VISJET 2.0 User Manual
Contents
1. For Windows 98 users they should set their colours to 16 bit high colour Using 24 bit true colour may cause VISJET failure to display the 3D graphics window 2 JETLAG 2 1 JETLAG Introduction JETLAG is a robust LAGrangian JET model that handles an arbitrarily inclined round buoyant jet in a current with a three dimensional trajectory It uses a Lagrangian Projected Area Entrainment PAE concept which assumes that the forced entrainment the vortex entrainment in the bent over jet plume is equal to the ambient flow intercepted by the windward face of the plume element The model has a rigorous theoretical basis and its connection with Eulerian models can be established it is consistent with the concept of asymptotic flow regimes e g the advected puff and thermal in the bent over phase JETLAG is unique in that the Lagrangian model does not strictly speaking solve the usual Eulerian governing differential equations of fluid motion and mass transport Instead the model simulates the key physical processes expressed by the governing equations The unknown jet trajectory is viewed as a series of non interfering plume elements which increase in mass due to shear induced entrainment and vortex entrainment forced entrainment due to the crossflow while rising by buoyant acceleration The model tracks the evolution of the average properties of a plume element at each step by conservation of horizontal and vertical momen2. ii Click the toolbar Por press the right mouse button and select Move Press the mouse left button you can move the viewing window up down left and right Use the animation particle function to see the evolution and spread of the jet as well as how the velocity changes as the plume comes up to the surface Click the toolbar to see the evolution and spread of plume from the jet port to water surface Close this file to start the next tutorial 34 4 8 Example 7 Horizontal buoyant jet in stratified crossflow Zarautz Marine Outfall Spain The file is tut7 vj This is about the same single horizontal buoyant jet considered in Tutorial 6 but the jet is discharged into a stratified crossflow Since the direction of jet momentum is different from the direction of buoyancy in the presence of the crossflow the jet has a three dimensional trajectory The main parameters are as follows Ambient Parameters Depth m Salinit t Temperature C 0 15 30 15 22 25 32 75 34 20 Current velocity 0 2 m s Current Angle 90 N B The salinity is given in parts per thousand ppt Outfall Parameters Depth 34 75 m Temperature 20 C Salinity 0 0 ppt N B The effluent salinity and temperature are specified rather than density Riser Parameters Distance Om T Radius 0 05 m B Radius 0 05 m Height 2m Jet Parameters Flow 0 025221 m s Diameter 0 12 m Port height 2m Vertical angle 0 Horizontal angle 90 General Notes
3. 2 4 Output file SUSPEND SUSPEND is a standard output file Discharge parameters and characteristic length scales are also printed in addition to the numerical results The x y Z co ordinates of the computed jet trajectory are printed along with the jet half width average dilution and velocity and average density deficit 2 5 References Cathers B and Peirson W L 1991 Verification of plume models applied to deepwater outfalls in Proceedings of the International Symposium on Environmental Hydraulics Hong Kong Lee J H W and Cheung Y K ed December 1991 Vol 1 Balkema pp 261 266 Chan C H C and Lam K M 1998 Centreline velocity decay of a circular jet in a counterflowing stream Physics of Fluids Vol 10 3 pp 637 644 Chen G Q and Lee J H W 2000 Numerical experiment of two dimensional line thermal Journal of Hydrodynamics Ser A Vol 15 No 4 pp 411 423 Cheung V 1991 Mixing of a round buoyant jet in a current Ph D thesis Dept of Civil amp Structural Engineering University of Hong Kong Hong Kong Cheung V and Lee J H W 1996 Discussion of Improved prediction of bending plumes Journal of Hydraulic Research Vol 34 No 2 pp 260 262 Cheung V and Lee J H W 1999 Discussion of Simulation of oil spills from underwater accidents model development Journal of Hydraulic Research Vol 37 pp 425 429 Chu P C K and Lee J H W 1996 Mixing of
4. 123 3 the buoyant jet center maximum rise height 5 86 m corresponding average dilution 225 4 The computation will be stopped at trapped level 5 16 m with corresponding average dilution 274 Click Key parameters and length scales in menu More Info in Data output window to see key input parameters and length scales that govern the mechanics of buoyant jet mixing For example discharge length scale lq 0 089 m momentum length scale Im 1 66 m Buoyancy 29 length scale 3 52 m jet plume length scale In 1 14 m characteristic dilution for momentum dominated far field Sm 18 7 and for buoyancy dominated far field S 84 1 5 Observe what happens when the ambient current is increased to 0 3 m s Input 0 3 under the Current column in ambient window resimulate the model Click the toolbar then save this file If you have problems you can open the file tut4a vj in the folder tutorial files You will find the sewage will be more trapped as shown in screen figure or from SUSPEND file In this case trapped level 2 93 m with corresponding average dilution 390 7 6 Compute a vertical buoyant jet in uniform crossflow based on this case You just need to change density to 1 025 at depth 0 m in the input jet parameters resimulate the model Click the toolbar then save this file If you have problems you can open the file tut4b vj in the folder tutorial files For this case you will find that the sewage plume
5. Temperature 0 C Density 1 0 g ml Riser Parameters Distance Om T Radius 0 05 m B Radius 0 05 m Height 2m Jet Parameters Flow 0 025221 m s Diameter 0 12 m Port height 2m Vertical angle 0 Horizontal angle 90 General Notes 1 Study how to modify input parameter based on file tut1 vj i At the startup window Select Open open tut1 vj in the folder tutorial files ii Input depth to 32 75 m and current to 0 2 m s in ambient parameter window iii Click Outfall structure in input parameter window then click Outfall_1 and modify depth to 34 75 m iv Click jet1 and change flow to 0 025221 m s diameter to 0 12 m vertical angle to 0 and horizontal angle to 90 v Resimulate the model Click the toolbar then save this file If you have problems you can open the file tut6 vj in the folder tutorial files 2 Navigate through and view the jet from different angles i Click toolbar Kor press the right mouse button and select Rotate ii When the cursor is moved in the vertical direction of the screen the rotation is about a horizontal axis iii If the cursor is moved in the horizontal direction of the screen rotation is about a vertical axis 33 Zoom and move screen figure i Click the toolbar amp or press the right mouse button and select Zoom By moving the cursor upward you can zoom out from the current setting By moving the cursor downward you can zoom in towards the center of current setting
