File: README.TXT Visual Plumes Model System Readme Documentation Version 1.0 30 April 2001 14 August 2001 Update Center for Exposure Assessment Modeling (CEAM) National Exposure Research Laboratory - Ecosystems Research Division Office of Research and Development (ORD) U.S. Environmental Protection Agency (U.S. EPA) 960 College Station Road Athens, Georgia 30605-2700 706/355-8400 ----------------------------------------------------------------------------- >> Abstract << Visual Plumes is Windows software for simulating jets and plumes and for assisting in the preparation of mixing zone analyses, TMDLs, and other water quality applications. This file contains information to help you install and run Visual Plumes, as well as product news, including descriptions of recent additions and changes, hints, caveats, and other relevant comments. >> Table of Contents << Abstract Introduction System Requirements Installation Filename convention Project list file Support Hints Limitations Recent changes Earlier changes Troubleshooting Extra (optional) files Mixing zone course material: Introduction Mixing zone course material: Table of contents Mixing zone course material: Optional folders Example: Fan-Run-16 (optional exercise) Another optional example References >> Introduction << The U.S. EPA Visual Plumes model can be installed using either: 1) the Visual Plumes compact disk (CD-ROM) or 2) files downloaded from the U.S. EPA Center for Exposure Assessment Modeling (CEAM) Web site. Distribution and installation instructions are located in the Installation section below. Visual Plumes has passed peer review, i.e., it has been peer reviewed, the reconciliation process has been completed, and permission to disseminate Visual Plumes has been granted. Events accompanying "small-science" software development make it difficult to synchronize final versions of both software and the manual. For example, an update of the context-sensitive help is not available at this writing. The passage of time has given users time to identify problem areas and to request additions and changes. Consequently, some screen depictions shown in the manual (and other guidance) are no longer identical to current renditions. Until software and guidance are synchronous, it appears most appropriate to give the documentation a "draft" designation. The authors apologize for the problems associated with this situation and invite users to let EPA know the value of mixing zone modeling software and guidance so that more resources may be devoted to it in the future. The instructional material found in the folder entitled "Mixing zone course units" is based on the California State Water Resources Control Board mixing zone course (February 2000, presented by Walter Frick and Debra Denton) and subsequent similar courses. These materials are intended as classroom visual aids, however, they will hopefully also prove useful in an unassisted context. >> System Requirements << The Visual Plumes model is designed to operate in the Microsoft Windows environment. Properly configured it should run on Windows 95, 98, NT, or 2000 operating systems. >> Installation << An installation program must be executed before Visual Plumes will run correctly. The system can be installed from files downloaded from the U.S. EPA CEAM Web site (http://www.epa.gov/ceampubl/vplume.htm) or from CD-ROM. To install the Visual Plumes model distributed through the U.S. EPA CEAM Web site, simply download the self-extracting executable file INSTALL_VPLUMES.EXE from the following URL: http://www.epa.gov/ceampubl/vplume.htm. Save INSTALL_VPLUMES.EXE to a local drive on your target computer system. Execute INSTALL_VPLUMES.EXE by double-clicking the file using Windows Explorer or My Computer. Read and follow the prompts to automatically uncompress and the install the Visual Plumes model to your computer system. To install Visual Plumes from CD-ROM, run the installation file Setup.exe found in the "Visual Plumes (VP) Setup" folder. Read and follow the instructions presented by the setup program to install Visual Plumes to your computer system. Regardless of the installation medium (CD-ROM or Web download), it is recommended that you adopt the default folders and settings, creating a file folder called Plumes. When done, the VP executable, Plumes.exe, will be found in that folder. The name Plumes continues the DOS tradition. The executable can be renamed, for example, you might call it VP.exe. For updates normally only Plumes.exe will need to be replaced. The Visual Plumes model will be updated periodically. Check the U.S. EPA CEAM Web site (http://www.epa.gov/ceampubl/vplume.htm) for the most recent version. The update file, UPDATE_VPLUME.EXE, is available for download. Save UPDATE_VPLUME.EXE to a local drive on your target computer system. Execute UPDATE_VPLUME.EXE by double-clicking the file using Windows Explorer or My Computer. Read and follow the prompts to automatically uncompress and the install the file Plumes.exe to the "Plumes" folder on your computer system. Test run Plumes.exe. If you have problems it may be necessary to first change the Windows properties of the files. That is, before you access the example files you may have to first deselect their 'read only' property: in Windows Explorer, select all the project files (the project database files with extension .db, and