valid Match Expiry Status Perpetual Direct Boundary Element Model Indirect Boundary Element Model Acoustic Finite Element Model Structural Coupling Multi domain Model Mult
248. on Select Model Analysis Sequences e Create a New Analysis Sequence To create a new analysis sequence right click on Analysis Sequences and select New A dialog box with new analysis sequence opens up Go through all the tabbed windows to modify analysis parameters To accept changes click OK Figure 7 1 e Edit an Analysis Sequence Select Analysis Sequences gt lt Analysis Sequence Name gt Right click on it and select Edit to open the analysis sequence edit dialog box Make changes and click OK Figure 7 2 e Run an Analysis Sequence To run acoustic analysis right click on the desired analysis sequence and select Run You could also run a selected analysis sequence from the Main menu Analysis Run or by clicking on the blue run button Figure 7 3 Make sure Coustyz model setup is completed before running the analysis e Abort the analysis run To abort a run right click on the analysis sequence running current analysis and select Abort You could also abort a run from the Main menu Analysis Abort or by clicking on the red abort button Figure 7 4 Coustyr won t stop the analysis run immediately The analysis continues to run until it reaches a valid state to abort gracefully This may take a few minutes See Figure 7 5 Figure 7 2 shows an Analysis Sequence edit dialog box The dialog box consists of five tabbed windows storing different parameters The first tabbed window Description could be used to add the descrip
249. only when Use Fixed Inte gration Order is not selected For FMM case this option is not enabled The presence of Green s function which has 1 r factor effects the accuracy of the element integrals computed by Gauss quadrature procedure when two elements are very close to each other 7 1 Inputs 205 Table 7 3 Variable integration order used for element matrix computations Note D is the distance between centroids of the elements and L is the average length of the elements Quadrilateral Triangle Medium Fine Finest Medium Fine Finest D L lt 2 5 9 11 9 9 9 2 lt D L lt 5 5 7 9 9 9 9 5 lt D L lt 20 3 5 5 9 9 9 20 gt D L 3 3 3 9 9 9 We need more integration points for evaluating element integrals accurately for very close elements than compared to elements which are further away Table 7 3 shows quadrature rules which are formulated based on multiple numerical experiments conducted over ele ments at various distances with variable number of quadrature points and the accuracy of the element matrix computations For a given accuracy level the number of integration points required increases with the decrease in the ratio D L where D is the distance be tween the centroids of the elements and L is the average edge length of the two element edges Figure 7 12 Medium This option is selected when medium accuracy of the solution is acceptable Table 7 3 shows the integration orders used for q
250. ons are defined with unique names in Coustyz A boundary condition can be applied to selected elements by setting the boundary condition to the unique name defined Refer to Chapter 6 on how to define boundary conditions Add to Set This option allows user to add selected elements to a pre defined Set Refer to Section 4 4 on how to define a Set Elements or nodes are grouped together to form a Set Operations on a Set is propagated to all its components For example it is easy to apply or change boundary conditions on the Set than on each element in the Set Remove from Set This option is used to remove selected elements from their current Sets Refer to Section 4 4 for more information on Sets Add to a New Set This option allows user to add selected elements to a new Set A new set with a default name New Set or New Set i i is a number is created Refer to Section 4 4 on how to rename the Set 42 Getting Started 4 2 3 2 Operations on Displayed Nodes To use operations on displayed nodes first make nodes visible in the GUI Operations on Selection Unselect All Select All Displayed Elements Select All Bad Elements Selected Elements gt Select All Displayed Nodes Select All Bad Nodes Selected Nodes Unselect Selected Faces gt Depiay styles Display Connected Elements Hide Add to Set gt Remove from Set 3 Add to a New Set Figure 4 9 GUI operations available for selected nodes Select
251. orted natural mode data includes the natural frequencies and the corresponding mode shapes These values could later be used to define acoustic excitation as boundary conditions on the BE mesh which is generated from the structure FE mesh The supported file formats are Nastran OP file Nastran Punch File Ansys Results File and I DEAS Universal File The natural mode data can be cleared by selecting Clear Natural Mode Data on the right click menu 8 I CA Users vijay Coustyx Examples Indirect Nasal ewisGearCasing Model cyx File Edit Preferences Help Ded mM a AA Se Case Word RegExp 3 43 Model LE Type lt MultiDomain gt LE Version lt 1 00 00 gt 5 Model Description 3 43 Structures E AA HDD H Materials Structmesh_0 CJ Planes C Interfaces Rename Y Boundary Condit copy Direct BE Meshes Paste 2 FE Meshes Delete E Domains Context Script Open El p p Analysis Sequend Plose Edit Help Load Freq Response Data lear Freq Response Data Load Natural Mode Data Nastran OP2 File Clear Natural Mode Data Nastran Punch File Ansys rst File Figure 5 4 Loading natural mode data into Coustyx model 5 1 3 1 Copy to Frequency Response Data Select Model Structures lt Structure Mesh Name gt Natural Mode Data gt lt Mode gt Right click on the desired mode lt Mode gt and select Copy to Freq Response Data refer to Figure 5 6 The mode information from the Natural Mode D
252. ose Edit Help _ Load Freq Response Data Clear Freq Response Data Nastran OP2 File Ie Nastran Punch File Ansys rst File Figure 9 30 Load frequency response data into Coustyx 324 Tutorial Gear Box Radiation e Select the appropriate frequency response data file to be loaded from the browser and click Open 9 5 1 4 Generate BE Mesh e Select Model Structures Structmesh 0 or lt Struct Mesh Name gt e Right click on Structmesh 0 or lt Struct Mesh Name gt and select Open to view the structure mesh in the GUI The structure mesh will appear as shown in Figure 9 31 3 Modell File Edit Preferences Help Ogee BIANCO SA 5 Model Structmesh 0 E Type Indirect gt E Version lt 1 00 00 gt x E Model Description tt 2 OG Structures ED Structmesh 0 co Ly Materials Ol CJ Planes kel 19 Indirect BE Mesh lt Mesh gt E Context Script C Analysis Sequences log 17 45 34 Importing Nastran Bulk Data BDF File 17 45 34 Import File Done I Selected Coord Nodes y Selected Elements 53 Fil Hole 53 Skin Gy stitch Seams y Delete Elements Sy Element Orientation Coord Node Id X Y z WorkDirsC Users vijay Coustyx trunk Examples MultiD omain StructureModels Nas
253. osition Vector X component 0 0 Y component 0 0 Z component 0 0 Source Strength Strength Type Amplitude v Frequency Dependence Type Constant x Real 1 0000000000000 Imaginary 0 0 Direction Vector X component 0 0 Y component 0 0 Z component 1 0000000000000 E Cas Figure 4 44 Dipole 4 5 5 Quadrupole A quadrupole source is defined by a location R x yr zr and a tensor quantity T with its quadrupole moments or amplitudes in various directions Figure 4 45 Tu Tie Ti T Ta Toe Ta Ta T32 T33 The components in the tensor of quadrupole amplitudes Tf are related to the components in the tensor of quadrupole moments T as follows A Tij jkZoTij where Zo poc is the characteristic impedance of the fluid medium c is sound speed po is ambient density k w c is wave number w is frequency in radians sec and j y 1 In the tensor of quadrupole source moments each term has a dimension of L T Dimensionally this is equivalent to V or DI where V is volume velocity I is some characteristic length and D is dipole moment The terms in the tensor of quadrupole amplitudes have dimensions of M L T The pressure p at any point Q z y z due to a quadrupole is given by the following expression 92 Getting Started 2 2 2 Ta Se Tap sg Taz gm 2 a Tiz Ta LEG P Q jkZ Tr Ty ESQ 4 8 amp G Q R T23 T32 ae where G Q R is the Green s function eva
254. otalFreqsteps i for var irange 1 irange lt nRanges irange irange l i I war Freq FREQUENCY_RANGE_START irange i for var ifreq 1 ifreq lt FREQUENCY RANGE NFREQS irange ifreq ifreqt 1 i i SetFrequency Freq i BuildRHSFMM i var Residual SolveUsing GMRES FMM i Vrite nalysisResults ResultsFile H var PoverData ComputeSoundPover var RadiatedSoundPower PowerData 1 var InputPover PoverData 3 var RadiationEfficiency PowerData 4 var StringPower FormatFloat 1E Eval Frequency StringPower StringPower FormatFloat 1E RadiatedSoundPower StringPower StringPower FormatFloat 1E InputPower StringPower StringPower FormatFloat 1E RadiationEfficiency Out To File PowerFile Eval StringPower Figure 7 46 Analysis script Bibliography 1 American National Standard Specification for Sound Level Meters Acoustical Society of America 1983 Reference no ANSI S1 4 1983 R2006 2 ISO 3744 Acoustics Determination of sound power levels of noise sources using sound pressure Engineering method in an essentially free field over a reflecting plane International Organization for Standarization ISO 1994 Reference no ISO 3744 1994 E 3 ISO 3745 Acoustics Determination of sound power levels of noise sources using sound pres sure Precision methods for anechoic and hemi anechoic rooms International Organization for Standarization ISO 2003 Refer
255. ousing The first five modes are purely classical modes of the top plate For some of the higher modes the side and the bottom surfaces of the gearbox undergo deformation as well Figure 9 3 shows the first five free vibration modes of the gearbox housing 9 3 3 Forced Response Modal Superposition Forced response analysis is performed using modal superposition in the frequency range of 100 1000 Hz In modal superposition FEA computes the modal basis and a subset of the computed modes are used to compute the forced response via superposition The loads applied on the housing are an in plane force of unit amplitude in frequency domain is applied in y direction to one of the shafts and an equal but opposite force is applied to the 296 Tutorial Gear Box Radiation a Mode 1 157 Hz b Mode 2 329 Hz c Mode 3 366 Hz d Mode 4 505 Hz e Mode 5 543 Hz Figure 9 3 Surface normal velocity distribution for the first five free vibration modes 9 4 Coustyx MultiDomain Model 297 other Note that y is in the direction of a line connecting the centers of both the shafts The radiation from the resulting housing vibration is computed in the frequency range 100 1000 Hz with a frequency resolution of 15 Hz The output punch file contains the nodal velocities or accelerations at each frequency This data is loaded into Coustyx model and is later applied as the velocity boundary condition to predict noise generated by the gea
256. ovided or by changing the composition of red green and blue If this checkbox is unchecked the colors are not changed Display Connected Nodes Displays all the coordinate nodes connected to the selected element Select Connected Elements Through Feature Angle This option is used to select all the 2D elements that are connected to the current element s in the GUI through feature angle s less than the specified feature angle in Preferences 3D Viewer Figure 4 3 Refer to Figure 4 4 for the definition of feature angle between two connected elements Note that this function is applicable only for 2D elements Select Elements Connected Through Coord Nodes This option is used to select all the elements that are connected to the current element through coordinate nodes This can be useful when the mesh consists of several disconnected pieces and one contiguous set of elements are needed for selection Select Elements Connected Through Variable Nodes This option is used to select all the elements that are connected to the current element through variable nodes The variable node considered for the MultiDomain model is P pressure node and for the Indirect model is y pressure jumps node This function is especially useful to identify pressure jumps along junction constraints in Indirect models Note that this function is available only for BE meshes Hide This option is used to hide selected elements Set Boundary Condition Boundary conditi
257. p File or Ansys Results rst Files respectively Te ModelLye File Edit Preferences Help Deg Loc S Sy Model Type lt Indirect gt E Version lt 1 00 00 gt Model Description E structure CJ Materials Structures CJ Planes Indirect Bl Context Se Cop 2 Analysis S Paste Delete Rename Open Edit Help Import b Abaqus np File Nastran Bulk Data bdf File Ansys Results rst File Figure 9 29 Import a finite element structure mesh e Select the appropriate FE structure data file to be imported from the browser and click Open 9 5 1 3 Load Frequency Response Data e In Coustyx model main menu select Model Structures Structmesh_0 or lt Struct Mesh Name gt e Right click on Structmesh 0 or lt Struct Mesh Name gt and select Load Freq Response Data Nastran Punch File as shown in Figure 9 30 The other valid data formats from which frequency response data can be loaded into Coustyx are Nastran OP2 File and Ansys rst File 9 5 Coustyx Indirect Model 323 File Edit Preferences Help Model Type lt Indirect gt Model Description Del BB 4A Version lt 100 00 gt gt Indirect BE Mesh Context Script i CJ Analysis Fenneng Structmesh 0 Rename Copy Paste Delete Open Close Edit Help Rename Copy Paste Delete Open Cl