6. 1 At the startup window select Open open tut6 vj in the folder tutorial files 2 Modify ambient parameters and outfall parameters to the values shown above in the input parameter window The density p will be automatically computed from the supplied salinity and temperature using the equation of state Save this file If you have problems you can open the file tut7 vj in the folder tutorial files 3 Use the cutting plane function to view the horizontal section or vertical section of the jet and examine some characteristics of jet cross section 35 i ii Click toolbar E or press the right mouse button and select the type of plane to display the cutting plane in Cutting plane parameter window a Horizontal cutting plane For example by selecting the Horizontal plane and inputting the desired distance 12 m you will get a cutting horizontal plane located at z 12 m You can also locate the cutting plane by directly clicking at any position at the jet section you like b Vertical cutting plane You may obtain the cutting vertical plane in a similar manner by selecting the Vertical plane for example by selecting the Vertical plane Side View and inputting desired distance 3 m a cutting vertical plane located at y 3 m will be obtained for the Vertical plane Cross section View selection and inputting the distance 5 m a cutting vertical plane located at x 5 m is obtained c Normal and arbitrary cutting plane You can obtai
7. Symposium on Environmental Hydraulics Hong Kong Lee J H W and Cheung Y K ed December 1991 Vol 1 Balkema pp 243 248 Horton P R Lee J H W and Wilson J R 1997 Near field JETLAG modelling of the Northwest New Territories Sewage Outfall Urmston Road Hong Kong Proc 13th Australasian Coastal and Ocean Engineering Conference Pacific Coasts and Ports 97 Christchurch New Zealand Sept 97 Vol 2 pp 561 566 10 Lam K M and Chan H C 1997 Round jet in ambient counterflowing stream Journal of Hydraulic Engineering ASCE Vol 123 10 pp 895 903 Lee J H W and Neville Jones P 1987 Initial dilution of horizontal jet in crossflow Journal of Hydraulic Engineering ASCE Vol 113 HY5 pp 615 629 Lee J H W and Neville Jones P 1987 Design of sea outfalls Prediction of initial dilution and plume geometry Proceedings of the Institution of Civil Engineers Part 1 Design and Construction Vol 82 pp 981 994 Lee J H W and Cheung V 1990 Generalized Lagrangian model for buoyant jets in current Journal of Environmental Engineering ASCE 116 6 1085 1105 Lee J H W and Chu P C K 1995 Application of video image processing in the study of environmental flows Proc 10th ASCE Engineering Mechanics Conference University of Colorado Boulder Vol 2 pp 1014 1017 Lee J H W Rodi W amp Wong C F 1996 Turbulent line momentum puffs Journal of En
8. University Massachusetts Institute of Technology McGill University Monterey Institute of International Studies National Center for High Performance Computing Taiwan National Institute of Water amp Atmospheric New Zealand National Taiwan University National Water Research Institute Canada NATO Saclant Undersea Research Centre OGI School of Science amp Engineering Rutgers University Seoul National University South China Sea Institute China The Department of Environmental Protection Australia The Hong Kong Polytechnic University The University of Hong Kong The University of Queensland Tianjin University Tongji University Tsinghua University Universidade Do Porto University of Alberta University of Arizona University of Canterbury University of Hawaii University of Karlruhe University of Michigan University of Southern California University of Toronto University of Wisconsin Madison Univ Metropolitana Venezuela Consulting Engineering Firms Applied Science Associates USA Atkins China Ltd HK Battelle USA CDM International Inc CH2M HILL Joiner Engineering Montgomery Watsons HK Ltd Mott Connell Ltd HK Mouchel Asia Ltd HK Patterson Britton amp Partners Australia Tetra Tech Inc Other Individual Users From Australia Brazil Canada Germany Greece India Iran Italy Korea New Zealand Portugal P R China Taiwan China Saudi Arabia United Kingdom USA Venezuela
9. a bent over jet in crossflow Proc 11th ASCE Engineering Mechanics Specialty Conference Fort Lauderdale Florida May 1996 pp 910 913 Chu P C K Lee J H W and Chu V H 1999 Spreading of a turbulent round jet in coflow Journal of Hydraulic Engineering ASCE Vol 125 No 2 pp 193 204 Chu V H and Goldberg M B 1974 Buoyant forced plumes in crossflow J Hydraulics Div ASCE Vol 100 HY9 pp 1203 1214 Chu V H 1977 A line impulse model for buoyant jets in a crossflow in Heat Transfer and Turbulent Buoyant Convection Spalding D B ed Hemisphere Washington D C Vol 1 pp 625 636 Chu V H 1994 Lagrangian scalings of jets and plumes with dominant eddies in Recent Research Advances in the Fluid Mechanics of Turbulent Jets and Plumes NATO ASI Series E Applied Sciences Vol 255 Davies P A and Valente Neves M J eds Kluwer Academic Publishers Dordrecht pp 45 72 Chu V H and Lee J H W 1996 A general integral formulation of turbulent buoyant jets in crossflow Journal of Hydraulic Engineering ASCE Vol 122 No 1 pp 27 34 Fischer H B etal 1979 Mixing in Inland and Coastal Waters Academic Press San Diego California Frick W E 1984 Non empirical closure of the plume equations Atmospheric Environment Vol 18 No 4 pp 653 662 Gordon A D and Fagan P W 1991 Ocean outfall performance monitoring in Proceedings of the International
10. flow Hong Kong Strategic Sewage Disposal Scheme SSDS 5 Advanced graphics features for experienced users 5 1 Main components 5 1 1 Toolbar 5 1 2 Cross section view 5 1 3 3D outfall view 5 1 4 Result data view 5 2 Graphics manipulation 5 2 1 Actions 5 2 1 1 Zoom 5 2 1 2 Move 5 2 1 3 Rotate 5 2 1 4 Cutting plane 5 2 1 5 Pick 5 2 1 6 Solid animation 5 2 1 7 Particle tracing 5 2 1 8 Refresh 5 2 2 Option 5 2 2 1 Fast display mode 5 2 2 2 Display cutting plane 5 2 2 3 Show concentration change 5 2 2 4 Show velocity change 5 3 Option menu command 35 37 40 42 43 1 Introduction 1 1 VISJET Visualization and Lagrangian Modeling for rosette plumes in an ambient current For environmental impact assessment and outfall design studies it is desirable to take into account the effect of an ambient current on the initial mixing of buoyant wastewater discharges The prediction of the concentration or dilution of a pollutant or passive scalar along the unknown jet trajectory of a buoyant effluent discharge is a complicated fluid mechanics problem which is not fully resolved In particular there are very few mathematical models which can treat satisfactorily a three dimensional jet trajectory such as a horizontal jet into a perpendicular cross flowing tidal current a common outfall design configuration For impact assessment post operation monitoring and risk analysis it is necessary to have a model that is capable
11. freshwater Compute the mixing for this discharge which is inclined at 20 degrees to the horizontal and compare your computed results with the corresponding observed jet in a laboratory experiment The main parameters are as follows Ambient parameters Depth below surface m Density Sigma t or Density g ml 0 18 0 1 018 7 18 0 1 018 Current velocity 0 0 m s Current Angle 90 N B density g ml 1 0 001 Sigma t Outfall parameters Depth 9 0m Density 1 004 g ml Sigma t 4 unit Riser Parameters Distance Om T Radius 0 05m B Radius 0 05m Height 2m Jet Parameters Flow 0 00626 m s Diameter 0 1m Port height 2m Vertical angle 20 Horizontal angle 0 General Notes 1 Animate the jet evolution and compare the computed results with the corresponding observed jet in a laboratory experiment Note the irregular edge of the real turbulent jet the model computes only the average turbulent mean properties 2 Click View suspend file More info in data output window to see the printout of the computed results in a SUSPEND file 3 The SUSPEND file shows key input parameters and length scales that govern the mechanics of buoyant jet mixing For example Total Q 0 00626 m s jet velocity 0 8 m s Jet densimetric Froude number F4 6 86 22 4 The following is the observed dyed jet of the Wah Fu outfall discharge in this experiment the jet is a 1 11 scale model of the actual outfall discharged