project list files with extension .lst) and then right click: select Properties, and click off the Read-only option. The Visual Plumes user guide contains extensive information on the proper use of the model. The file USER_GUIDE.EXE is available for download from the U.S. EPA CEAM Web site (http://www.epa.gov/ceampubl/vplume.htm). Save USER_GUIDE.EXE to a local drive on your target computer system. Execute USER_GUIDE.EXE by double-clicking the file using Windows Explorer or My Computer. Read and follow the prompts to automatically uncompress and the install the file VP-Manual.pdf to the "Plumes\Manual" folder your computer system. For those installing the model system from CD-ROM, the user guide (VP-Manual.pdf) can be found in the "Visual Plumes Guidance" folder. >> Filename convention << Be aware of the new naming convention. For the main project file (which stores the diffuser table), it is the project name followed by .vpp.db, for example, MD-Pathogen.vpp.db (project name: MD-Pathogen, followed by project marker: .vpp, followed by database file extension:.db). There should be no periods in the project name itself. When opening a project from within VP, VP will only show the project names in the dialog box. The ambient files follow a similar format, a project name followed by .XXX.db, where XXX is a numeric sequence like 001, 002, etc., for example, MD-Pathogen.001.db or Winter-such-and-such.010.db. Note there can be many ambient files and, internally, a project might refer to ambient files from other projects. (Spaces are not recommended in the file name.) >> Project List file << Visual Plumes creates and maintains project "list" files. List files record many (but not all) customized settings. The list filename format is the project name followed by .lst, for example, MD-Pathogen.lst. (For advanced users, the time-series files follow a similar format.) >> Support << After trying VP, you may wish to call me at 706/355-8319 for a short phone tutorial. If you are doing official work you are always welcome to let me know so that I can provide the latest version of VP. Let me know if you have questions. (Email: frick.walter@epa.gov). >> Hints << In the ambient tab input table: to extrapolate below a pair of ambient data points an additional line reflecting deeper depths should be appended, even if depth is the only value on the line. This makes the appropriate changes to the ambient input table on the Text tab and stratification profile on the Graphics tab. A brief troubleshooting section is found in the manual. >> Limitations << Important: In the usual depth mode, a surface (zero depth, 0) line must be specified in the ambient table. Without this line the ambient array is not set up correctly. One user reported that VP does not run DKHW (and presumably other models) when installed in the E: partition. The same problem occurs when VP is installed as a subdirectory, as for example, to Program Files. >> Recent changes << * Additional controls on display of the input tables on the Text tab are found on the Special settings tab. The ambient table is now echoed. Display can show the tables filled in or only those numbers explicitly entered in the tables. The latter option makes the differences between runs more apparent. This selection is not recorded in the List file. * UM3 includes a new output criterion, the "matched energy radial vel[ocity]" message. For a plume in shallow water in which the radius becomes greater than the depth of the element, UM3 computes the depth and velocity at which the sum of the kinetic and potential energies in the plume element correspond to the total energy of flow out of an annulus (a cylinder with a vertical axis) surrounding the element. An experimental program is being developed to estimate additional dilution attained in the spreading region around plumes discharged vertical into shallow water (as, for example, large thermal discharges). For more information, call (see Support). * VP now does a better job creating DOS PLUMES VAR files. The biggest problem revolves around translating VP's three-dimensional input into DP's 2-D input. Fidelity between the two inputs is not always easy to establish because UM and UM3 are substantially different models. However, RSB output should still be identical. New users wishing to run DOS PLUMES should consult the DOS PLUMES guidance bundled with VP. * Corrected is a serious bug in the far-field 4/3-power-law solution. * VP now supports three graphics series: red, blue, and green. (Also, black for verification). * An exit-without-saving option has been added to the File menu. * VP now maintains a list of previously accessed projects on the File menu. * VP maintains more information in the list file, e.g., the graphics tick increment is now maintained. >> Earlier changes << These changes were made after the WA and OR mixing zone courses, Dec 2000, but before April 2001. * The farfield increment is now on the Special Settings tab, use it to control the number of intermediate steps between the acute and chronic mixing zone distances. * Input for the UM3 Taylor (aspiration) entrainment coefficient has been added to the Special Settings tab. * The second ordinate has been enabled on the Custom-graph-coords radio control box on the Special Settings tab. This allows output to a second y- axis on the Graphics tab (custom graphic). Control