258. pecify the orientation of the X axis here See Figure 7 33 for definition Y Axis Specify the orientation of the Y axis here See Figure 7 33 for definition Center Specify the center of the sphere surface here Select the coordinates of the sphere center to be same as the acoustic center of the source As the location of the acoustic center is frequently not known select the geometric center of the source instead Radius The radius of the sphere surface shall be equal to or greater than any of the following e twice the largest source dimension of the lowest frequency of interest and elm Microphone Array Choose any of the available types of microphone arrays from the drop down menu 248 Analysis Sequences Name Description Units _ Solver Controls Binary Results Sensors IGlass Sound Power Standards Sound Power F Create a Sound Power File Analysis Sequence Outputs File Name soundpower_from_standards dat 1503745 1503745 Specifications Lowest Frequency Hertz 50 000000000000 Ambient Pressure Pascals 101325 000000 Measurement Surface Sphere Sphere Grid Data Ambient Temperature Celsius 230000000000 0 000000 Probe Positions Number of Probe Positions 0 000000 1 000000 o 0 000000 0 000000 0 00 r 2 0000000000000 Figure 7 41 IS03745 sound power standard window 7 2 Outputs 249
259. ping Specify non zero damping to restrict infinite responses at natural frequencies e Apply loads Apply nodal forces and or moments prior to performing forced response analysis e Perform modal superposition Select analysis frequencies and the participating modes to compute forced response 5 3 1 Load Natural Mode Data See Section 5 1 3 for details on how to load natural mode data The natural modes are assumed to be ortho normalized with respect to the mass matrix That is ATMA I and ATKA OP where A ajap an is the modal matrix containing natural mode vectors a M and K are finite element mass and stiffness matrices Q Diag w w2 w is the natural frequency and I is a unit matrix 104 Pre processing Features A File Edit Analysis Preferences Help Dee BIBOS bul y E 3 Model 2 Type lt Indirect gt Version lt 1 00 00 gt Model Description Units 3 Structures a Materials Structmesh_0 Planes D Indirect BE Mesh i Context Script Copy Y Analysis Sequen Paste Delete Rename Open Close Edit Help Load Freq Response Data Clear Freq Response Data Load Natural Mode Data gt Clear Natural Mode Data Export Nastran Bulk Data bdf File Figure 5 8 Export mesh 5 3 Forced Response Analysis using Modal Superposition 105 5 3 2 Modify Modal Damping Modal damping is the only damping model allowed in Coustyr Modal damp
260. pound force second inch lbf s and foot pound force second ft lbf s Other unit systems can be set by choosing other and entering the values for Length scale factor and Mass scale factor Figure 3 2 Length scale factor The length scale factor is the conversion factor from model length units to meters For example if the model unit for length is millimeter mm then the length scale factor is 0 001 since 1 mm 0 001 m Table 3 1 shows length scale factors for some commonly used length units Conventions in Coustyx 9 meter kilogram second SI units millimeter newton second meter kilogram force second millimeter kilogram force second inch pound force second foot pound force second other Length scale factor 1 0000000000000 Mass scale factor 1 0000000000000 Note Model units are presently only used in the computation of sound power levels from ISO standards Modifying model units does not rescale the model Figure 3 2 Edit units dialog box 3 2 Units 21 Table 3 1 Length scale factors Model units Length scale factors meter 1 millimeter 0 001 inch 0 0254 foot 0 3048 Table 3 2 Mass scale factors Model units Mass scale factors kilogram 1 gram 0 001 pound Ib 0 45359 Mass scale factor The mass scale factor is the conversion factor from model mass units to kilo gram For example if the mo
261. provides a Tutorial which outlines detailed steps to build Coustyx MultiDo main and Indirect models from Finite Element meshes It also explains how to perform acoustic analysis on these Coustyx models Chapter 2 Installing Coustyx For installation on windows you will need the windows installer file Coustyx msi on your local computer If you have not received Coustyr on a CD please visit http www coustyx com and follow the downloading instructions provided on the web site Coustyx is compatible with Windows XP 2000 and Vista For installation on linux machines contact us at salesQansol com 2 1 Software Installation To start installation of Coustyx double click on Coustyx msi or Setup exe The installer will guide you through the steps required for the installation Important You will need Admin privileges to install Coustyx Log into an account with administrator privileges 2 1 1 License Agreement Before proceeding any further please read the Coustyx user s license agreement carefully If you agree with all the terms and conditions specified in the agreement you can select I Agree to proceed further If you do not agree cancel the installation 2 1 2 Select Installation Folder By default the folder selected to install Coustyz is C Program Files Ansol Coustyx You can change the installation folder by browsing through the folders using Browse button The Disk Cost button lists all
262. pt o e e 182 Beta Frequency Dependence Script o nrk ras 182 Gamma Frequency Dependence Script kara 183 Applying boundary conditions through elements 184 Creating a new set a group of elements and nodes 185 Add elements to a Seto oc aon a AAA SEE RT a Eee 186 Applying boundary conditions through sets o 187 Creating new analysis sequence 2 2 e 191 Analysis sequence edit dialog box 00 00 ee eee eee 192 Run new analysis sequence oao cca sasaaa aea aos u knr nrk ras 192 Abort the analysis TUN 4 aa 4 24424000604 ped d dete ens 193 Abort M S LO aars ddmd ey dd ASKE Re ee eae See A 193 Solver controls Window s s g se aaee A II f Gled Sa kg 195 Suggested number of FMM levels e 197 Computational cell hierarchy constructed at different FMM levels 198 Solution Method FMM occurred 2684 042 wee eed 199 A 5 oi ste Svd EGG AAN GK Ray eM ants ace bye Sue Sy te 200 Direct Solution Method sumarse Sa Eg 201 Variable Order Integration Scheme 206 Frequency ranges window onos s e es i e ea aa a e e e 207 Load frequencies window lt se saasaa aceda a deed aa a eee ees 208 Load trequencies from file window s 44 s k 222 84464 a Wee a 208 Load frequencies from the structure frequency response data 209
263. ption Radius This option sets the radius of the sphere Any value greater than zero is valid No of divisions in zenith angle direction The number of divisions in 0 direc tion refer to Figure 7 23 No of divisions in azimuth angle direction The number of divisions in direc tion refer to Figure 7 23 Structure Mesh This option is selected to use existing structure mesh in the model as the field point grid To use a structure mesh first Import the mesh into Structures model tree member Refer Section 5 1 1 on how to import a structure mesh into Coustyr model Then select the structure from the list of structure names provided in the drop down menu Figure 7 29 Note that the iglass data is created only for the visible faces of the structure mesh 7 2 Outputs 223 Analysis Sequence xi Name analysis Sequence Description Solver Controls Frequency Ranges Outputs Script Binary Results Sensors IGlass Glass IV Create a IGlass File File Name figlass igl Browse m Field Point Grids Name Type Field Mesh Name NewFieldPointGrid Type z m Annular Grid Data Center 0 000000 0 000000 0 000000 0 000000 0 000000 0 000000 Inner Radius 0 0 Outer Radius 1 0000000000000 f divisi in radi ion fi No of divisions in circular direction fe OK l Cancel Figure 7 26 IGlass Annular Disc field point grid types 224 Analysis Sequences
264. ption Use Native License From the tabbed window License Key select the option Use Network Dongle Enter the Server IP Address or Server Name in the Server Host Name box and click on Find Dongle to look for the network dongle When the local computer finds a network dongle the Dongle ID and the License Key will be updated Press OK to register and exit the window or press Cancel to discard changes before exiting the window Figure 2 5 2 3 1 3 If you are using Coustyx without a dongle Copy the Computer ID Figure 2 4 and email it to salesQansol com in order to get your license key After receiving the key open Install License Key window from the Start menu Start All Programs Coustyx32 or Coustyx64 InstallLicenseKey Copy and paste the license key into the License Key box You can verify the features licensed under this key from the tabbed window License Features Figure 2 6 If the license key is invalid or expired appropriate information is highlighted Figure 2 7 Contact us to renew your expired license Click on the Copy License Information button to copy the information if you need to send us your license details Press 2 3 License Key Installation 13 Install License Key 0 Use Native License Use Altair GridWorks License Computer ID 0021708A7C31705F22AA Gisetemor vende gt Er gt Dongle ID Sentinel USB E5608EF2531F 12634832 3 Nov 2009 4
265. put window values in the file from m to mm A Scale factor of 1 imports the values as they are 7 2 3 IGlass IGlass files are data files used to visualize in three dimension the boundary element solution from Coustyz In addition to the generation of surface potentials data on the boundary element mesh the user has the option of creating different field point grids to get surface color maps of pressures and particle velocities Figure 7 22 shows the IGlass outputs window 7 2 3 1 Create an IGlass File This option is selected when the user wants to save the output data for IGlass post processing visualization The surface potentials of the boundary element mesh are saved to a binary file with extension igl If any field point grids are selected the acoustic variables at these field points are also computed and stored into the file After the analysis the user can open the file using the IGlass Viewer 7 2 3 2 Field Point Grids Coustyx offers a variety of field point grid options to visualize acoustic field generated by the boundary element solution Type There are six different types of field point grids offered by Coustyr They are Quadri lateral Triangle Annular Disc Box Sphere and Structure Mesh The field point 7 2 Outputs 217 E Analysis Sequence Name Analysis Sequence Description Solver Controls Frequency Ranges Outputs Script Binary Results Sensors IGlass Sensors V Create an Asc
266. qual number of divisions on all sides The coordinates of the vertices are entered in the table Figure 7 25 No of divisions N The number of divisions in a triangle grid Each side of the triangle is divided into equal number of divisions N 218 Analysis Sequences Analysis Sequence Description Solver Controls Frequency Ranges Outputs Binary Results IGlass iGlass Create a IGlass File File Name iglass igl Field Point Grids IE EE Field Mesh Name newFieldPointGrid Type Quadrilateral Quadrilateral Grid Data 7 0 000000 Corner 2 0 000000 0 000000 0 000000 0 000000 0 000000 0 000000 Corner 4 0 000000 9 000000 No of divisions N1 No of divisions N2 Figure 7 22 IGlass output window 7 2 Outputs 219 N2 3 4 QUADRILATERAL GRID ANNULAR DISC GRID 3 N 2 TRIANGLE GRID N2 CUBE GRID SPHERE GRID Figure 7 23 IGlass field point grid types Quadrilateral Triangle Annular Disc Box and Sphere 220 Analysis Sequences Analysis Sequence xl Name analysis Sequence Description Solver Controls Frequency Ranges Outputs Script Binary Results Sensors IGlass ciGlass IV Create a IGlass File File Namesfiglass igl Browse Field Point Grids Field Mesh Name NewFieldPointGrid Type Quadrilateral m Quadrilateral Grid Data oono 0 000000 0 000000 0 000000 0 000000 0 000000 0
267. r new element with linear interpolation Quadratic new element with quadratic interpolation Cubic new element with cubic interpolation Selected Coord Nodes la Selected Elements Fill Hole J New Element Delete Elements Y Element Orientation Shape TRIANGLE X 1 2 3 Coord Node m Order LINEAR v Clear Node ucleanallodesy accept L Figure 5 32 Create new element window 5 7 Stitch Seams The Stitch Seams tabbed window is located at the bottom pane the Mesh Viewer window This function could be used to fill gaps between disjointed parts of a structure mesh by generating new triangle elements between the seams defined Refer to Figure 5 34 5 7 1 Set Parameters Seams form closed loops When this option is enabled Coustyx assumes that the seam forms a closed loop and tries to find a closed path by connecting the selected coordinate nodes 5 7 Stitch Seams 131 3 3 4 1 2 1 2 Linear 3 3 6 4 5 A 7 8 1 6 2 1 5 2 Quadratic Cubic TRIANGLE QUADRILATERAL Figure 5 33 New elements coordinate node connectivity 132 Pre processing Features E Selected Coord Nodes Gy Selected Elements Gy Fil Hole Gy skin GJ Stitch Seams C Delete Elements 53 Element Orientation Seams form closed loops aa pelsin ss 1 11 Element Type LINEAR v New Set Name StitchedSeam_ Figure 5 34 Stitch Seam Dialog Panel If disabled Coustyr ass
268. ratios using Frequency dependent values Rayleigh Damping Rayleigh damping coefficents Alpha a and Beta 8 are defined through this option See Figure 5 12 Damping ratio for each selected mode is computed from a and 8 as follows Bw amp Qu 2 where is damping ratio and w is the natural frequency at it mode The above equation 108 Pre processing Features is derived from the definition of modal damping and the relation between rayleigh damping coefficients and the damping matrix C aM K where C is the damping matrix M and K are mass and stiffness matrices Edit Selected Modal Damping Ratios y Helo Specification Rayleigh Damping Rayleigh Damping Coeffidents Alpha 0 10000000000000 Beta 1 000000E 005 Coc conca Figure 5 12 Edit selected modal damping ratios using Rayleigh damping coefficients 5 3 3 Apply Loads Select Model Structures lt Structure Mesh Name gt Loads New Load Node ID 100 Force Moment Force Frequency Dependence Type Real x 0 0 Imaginary X 0 0 Real Y 0 0 Imaginary Y 0 0 Real z 0 0 Imaginary Z 0 0 Figure 5 13 Apply nodal force and moment Apply non zero forces and or moments to perform forced response analysis Note that Coustyx presently allows to only specify loads on the nodes A nodal load is identified by the node id and the force and or moment applied at that node To specify a