12. specified by the user The meanings of the angles are shown in the cutting plane parameters 5 2 1 5 Pick Select or press the right mouse button and select Pick Using the cursor the user can pick or select any point on the jets and display the computed properties of the disk including the centre s position radius thickness orientation concentration and velocities containing that point 5 2 1 6 Solid animation Select a The animation of the jet evolution will be re run 42 5 2 1 7 Particle tracing Select Tracer pattern following the fluid gives a feeling for the velocity at different elevations 5 2 1 8 Refresh Select The evolution process of the jets will be re run in the 3D Outfall View 5 2 2 Option 5 2 2 1 Fast display mode Press the right mouse button and select Fast Display The fast display mode has less demand upon the graphics capability of the computer and allows a faster response in changing the displayed graphics When displaying multiple jets the normal display mode has the transparent effect The user could tell which jet is far from him and which is near to him The fast display mode does not have the transparent effect the user would not see the jet which is hindered by the front one Also with the fast mode the user could not see the change of concentration on the jet 5 2 2 2 Display cutting plane Press the right mouse button and select Display Cutplan
13. will not be trapped and reach the free surface 8 Close this file to start the next tutorial or change the parameter values to create your own run 30 4 6 Example 5 Vertical dense jet in uniform cross flow The file is tut5 vj Consider a single vertical dense jet discharged into a uniform crossflow In some applications the jet or plume discharge is negatively buoyant i e the effluent discharge is heavier than the ambient fluid e g concentrated brine discharge from desalination plants The main parameters are as follows Ambient Parameters Depth 40m Density 0 9756 g ml Current velocity 0 2 m s Current Angle 90 Outtfall Parameters Depth 22m Temperature 0 C Density 1 g ml Riser Parameters Distance Om T Radius 0 05 m B Radius 0 05 m Height 2m Jet Parameters Flow 0 03 m s Diameter 0 1m Port height 2m Vertical angle 90 Horizontal angle 0 General Notes 1 Study how to modify input parameter based on file tut1 vj i Atthe startup window select Open open tut1 vj in the folder tutorial files ii Modify depth to 40 m and ambient density to 0 9756 g ml current to 0 2 m s in ambient parameter window and flow to 0 03 m s in jet parameters window iii Resimulate the model Click the toolbar save this file If you have problems you can open the file tut5 vj in the folder tutorial files For this case the ambient density pa 0 9756 g ml is less than the jet density pj 1g ml itis
14. 999 which handles an arbitrarily inclined round buoyant jet in a current with a three dimensional trajectory Since its inception around 1989 Lee and Cheung 1990 JETLAG has proved to be a robust model that has been applied and verified in many situations e g Cathers and Pierson 1991 Gordon and Fagan 1991 Horton et al 1997 see next section The model also includes a general formulation for jet mixing in a weak crossflow the near far field transition and has been validated against all available basic laboratory data including jets issuing into a counterflow Chan and Lam 1998 Lam and Chan 1997 Major advances in our understanding of jet plume in crossflow have been made possible in recent years with the development of non intrusive laser induced fluorescence LIF and digital image processing techniques and 2D 3D turbulence models Chu et al 1996 Chen and Lee 2000 Lee Kuang and Chen 2002 Lee Chen and Kuang 2002 These findings have been incorporated in the current version of JETLAG In particular a novel treatment of the transition from the jet olume dominated to the ambient current dominated regime is included The coflowing jet situation has also been entirely re modeled Lee et al 2000 These studies have also greatly facilitated the interpretation of the Lagrangian model predictions in relation to the complex bifurcated scalar field in the bent over phase of the buoyant jet 2 3 List of JETLAG VISJET Users and Prototype Outfal
15. Concentration Info window You will see that the concentration at a point where adjacent plume elements overlap is larger than that at a non overlap point because of the plume merging ii Click the jet number shown in input parameter window to get the jet cross sectional area area of this Lagrangian element for the selected jet the total plume area with overlapped area subtracted and sum of areas of the jets summation of the projected area of each individual jet in this cutting plane For example in this case with selecting Vertical plane cross section view and setting distance 16 m the area of jet1 jet2 jet3 jet4 jets and jet6 is 7 9 32 2 66 9 71 5 66 9 and 32 2m respectively the sum of the areas of the six jets is 277 6 m and total jet area in the plane is 214 7 m excluding overlap The ratio of the total jet area to the sum of areas is a measure of reduced dilution due to plume merging You can also obtain the composite dilution in the Cutting plane window Note the computed composite dilution is only valid up to the point where the plume surfaces or settles to an equilibrium level Create three identical six jet risers and observe the merging between adjacent jets and also between plumes from adjacent risers in both uniform flow and under stratified ambient conditions Create different orientations of the diffuser axis with respect to the current by changing the current angle in the ambient parameter window as well
16. D visualization is quite resource demanding so users need to have suitable computer hardware for running VISJET 2 0 with satisfactory performance The minimum system requirements are Pentium Il 400 MHz 128 MB RAM 100 MB free hard disk space Windows 98 SE ME NT 4 0 2000 and XP e Screen resolution 1024 x 768 supporting 16 bit high colour e 3D graphics board with 4 MB memory To ensure a reasonable performance some of the special virtual reality features such as the disturbance of the water surface and the more realistic atmosphere representation are turned off by default if your system only satisfies the minimum requirements To run VISJET 2 0 with all the special visualization features switched on it is recommended that your system should have e Pentium Ill 1 GHz e 256 MB RAM e 3D graphics board with 16 MB memory Running VISJET 2 0 will take up at least 20 MB memory More memory will be used up when greater number of jets is modeled for 20 jets 39 MB memory will be occupied Also displaying the cut plane will require much more memory during the creation process for 20 jets 80 MB memory is needed at the peak Therefore when working with a large number of jets users should make sure that sufficient memory is available In most cases the user will probably be working with less than 20 jets The VISJET file with an extension vj has a minimum size of about 100 KB With 20 jets the file size will increase up to about 3 MB