over the right axis is different from the other graphics settings. Instead of double-clicking in the margins of the graphics panel, the Right-axis settings button on the custom graphic is used to reveal the control panel for this axis (see next comment). * The Right-axis-settings button on the custom graph panel of the Graphics tab may be used to create the right axis and control the corresponding settings and values. When struck, the settings panel becomes visible. When satisfied with the settings, click the Show right axis radio button and strike the Apply settings button to show the right axis plots. The variable plotted is specified on the Special Settings tab (see previous comment). * As part of our effort to provide a common platform for several competing models to help researchers refine their products and to make it easier to compare models both between them and with verification, a "verification" capability has been added to VP. An example is available in the files associated with the Fan-Run-16 project, including the Fan16.txt verification data file. For further information see the note in the project's memo pad when running this example. Verification in x-y format can now be superimposed on Visual Plumes predictions on the Graphics tab. Clicking the "Verify" button gives access to ASCII input file. An example of file input data excerpted from the example Fan16.txt file is: side view 0.0001 1.0145 0.0068 1.0157 0.0149 1.0158 0.0197 1.0161 0.0264 1.0159 density profile 17.3 0.0 25.2 1.0 Blank lines will cause a space between data. The key words (side, profile, path, dilution, effdilution, concentration, and generic) will shift plotting to the corresponding graphic panel, namely, the elevation, density profile, plan view, and dilution on the four-panel graphs, and dilution, concentration, and the generic custom panels. Units should correspond to the ones chosen in Visual Plumes. * A clear graphics button has been added to the Graphics tab to allow verification data to be cleared from the graphics panels. * The "Thick" button on the Graphics tab increases the thickness of the solid lines when increased legibility is needed. >> Troubleshooting << Sometimes users encounter problems. When those problems can be clearly linked to a cause the necessary changes are made to prevent the problem in the future. However, some file handling and initialization problems are difficult to identify or may be system specific. Try to remember to Exit without saving when encountering a serious problem. This can protect important work. Then back up important project files before experimenting further. A remedy that sometimes works is to exit VP and restart. If that still does not work the offending files can sometimes be reconditioned using the reset commands on the Edit menu or the right-click options on the diffuser and ambient data tables. If that does not work the project files should be replaced by backup files and the VPSETUP file might be erased before restarting VP. Please help us improve VP by contacting us about problems (Walter Frick, 706-355-8319 or frick.walter@epa.gov). >> Extra (optional) files << Visual Plumes software includes many peripheral files that are not typically pertinent to the user. Noteworthy in this regard are many graphics files, for example, encapsulated postscript files with the EPS extension. For example, the DOS-PLUMES folder has a Original Files folder containing a file called FBF93G8.eps. This is Figure 8 from Frick, Baumgartner, and Fox, 1994, showing the difference between UM model predictions with and without correction for the negative volume anomaly (relating to the "overlap" message sometimes encountered in running DOS PLUMES). It may viewed in an application like GSview32.exe Version 3.4 (copyright 1993-2000, Ghostgum Software Pty Ltd. Files with the PLT extension are Hewlett-Packard graphical language files that may be accessed by special purpose applications like AutoCAD (copyright). Such programs have usage requirements and idiosyncracies too numerous to list. Users may peruse these files when wishing to use graphics used in Visual Plumes. In general, the pertinent files are important into the guidance files and the original files may be ignored. >> Mixing zone course material: Introduction << The instructional materials are concentrated in Microsoft PowerPoint presentations in the "Mixing zone course units" folder and are roughly listed in introductory to advanced categories by the "A1" through "A9" prefixes. For those users who do not have access to MS PowerPoint, a viewer is found in the "A Powerpoint Viewer" folder. Because the MS PowerPoint format does not meet Web accessibility standards for people with disabilities, the mixing zone course materials are currently not included in the files downloaded from the U.S. EPA CEAM Web site. The mixing zone course materials are included in the CD-ROM version of Visual Plumes only. There are plans to add a Web accessible version of the course materials to the U.S. EPA Web site in the future. VP software and documentation is contained in the "Visual Plumes (VP) Setup" and "Visual Plumes Guidance" folders. WordPerfect and PDF versions of the draft manual may be found in the "VP Manual" folder of the "Visual Plumes Guidance" folder. >> Mixing zone course material: Table of contents << A1 solarIntro: mzintro-Dec 