269. rbox housing in this frequency range 9 4 Coustyx MultiDomain Model Coustyx MultiDomain model is created by importing the FE mesh The frequency response data from the FEA analysis is loaded into Coustyx and is applied as a structure velocity boundary condition on the gearbox housing The analysis parameters are then set and the acoustic analysis is run to compute radiation predictions 9 4 1 Problem Setup Follow the steps to setup Coustyx model and perform acoustic analysis on the gearbox housing Open Coustyx from the start menu of your computer 9 4 1 1 Create a New Model e In the main menu select File New Model The window in Figure 9 4 will then appear e Choose the model type Multidomain Model and select model units meter kilogram second ST units Note that the selection of model units is consistent with the unit of length in the structure mesh Click OK to proceed 9 4 1 2 Import FE Structure Mesh e In Coustyx model main menu select Model Structures e Right click on Structures and select Import Nastran Bulk Data bdf File as shown in Figure 9 5 to import mesh from Nastran bulk data format The FE meshes from Abaqus and Ansys data formats can be imported by selecting Abaqus inp File or Ansys Results rst Files respectively e Select the appropriate FE structure data file to be imported from the browser and click O pen 9 4 1 3 Load Frequency Response Data e In Coustyx mode
270. re 4 21 Effect of complex speed of sound c cr jci on the pressure variation with distance from a point source to Chapter 3 4 3 3 2 Ambient Density The value for the ambient density po of the fluid medium is defined here Ambient den sity can be defined as a frequency dependent real value The variation with frequency can be introduced by defining the ambient density to be a frequency dependent type Table or Script Note that the units used for ambient density along with the units for speed of sound determine Coustyx model units For more information on the unit conventions followed in Coustyx refer to Chapter 3 4 3 4 Planes Select Model Planes Planes is the model tree member used to define ground or symmetry planes Symmetry planes are defined to exploit the symmetry of a structure geometry and its boundary conditions by modeling only a portion of the full model This reduces the size of the problem significantly and also results in faster analysis Coustyx provides options to define four different types of planes Symmetry Anti symmetry Ground and Baffle A plane is uniquely defined by a point on the plane and its normal vector A maximum of three planes from symmetry or anti symmetry plane types can be defined per model When multiple planes other than baffled plane are defined they must be orthogonal to each other e Define a New Plane Right click on Planes and select New and proceed with entering new parameter
271. reated to fill the hole can be conveniently added to a Set during the process This option specifies the name of the new Set Baffle Plane Option This option is available only for Indirect BE meshes in Indirect BE mod els When selected the elements created to fill the hole are considered to be on a baffle plane 114 Pre processing Features Delaunay Triangulation Optimization ber ie f r Minimum Triangle Vertex Anale 30 4 Triangle Area Ratio 15 Figure 5 18 Display Connected Nodes 5 5 Skin 115 5 4 3 Procedure to Fill Hole Follow these steps to fill a hole e Open any mesh in the GUI by right clicking on the mesh and selecting Open e Set the parameters for hole filling in the Fill Hole tabbed window Refer to the Sec tion 5 4 1 and Section 5 4 2 to set Delaunay Triangulation Optimization Parameters and Fill Parameters Refer to Figure 5 17 Select few elements whose edges coincide with the hole edge To select an element in the GUI Left click on the element with the shift key held down e Display connected nodes for the selected elements Right click on the selected elements with the shift key held down and select Operations on Selection Selected Elements Display Connected Nodes Figure 5 18 e The Delaunay Triangulation method requires at least three nodes to be identified on the edge of the hole to auto fill the hole with triangle elements Refer to Figure 5 16 Choose thre
272. ression does not match that of any case and no default statement is found in the compound statement then a runtime error is generated Example for var month 1 month lt 12 month month 1 4 var quarter switch month 4 case 1 case 2 case 3 quarter Winter break case 4 case 5 case 6 quarter Spring break case 7 case 8 case 9 quarter Summer break case 10 case 11 case 12 quarter Fall break default quarter Invalid Out Month Eval month Quarter Eval quarter Output Month 1 Quarter Winter 8 6 Statements 277 Month 2 Quarter Winter Month 3 Quarter Winter Month 4 Quarter Spring Month 5 Quarter Spring Month 6 Quarter Spring Month 7 Quarter Summer Month 8 Quarter Summer Month 9 Quarter Summer Month 10 Quarter Fall Month 11 Quarter Fall Month 12 Quarter Fall 8 6 14 Variable Scope Visibility Rules A variable may be declared using a declaration statement anywhere in a program A variable that is declared within a compound statement is visible to all subsequent statements within that compound statement It is not visible to statements that precede the declaration or to statements that are outside of the compound statement The variable x is not visible to statements here 1 The variable x is not visible to statements here var X the variable x is visible to all statements here The variable x is not visible to state
273. rough shafts and bearings an in plane force F of unit amplitude in frequency domain is applied to one of the shafts and an equal but opposite force is applied on the second shaft The direction y is assumed to be along the line connecting the centers of the two shafts The noise radiation from the resulting housing vibration is computed in the frequency range 100 1000 Hz 294 Tutorial Gear Box Radiation 9 3 Finite Element Analysis The finite element analysis FEA of the gearbox housing is required prior to solving the acoustic radiation problem for the following reasons e The gearbox structure mesh generated in FEA is imported into Coustyx to build the model to solve the acoustic problem e The structural response due to forces on the housing at each frequency in the frequency domain is loaded into the Coustyx model These values are used as the input velocity boundary condition Coustyx can read FEA data from NASTRAN ABAQUS and ANSYS softwares 9 3 1 FE Mesh Modeling In the FE model plate elements are used to discretize the box surfaces The shafts are connected to the housing using rigid elements concentrated mass of 10 grams is attached to center of the top plate to account for the mass of the stinger and the moving part of the shaker The FE model used for the structural analysis shown in Figure 9 2 has 974 nodes 943 quadri lateral plate elements 1 concentrated mass and 4 rigid elements Figure 9 2 FE mod
274. s Analysis Sequence Right click and select Edit To start acoustic analysis select Model Analysis Sequences Analysis Se quence Right click and select Run to perform acoustic analysis on the gearbox housing with the applied vibrations for the desired frequencies 9 4 3 Post processing Outputs Coustyx creates the following output files based on the choices made in Outputs tab in Analysis Sequence 9 4 3 1 results dat A binary results file is saved by Coustyx for later use When the model is re run Coustyx directly uses these results if the checksum of the model matches with the checksum in the results file This file can t be interpreted by the user and is only for Coustyx use 9 4 3 2 sensors dat The pressure and particle velocity at the sensor locations are written into this ASCII text file Since we didn t add any sensors to the gearbox housing radiation problem this file is empty 9 4 Coustyx MultiDomain Model 317 Name Analysis Sequence FMM Use FMM 7 Precompute Near Field Matrices Residual 0 50000000000000 0 50000000000000 1000 Integration 7 Use Fixed Integration Order Integration Order for Triangular Elements Integration Order for Quadrilateral Elements variable Order Int scheme Medium Figure 9 23 Analysis solver controls 318 Tutorial Gear Box Radiation i Analysis Sequence E Name Analysis Sequence
275. s 6 5 Applying BCs 185 File Edit View Preferences Help Dea BOL 2 63 A 1 Type lt MultiDomain gt Version lt 1 33 00 gt Model Description Structures Materials Planes Interfaces i Boundary Conditions aay Direct BE Meshes i o NewMeshCreatedFromSkin i Coord Nodes a Elements amp P Nodes AQ Pn Nodes ee CJ Constraint Equations ans FE Meshes Sets Domains Enst Rename tod Analysis Se Copy Paste Delete Open Close Edit Help New Figure 6 41 Creating a new set a group of elements and nodes Boundary Conditions Figure 6 42 Add elements to a set 6 5 Applying BCs 187 File Edit View Preferences Help Da BROS 6a Bat Type lt MultiDomain gt Version lt L33 00 gt Model Description CJ Structures Materials Planes Interfaces t J Boundary Conditions Direct BE Meshes E NewMeshCreatedFromSkin Coord Nodes A Elements 0 P Nodes AD Pr Nodes Constraint Equations Sets AQ Hole_ Hole 1 2 FE Meshes Domains pirane Context Script Copy Analysis Sequenc Paste Delete Open Close Edit Help Replicate Elements Display Style CaordNodes 3 Display All Hide All 18 08 02 Opening file wait Set Boundary Condition 18 08 02 Parsing input file C Users vijay Coustyx trunk Exa 18 08 02 Opening file wait Done Select Unselect Add
276. s Normal Velocity This attribute displays the component of acoustic particle velocity amplitude with phase in the Surface Normal direction Velocity This attribute displays the acoustic particle velocity vector amplitude with phase on the surface of the boundary element mesh and at field point grids Sound Intensity This attribute displays the time averaged sound intensity vector on the boundary element mesh and over field point grids 228 Analysis Sequences JUNICE Fes Plu Surface Pressure Minus Field Point Pressure Figure 7 30 IGlass viewer showing sound pressure distribution on the exterior surface of a housing 7 2 Outputs 229 Normal Sound Intensity This attribute displays the component of the time averaged sound intensity in the Surface Normal direction Indirect Model For an Indirect model the Attribute drop down menu lists the following outputs Displacement This attribute displays the acoustic particle displacement vector at field point grids The acoustic particle displacements over the boundary element surface is not shown Surface Normal This attribute displays the surface normals on the boundary element mesh and field point grids Even though this attribute is not an acoustic property it is listed to clarify the normal vectors used to compute Normal Velocity Plus or Normal Velocity Minus and Normal Sound Intensity Plus or Normal Sound Inten
277. s 4000 Minimum Triangle vertex Angle 30 New Set Name Hole 1 Maximum Triangle Area Ratio 1 5 Fill Hole Figure 5 17 Fill Hole Parameters The parameters used by the Delaunay Triangulation method can be modified here The default set of parameters provided by Coustyx are sufficient for most of the cases Coustyx goes through number of iterations to optimize the shapes of triangles in the hole while satisfying the limits defined by the parameters Minimum Triangle Vertex Angle and Maximum Triangle Area Ratio Figure 5 17 Maximum Number of Iterations The maximum number of iterations allowed before termi nating the Delaunay Triangulation method Minimum Triangle Vertex Angle The minimum vertex angle of the triangle allowed If the triangle element formed by Delaunay Triangulation method has a vertex angle smaller than this that is if the element is skinny the algorithm calls for more iterations to optimize the mesh Maximum Triangle Area Ratio The maximum ratio of the largest to the smallest triangle areas allowed If the triangle elements formed by Delaunay Triangulation method have the maximum triangle area ratio higher than the specified parameter the algorithm calls for more iterations to optimize the mesh 5 4 2 Fill Parameters Element Type This option specifies the type of triangle elements to be created to fill the hole Linear or Quadratic triangle elements can be created New Set Name All the triangle elements c
278. s Traversed by a Probe Enter the number of cir cular paths traversed by a microphone on each half of the sphere Meridional Arc Traverses Figure 7 42 shows meridional arc traversed by a micro phone The meridional arc is the path traversed along a semicircular arc about a horizontal axis through the center of the source The paths are selected such that the annular area associated with each path is the same 250 Analysis Sequences Figure 7 42 1503745 Meridional paths for a moving microphone 7 2 Outputs 251 Number of Probe Traverses Enter the number of microphone traverses at equal increments of azimuth angle around the source Figure 7 42 The least number of microphone traverses is eight Figure 7 43 IS03745 Spiral path for a moving microphone Spiral Path This method uses a traverse along one meridional path and simultane ously traverses the microphone through an integral number of circular paths thus forming a spiral path around the vertical axis of measurement surface Figure 7 43 shows spiral path traversed by a microphone The least number of circular turns that shall be completed by the microphone is five Number of Circular Paths Traversed by a Probe Enter the number of com 252 Analysis Sequences plete circular turns traversed by a microphone to form the spiral path Fig ure 7 43 The least number is five Hemisphere Use hemisphere measurement surface when you want to simulate mea
