CFDesign1 Oct, 2004 By: Joe Greco Cadalyst
Upfront CFD analysis tool proves easy to use.
The goal of every product design company is to shorten the time it takes to go from art to part. A crucial portion of any product development cycle is when design engineers send a model to the analysis department. Frequently there are a number of iterations, and the development cycle is lengthened and deadlines missed. However, the past few years have seen an an effort to put more analysis tools into the hands of design engineers so that the final model that is analyzed is much more useful. This upfront analysis has gained popularity in the areas of FEA and mold flow analysis, and now users of CFD (computational fluid dynamics) are realizing the benefits as well. One of the leading programs in this area is CFdesign from Blue Ridge Numerics, now in its seventh release.
Time to Get StartedAfter a somewhat tricky installation that requires setting up a license server via LMTools, the program opens to a simple user interface that features only two menus: File and Help. About two dozen tools are located at the top of the screen, mainly for different view settings and navigation controls. Like most mechanical CAD products, CFdesign also uses mouse shortcuts to rotate, pan, and zoom. There are also tools to create, open, and save files. Though the icons don't quite look like the ones found on a standard Windows toolbar, they're easy to figure out. It's also easy to customize the application by dragging or hiding toolbars. In addition, CFdesign houses what it calls a Feature Tree, which is reminiscent of those found in mechanical CAD programs.
Only eight other tools are required to run the software, and they are set up so that they follow the logical sequence of how you'll use them. Each time you select one, the options shown in an area known as the Task Dialog Region update to reflect the next tool. I found most of the dialog boxes well designed and easy to navigate.
Figure 1. CFdesign offers many different options when setting up the parameters of the CFD simulation.
CFD AnalysisYou can start an analysis in one of two ways. When you open the program from its desktop shortcut, you're greeted with the user interface described above, and you start the New command to import a Parasolid or ACIS file. However, when you use a mechanical CAD product such as SolidWorks, Solid Edge, Inventor, and Pro/ENGINEER Wildfire, CFdesign can be linked to those products. This means while working in the CAD program, you can click on the CFdesign button and the model automatically transfers into Blue Ridge Numerics' analysis software. CFdesign retains associativity with the CAD program, so any model changes are reflected in CFdesign. When you use this technique, the CFdesign user interface eliminates a few icons, such as New, because you create a new analysis file by transferring the model.
Hands-On CFdesign TestI loaded the Solid Edge link when I first installed CFdesign to test with that application. The instant I pressed the CFdesign button in Solid Edge, the three-part valve assembly was in the analysis application. Once in CFdesign, I followed the sequence of the tools, which allowed me to first apply loads to the model, such as the temperature, pressure, and velocity that the liquid would have when entering the valve (figure 1).
When you're setting the parameters, CFdesign makes it easy to go back if you miss something. For example, when I was setting up the parameters for the inlet face, I set the velocity but forgot to add the temperature values before going to the next step. However, I pressed the Restore Previous Selection button and quickly was taken back to input my desired values.
The next tool is for setting the mesh size, which can be confusing if you're unsure what this value should be. The on-screen Help doesn't provide any assistance here, although the printed manual helps a little. In general, I found this built-in Help system below average because it lacks detail and images. However, a separate PDF-based Help system is much more useful. After setting the mesh size, you assign the materials. This includes specifying the material properties of the valve and the properties of the fluid moving through it. After you set all the parameters and select the type of analysis—flow and/or thermal—you run the analysis.
Figure 2. This image shows the results of thermal static temperature analysis in CF.design. Notice the MCAD-like feature tree on the left that lets you edit parameters.
In the case of the valve, the results (figure 2) display anything from velocity throughout the device, pressure, temperature, viscosity, forces, and stresses. Via the history tree, you can edit parameters and rerun the analysis. You can also save the results as a bit-mapped image or what Blue Ridge calls a Dynamic View that you can pan, zoom, and rotate inside a free viewer, called the CFDesign Communication Center, downloadable at www.cfdesign.com/Support/Downloads.The viewer also works as a plug-in with Microsoft Word, PowerPoint, and Internet Explorer.
No Experience NeededWhile some understanding of fluid flow and thermal dynamics is helpful to run the software, Blue Ridge's claim that no CFD experience is necessary is accurate. I had very little prior CFD experience and was able to get though the valve analysis by following the tutorial. After that, I was able to analyze another component with no help. For those looking to cut product development time by reducing CFD iterations, CFdesign is worth a look.
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