17. VISJET 2 0 User Manual 1 Introduction 1 1 VISJET Visualization and Lagrangian Modeling for rosette plumes in an ambient current 1 2 Summary of graphics features 1 3 VISJET main window layout 1 4 Notes on system requirements for using VISJET 2 0 2 JETLAG 2 1 JETLAG Introduction 2 2 The origin of JETLAG 2 3 List of JETLAG VISJET users and prototype outfall applications 2 4 Output file SUSPEND 2 5 References 3 User Interface 3 1 Input parameters 3 1 1 Ambient parameters 3 1 2 Outfall parameters 3 1 3 Riser parameters 3 1 4 Jet parameters 3 1 5 Cutting plane parameters 3 2 Output parameters 3 2 1 Key parameters and length scales 3 2 2 Disk information 3 2 3 Cross section concentration 3 2 4 Cross section area information 4 Tutorial Examples 4 1 Example 1 Vertical buoyant jet in stagnant fluid 4 2 Laboratory Example Wah Fu Outfall Discharge 4 3 Example 2 Horizontal buoyant jet in stagnant stratified fluid 4 4 Example 3 Multiple buoyant jets in stagnant fluid 4 5 Example 4 Vertical buoyant jet in stratified crossflow 4 6 Example 5 Vertical dense jet in uniform crossflow 4 7 Example 6 Horizontal buoyant jet in uniform crossflow Zarautz Marine Outfall Spain ROM a gt ONO O 12 17 20 22 24 27 29 31 33 4 8 Example 7 Horizontal buoyant jet in stratified crossflow Zarautz Marine Outfall Spain 4 9 Example 8 Buoyant jets from a rosette shaped ocean outfall riser in natural
18. a negatively buoyant discharge On the screen you will see the dense plume first moves upwards due to its initial momentum reaches a maximum height and then bends downwards to reach the seabed 2 Open the SUSPEND file Click View suspend file in menu More info in Data output window to see the computed results the buoyant jet center maximum rise height 2 69 m and corresponding average dilution 43 9 Plume hits the seabed z 20 0 m with average dilution 4865 31 Click Disk in Data output window the information on the Lagrangian elements disks is shown For example the disk 703 located at 8 3557 0 1 288 has the following properties visual radius 1 50 m thickness 0 0027 m vertical angle 19 6 horizontal angle 0 average velocity 0 21 m s maximum concentration 0 022 average dilution 98 6 and average concentration 0 0101 Close this file to start the next tutorial 32 4 7 Example 6 Horizontal buoyant jet in uniform crossflow Zarautz Marine Outfall Spain The file is tut6 vj Consider a single horizontal buoyant jet discharged into a perpendicular uniform crossflow Since the direction of jet momentum is different from the direction of buoyancy in the presence of the crossflow the jet has a three dimensional trajectory The main parameters are as follows Ambient Parameters Depth 32 75 m Density 1 0256 g ml Current velocity 0 2 m s Current Angle 90 Outfall Parameters Depth 34 75 m
19. age dilution 213 5 When will the plumes from adjacent risers merge Decrease the distance between risers to find the pattern of plume interaction 6 Close this file to start the next tutorial or change parameter values to create your own run 28 4 5 Example 4 Vertical buoyant jet in stratified crossflow The file is tut4 vj Consider a single vertical discharge into a horizontal crossflow of uz 0 1 m s at a depth of 14 m below the free surface The receiving water is linearly stratified The main parameters are as follows Ambient Parameters Depth below surface m Density Sigma t 0 0 22 9 14 0 25 0 Current velocity 0 1 m s Current Angle 90 Outfall Parameters Depth 16m Temperature 0 C Density 1 g ml Riser Parameters Distance 20m T Radius 0 05 m B Radius 0 05 m Height 2m Jet Parameters Flow 0 0147 m s Diameter 0 1m Port height 2m Vertical angle 90 Horizontal angle 0 General Notes 1 2 Click Open in the startup tips window then select and open file tut4 vj in the folder tutorial files Animate the jet Click the toolbar evolution and observe how the jet is bent over into a trapped submerged layer Click View suspend file in menu More info in Data output window to see the printout of the computed results in a SUSPEND file In the SUSPEND file you will find some information about trap level For this case the neutral buoyancy level 4 85 m with a corresponding average dilution
20. any applications followed by more complicated situations The first example is for a single vertical buoyant jet discharge into an otherwise stagnant fluid For a single jet the riser flow is the same as the jet flow The main parameters are as follows Ambient Parameters Depth 20m Density 1 0256 g ml Current velocity 0 0 m s Current angle 90 Outfall Parameters Depth 22m Temperature 0 C Density 1 0 g ml The density of the effluent is entered as input There are two possible formats i if density is input directly a zero value 0 0 must be entered for temperature ii alternatively both the temperature and salinity of the effluent can be entered as input and the effluent density will then be computed by the model Riser Parameters Distance Om T Radius 0 05 m B Radius 0 05 m Height 2m For single jet the riser distance is immaterial set to zero Jet Parameters Flow 0 03 m s Diameter 0 1m Port height 2m Vertical angle 90 Horizontal angle 0 General Notes 1 Study how to input parameters i Click New in the startup tips window ii Click Add a level twice input ambient parameters as shown above 20 iii Click Next select Create a scenario with riser Then click Create an outfall and click Outfall_1 and input the above outfall parameters iv Click Riser1 input the above riser parameters v Click Jet1 input the above jet parameters vi Click Finish If you have problems with th
21. ap level the computation will be stopped after the first oscillation in VISJET at trapped level 5 41 m corresponding average dilution 53 9 and visual radius 1 61 m Close this file to start next tutorial or change input parameters to make your own run 25 The following shows two examples of real life examples of a plume or buoyant jet in stagnant fluid i the trapped smoke plume from the Lamma Island power station in the early morning when there was a temperature inversion ii laboratory experiments of a plane two dimensional vertical buoyant jet in linearly stratified fluid Smoke plume from Lamma Island Power Station trapped in atmospheric inversion layer 26 4 4 Example 3 Multiple buoyant jets in stagnant fluid The file is tut3 vj Consider the horizontal buoyant jet example in Tutorial 1 again but this time instead of using one jet divide the flow of 0 03 m s into 4 jets each discharged from a different riser So now we have FOUR horizontal buoyant jets in a uniform stagnant fluid but each port discharges 1 4 of the original flow The main parameters are as follows Ambient Parameters Depth 20m Density 1 0256 g ml Current velocity 0 0 m s Current Angle 90 Outfall Parameters Depth 22m Temperature 0 C Density 1 0 g ml Riser Parameters Distance O m riser1 20 m riser2 40 m riser3 60 m riser4 T Radius 0 05 m B Radius 0 05 m Height 2m The distance from the most offshore end
22. as multiple diffusers Try to explore all the functions on the preceding tutorials 1 7 38 The following photo shows the observed jet mixing of an 8 jet rosette jet group in a laboratory experiment Congratulations You have successfully finished all the tutorials 39 5 Advanced graphics features for experienced users 5 1 Main components 5 1 1 Toolbar a parkea The toolbar can be moved around the whole screen and provides quick access to various actions for manipulating the images in the 3D outfall View and the Cross Section View Click To move zoom X rotate cutting plane al pick m solid animation H particle tracing refresh 5 1 2 Cross section view The Cross Section cutting plane projection View shows the cross sections of the buoyant jets projected on the cutting plane The jet sections are coloured Moving the mouse or pointing device inside the panel and click this view will be selected Moving the mouse with the left button being pressed down the cross section will be zoomed in or out Moving the mouse with the left button and the key CTRL being pressed down you can drag the cross section into any position in this view 40 5 1 3 3D outfall view This view provides the users with the 3D animation of the jets simulated Users can obtain different look of the jets from different angles 5 1 4 Result data view WD Posten and Concermation to x hoa jy ows z Concerrati