279. s for the real and imaginary values of the normal velocity Click OK to save the boundary condition 9 4 1 8 Apply Boundary Conditions The boundary conditions defined earlier are applied to the elements in the Coustyx BE mesh before running acoustic analysis e Apply structure velocity boundary condition to all the elements in the Coustyx BE model Select Model Direct BE Meshes NewMeshCreatedFromSkin Right click on NewMeshCreatedFromSkin and select Open to view the boundary ele ment mesh in the GUI Right click on the mesh while holding down the shift key to view the context menu and select Select All Displayed Elements Again right click on the mesh while holding down the shift key and select Selected Elements Set Boundary Condition Structure Velocity BC as shown in Figure 9 18 If the boundary condition Structure Velocity BC is inactive it implies that it has already been applied over the selected elements e Apply rigid boundary conditions on all the elements created to fill holes Note that we don t have structure velocities for these as they are newly created in Coustyx and not present in the original structure Since the elements filling the holes are conveniently added to sets named Hole_1 Hole_2 and so on we can apply the boundary conditions on them through these sets In the main model menu select Model Direct BE Meshes NewMeshCre atedFromSkin Sets
280. s information Click OK to accept e Edit Planes Select Planes lt Plane Name gt Right click on lt Plane Name gt and select Edit Proceed with editing the parameters Click OK to accept 60 Getting Started Name New Plane Type Symmetry z Origin x component 0 0 Y component 0 0 Z component 0 0 Normal Vector x component 0 0 Y component 0 0 2 component 1 0000000000000 a Gas Figure 4 22 Creating a new plane lt y symmetry plane anti symmetry plane Pulsating sphere Oscillating sphere Figure 4 23 Descriptions for different types of planes Note arrows represent velocity vectors at those points 4 3 Model Setup 61 Name The name of the new plane can be entered here Type The different types of planes that can be defined in Coustyx are Symmetry symmetry plane is defined when both the geometry and boundary condi tions are symmetric with respect to the plane Example Consider a sphere model with uniform radial velocity pulsating sphere The sphere geometry and the ra dial velocity boundary condition are symmetric with respect to any plane passing through the center of the sphere Figure 4 23 shows a sphere with the velocity vectors plotted by arrows The size of this problem could be halved by defining a symmetry plane and modeling only half of the sphere geometry Anti symmetry An anti symmetry plane is defined when the geometry is symmetric and the boundary conditions are ant
281. s met a N nearest structure nodes are found b maximum search distance from the BE node position is reached c when the percentage weight at the farthest point is less than a user defined tolerance If no interpolation points are found during the search a zero nodal velocity is assigned to the BE node 6 3 Multi Domain Model BCs The primary variables in MultiDomain models are pressure p and normal derivative of pressure pn And the boundary conditions are applied in terms of pressure velocity and impedances on the BE surfaces 150 Boundary Conditions Before we discuss how to define different boundary conditions the user should understand the distinction between Mesh Normal and Domain Normal in a MultiDomain model Figure 6 4 in order to assign the boundary velocities correctly e Domain Normal is defined to be always pointing away from the domain of interest Figure 6 4 shows opposite domain normals for interior and exterior problems but having the same mesh normal For the exterior problem the domain of interest is the exterior region and hence the domain normal is pointing inward while the domain normal for the interior problem is pointing outward Coustyr MultiDomain BE formulation is derived based on the assumption that the domain normal always points away from the domain of interest All the derivatives in the formu lation are with respect to the domain normal Hence the boundary conditions in a MultiDomain m
282. s of two columns the first column contains the frequency of analysis in hertz and the next contains the sound power level computed from the chosen standard 7 2 4 2 Weighting Filters Weighting filters in acoustics are used to enhance or attenuate measured sound pressure levels based on the spectral content of sound to closely simulate the perceived loudness by human hearing The sound pressure levels at frequencies at which human ear is less sensitive are weighted less than those at which human ear is more sensitive Figure 7 31 plots the relative response functions for the following filters Z weighting A weighting B weighting C weighting and D weighting See Table 7 5 1 10 30 100 300 1000 3000 10000 20 T T TT TTTT T T TT TTTT T TUT TT Try Weighting dB 80 L L L EAT L L L FE F TT L L L ter 20 200 2000 20000 Frequency Hz Figure 7 31 Relative response plots for different weighting filters Z Zero Filter Use this filter to apply zero weight The measured value is not modified when this filter is used Figure 7 31 A Filter Use this filter to attenuate sound at very high and very low frequencies This filter 232 Analysis Sequences enhances sound pressure levels in the frequency range between 1kHz to 6kHz where the human ear is most sensitive A weighting is the most commonly used filter Figure 7 31 B Filter Use this filter to assess loud noise Figure 7 31 C Filter Use
283. s the monopole volume velocity The dipole moment D Vd where d is the distance between the two monopole sources that make up the dipole The dipole amplitude and the dipole moment D are related as follows A jkZ D where Z poc is the characteristic impedance of the fluid medium c is sound speed po is ambient density k w c is wave number w is frequency in radians sec and j y 1 Note that the amplitude A has dimensions ML T whereas the dipole moment D has dimensions FT The wave equation for a dipole source is given by d Vip k p jkZo V R gnr Q V R dn Q 4 7 where p is the pressure at a point Q z y 2 Position Vector The location R of the dipole source is set by X component Y component and Z component Note that the units should be consistent with the geometry units Source Strength The dipole source strength could be set to be any of the following two types Amplitude A or Dipole Moment D Choose the type from the drop down menu Strength Type Then define the value of the dipole source strength amplitude A or dipole moment D through any of the frequency dependent types Constant Table or Script Note that the units used here should be consistent with the rest of the model inputs 4 5 Acoustic Sources 91 Direction Vector The direction of the dipole n is set by X component Y component and Z component New Source A ID 1 Type Dipole z P
284. sing any of the frequency dependence types Constant Table or Script Figure 6 25 6 4 8 Non uniform Normal Velocity Continuous BC x New Boundary Condition F Name New BC Type Nonuniform Normal Velocity Continuous E Normal velocity 1 Ejfunction GetNormalVelocity in PosnVec in NormalVec 2 AngularFreq SoundSpeed WaveNumber and AmbientDensity are predefine read only variables that can be used here The following is just an example change the formula to suit your ne var VMag 12 0 var Vn VMag e3 NormalVec return Eval Vn Figure 6 26 Non Uniform Normal Velocity Continous This Boundary Condition is applied on the element with non uniform normal velocity on both sides of the boundary The BC is continuous which implies that the normal velocity at the same point on side 1 v and side 2 v are identical refer to Figure 6 16 for side 1 and side 2 definitions Figure 6 26 n where vno X n is the normal velocity that varies with position x and normal velocity n on the element The normal velocity is defined in the script by the function GetNormalVelocity which takes in the predefined position vector PosnVec and normal vector NormalVec as the arguments Other predefined variables such as AngularFreq w SoundSpeed c WaveNumber k 2 AmbientDensity p and reference frame unit vectors el e2 e3 can also be used in the script Figure 6 26 VI X 1 v
285. sity Minus Also the Plus and Minus values in the Indirect BE solution are defined with respect to the surface normals The plus side of a boundary element is the side at the leading end of the surface normal and the minus side is the side at the trailing end For the boundary element mesh in Indirect model the surface normal is in the direc tion of the Element Normal Surface normals for different types of field point grids provided in Coustyx Figure 7 23 are defined below For Quadrilateral and Tri angle grids the surface normals point into the surface for grid coordinates defined in the order shown in Figure 7 23 For Annular Disc grid the surface normal is in the direction of the disc normal For Cube grid the surface normals on all faces of the cube point outward when the grid coordinates are defined in the order shown in Figure 7 23 For Sphere grid the surface normal at any position on the grid points radially away from the center Pressure Plus This attribute displays the sound pressure amplitude with phase on the positive side or the plus side of the boundary element mesh and at field point grids Note that the plus side of a boundary element is the side at the leading end of the element normal refer to Figure 6 16 For field point grids there is no distinction between the positive side plus side and the negative side minus side Hence same values are displayed for Pressure Plus and Pressure Minus Pressure Minus This attri
286. specify additional constraints in the interior region of a MultiDomain model while solving an exterior radiation problem Chief points which are also called Over determination points are widely used to avoid large errors in the solutions to a radiation problem at the natural frequencies of the interior region under complimentary boundary conditions To obtain accurate solutions at all frequencies specify random distribution of chief points in the interior region A chief point is identified with an ID and coordinates X Y Z Right click and select Edit to review or modify the list of Chief Points from a table Figure 4 30 Id The id of a Chief Point Note that each Chief Point should have unique Id 4 3 Model Setup 75 Model 12 Type lt MultiDomain gt Version 2 00 00 gt Model Description Structures Materials Planes 7 Interfaces E Boundary Conditions E Y Direct BE Meshes Ei NewMeshCreatedFromskin gt Coord Nodes EH Elements G Prev k Next Constraint Equations Ep Sets Y Hole 1 Y PSHELL1 FE Meshes Y Direct BE Meshes EQ NewMeshCreatedFromSkin Xfm Matrix 09 19 51 Opening file wai Opening file wai y Parsing input file C users delores Coustyx trunk Examples Opening file wait Done Figure 4 29 Side of Mesh on Domain Function 76 Getting Started 0 000000 1 1 2 2 0 425325 3 3 0 262866 4 4 0 00000
287. splayed Elements Operations on Selection Unselect All Select All Displayed Elements Selected Elements Select All Displayed Nodes Selected Nodes Figure 9 9 Select all displayed elements in the GUI Again right click on the mesh while holding down the shift key and select Selected Elements Display Style to view a pop up window shown in Figure 9 10 Pick the option Show Edges and click OK 9 4 Coustyx MultiDomain Model 303 Display Show Faces Transparent Show Edges Display Nodes V Apply Resolution level 1 Apply Color Red 200 Green 200 ES Blue 255 Go a Figure 9 10 Element Display Style Window 304 Tutorial Gear Box Radiation To unselect all the elements right click on the mesh again while holding down the shift key and select Unselect All e Create seams at the hole edges to avoid skinning the interior surface of the gearbox housing Select the tabbed window Skin from the series of tabs located below the structure mesh Move the cursor to the structure mesh in GUI Left click on the elements around the edge of a hole while holding the shift key Make sure to select elements with nodes on the hole edge as shown in Figure 9 11 Figure 9 11 Select elements for creating a seam Right click on the mesh while holding down the shift key to view the context menu and select Selected Ele
288. st button to auto fill the measurement surface variables in agreement with the standard Verify the input you have entered by clicking on the Check button Coustyx checks to see if the input variables satisfy the standard requirements If the standard requirements are not met a message window pops up to help you make appropriate corrections X Axis Specify the orientation of the X axis here See Figure 7 35 for definition Y Axis Specify the orientation of the Y axis here See Figure 7 35 for definition Center Specify the center of the quadrant surface here Select the coordinates such that the center is in the middle of the reference box and its images in the reflecting planes Radius The radius of the quadrant surface shall be equal to or greater than twice the characteristic source dimension do and not less than 1m Microphone Array Figure 7 35 shows a microphone array on the quadrant surface The microphone positions are listed in Table 7 6 Number of Probe Positions Specify the number of microphones associated with equal areas spread over the quadrant surface Choose the number of microphones to be 5 or 9 from the drop down menu Octant Use octant measurement surface when the source under test is in front of a corner Figure 7 36 shows a octant measurement surface centered at Center Click on the Suggest button to auto fill the measurement surface variables in agreement with the standard Verify the input you have entered by clicking on
289. stores them for usage in matrix vector computations at each iteration If this option is un ticked Coustyx computes the near field matrices during each iteration This increases the total analysis run time but helps avoid using memory to store these matrices If memory usage is not an issue we advise the users to precompute near field matrices for speeding up the analysis Figure 7 6 FMM Transition Method This option is enabled only when the option Use FMM is se lected Speed Select this option for faster run times The solution is accurate at higher frequen cies However the solution may be less accurate at low frequencies Best blend Select this option to blend Speed and Accuracy methods This method uses Speed method at higher frequencies and Accuracy method for low frequencies Accuracy Select this option to obtain accurate solutions at all frequencies This method however may be slower than the other two methods Number of FMM Levels This option is enabled only when the option Use FMM is selected Proper selection of number of FMM levels is very important to run the analysis efficiently Always use the Levels Suggested in the edit dialog box Figure 7 7 Level 0 represents a cube root cell enclosing the entire acoustic model Level 1 represents eight children cells formed by sub dividing the root cell into eight octants Each of the children cells are further divided into eight more to represent the next level This is applied r