2000.ppt: a general introduction to plumes (and mixing zone analysis) Other material includes zipped copies of graphics. A2 Grace: (permission to use some of the prints in this unit is pending) broadwalk.ppt: site diversity, motivation, design complexity, monitoring snapshots walkpic.zip includes zipped graphics found in this unit A3 List: (graphics reproduced courtesy of Academic Press) broadwalk.ppt: site and environmental complexities, model uncertainty, more on siting Fischpic.zip includes zipped graphics found in this unit A4 JennKeyes: KeyesHydDays.ppt: Jennifer Keyes' Hydrology Days 1999 VP presentation (A good look at VP capability but many changes to VP since then) jenn.zip has zipped version of KeyesHydDays.ppt jenngraf.wpd: tide movement for 2 fresh water flows illustrating problem of recirculation paper2wf.wpd: Keyes, Frick, and Dufour paper published in Hyd. Days 1999 proceedings A5 Lagrange: Lagmodels.ppt: Look at a big outfall, general plume behavior, data stuff, lagrangian model lagmodels2.ppt: model complementarity and comparison, verification, plume element, gravitational collapse, 3-d model Phil Roberts Boston outfall turret design work, experimental visualization Shallow Water Capability.ppt: DOE course slides illustrating very-shallow-water capability Lagpic.zip and subdirectories: zipped graphics A6 Winiarski: lagdensity.ppt: the very important topic of nascent density lagdensity.zip: zipped file of above WiniFrick.ppt: Lagrangian Plume Modeling 101. Plume element, dynamics, time stepping WiniFrick.zip: zipped file of above lwgraf.zip includes zipped graphics found in this unit A7 HydroQual Wu HydroWu.ppt: graphics from a bigger project, a good example HydroWu.zip: zipped file of above roywugrafs.zip: Benjamin Wu and Roy Walters graphics A8 Mamala Cast11 pet.zip: Jones and Petrenko data casts in Mamala Bay, Hawaii (needs SigmaPlot) Mamala.ppt: Mamala Bay data, UM, RSB, and CORMIX comparisons (users: excuse my efforts at drama); this is material to help develop confidence in models Mamala.zip: zipped file of above petwrgraf.zip: zipped graphics including Frick, Sproul, Stewart Honouliuli stuff Walt.ppt: Monitoring and experimentation (LIF, laser indued fluorescence) schematics (courtesy of Phil Roberts) A9 Cormix Cormixclass.ppt: A look at Cormix, DOS PLUMES Cormix class, VP contrast Cormixclass.zip: zipped file of above cormixpic.zip includes zipped graphics found in this unit Note: Cormix may be obtained from Robert Doneker (doneker@ese.ogi.edu). This unit is optional. Phils crabs (optional) Plumes.ppt: More experimental results courtesy Phil Roberts: plume patchiness. Original files are animated. Part of study on how animals find food. Tides (optional) Chapman.ppt: critical tide factors Chapman.zip: zipped file of above Zipped files relating to Frick-Chapman tide model. Such models can be used to synthesize data for VP time-series input. Walters (optional) Royw.ppt: Circulation model capabilities courtesy of Roy Walters Such models could help determine beach impacts Royw.zip: zipped file of above Roywpic.zip includes zipped graphics found in this unit >> Mixing zone course material: Optional Folders << DOS-PLUMES Contains DOS manual (3rd Edition) and software (background reference for VP) Optional-Presentations HydrologyDays2001Parta.ppt: Part 1 of a poster presented at AGU Hydrology Days 2001, Colorado State Univ, 2-5 April 2001. Compressible flow and turbulence theory inspired by the concept of entrainment into plumes. HydrologyDays2001Partb.ppt: Part 2 of a poster presented at AGU Hydrology Days 2001, Colorado State Univ, 2-5 April 2001. plumemovie.ppt: excellent LIF movie courtesy of Phil Roberts Note: if click does not animate, avi movie files may need to be re-linked VisualB&P.ppt: A poster describing Visual Plumes and Visual Beach (under development), prepared for EPA, Athens Open House, 27 April 2001. Walt.ppt: more LIF courtesy of Phil Roberts Public-domain MS Powerpoint Viewer For those who don't have it, a public domain MS PowerPoint viewer >> Example: Fan-Run-16 (optional exercise) << One way to get a feeling for new software is to run a prepared example. The Fan-Run-16 project provides an informative simple example of a Visual Plumes project. To run this example, start Visual Plumes by clicking (or double clicking) on the Plumes.exe program in Windows Explorer (or similar platform, or the Plumes icon if the program has been put on the desktop). The first time it is worthwhile to read the credits window notes. If this is the first time Plumes.exe is run, VP will not yet have established a file called VPSETUP, which contains the name of the last project run in VP. If this file is absent, VP starts with the "How to proceed..." panel that helps to customize the program tabs. Based on the target model selected, VP specifies required columns and attaches the chosen model to the yellow and blue model icon. The headers on the required columns can be seen to change as different models are targeted. (This does not prevent the user from subsequently selecting other models from the Models menu, however, the input requirements can change when that is done.) For this exercise, select the UM3 model and press the Continue button. VP establishes a new project called "VP Plume 0" (or other number if a project by that name already exists). There are always at least two