23. at the same jet densimetric Froude number of 6 8 23 4 3 Example 2 Horizontal buoyant jet in stagnant stratified fluid The file is tut2 vj The ambient receiving water often has a vertical variation of salinity and or temperature leading to density stratification The jet may cause so much mixing that the mixed effluent stays trapped below the free surface In this example we compute the mixing for a horizontal buoyant jet in a stratified fluid The main parameters are as follows Ambient Parameters Depth below surface m Density Sigma t 0 8 0 1 8 4 4 11 0 7 12 2 10 13 2 13 15 3 16 16 5 19 16 6 20 16 6 N B Density g ml 1 0 001 Sigma t Current velocity 0 0 m s Current Angle 90 Outfall Parameters Depth 22m Temperature 0 C Density 0 999 g ml Sigma t 1 unit Riser Parameters Distance Om T Radius 0 05 m B Radius 0 05 m Height 2m Jet Parameters Flow 0 0147 mes Diameter 0 125 m Port height 2m Vertical angle 0 Horizontal angle 0 General Notes Density g ml 1 008 1 0084 1 011 1 0122 1 0132 1 0153 1 0165 1 0166 1 0166 1 Click Open in the startup tips window then select and open file tut2 vj in the folder tutorial files 2 The density variation of the ambient fluid can be specified in either of the following two ways i the salinity and temperature at each depth are entered from which the density will be computed by the model by the equation of state ii
24. e The cutting plan can be displayed or hidden 5 2 2 3 Show concentration change Press the right mouse button and select Show Concentration Change Display the change in concentration by gradual change in colour 5 2 2 4 Show velocity change Press the right mouse button and select Show Velocity Change Display the change in velocity by gradual change in colour 5 3 Option menu command The Option Menu offers the following commands Animation speed Select the animation speed among fast medium and slow Continuous mode Require the simulation to continue up to the maximum simulation step Max number of steps Allow the user to specify the maximum number of simulation steps default no is 1500 Disturbance of the Show or stop the animated disturbance of the water surface water surface Water surface Allow the user to change the display properties of the water surface property 43
25. e input parameters you can open the file tut1 vj in the folder tutorial files to examine the correct input parameters Click Outfall_1 Riser_1 and Jet_1 to observe the input parameters Use the animation function to see the evolution and spread of the jet Click toolbar to see the rise and growth of the jet from the discharge port to water surface In the Lagrangian model the jet path is made up of a series of plume elements disks which vary in position width and velocity as they mix with the surrounding fluid Study how to get the jet characteristics of each Lagrangian element information about the computed average velocity maximum concentration and average dilution at that height i Select toolbar 4or press the right mouse button and select Pick ii Putcursor at any point on the jet you want to get the information in the data output window iii Move scroll bar up or down at the right of the data output window to choose the disk number For example the center of Disk 46 is located at 0 0 0 11 visual radius 0 048 m thickness 0 037 m vertical angle 90 horizontal angle 0 average velocity 2 8 m s maximum concentration 1 0 average dilution 1 4 and average concentration 0 7332 The dilution is a measure of the degree of mixing achieved by the jet the inverse of dilution is the relative concentration of any pollutant contained in the discharge Save file you can select Save as in main menu Fi
26. ed disk will be displayed Disk no The sequence no of the selected computed disks for the selected jet Centre position The x y z co ordinates of the center of the selected disk which is the computed jet trajectory Radius Jet half width of the selected disk Thickness Thickness of the selected disk Angle Vertical angle is the angle between the jet axis and the horizontal plane horizontal angle is the angle between the x axis and the projection of the jet axis on the horizontal plane Velocity Jet velocity of the selected disk Concentration Maximum average concentration of the selected disk 17 3 2 3 Cross section concentration The following information related to the cross section concentration will be displayed Position The x y Z co ordinates at the position of the point selected by the mouse or pointing device Concentration Average concentration at the above position 3 2 4 Cross section area information The following information related to the projected area of the jets will be displayed Total area The total projected area of the jets on the cutting plane the overlapped areas are not double counted Sum of areas The sum of all the projected areas of the individual jets Selected jet area The projected area of the selected jet Horizontal span The horizontal span of the projected region for the selected jet defined by bounding box Vertical span The vertical span of the projected region for the selected je
27. flow of the riser All jets discharge horizontally vertical angle 0 only the horizontal jet discharge angle relative to the current is different 0 coflow 90 perpendicular crossflow 180 counterflow Use the animation function to see the computed rosette jet group pattern and how different jets merge with each other Click the toolbar to see active process of evolution and spread of the jet from source to trapped level Use the Rotate Zoom and Move functions to view the jet cross section from different angles Observe how the plumes can merge with each other even kinematically The merging of the multiple plumes is related to the definition of near field dilution and mixing zone in environmental impact assessment View the jet from a horizontal plane and in a vertical section i Click toolbar and select Horizontal plane or Vertical plane with desired distance and input data in Cutting Plane window For example by selecting Vertical plane cross section view and setting distance 16 m you will get a cutting vertical plane and this plane is also shown in small window in the screen Cross Section ii Click any point in Cross Section window then you can use toolbar Q to zoom the plane or use toolbar P to move the plane in Cross Section window View some characteristics of jet cross section i Put the cursor on any blue point in Cross Section window you will get the position of this point and concentration in
28. gineering Mechanics ASCE 122 19 29 Lee J H W and Chu P C K On the added mass of a turbulent jet in crossflow Proc 27th IAHR Congress August 1997 San Francisco Vol 1 it Environmental and coastal hydraulics pp 269 274 Lee J H W and G Q Chen The jet in crossflow and the puff analogy Proc 12th ASCE Engineering Mechanics Conference La Jolla California May 17 20 1998 H Murakami and J E Luco Ed pp 1792 1795 Lee J H W Li L and Cheung V 1999 A semi analytical self similar solution of a bent over jet in crossflow Journal of Engineering Mechanics ASCE Vol 125 pp 733 746 Lee J H W Cheung V Wang W P and Cheung S K B Lagrangian modeling and visualization of rosette outfall plumes Proc Hydroinformatics 2000 lowa July 23 27 2000 CDROM Lee J H W Kuang C P and Chen G Q 2002 The structure of a turbulent jet in crossflow effect of jet to crossflow velocity China Ocean Engineering Vol 16 No 1 pp 1 20 Lee J H W Chen G Q and Kuang C P 2002 Mixing of a turbulent jet in crossflow the advected line puff in Environmental Fluid Mechanics theories and applications Ed H Shen et al American Society of Civil Engineers in press Muellenhoff W P et al 1985 Initial mixing characteristics of municipal ocean discharges Report EPA 600 3 85 073 USEPA Newport Oregon Schatzmann M 1981 Mathematical modeling of submerged disc