290. styx as follows Pres where x y z are components of absolute vector nz ny n are components of relative vector Side of Mesh on which Domain is This is used to set the side of the Mesh on which the Domain is present Right click on Side of Mesh on which Domain is to select Side of Mesh on which Domain is Positive or Negative Figure 4 29 The positive side of a mesh is defined as the side with positive mesh normal For example consider a sphere mesh with all the element normals pointing inward The sphere interior is on the positive side of the mesh as the mesh normals point inward and the exterior is on the negative side of this mesh If you are interested in solving the exterior acoustics problem for this mesh where the mesh normals point inward then you need to set the flag to Negative To solve the interior problem set the flag to Positive To view element orientations use the tabbed window Element Orientation located at the bottom of the Mesh Viewer window refer to Section 5 11 Note that in order to specify this flag we need to have all the elements of the mesh to be ori ented consistently For a MultiDomain model Coustyx automatically generates consistent BE mesh normals when skinned from a FE mesh Boundary Condition Mapping This lists all the boundary conditions applied on the ele ments of a mesh 4 3 9 5 Chief Points Select Model Domains lt Domain Name gt Chief Points Chief points are used to
291. sure level over the measurement surface in decibels N 1 Dot 10 log 19 a pa m dB i 1 N is the number of microphone positions associated with equal partial areas on the measure ment surface W is the weight applied by the filter at the frequency of analysis Figure 7 31 Lpi is the sound pressure level measured at a microphone position p Lpi 101089 E dB Po where p is the root mean square pressure in Pascals and py 2 x 107 Pa 7 2 4 5 ISO 9614 1 ISO9614 1 is an international standard that specifies a method for determining the sound power level of a noise source by measuring the component of sound intensity normal to a mea surement surface enveloping the source Figure 7 44 Definitions of some commonly used terms in the standard 7 2 Outputs 255 Analysis Sequence Y Create a Sound Power File File Name soundpower from standards dat Method 150 9614 1 1993 E Standard 1509614 1 Grade of Accuracy Measurement Surface Parallelepiped Grid Data Help D am 0 00 0 00 Grid Dimensions Li 2 000000000001 L2 2 00000000000 L3 1 00000000000 Number of Probe Positions NL 1 Figure 7 44 ISO9614 1 sound power standard window 256 Analysis Sequences e Measurement surface hypothetical surface enveloping the noise source on which measurement points are located The measurement surface terminates on the reflecting pl
292. surements taken in a semi anechoic room The definitions of Center X Axis and Y Axis are simi lar to that shown in Figure 7 33 Click on the Suggest button to auto fill the measurement surface variables in agreement with the standard Verify the input you have entered by clicking on the Check button Coustyr checks to see if the input variables satisfy the standard requirements If the standard requirements are not met a message window pops up to help you make appropriate corrections X Axis Specify the orientation of the X axis here See Figure 7 33 for definition Y Axis Specify the orientation of the Y axis here See Figure 7 33 for definition Center Specify the center of the hemisphere surface here Select the coordinates of the center by projecting the acoustic center of the sound source on the floor of the semi anechoic room As the location of the acoustic center is frequently not known select the geometric center of the source instead Radius The radius of the hemisphere surface shall be equal to or greater than any of the following e twice the largest source dimension or three times the distance of the acoustic center of the source from the reflecting plane whichever is larger A of the lowest frequency of interest and elm Microphone Array Choose any of the available types of microphone arrays from the drop down menu Fixed Positions Choose this option to specify an array of fixed microphone positions associated with
293. system or the maximum number of CPUs allowed by the user s license whichever is smaller Number of CPUs requested This option is activated by un checking the option Use Max imum Possible Number of CPUs The user can then select the number of CPUs to be available to Coustyz If the number of CPUs selected is higher than the maximum allowed by the user s license Coustyr automatically selects the latter Figure 7 6 7 1 1 2 Formulation Type This option is valid only for MultiDomain models For Indirect models variational formulation is the only choice available Variational Select this option to perform the analysis using the variational formulation HIE Collocation Select this option to perform the analysis using the Helmholtz Integral Equa tion HIE collocation method Burton Miller Galerkin Select this option to perform the analysis using the Burton Miller formulation 7 1 Inputs 195 Name Analysis Sequence Solver Controls Frequency Ranges Outputs Script Parallel Processing Use Maximum Possible Number of CPUs Number of CPUs requested FMM Y Use FMM V Precompute Near Field Matrices Number of FMM Levels Solution Method GMRES Preconditioner Type Number Bands including Diagonal Convergence Criterion Residual as a Percentage 0 50000000000000 Change in Sound Power as a Percentage 0 50000000000000 Number of Vectors in Krylov Subspace at R
294. t Seam e Create seams around all the four holes in the gearbox housing following the instructions given above 328 Tutorial Gear Box Radiation Operations on Selection Unselect All Select All Displayed Elements Unselect Selected Elements Espin le Select All Displayed Nodes Display Connecter Modes Selected Nodes Select Elements Connected Through CoordNodes Hide Set Boundary Condition Add to Set Remove from Set Figure 9 36 Display connected nodes for creating a seam Figure 9 37 Pick nodes to create a seam 9 5 Coustyx Indirect Model 329 e Right click on the mesh while holding down the shift key and select Unselect All to unselect all elements e Skin the finite element structure mesh to generate a boundary element mesh for Coustyx Left click on any element on the exterior surface of the gearbox housing mesh while holding the shift key Make sure you select only one element From the tabbed windows located below the structure mesh select Skin Create Skin Once the skin is created select Skin Create Mesh From Skin to generate a boundary element mesh e To verify the creation of boundary element mesh from the main model menu select Model gt Indirect BE Mesh Right click on it and select Open to view the boundary element mesh created from skinning the FE structure mesh 9 5 1 5 Define Material Properties e In the main model menu select Model Materials
295. t statement throw throw exp try statement catch statement try statement catch IDENTIFIER statement function_defn function IDENTIFIER parameter list statement parameter list parameter list 1 parameter list 1 parameter parameter list 1 parameter parameter gt in IDENTIFIER out IDENTIFIER inout IDENTIFIER assign_decl_exp assign_exp decl_list decl list gt var identdecl list identdecl list identdecl list identdecl identdecl 286 Language Syntax Table 8 2 Coustyx Language Grammar contd Non Terminal Symbol Expansion identdecl assign exp gt addr exp gt or list and list binary relop unary gt aoterm list gt list 1 IDENTIFIER IDENTIFIER exp IDENTIFIER exp addr exp addr exp exp addr exp IDENTIFIER or list or_list and list and list and list amp binary binary binary relop binary binary binary binary binary binary binary binary binary binary binary unary I addr aoterm list J unary unary unary floating point constant string constant TRUE FALSE aoterm exp IDENTIFIER list exp list 1 list 1 exp exp 8 10 Special Functions Syntax 287 Tan or tan Obtain tangent of an angle The angle is assumed to be in radians Example Tan 7 4 1 Asin or asin Obtain the arc sine inverse functio
296. t BE models are defined with respect to Element Normals This is in contrast with the MultiDomain model where the boundary conditions are defined with respect to the Domain Normal Figure 6 4 For an Indirect model Coustyx allows the user to define different boundary condition types on either side of the mesh For any element Side 1 is always considered to be on the positive side of the element normal and Side 2 on the negative side Refer to Figure 6 16 for the element sides definition The Boundary Conditions offered in Indirect models could be categorized into three broad groups for better understanding e Continuous BCs A Continuous BC is one where the Boundary Condition type known pressure known velocity or known impedance and value on both sides of the element boundary are the same Continuous BCs employ lesser number of variables compared to Discontinuous BCs mentioned below Thus these BCs are very attractive from the problem size and analysis speed points of view It is imperative that the user apply these BCs wherever possible to take advantage of smaller problem sizes However there are certain cases where usage of Discontinuous BCs are very much necessary refer to Discontinuous BCs below e Discontinuous BCs Coustyx allows discontinuous boundary conditions with the same boundary condition type known pressure known velocity or known impedance with un equal values specified on both sides of the element boundary
297. tDensity Density of the acoustic fluid medium set by material properties WaveNumber Wavenumber k Angular Freq SoundSpeed 8 4 Function Calls Functions are called by invoking their name and supplying arguments in parentheses Func tions may be pre defined or defined by the user Examples of function calls sin Theta ln x exp y Clear Set_Window 0 1 0 75 Set_Viewport 0 1 0 75 PartialDiff Time 2 0 1 Time Time Parentheses are mandatory even if no arguments are passed to the function 8 5 Expressions Expressions may be formed by using constants variables function calls and the following symbols Arithmentic Operators Addition or string concatenation Subtraction Multiplication Division To the power of Parentheses Open parenthesis Close parenthesis Relational operators RELOPS gt Greater than lt Less than Equal to lt Less than or equal to gt Greater than or equal to Not equal to Boolean operators amp Boolean AND operator Boolean OR operator Boolean NOT operator Array operators Start of an array list or array element extractor End an array list or array element extractor 8 6 Statements 267 Separator for array list and argument list elements Examples 1 2 1 0092 Pi 0 1 x72 3 Pi Translate 0 001 e1 0 002 e2 Rotate Time Dmega e3 Sin Theta Cos Theta 0 Body Frame Reaction Vector Sun Body 6 el 2 0 1 2 3 4 5 6 2
298. tatement cs rsa suap ri do 268 8 6 6 Symbolic Form and Evaluation of Expressions 269 SO iW Statement o coca a sra RARER SERS 270 808 AE 271 8 6 9 while Statement s se sando a Ge Bee ma AE do deal 272 8 6 10 do while Statement svaks esse a sa GE Ge 273 80 11 break Statement co sea a a STAGE AE Gs G Ge sa Saa VG 273 8 6 12 continue Statement o s cg 4542 aw PG Ge AE GA EE GE 274 8 6 13 switch Statement s x s s osos e KE RK KE G GE a a MM GEER EO 275 8 6 14 Variable Scope Visibility Rules serer nesau dodania taniu 277 8 6 15 Function Definition 2 4 6664 4 a rake GEGEN SES GS 278 8 6 16 try catch and throw Statements 282 S 0 17 Statement Label usa a a a a taa 283 CONTENTS ix 86 18 Goto Statements 44454 64 en eee dhe EG GATE Ge SG nd 283 Gr Edot laput so oa aga ak d 44 4 9 ee ke dd AAA deig seig 284 88 Grammar sesssakt satan RN 284 8 9 Regular Functions Syntaks ads Dobbel aka ka SG SSS TETEN 284 8 10 Special Functions Syntax s gt s sosie saa so BEBE GA Head ka EES 287 8 10 1 Associated Legendre Function ear vr vr vr 287 8 10 2 Legendre Polynomials 1 ss sa c ewp ey sadel SE a 288 640 9 Sphencal Harmonie gt aa 81 15 ss PST e eR EST SEE ER 288 8 10 4 Spherical Hankel Function of First Kind 289 8 10 5 Spherical Hankel Function of Second Kind arr o 289 8 10 6 Cylindrical Hankel Function of First K
299. tegories Any non uniform boundary condition could be expressed in this general form The general equation for this BC is given by a x nx p B X x 0n y X nx 6 5 162 Boundary Conditions where p is the pressure vn is the normal velocity at a point on the element and a 8 y are variables that vary with position x and normal nx over the element The values for a 3 and y could be computed from the script function GetAlphaBetaGamma The input arguments for this function are predefined position vector Posn Vec and normal vector Normal Vec at a point It outputs the values for Alpha a Beta 8 and Gamma y which are used in the BC Other predefined variables that can be used in the script are AngularFreq w frequency in radians sec SoundSpeed c speed of sound in the medium with the same Ww units as those defined in materials WaveNumber k 2 and AmbientDensity p density of the medium with the same units as those defined in materials Figure 6 15 6 4 Indirect BE Model BCs The primary variables in Indirect BE models are pressure jumps or double layer potential n and velocity jumps or single layer potential o The Boundary Conditions however are applied in terms of acoustic physical quantities pressure velocity and impedance Please note that all the derivatives in Indirect BE formulation are with respect to the Mesh Normal or Element Normal Hence all the boundary conditions in Indirec