data files attached to any given project; the first is called the project file and has a ".vpp.db" extension and the second is an ambient file that will have an extension like ".001.db". One of the hardest ideas for new users to get used to is that the "db" files are direct access files, which means that the files are updated any time a value is entered or modified. This means that a "Save" option is redundant, the files are constantly being saved. The down side is that sometimes users make changes they end up not wanting. VP does allow the re- establishment of backup files, which it creates when it opens a project. One can also exit without saving. For important files, it is highly recommended that backup files are kept in a separate folder. This "getting started" exercise is a quick tour of the Fan-Run-16 project. To open it, choose the "Open project" command from the file menu, navigate to the folder where VP has been installed, and select and open the "Fan-Run-16.vpp.db" project file. Take a look at the tab pages by clicking on the tabs at the top. Read the project memo on the Diffuser tab; to read all of it, click in the memo space and use the arrow keys to navigate. Note one ambient file is listed in the Ambient file list, the model icon should show "UM3" under it. The "base case" is specified for running. Input data are listed on the first line of the diffuser table in the middle of the tab. Since all the required diffuser and ambient data have been specified, pressing the "Parameters for selected row" button will calculate the (densimetric) Froude number for the case. Note that columns headed by "n/r" are not required and have not been filled with data. The optional panel at the bottom contains information for linking time- series files and may be ignored. Notice that most components have hints on the status bar at the bottom of the screen. A nice feature about VP is the ability to select units. On the diffuser tab, click on the Effluent Flow column unit (which should show about 0.000267MLD or million liters per day). A pop-up list appears. Clicking on one of the selections makes the conversions. The Effluent density(*) column allows conversions between salinity and density units. The * reminds the user that this is a mixed units column, essentially there is a three-way relationship between density, salinity, and temperature. See the manual for more detail. Establish the graphics page by clicking on the Graphical Output tab. Click on the Style buttons to get a feel for the available graphics panels; the "cus" option plots variables specified on the Special Settings tab. For now, select the "4-pl" (four panel option), those are the panels for which verification data are available. Click the Verify button at the bottom left and select the Fan16.txt verification file from the dialog window (some navigation may be necessary). The file contains x-y data points (referenced in the project memo on the diffuser tab) outlining the plume to be simulated on the Plume Elevation panel and the density stratification on the Ambient Properties panel. The plume outline should now be visible, if not, the axes may have to be adjusted. The Help button at the upper left gives basic instructions on manipulating graphics. The Scale is often useful when scaling graphics for the first time. It is useful to bear in mind that many settings were previously customized when this project was created. VP keeps settings information in the project "list" file, in this case, "Fan-Run-16.lst". If the settings are changed the more important ones (like axis scales) are updated and maintained in this file. Fan Run 16 is a buoyant plume discharged to stagnant, stratified ambient. Its entry angle into the trapping level (level of neutral buoyancy) causes some of the plume material to penetrate against the prevailing motion of the plume, which is generally from left to right. Note that depth does not correspond to the actual depth in the original experiment, in fact, often plume experiments are inverted. However, the density stratification is faithfully expressed. Now run UM3 by selecting it from the Models menu or by finding the model icon and clicking on it or by pressing the u hot key. The predicted plume using the inputted and default settings appears in red. Notice that UM3 predicts variables in addition to those that have corresponding verification data available. Also, notice the "diln" and "con" are not very interesting because the plot only has a single value. These two "summary" graphic panels are intended for showing the end results of multiple runs. Go to the diffuser tab and check the Average plume boundary option on the Model Configuration checklist and run UM3 again. VP now plots an internal plume boundary at which the concentration matches the average plume element concentration (based on the 3/2 power profile simulation). This helps illustrate the fact that concentration tends to be greatest at the center of the plume and "feathers" out to a value that matches the ambient. At the plume boundary it is difficult to distinguish plume from ambient. Select the Text Output tab and examine it. Notice that the trapping level is at 89.2cm depth. The average dilution at maximum rise is 57.8. To add or remove output variables, use the "Text output settings" panel on the Special Settings tab. For example, the Time