29. harges into coastal waters Proc 19th IAHR Congress New Delhi Vol 3 pp 239 246 Wood I R 1993 Asymptotic solutions and behaviour of outfall plumes J Hydr Eng ASCE Vol 119 pp 555 580 Wright S J 1977 Effects of ambient crossflow and density stratification on the characteristic behavior of round turbulent buoyant jets Report No KH R 36 W M Keck Lab of Hydr and Water Resour California Inst of Tech Pasadena Calif 11 3 User Interface 3 1 Input parameters 3 1 1 Ambient parameters Specify the vertical structure of the ambient water Name Meaning Depth Depth below surface m Salinity Density Ambient salinity ppt or psu if temperature not equal to 0 Ambient density g ml if temperature 0 Temperature Ambient temperature C Current Horizontal current speed m s assuming in the x direction Notes Acceptable range Salinity 0 100 ppt psu Density 0 5 1 5g ml 0 100 C Only stable ambient stratification is allowed i e p di lt pa dj if dj lt dj d depth below free surface 12 3 1 2 Outfall Parameters Specify the properties of the outfall Outfall parameters with riser Name Depth Salinity Density Temperature Length Width diameter Meaning Depth below surface m Effluent salinity ppt or psu if temperature not equal to 0 Effluent density g ml if temperature 0 Effluent temperature C Length of the ou
30. l Applications The Lagrangian model JETLAG VISJET has been extensively validated against laboratory experimental data of buoyant jets in a crossflow by many investigators It has also been verified in field experiments and applied to a number of actual outfall studies The users and applications include Sydney Deepwater Ocean Outfall post operation environmental monitoring study Zarautz Marine Outfall Spain Shek O Outfall beach pollution study Urmston Road Sewage Outfall Northwest New Territories Hong Kong post operation monitoring study Hong Kong Strategic Sewage Disposal Scheme SSDS Environmental Impact Assessment Project Shanghai Stage 2 Sewage Outtfall North Point Outfall Hastings Outfall Sidmouth outfall Gosport outfall Jaywick outfall United Kingdom Stonecutters Island Interim Outfall Harbour Area Treatment Scheme HATS Bhabha Atomic Research Centre Isotope Division Trombay India List of Users Academic Institutions Alaska Department of Environmental Conservation British Columbia Government California State Water Resources Control Board City University of Hong Kong Clarkson University Duke University Fisheries and Oceans Canada Goddard Earth Sciences Technology Center NASA Goddard Space Flight Center Hong Kong University of Science and Technology Indian Institute of Technology Bombay Iran University of Science and Technology Korea Ocean Research and Development Institute Loughborough
31. le The angle between the projection of the normal vector on the horizontal plane and the flow direction x axis 90 for a vertical section side view and 0 for a vertical section cross section view Distance Distance from the discharge point No greater than 25 times of water depth 16 3 2 Output parameters 3 2 1 Key parameters and length scales The following are the key parameters and length scales for each jet Depth Port depth m Diameter Port diameter D m U Initial jet velocity Uj m s Ua Ambient current velocity Ua m s Dp pa Dimensionless initial density difference pa 0 pj pa 0 Pj Initial effluent density g ml Pa Ambient density at source level pa 0 g ml Ver Ang Vertical discharge angle degree Hor Ang Horizontal discharge angle 8 degree Fd Jet Densimetric Froude no F Vj gD pa 0 p pa 0 Qj Volume flux discharge flow Q Vj nD 4 m s M Momentum flux M Vj nD7 4 m s B Buoyancy flux Qg pa 0 p Pa 0 m s la Discharge volume geometric length scale la Q M m Im Cross momentum length scale Im M7 U5 m lb Cross buoyancy length scale B U m Im Jet plume length scale Im M B m Sm Characteristic dilution for momentum dominated far field mdff Sm Ua Im Q S Characteristic dilution for buoyancy dominated far field bdff S Ua lb Q 3 2 2 Disk information The following information about the comput
32. le to save the file file format vj for later reuse or modification Compute a horizontal buoyant jet in stagnant fluid based on this case You just need to change the vertical angle 90 to 0 in the input jet parameters resimulate the model Click the toolbar then save this example If you have problems you can open the file tut1a vj in the folder tutorial files Notice the dilution is increased for this jet as the length of the jet path is greater than that of the vertical jet at the same vertical position For example Disk 296 the disk center is located at 2 03 0 0 11 visual radius 0 27 m thickness 0 0066 m vertical angle 8 4 horizontal angle 0 average velocity 0 50 m s maximum concentration 0 226 and average dilution 7 5 You can also predict the jet from an actual outfall and compare it with observations in a laboratory experiment You can also try the Create a scenario without riser at 1 iii Close this file to start next tutorial 21 4 2 Laboratory Example Wah Fu Outfall Discharge The file is WahFu vj Consider the Wah Fu Outfall which discharges domestic wastewater from a housing estate in the form of a number of submerged buoyant jets at a depth of about 7 12 m The jets are sufficiently spaced apart so that they may be considered independent of each other In this development salt water is used for flushing so that the jet discharge is brackish water i e a mixture of sea water and
33. lve Realism of ambience External factors such as direction of ambient flow currents and reference objects are displayed to provide a proper context for the data to be visualised Colour coding Colour is assigned to the jet according to the effluent concentration Data interrogation If the user wishes to know about data values defined at a point on a jet such as velocity or concentration it is possible to locate the point of interest with a pointing device to interactively retrieve the data required Jet inspection by intersection The user can use a cutting plane at different positions to intersect the jets and observe the resulting sections This is helpful in understanding how the jets merge and in computing composite dilution accounting for jet merging 1 3 VISJET Main window layout The Main components in the VISJET window xham y ows 2 70n Concertraion 0 Cutting Plane O Horizoritsl plane Bove Iese Rotate v Plane Pick wf v Displey Cut Plane v Simulation Concentratian Simulation Velocity Display Mede The right panel is for data input The left panel is for the 3D graphic output or Outfall View The top part of the middle panel shows the projection on the cutting plane The lower part provides the numerical results of the simulation The toolbox allows the user to manipulate the view of the graphic outputs and the cutting plane 1 4 Notes on system requirements for using VISJET 2 0 1 3