300. tensity Plus This attribute displays the normal component of the time averaged sound intensity over the positive side or the plus side of the boundary element mesh and at field point grids For field point meshes there is no distinction be tween the positive side plus side and the negative side minus side Hence same val ues are displayed for Normal Sound Intensity Plus and Normal Sound Intensity Minus Normal Sound Intensity Minus This attribute displays the normal component of the time averaged sound intensity over the negative side or the minus side of the bound ary element mesh and at field point grids For field point meshes there is no distinction between the positive side plus side and the negative side minus side Hence same values are displayed for Normal Sound Intensity Plus and Normal Sound Intensity Minus 7 2 4 Sound Power Levels from ISO Standards Coustyx provides options to compute sound power levels from any of the following standard methods ISO 3744 ISO 3745 and ISO 9614 1 Figure 7 32 shows the Sound Power Standards outputs window 7 2 Outputs 231 7 2 4 1 Create a Sound Power File This option is selected when the user wants to create an output data file with sound power levels computed from ISO standards The output file is entitled soundpower from_standards by default You can modify the file name by typing in a new name or by selecting an existing file through the Browse button The output file consist
301. th buffer 16 17 57 20 No of bits on Depth buffer 16 Add Selected Faces to Set Remove Selected Faces from Set Switch Sides Add Face 1 of Selected Elements to Set Add Face 2 of Selected Elements to Set Figure 4 36 Menu options for faces in a Set Select Selects all the faces of the Set in the GUI Unselect Unselects faces of the Set in the GUI 84 Getting Started Add Selection to Set Adds selected faces to the current Set Remove Selection from Set Removes selected faces from the current Set Switch Sides This option is available for BE meshes surface elements only See Fig ure 6 16 for the description of Side 1 and Side 2 of a surface element When selected Coustyz switches the selection side of the element from the current face to its opposite It modifies the component list of the Set with the new face selection For example consider a Set which contains Side 1 of an element as its Face component When Switch Sides is applied the Set is modified and the Side 2 of the element that is the opposite side is saved in the place of Side 1 Tf you press Switch Sides again you will get back to the original Set configuration Note that this option is enabled only when the Face components of the Set are selected in the GUI Also this option is available only for BE meshes Add Face 1 of Selected Elements to Set This option is available for BE meshes sur face elements only See Figure 6 16 for the description of Side 1 and Sid
302. that are of precision grade or grade 1 accuracy Figure 7 41 Definitions of some commonly used terms in the standard e Measurement surface A hypothetical surface enveloping the noise source on which measurement points are located For measurements in semi anechoic rooms the measure ment surface terminates on the reflecting plane ISO 3745 allows two different measurement surfaces They are Sphere Hemisphere Lowest Frequency Specify the lowest frequency of interest in hertz The measurement sphere or hemisphere radius is selected based on this value Ambient Pressure Specify the barometric pressure during the measurements in Pascals This is used to compute environmental corrections to the sound power level value Ambient Temperature Specify the air temperature during measurements in degrees Celsius This is used to compute environmental corrections to the sound power level value Sphere Use sphere measurement surface when you want to simulate measurements taken in an anechoic room The definitions of Center X Axis and Y Axis are similar to that shown in Figure 7 33 Click on the Suggest button to auto fill the measurement surface variables in agreement with the standard Verify the input you have entered by clicking on the Check button Coustyx checks to see if the input variables satisfy the standard requirements If the standard requirements are not met a message window pops up to help you make appropriate corrections X Axis S
303. the Check button Coustyx checks to see if the input variables satisfy the standard requirements If the standard requirements are not met a message window pops up to help you make appropriate corrections X Axis Specify the orientation of the X axis here See Figure 7 36 for definition Y Axis Specify the orientation of the Y axis here See Figure 7 36 for definition Center Specify the center of the octant surface here Select the coordinates such that the center is in the middle of the reference box and its images in the reflecting planes Radius The radius of the octant surface shall be equal to or greater than twice the char acteristic source dimension do and not less than 1m Microphone Array Figure 7 36 shows a microphone array on the octant surface The microphone positions are listed in Table 7 6 Number of Probe Positions Specify the number of microphones associated with equal areas spread over the octant surface Choose the number of microphones to be 2 or 3 from the drop down menu 7 2 Outputs 239 ie Key microphone positions Additional microphone positions Center N Figure 7 35 1503744 Microphone array on the quadrant 240 Analysis Sequences Center A O Key microphone positions O Additional microphone positions Center N Figure 7 36 ISO3744 Microphone array on the octant 7 2 Outputs 241 Parallelepiped Use par
304. the available drives on your computer to which Coustyx can be installed along with each drive s available and required disk space Figure 2 1 If you see the error message shown in Figure 2 2 this means that you need to do a Windows Update 2 1 Software Installation Select Installation Folder CodS TT i The installer will install Coustyx32 to the following folder To install in this folder click Next To install to a different folder enter it below or click Browse Folder ExProgram Filest nsolCoustyx324 Figure 2 1 Select path window iz Coustyx Xx There is problem with this Windows Installer package program run as part of the setup did not finish as expected Contact your support personnel or package vendor Figure 2 2 Windows installer error message 6 Installing Coustyx 2 1 3 Confirm Installation After the installation folder is selected you will need to confirm to proceed with the installation You can go back to the previous page to change the installation folder using Back button Once the installation is finished close the window by clicking on Close button 2 2 Dongle Device Driver Installation If you have been provided a USB dongle then the dongle device driver needs to be installed first You will need Admin privileges for this step e To install the dongle device driver open the Coustyz file folder and double click on the icon labeled SentinelDongleDeviceDriver exe
305. the hole in a specific direction Pick the nodes until a unique closed loop is identified by the appearance of triangle elements filling the hole as shown in Figure 9 39 Figure 9 39 Fill hole using triangle elements e The elements created to fill the holes are automatically added to a new set created with the name Hole_1 in Fill Hole New Set Name 9 5 Coustyx Indirect Model 331 e From the tabbed windows located below the structure mesh select Fill Hole Fill Hole e Repeat the above instructions to fill all the four holes in the gearbox housing 9 5 1 7 Define Boundary Conditions e Edit the existing default boundary condition In the Coustyx main model menu select Model Indirect BE Mesh Bound ary Conditions Default Right click on Default and select Edit to make changes to the default boundary conditions applied to all the boundary elements The window in Figure 9 40 will appear res ea OF o Edit Boundary Condition EX Name Default Type Uniform Velocity Continuous X Help Velocity Frequency Dependence Type Constant Real x 0 0 Imaginary X 0 0 Real 0 0 Imaginary Y 0 0 Real Z 0 0 Imaginary Z 0 0 ox Cancel j Figure 9 40 Edit boundary conditions window Type in the new name Structural Velocity BC Select Structure Velocity Continuous from the drop down menu for Type The window in Figure 9 41 will appear
306. the instructions given earlier in Section 9 5 1 4 to display element edges in the mesh Left click on the elements around the edge of a hole while holding the shift key Make sure to select elements with nodes on the hole edge similar to the Figure 9 9 Right click on the mesh while holding down the shift key to view the context menu and select Selected Elements Display Connected Nodes similar to the Figure 9 12 Left click on the displayed nodes while holding the shift key to pick the nodes on the edge of the hole in a specific direction Pick the nodes until a unique closed loop is identified by the appearance of triangle elements filling the hole as shown in Figure 9 15 Figure 9 15 Fill hole using triangle elements 308 Tutorial Gear Box Radiation e The elements created to fill the holes are automatically added to a new set created with the name Hole_1 in Fill Hole New Set Name e From the tabbed windows located below the structure mesh select Fill Hole Fill Hole e Repeat the above instructions to fill all the four holes in the gearbox housing 9 4 1 7 Define Boundary Conditions e Edit the existing default boundary condition In the Coustyx main model menu select Model Boundary Conditions Default Right click on Default and select Edit to make changes to the default boundary conditions applied to all the boundary elements The window in Figure 9 16 will appear
307. the length of the rectangular partial area formed by these subdivisions satisfies the criterion Ea lt 3d where L2 is the length of parallelepiped in Y direction and d is the measurement distance Refer Figure 7 37 The microphone positions are in the center of each partial area and at each corner of the partial area excluding the corners intruding into reflecting planes 244 Analysis Sequences N3 Number of subdivisions in Z direction Figure 7 39 Select the value of N3 such that the length of the rectangular partial area formed by these subdivisions satisfies the criterion 13 lt 3d where L3 is the length of parallelepiped in Z direction and d is the measurement distance Refer Figure 7 37 The microphone positions are in the center of each partial area and at each corner of the partial area excluding the corners intruding into reflecting planes Reference box O i 4 Measurement surface 6 O 2 F R ji A A o 5 p z 4 Z P gt O P Lo 3 Y a V g Y Corner1 a d y L1 1 d gt x Microphone positions d Measurement distance Figure 7 39 IS03744 Parallelepiped measurement surface with microphone positions for a source placed on the floor against a wall Parallelepiped against corner Use this measurement surface when the source under test is placed on a floor against two walls Figure 7 40 shows a parallelepiped measurement surface whose
308. the measurement distance The recommended value for d 1m N1 Number of subdivisions in X direction Figure 7 45 Select the values of N1 N2 N3 such that there is a minimum of one probe position per square metre and a minimum of 10 positions distributed as uniformly as possible according to segment area over the measurement surface N2 Number of subdivisions in Y direction Figure 7 45 Select the values of N1 N2 N3 such that there is a minimum of one probe position per square metre and a minimum of 10 positions distributed as uniformly as possible according to segment area over the measurement surface N3 Number of subdivisions in Z direction Figure 7 45 Select the values of N1 N2 N3 such that there is a minimum of one probe position per square metre and a minimum of 10 positions distributed as uniformly as possible according to segment area over the measurement surface The sound power level Lw from IS09614 1 standard is computed as follows N P Ly 1010819 p z dB W i 1 where Py 1071 is the reference sound power N is the total number of measurement positions and segments W is the weight applied by the filter at the frequency of analysis Figure 7 31 P is the partial sound power for segment i that is Pi LuSi where Ini is the signed magnitude of the normal sound intensity component measured at position 7 on the measurement surface S is the area of segment i 7 2 Outputs 259 7 2 5 So
309. this filter to assess loud noise Figure 7 31 D Filter This filter is used to assess loud noises in the aircraft industry Figure 7 31 7 2 4 3 ISO 3744 ISO 3744 is an international standard that specifies a method to determine sound power levels of noise sources using sound pressure measurements 2 The sound pressure levels are measured on a measurement surface enveloping the source This method is applicable in an essentially free field near one or more reflecting planes This method produces results that are of engineering grade or grade 2 accuracy For precision grade grade 1 accuracy use methods specified in ISO 3745 Figure 7 32 Definitions of some commonly used terms in the standard 2 e Measurement surface A hypothetical surface enveloping the noise source on which measurement points are located The measurement surface terminates on one or more reflecting planes ISO 3744 allows six different measurement surfaces They are Hemisphere Quadrant Octant Parallelepiped Parallelepiped against wall Parallelepiped against cor ner Reference box A hypothetical surface which is the smallest rectangular parallelepiped that just encloses the source and terminates on the reflecting plane or planes Characteristic source dimension d Half the length of the diagonal of the box con sisting of the reference box and its images in adjoining reflecting planes Hemisphere Use hemisphere measurement surface when there is on