variable might be added by pressing the down-arrow symbol on the Selection List window. The identifier "Time" will then appear on the Selected Variables list. Click on the word "Time" to add it to the list. Variables may be removed from the list by toggling the selection again. This is the time for the plume element to reach the specified point and factors into the decay of some pollutants, like bacteria. Return to the graphics tab and select Series 2 (blue). VP automatically goes to the diffuser tab, assuming some input changes are coming or that another case is to be selected to be run. Notice, if there were multiple cases (like there are in the Astoria project) the solid right-pointing arrow will indicate the selected case. Simply clicking on a line of data will select the case. However, right now move to the Special Settings tab and modify the value of the aspiration coefficient to 0.12. UM3 has only one tuned coefficient and this is it. Generally, a value of 0.1 is recommended. Note that the status line indicates this value is not updated in the project list file. On exiting the project the new value will revert back to 0.1. Run UM3 again. Note the differences in rise and plume position. To view the outer boundary, the Average plume boundary option on the diffuser tab must be turned off. To avoid clutter, the blue inner plume symbols might be removed by pressing the Clear 2b button (note that the status bar explains what is cleared by this button). Now run UM3 again. This kind of exercise for many runs might be done to optimize the aspiration coefficient. In this case it appears that the higher entrainment coefficient possibly better simulates the plume trajectory. The 0.1 coefficient has the advantage of usually (but not necessarily always) giving a more conservative dilution estimate (see lower right dilution panel). Much more could be done and deduced from this exercise. For example, not much entrainment occurs beyond the trapping level where the plume element enters the spreading layer. This is quite different from the DOS Plumes UM prediction because UM3 addresses the "overlap" problem described in the DOS Plumes manual. The user could try running the other models (except PDS, which is a surface discharge model, and NRFIELD, which is a multi-port model). Further experimentation is encouraged. Remember that if a backup folder of the files has not been made it may be difficult to remember the original contents of the project. A backup folder will help avoid re-installing VP to recover the original files. To terminate this session, press the close button at the upper right corner or select Exit from the File menu. Remember, your diffuser and ambient input data changes have been saved all along. For polished work the graphics can be substantially customized. Double click in a graphics margin to bring up the customizing dialog window for each graphic. Axis, titles, fonts, and more can all be changed, however, remember only the more important settings are maintained in the project list file. The To File button can be used to make bitmap copies of the graphics panels (under the same project name). They can then be further processed in programs like Paint. The 4-panel graphics are first enlarged before they are saved and are considerably higher quality than the VP graphics. The plume manual provides a step-by-step tutorial on developing VP project files. >> Another optional exercise << The "nonlinear-vs-linear" project is interesting in that it illustrates multiple runs and also the importance of the non-linear equation of state on plume behavior. Linear theory holds that all three basic runs contained in the file (one for each ambient profile, or file on the ambient list) would give the same prediction for all eight plume temperatures on the diffuser tab. This is because the cases have been set up to have the same densimetric Froude number. (Test this by establishing a case on the diffuser table by clicking on a line, followed by pressing the Parameters for selected case button in the lower left panel. The Base or selected case on the Case selection radio button box must be pressed to use the Froude number button. When satisfied, select the "Sequential, all ambient list" option again.) It is recommended that both DKHW and UM3 be run with this data (change the plotting color for the second model). Reveal the dilution graph panel by pressing the "diln" radio button on the Style box. Notice the wide range of maximum rise dilutions for the three sets of eight cases. On the other hand, both models predict similarly. This exercise illustrates the potential dangers inherent in similarity (or length scale) modeling and dimensional analysis when fluids wit non-linear equations of state are being considered. The three ambient input files may be viewed by clicking on the corresponding file names on the ambient file list on either the diffuser or ambient tabs. These files are manipulated through pop up menus that appear upon right clicking on the ambient file list on the diffuser tab. More detail is available in the manual. >> References << Frick, WE, DJ Baumgartner, and CG Fox, 1994. Improved prediction of bending plumes. Journal of Hydraulic Research, Vol 32, No 6 Walter Frick frick.walter@epa.gov 706/355-8319 24 July 2001 -----------------------------------------------------------------------------