34. m outfall depth If the input variables are outside the specified range then the upper lower limit will be assumed 14 3 1 4 Jet parameters Specify the properties of the jet Name Flow Diameter Port Height Vertical angle Horizontal angle Salinity Density Temperature Notes Meaning Acceptable range Effluent flow from the port No less than 1 0E 8m s m s Port diameter m No less than 1 0E 4m Port height m No greater than riser height Vertical jet discharge angle relative to Horizontal plane 90 for a vertical port Horizontal angle of current direction with respect to jet discharge 90 fora perpendicular crossflow Effluent salinity ppt if Salinity 0 100 ppt temperature not equal to 0 Effluent density g ml if Density 0 5 1 5g ml temperature 0 Read only Effluent temperature 0 100 C C Read only If the input variables are outside the specified range then the upper lower limit will be assumed 15 3 1 5 Cutting plane parameters A cutting plane in VISJET is defined by its normal vector The orientation of the normal vector is defined by the vertical and horizontal angle as in the JETLAG model refer to How To under Startup Tips The control parameters for the cutting plane Vertical angle The angle of the normal vector of the cutting plane relative to horizontal plane 90 for a horizontal plane 0 for vertical plane Horizontal ang
35. n the cutting plane normal to the jet trajectory by selecting the Normal plane and inputting Disk No The user can also define a cutting plane by specifying the horizontal and vertical angle of the plane in the H Angle and V Angle The cross section of the jet cut by this plane is also shown in the small window on the screen which is called Cross section window Put the cursor in any point in the gray Cross section you will get the position of this point and the concentration in Concentration Info window The area of the jet cross section is shown in the Area window Click any point in Cross section window then you can use toolbar Q to zoom the Cross section or toolbar gt to move the Cross section Use Continuous Mode to continue computation of the buoyant jet spread after the jet is trapped by stratification i i ii Select Continuous Mode in main menu Option Resimulate the model Click the toolbar E Show the spread of jet Click the toolbar Close this file to start next tutorial 36 4 9 Example 8 Buoyant jets from a rosette shaped ocean outfall riser in natural flow Hong Kong Strategic Sewage Disposal Scheme SSDS The file is tut8 vj In modern ocean outfalls sewage effluent is often discharged through a number of adequately spaced outfall risers the effluent is discharged as a jet group from each of the risers in a rosette like pattern The planned ocean outfalls for the Hong Kong Strategic Sewage Disp
36. of giving predictions for an arbitrarily inclined buoyant jet in a crossflow covering the entire range of ambient current velocities and stratification conditions VISJET is a Windows based flow visualization tool to portray clearly the evolution and interaction of multiple buoyant jets discharged at different angles to the ambient current The modeling engine is a robust Lagrangian model JETLAG which has been tested extensively against theory basic laboratory experimental data field verification studies and applications It is aimed to facilitate the environmental impact assessment and outfall design studies It is able to 1 Predict the initial mixing of buoyant wastewater discharges in a current and 2 Communicate the predicted impact effectively to the user or stakeholder 1 2 Summary of graphics features The system has the following features Three dimensional graphics 3D colour graphics is used to display the spatial layouts of all jet trajectories The user can adjust the virtual viewpoint or viewing direction The 3D view is displayed instantly to give the user real time visual feedback The system supports zoom in and zoom out to allow the user to have a close up look at features of small scales Animation The evolution of jets and other time varying properties such as velocity can be displayed with special animation effects to enhance the understanding of the data displayed Users can have a sense on how the wastewater jets evo
37. on 0 l This panel displays the information resulted from the simulation These include the disk information the cross section concentration and area Information about the cutting plane is provided 41 5 2 Graphics manipulation 5 2 1 Actions 5 2 1 1 Zoom Select amp or press the right mouse button and select Zoom By moving the cursor upward you can zoom out from the current setting By moving the cursor downward you can zoom in towards the centre of current setting 5 2 1 2 Move Select F or press the right mouse button and select Move Simply using the mouse or pointing device will allow you to move the viewing window to where you want 5 2 1 3 Rotate Select amp or press the right mouse button and select Rotate By moving it in the vertical direction rotation can be made about the horizontal axis running along the screen If the cursor is moved in the horizontal direction rotation will be made about the vertical axis running along the screen 5 2 1 4 Cutting plane Select E or press the right mouse button and select Plane Five options are provided when defining a cut plane 1 Horizontal plane the plane parallel to the surface of the sea 2 Front vertical plane the plane parallel to the current 3 Side vertical plane the plane normal to the current 4 Normal plane the cross section plane normal to the jet trajectory 5 User specified plane two angles need to be
38. osal Scheme SSDS as well as the Shanghai Sewage Project Outfall are examples of outfalls of this type The main parameters for the SSDS outfall with a six jet group are as follows Ambient Parameters Depth m Salinit t Temperature C 0 25 5 27 7 5 5 31 2 27 8 11 33 7 25 0 16 5 34 2 23 6 22 34 5 23 0 Current velocity 0 2 m s Current Angle 90 N B The salinity is expressed in parts per thousand ppt Outfall Parameters Depth 24 0m Temperature 25 C Salinity 10 ppt Riser Parameters Flow 0 94164 m3 s Distance Om T Radius 1 5m B Radius 2m Height 3m Jet Parameters jet 1 jet 2 jet 3 jet 4 jet 5 jet6 Flow m s 0 15694 0 15694 0 15694 0 15694 0 15694 0 15694 Diameter m 0 25 0 25 0 25 0 25 0 25 0 25 Port height m 2 2 2 2 2 2 Vertical angle 0 0 0 0 0 0 Horizontal angle 0 60 120 180 240 300 Salinity ppt 10 10 10 10 10 10 Temperature C 25 25 25 25 25 25 General Notes 37 In the Cutting plane window the user can obtain a Composite dilution for merged bent over jets when the Vertical plane cross section view is selected At the startup window select Open open tut8 vj in the folder tutorial files In this case the measured salinity and temperature at different depths are used as input linear variation is assumed between the consecutive adjacent levels The sum of the six jet discharge flows is equal to the
39. riser is indicated above the spacing between two adjacent risers is 20 m Jet Parameters Flow 0 0075 m s Diameter 0 1m Port height 2m Vertical angle 0 Horizontal angle 0 General Notes 1 You can also change the orientation of the diffuser axis with respect to the current by changing the default current angle 90 in the ambient parameter window 2 Click Open in the startup tips window then select and open file tut3a vj in the folder tutorial files 3 Do the following to add three new risers with one jet on each riser i Highlight Riser1 click Add riser2 and the jet from this riser will be created ii Highlight the new riser and its jet1 input the corresponding parameters then specification of the riser and the associated jet will be completed 27 iii Repeat the procedure to create other two risers and their associated jets Resimulate the model Click the toolbar then save this file Use the animation function Click the toolbar to see the evolution and spread of the jets If you have any problems you can consult tut3 vj to look up the correct input parameters 4 Open the SUSPEND file Click View suspend file in menu More info in Data output window to see the results and determine the dilution for this case of multiple jets You will find that each jet achieves an average dilution at water surface 397 the water quality is significantly improved by this design compared with the case in tutorial 1 aver