310. tic analysis on the gearbox housing Open Coustyx from the start menu of your computer 9 5 1 1 Create a New Model e In the main menu select File New Model The window in Figure 9 28 will then appear e Choose the model type Indirect Model and select model units meter kilogram second ST units Note that the selection of model units is consistent with the unit of length in the structure mesh Click OK to proceed New Model 54 Select Model Type Multidomain Model 9 Indirect Model Select Model Units 9 meter kilogram second SI units gt millimeter newton second gt meter kilogram force second millimeter kilogram force second inch pound force second D foot pound force second D other Length scale factor 1 0000000000000 Mass scale factor 1 0000000000000 Note Model units are presently only used in the computation of sound power levels from ISO standards Modifying model units does not rescale the model oc cancel Figure 9 28 New Model Selection Window 322 Tutorial Gear Box Radiation 9 5 1 2 Import FE Structure Mesh e In Coustyx model main menu select Model Structures e Right click on Structures and select Import Nastran Bulk Data bdf File as shown in Figure 9 29 to import mesh from Nastran bulk data format The FE meshes from Abaqus and Ansys data formats can be imported by selecting Abaqus in
311. tion Figure 7 40 Select the value of N3 such that the length of the rectangular partial area formed by these subdivisions satisfies the criterion 43 lt 3d where L3 is the length of parallelepiped in Z direction and d is the measurement distance Refer Figure 7 37 The microphone positions are in the center of each partial area and at each corner of the partial area excluding the corners intruding into reflecting planes The sound power level Lw from IS03744 standard is computed as follows Ly Lpf 1010819 dB 0 where S is the area of the measurement surface in square meters S 1 m Lyf is the weighted surface sound pressure level over the measurement surface in decibels N 1 Lot 10 log 19 E pa rten dB i 1 N is the number of microphone positions associated with equal partial areas on the measure ment surface W is the weight applied by the filter at the frequency of analysis Figure 7 31 Lpi is the sound pressure level measured at a microphone position p Lpi 10 logy E dB Po 7 2 Outputs 247 where p is the root mean square pressure in Pascals and pp 2 x 107 Pa 7 2 4 4 ISO 3745 ISO 3745 is an international standard that specifies methods to determine sound power levels of noise sources using sound pressure measurements in anechoic or semi anechoic rooms 3 The sound pressure levels are measured on a measurement surface enveloping the source This method produces results
312. tion 5 6 for more details 4 2 Operations on Mesh Viewer Window 47 Opent File Edit Preferences Help E Model LE Type lt Indirect gt H Version lt 1 00 00 gt E Model Description EG Structures E Structmesh 0 2 Materials C Planes 184 Indirect BE Mesh lt MewMeshCreatedFromskin gt LE Context Script 2 Analysis Sequences Done launay Triangulation Smallest angle created 38 054229 launay Triangulation Largest area ratio created 1 289647 Delaunay Triangulation No of iterations 13 C Selected Coord Nodes E3 Selected Elements Cy Fil Hole 33 skin Cy Stitch Seams 53 Delete Elements y Element Orientation Delaunay Triangulation Optimization Parameters Fill Parameters i jons 4000 lt 4 Element Type LINEAR y Minimum Triangle Vertex Anale 30 NewSet Name Pole gf EE Fill Hole kunde Funeereldelored atoi pA Ev amnlae Tadre Anant vinder Karate Inmndifiad Ela mantulindas rov mmr AAA AAA A A coil O O O A AA A E eed tae AA NRO gt ol Figure 4 12 Fill Hole 48 Getting Started Version lt 1 00 00 gt Model Description Structures o Struetmesh 0 Cy Materials C Planes Indirect BE Mesh lt NevMeshCreatedrromSkin gt Context Script C Analysis Sequences Elem with Elem with I i Parsing input file C users delores Coustyx trunk Examples indirect OpenCyind Opening file wait Done 150 Failed to find a path from Node with 1D 446 to Node with
313. tion of the analysis sequence All the required Inputs for Coustyx analysis are found in the tabbed windows Solver Controls and Frequency Ranges The Outputs window has options to save the results to a binary file compute acoustic variables at Sensor locations field points and save Glass file for post processing visualization Script tabbed window lists the summary of commands required to run an analysis The parameters in the script are set by the 191 File Edit View Preferences Help Dol BLANT S ag A 1 2 Type lt MultiDomain gt E Version lt 1 33 00 gt Model Description Structures if Analysis Sequences Analysis Sequences Rename Copy Paste Delete Open Close Edit Help New Figure 7 1 Creating new analysis sequence 192 Analysis Sequences Analysis Sequence Description Units Solver Controls Freque Multi frequency analysis Figure 7 2 Analysis sequence edit dialog box File Edit Analysis Preferences Dea LEE E lt Model Type lt Indirect gt Version lt 1 00 00 gt Model Description Units Structures Materials Planes Indirect BE Mesh lt 1 gt Context Script 3 43 Analysis Sequences a Analysis Sequence Rename Copy Paste Delete Open Close Edit Help Abort Figure 7 3 Run new analysis sequence 193 File Edit Analysis Preferences Hel D
314. tive side or the plus side of the boundary element mesh surface and at field point grids For field point meshes there is no distinction between the positive side plus side and the negative side minus side Hence same values are displayed for Velocity Plus and Velocity Minus Velocity Minus This attribute displays the acoustic particle velocity vector amplitude with phase on the negative side or the minus side of the boundary element mesh surface and at field point grids For field point meshes there is no distinction between the positive side plus side and the negative side minus side Hence same values are displayed for Velocity Plus and Velocity Minus Sound Intensity Plus This attribute displays the time averaged sound intensity vector over the positive side or the plus side of the boundary element mesh and at field point grids For field point grids there is no distinction between the positive side plus side and the negative side minus side Hence same values are displayed for Sound Intensity Plus and Sound Intensity Minus Sound Intensity Minus This attribute displays the time averaged sound intensity vector over the negative side or the minus side of the boundary element mesh and at field point grids For field point grids there is no distinction between the positive side plus side and the negative side minus side Hence same values are displayed for Sound Intensity Plus and Sound Intensity Minus Normal Sound In
315. tive side of the element is on the negative side 5 The surface pressures p and normal The surface pressures and normal ve velocities vn are directly obtained from the solution locities are derived from the single layer 0 and double layer u poten tials on the surface 56 Getting Started Table 4 3 continued No MultiDomain Indirect 6 Cant model ribs or any two Allows modeling of ribs or any two dimensional panels which don t dimensional panels which don t enclose enclose a volume These are automat a volume These are automatically ically removed during skinning generated during skinning 7 Can t model acoustic problems with Allows modeling of acoustic problems pressure jumps at the boundary with pressure jumps For example can model a 2 D circular disk with zero pressure jumps at the edges 4 3 2 Structures Select Model Structures Structures is a model tree member which is used to import a FE mesh load frequency response data and natural mode data The mesh imported here is the main geometry source for generating BE mesh for acoustic analysis The imported FE mesh can be manipulated using Manipulation Task Functions and then skinned to generate the BE mesh Refer to Section 5 5 4 3 3 Materials Select Model Materials Materials is the model tree member used to define the Speed of Sound and Ambient Density of the fluid medium surrounding t
316. uadrilateral and triangular elements For most of the problems this accuracy level is good enough Figure 7 12 Fine This option is selected when high accuracy of the solution is required Table 7 3 shows the integration orders used for quadrilateral and triangular elements Figure 7 12 Finest This option is selected when very high accuracy of the solution is required Ta ble 7 3 shows the integration orders used for quadrilateral and triangular elements Figure 7 12 7 1 2 Frequency Ranges The Frequency Ranges window in Figure 7 13 shows a table of frequency ranges The table contains columns Start Hz Delta Hz No Freqs End Hz e Start Hz is the start frequency in Hz e Delta Hz is the frequency resolution in Hz e No Fregs is the number of frequencies e End Hz is the end frequency in Hz The user can set a frequency range by inputting values in any of the three columns of the table the fourth value is derived from the other three Multiple frequency ranges can either be 206 Analysis Sequences Analysis Sequence Figure 7 12 Variable Order Integration Scheme 7 1 Inputs 207 Analysis Sequence Name Analysis Sequence Description Solver Controls Frequency Ranges Outputs Script Start Hz Delta Hz No Fregs End Hz 1 50 000000 5 000000 100 545 000000 Load Frequencies l OK Cancel Figure 7 13 Frequency ranges window manually add
317. uctures B C Materials C Planes C Interfaces CJ Boundary Conditions Direct BE Meshes CJ FE Meshes LY Domains Cy Domain Sources Material lt Air gt Context Script CJ Analysis Sequenc Figure 9 22 Set the side of the mesh on which the domain is Type lt Direct BE gt Boundedness lt Unbounded gt CJ Direct BE Meshes Side of Mesh on which Domain is lt Positive gt Rename Copy Paste Delete Open Close Edit Help Side of Mesh on which Domain is 316 Tutorial Gear Box Radiation Select Model Analysis Sequences and right click to create a new analysis sequence by selecting New Select Solver Controls tab to set solver parameters Refer to Figure 9 23 Ensure the default solver options are satisfactory Set Initial Guess Previous Solution from the drop down menu Move onto Frequency Ranges tab to specify analysis frequencies Refer to Figure 9 24 Enter the starting frequency to be 100 Hz in the table under Start Hz Enter a value of 15 Hz for the frequency resolution under Delta Hz Enter the final frequency to be 1000 Hz in the table under End Hz Now move onto Outputs tab where output file names are specified Ensure the default settings in Outputs tab are satisfactory Click OK to save the new analysis sequence To edit the analysis parameters any time select Model Analysis Sequence
318. umes that the seam does not form a closed loop and just tries to connect the selected coordinate nodes to form a curve Element Type This option specifies the type of triangle elements to be filled in the gap between disjoint seams Linear or Quadratic triangle elements can be created New Set Name All the triangle elements created to fill the gap can be conveniently added to a Set during the process This option specifies the name of the new Set 5 7 2 Procedure to Stitch Seams Follow the steps below to stitch a seam e Open any mesh in the GUI by right clicking on the mesh and selecting Open e Enable Stitch Seams Seams form closed loops if the seams are expected to form a closed loop If not disable this e Select elements that coincide with the seam edges To select an element in the GUI Left click on the element with the shift key held down Refer to Figure 5 35 e Display connected nodes for the selected elements Right click on the selected elements with the shift key held down and select Operations on Selection Selected Elements Display Connected Nodes See Figure 5 36 e Choose the nodes in the path of the seam to be created To select a node Left click on the node with the shift key held down Note You should only select nodes on the corners of the elements not mid side nodes Once three or more nodes are selected the seam connecting these nodes is drawn if Coustyx finds a valid path Seams are constructed b
319. unction call GetTransferImpedance which accepts PosnVec as the input and returns transfer impedance Other predefined variables that can be used in the script are AngularFreq w frequency in radians sec SoundSpeed c speed of sound in the medium with the same units as those defined in materials WaveNumber k 4 and AmbientDensity p density of the medium with the same units as those defined in materials Figure 6 21 The option Use Structure Velocity is enabled to define structure velocity used in Equa tion 6 7 Refer to Section 6 4 3 3 on how to use this option 6 4 4 Uniform Pressure Continuous BC This Boundary Condition is applied on elements with uniform pressure on both sides of the boundary The BC is continuous which implies that the values of pressure at the same point on side 1 p and side 2 p are identical refer to Figure 6 16 for side 1 and side 2 definitions pt p Da where po is the uniform pressure applied on both sides Figure 6 22 168 Boundary Conditions 1 Hfunction GetSullivanCrockerModelParameters in PosnVec out Porosity ES AngularFreq SoundSpeed WaveNumber and AmbientDensity are pred read only variables that can be used here The following is just an example change the formula to suit yo var Magn 12 0 Porosity Magn exp i WaveNumber PosnVec 2 PlateThickness 0 5 PosnVec 3 HoleDiameter 0 25 0100 03000n Figure 6 21 Non Uniform Perforated
320. und Power Coustyx automatically creates an ASCII data file entitled power dat while running an analysis This file contains acoustic sound power values computed at each analysis frequency It has five columns The first column contains analysis frequencies in Hertz The second and third columns contain the radiated active sound power and the reactive sound power respectively The input power is in the fourth column with the same unit The units of power are consistent with the material properties sound speed and ambient density The final column consists of the radiation efficiency The sound power W through an area S is given by w fias 7 1 where I PV is instantaneous sound intensity in the direction of particle velocity V and P is the instantaneous pressure at that point For more details on the definition of sound intensity refer to Section 7 2 5 1 Acoustic sound power definitions in Coustyz Radiated Active Sound Power Radiated Active sound power is the rate at which acous tic energy is radiated from a source It is computed from the mean active acoustic intensity Ia refer to Equation 7 11 over a surface S that is Wa f Lads 7 2 Reactive Sound Power Reactive sound power is a measure of the acoustic energy which keeps transforming back and forth between potential and kinetic energies The reactive sound power is computed from the amplitude of the reactive sound intensity I refer to Equa tion 7 12 over a sur
321. unded interior solution dominate the value of primary variable y on the surface This contaminates the solution for the exterior field Accurate results for the exterior problem could be obtained by specifying the structure velocity boundary condition on the exterior and a zero velocity or zero pressure boundary condition on the interior side of the boundary e The Boundary Conditions which relate pressures and normal velocities on one side of the boundary to the pressures and velocities on the other side are grouped together in this category Anechoic Termination BC Uniform Perforated BC Non uniform Perforated BC Uniform Arbitrary BC Non uniform Arbitrary BC fall under this category 5 gt Side 1 Side 2 Figure 6 16 Description of element normal and its sides For an Indirect model the Boundary Conditions are defined at Model Indirect BE Mesh Boundary Conditions To create a new Boundary Condition right click on Boundary Conditions and select New Figure 6 5 Below is the description of each of the boundary condition options provided in Indirect model 6 4 1 Transparent BC Transparent Boundary Condition is applied on the boundary across which the pressure and normal velocity is continuous Normally the transparent BC is not required in the Indirect BE models because this type of continuity can be achieved by simply removing the element from the model The portion of the surface where continuity conditions are enforced
322. ure and vp is the particle normal velocity in n direction at the surface of the material 146 Specific acoustic impedance Z poc R poc jX poc for a foam of 1 inch thickness measured using e A convention arr v rv rv ane 147 Interpolation for mismatched meshes 0 00 0 eee ee aan 148 Definition of domain na and mesh normals nm Note that domain normal always points away from the domain of interest Mesh normal however can point towards or away from the fluid All boundary conditions in a MultiDomain model are defined with respect to the domain normal 150 New Boundary CONCHA bo a Rae ee ES ees 151 Dummy Boundary Condition ss as eae ce ee Re a ee 152 Interface Boundary Condition 0 2 rv ee ee 153 Uniform Pressure BC soo tea eee eae dd ge eee Be eee eS ae SSD 4 153 Non Unitorm Pressure BG ceca oaos ae i ook aa 154 Uniformi Normal Velocity BG de ao la te Eee eS o 155 Uniformi Velocity BGs s ad ean RRR Aes kes dl A 156 Non Uniform Normal Velocity BC so s secaraa coce E e e rn nrk aa 158 Strpetue Velocity Da sio A bh eee eee re AES dre 159 Arbitrary Uniform BO 2442224444 EERE eee eee 160 Arbitrary Non Uniform BC e 161 Description of element normal and its sides 0 0 00002 eee 163 Transparent Bla oa ee eR a EMG Bee es g aS sea A 164 Anechoie Termination BE s aiiis ar bee ea ds bbe eae kake aes 164 Perforated Pl
323. ute Near Field Matrices Residual 0 50000000000000 0 50000000000000 1000 Integration 7 Use Fixed Integration Order Integration Order for Triangular Elements Integration Order for Quadrilateral Elements variable Order Int scheme Medium Figure 9 44 Analysis solver controls 336 Tutorial Gear Box Radiation e Move onto Frequency Ranges tab to specify analysis frequencies Refer to Figure 9 45 Enter the starting frequency to be 100 Hz in the table under Start Hz Enter a value of 15 Hz for the frequency resolution under Delta Hz Enter the final frequency to be 1000 Hz in the table under End Hz Analysis Sequence Sc Name Analysis Sequence Description solver Controls Frequency Ranges Outputs Script Start Hz Delta Hz No Freqs End Hz 1 100 000000 15 000000 61 1000 000000 id Cancel Figure 9 45 Set analysis frequencies e Now move onto Outputs tab where output file names are specified Ensure the default settings in Outputs tab are satisfactory Click OK to save the new analysis sequence To edit the analysis parameters any time select Model Analysis Sequences Analysis Sequence Right click and select Edit To start acoustic analysis select Model Analysis Sequences Analysis Se quence Right click and select Run to perform acoustic analysis on the gearbox housing
324. utputs 257 Reference box O O O Measurement surface O O O O 7 T M O Xx O Al O 2 O Oo Corner1 1 L1 1 2d O Microphone positions d Measurement distance Figure 7 45 IS09614 1 Parallelepiped measurement surface with probe positions 258 Analysis Sequences X Axis Specify the orientation of the X axis here See Figure 7 45 for definition Y Axis Specify the orientation of the Y axis here See Figure 7 45 for definition Corner1 Specify Cornerl of the parallelepiped surface here See Figure 7 45 for definition The parallelepiped is constructed using Cornerl as the starting point and L1 L2 L3 as its dimensions along X Y Z axis respectively L1 Length of the parallelepiped in X direction Figure 7 45 Specify the value of L1 such that it satisfies the definition L1 11 2d where l1 is the reference box dimension in X direction and d is the measurement distance The recommended value for d 1m L2 Length of the parallelepiped in Y direction Figure 7 45 Specify the value of L2 such that it satisfies the definition L2 12 2d where 12 is the reference box dimension in Y direction and d is the measurement distance The recommended value for d 1 m L3 Length of the parallelepiped in Z direction Figure 7 45 Specify the value of L3 such that it satisfies the definition L3 13 d where 13 is the reference box dimension in Z direction and d is
325. values in the file with jw v jw s where s s e is the displacement variation v is the corresponding velocity variation e Similarly when only acceleration data is available the velocity values can be obtained by setting the Omega exponent value to 1 v jw a where a apet is the acceleration variation e If the values in the file are velocity components then the Omega exponent is to be set to zero 3 3 3 Script The Frequency Dependence Type is defined as a Script when the frequency variation of the acoustic variable is given through a script Predefined variables for frequency AngularFreq or Frequency can be used here The AngularFreg variable is in radians sec and Frequency is in Hz A sample script with normal velocity varying linearly with frequency is shown in Figure 3 7 28 Conventions in Coustyx Name New BC Type Uniform Normal Yelocity h Normal Velocity Frequency Dependence Type Script 1 Hfunction FreqDependentNo t Use one of the predefined variables f AngularFreq or Frequency to compute the value AngularFreq is in Rad sec f and Frequency is in Hz var vn Frequency 10 return vn 2 3 4 5 6 7 8 9 Impedence Use Impedence Figure 3 7 Script to define frequency dependent acoustic variable for the boundary condition Chapter 4 Getting Started Coustyr User Interface UI assists the user in building an acoustic model by bringing pieces of the mode
326. var z 3 var z1 2 exitlabel Out Done Example 1 var x 1 var y 2 if x 0 goto exitlabel This is OK var z 3 exitlabel Out Done 8 7 End of Input The input Session is terminated by an end of file marker or by the special symbol End 8 8 Grammar The syntactical elements of the language are formally specified by the rules described in Table 8 1 and Table 8 2 8 9 Regular Functions Syntax Some of the functions that are stored in symbolic form and can be differentiated are listed below You can use these functions in Coustyx scripts Sin or sin Obtain sine of an angle The angle is assumed to be in radians Example Sin 7 2 1 Cos or cos Obtain cosine of an angle The angle is assumed to be in radians Example Cos 7 1 8 9 Regular Functions Syntax 285 Table 8 1 Coustyx Language Grammar Non Terminal Symbol Expansion e gt empty input e stmt list toplevel stmt list toplevel stmt list toplevel statement compound stmt stmt list stmt list stmt list statement statement assign decl exp compound stmt function defn if exp statement if exp statement else statement break continue return return exp for assign_declexp exp assign_exp statement while exp statement do statement while exp switch exp compound_stmt case exp statement goto IDENTIFIER IDENTIFIER statement defaul
327. window The error messages show the IDs of the incompatible elements These Bad Elements have inconsistent coordinate connectivity with respect to their neighboring elements The user needs to manually fix the mesh by treating the Bad elements appropriately The steps to be followed to treat Bad elements in a FE mesh are Press Skin Create Skin button If the FE structure mesh has elements with bad coordinate connectivity then Coustyx throws error messages in the log window and asks the user to fix these Bad Elements before attempting to skin again Figure 5 19 To unselect all displayed elements in the GUI right click with shift key held down and select Operations on Selection Unselect All Select all Bad Elements in the FE mesh by right clicking on the GUI while holding down the shift key and choosing Operations on Selection Select all Bad Elements Figure 5 20 Create a new set by choosing Model Structures lt Structure Mesh Name gt Sets Right click on Sets and select New Rename the new set to lt Bad Elements Set gt To add Bad Elements right click on lt Bad Elements Set gt and select Elements Add Selection to Set Figure 5 21 Go to Model Structures lt Struct Mesh Name gt Elements Right click and select Hide All to hide all the elements in the GUI Now display only Bad Elements to start fixing them Go to Structures lt Structure Mesh Name gt Sets lt Bad Elements Set gt
328. with Coustyx by specifying a velocity boundary condition on the exterior and a zero velocity or zero pressure boundary condition on the interior The discontinuous BC gives the option of specifiying different BCs on Side 1 and Side 2 Refer Figure 6 16 for the definitions of Side 1 and Side 2 Note that Coustyx always considers Side 1 of the boundary to be on the positive side of the normal and Side 2 on the negative side That is always the element normal points from Side 2 to Side 1 The possible side boundary conditions allowed in Coustyz are listed below Figure 6 28 6 4 10 1 Don t care This Boundary Condition is applied on the side of the boundary which doesn t come in contact with the fluid medium or on the side the user is not interested in Again consider the example of a vibrating surface which encloses a volume and the primary interest is in the exterior sound field The boundary condition on the interior side of the mesh doesn t affect the exterior solution In this case the user can apply Don t care BC on the interior side of the mesh Figure 6 28 6 4 10 2 Uniform Pressure This Boundary Condition is applied on the side of the element where the pressure is uniformly distributed That is there is no variation of pressure with position The pressure values can 174 Boundary Conditions xl Name New BC Type Discontinuous y Help m Discontinuous Side 1 side 2 Type Uniform Pressure Pressure
329. y using the color palette provided or by changing the composition of red green and blue If this checkbox is unchecked the colors are not changed Display Connected Elements Displays all the elements connected to the selected co ordinate node Hide This option is used to hide selected nodes Add to Set This option allows user to add selected nodes to a pre defined Set Refer to Section 4 4 on how to define a Set Remove from Set This option is used to remove selected nodes from their current Sets Refer to Section 4 4 for more information on Sets Add to a New Set This option allows user to add selected nodes to a new Set A new set with a default name New Set or New Set i i is a number is created Refer to Section 4 4 on how to rename the Set 44 Getting Started 4 2 3 3 Operations on Displayed Faces Figure 4 11 shows the menu of operations available on faces Operations on faces are activated only when faces are selected in the GUI Operations on Selection Unselect All Select All Displayed Elements Select All Bad Elements Selected Elements Select All Displayed Nodes Select All Bad Nodes Selected Nodes Selected Faces k Add to Set Remove from Set Add to a New Set Figure 4 11 GUI operations on faces available through the context menu activated by the right mouse button with the shift key held down Selected Faces This lists the operations that are performed only on the sel
330. ype Constant Value 8 100000E 004 Constant 0 00249000000000 Ca Lend Figure 6 20 Uniform Perforated 166 Boundary Conditions This type of Boundary Condition will have applications in perforated mufflers perforated BC defines a special type of transfer relation between the pressure normal velocity on either side of the surface The transfer relation in a perforated BC is given by pt p7 pocl Un Ven 6 7 where is the non dimensional transfer impedance of the perforated surface po is the acoustic medium density c is the speed of sound pt and p are surface pressures on side 1 and side 2 respectively vn is the acoustic normal velocity Us is the specified structure normal velocity The user can either select to use the transfer impedance relation derived from the Sullivan and Crocker model 3 or they can define their own transfer impedance from the following choices in the drop down menu Perforated Model Type 6 4 3 1 Sullivan and Crocker The non dimensional transfer impedance used in the Sullivan and Crocker model 3 is 0 006 iko tu 0 754 X where ko is the wave number t is the plate thickness d is the hole diameter and x is the porosity of the plate Figure 6 19 Note the actual relation from 3 is modified to accomodate e J convention used in Coustyx Note that the above relation would be valid only if the porosity is not too different from 0 042 4

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