40. t 18 4 Tutorial Examples 4 1 Example 1 Vertical buoyant jet in stagnant fluid 4 2 Laboratory Example Wah Fu Outfall Discharge 4 3 Example 2 Horizontal buoyant jet in stagnant stratified fluid 4 4 Example 3 Multiple buoyant jets in stagnant fluid 4 5 Example 4 Vertical buoyant jet in stratified crossflow 4 6 Example 5 Vertical dense jet in uniform crossflow 4 7 Example 6 Horizontal buoyant jet in uniform crossflow Zarautz Marine Outfall Spain 4 8 Example 7 Horizontal buoyant jet in stratified crossflow Zarautz Marine Outfall Spain 4 9 Example 8 Buoyant jets from a rosette shaped ocean outfall riser in natural flow Hong Kong Strategic Sewage Disposal Scheme SSDS 19 4 1 Example 1 Vertical buoyant jet in stagnant fluid The file is tut1 vj VISJET simulates the mixing of single or multiple buoyant jets discharged from one or more risers mounted on an ocean outfall In a particular application the input parameters for the ambient condition the outfall riser and jet characteristics are needed For example a single buoyant jet can be simulated by specifying a single jet on a single riser Multiple jets can be simulated by specifying a single jet on each of a number of risers Rosette jet groups on multiple risers can be simulated by specifying the multiple jet characteristics on each of the risers We start with several examples on how to use VISJET for simulating a single buoyant plume which is of interest in m
41. t al 1985 It uses a Lagrangian Projected Area Entrainment PAE concept to treat the buoyant jet in crossflow problem The model UOUTPLM has several important limitations a it can handle only jets with two dimensional trajectories e g vertical jet in crossflow b the shear entrainment hypothesis is incorrect c by virtue of the control volume formulation and the implementation of the entrainment computation the scheme can be unstable in regions of strong plume curvature d its connection with basic jet theory has not been established and e the interpretation of the model predictions in terms of the contaminant concentration field in the bent over jet is not clear Hence a great number of practical outfall discharge problems cannot be handled by JOUTPLM for example a horizontal buoyant jet in a crossflow dense plumes oblique jets and jet in coflow or counterflow Many outfalls located in shallow coastal waters around the world e g in SE Asia and in the UK fall into this category The prediction of mixing for these outfalls cannot be satisfactorily handled by the USEPA models Even within the category of jets with two dimensional trajectories the stated range of applicability for UOUTPLM is only VANG 5 to 90 where VANG is the initial discharge angle from the horizontal These significant limitations were removed in the newly developed and considerably more powerful JETLAG Lee and Cheung 1990 Cheung 1991 Cheung and Lee 1996 1
42. tfall m Width diameter of the outfall m Outfall parameters without riser Name Depth Temperature Salinity Density Length Radius Space between Jets Notes Meaning Depth below surface m Effluent temperature C Effluent salinity ppt or psu if temperature not equal to 0 Effluent density g ml if temperature 0 Length of the outfall m Radius of the outfall Outfall is defined as a pipe in this mode m Space between jets mounted on the outfall m Acceptable range Salinity 0 100 ppt psu Density 0 5 1 5g ml 0 100 C No less than 0 1m Acceptable range 0 100 C Salinity 0 100 ppt psu Density 0 5 1 5g ml No less than 0 1m No less than 0 001m If the input variables are outside the specified range then the upper lower limit will be assumed 13 3 1 3 Riser parameters Specify the properties of the riser Name Flow Distance Bottom radius Top radius Height Notes Meaning Sum of the effluent flow of all the ports mounted on the riser ms Distance from the offshore end of the outfall m Radius at the bottom of the riser m Radius at the top of the riser m The height of the riser m Acceptable range No less than 1 0E 8m s No greater than outfall length 2 bottom radius of riser O 5 width diameter of outfall 0 05 m 0 5 width diameter of outfall 0 01 m bottom radius of riser 0 1
43. the density is given directly in units of p g ml for this case the density is entered under the Salinity column in ambient parameter 24 window and a zero 0 0 value must be entered for temperature For this case the natural density stratification is represented by values given at 8 depths Animate the jet evolution and observe how the jet is trapped beneath the water surface Click View suspend file More info in data output window to see the printout of the computed results in a SUSPEND file The SUSPEND file shows key input parameters and length scales that govern the mechanics of buoyant jet mixing For example Total Q 0 0147 m s Densimetric Froude number Fa 8 22 Buoyancy flux Bj 0 0025 m s jet momentum length scale ly 0 97 and so on The computed jet characteristics co ordinates of the jet trajectory plume visual radius velocity concentration dilution etc are tabulated You will find some information about trap level For this case the neutral buoyancy level 5 1 m with a corresponding average dilution 38 1 and visual radius 1 14 m the buoyant jet center maximum rise height 7 1 m corresponding average dilution 41 1 and visual radius 2 58 m In the summer wet season the receiving water is often stratified and the sewage field may not reach the surface the submergence of the sewage may be desirable for protection of nearby beaches Notice that the computation can continue after the first tr
44. tum conservation of mass accounting for entrainment and conservation of mass heat all in a fixed reference frame The vortex entrainment is accurately determined while pressure drag is ignored The approach can also be shown to be equivalent to but more robust than the alternative of formulating and solving the Eulerian governing equations in natural co ordinates The model predictions have compared well with basic laboratory experimental data and it displays the correct asymptotic behaviour JETLAG reproduces the correct behaviour of i a round buoyant jet in stagnant or near stagnant fluid and ii a line puff impulse advecting at the ambient velocity in the bent over phase for momentum buoyancy dominated jets The current version of the model has been validated against experimental data by different investigators for straight jets and plumes vertical buoyant jet and dense plume in crossflow oblique momentum jet in crossflow horizontal buoyant jet in coflow horizontal buoyant jet in crossflow vertical buoyant jet in stratified crossflow coflow and counterflowing momentum jets buoyant plumes in weak current The detailed derivation of the model can be found in Lee and Cheung 1990 related studies and verification can be found in the references provided at the end of the user guide 2 2 The origin of JETLAG JETLAG has its roots in the model UOUTPLM initially developed by the United States Environmental Agency Frick 1984 Muenlenhoff e
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