Evaluating Commercial CFD Codes

Using commercial CFD codes makes a lot of sense for many businesses—even if they also make some use of noncommercial CFD solvers. These codes don't come cheap, however, and sometimes it's hard to port the work you did with one solver to a new one. So, if you are going to invest the money, you should take the time to make sure you get the right CFD package.

Issues to Consider

  • All-in-one or separate products? The advantage of an all-in-one offering, where the grid generator, flow solver, and post-processor are integrated into a single CFD code, is that you do not have to worry about incompatibilities between the different components. Also, you have a single source for the whole system, and you can get training for everything from them as well.

    All-in-one systems are frequently easier for the beginning CFD practitioner to learn. On the other hand, the individual components of an all-in-one system are usually not as powerful as the specialized codes. You must be sure that, whatever you get, it will be able to address your specific needs.

  • Will it model ALL the physics you need? The physics of fluids allows for almost endless combinations of factors which can become important. No CFD codes that I'm aware of can solve all possible flow regimes accurately. If all you need is a steady-state incompressible perfect gas solver, then there are plenty of options for you. If you have a very specialized configuration, it could be a different story.

    My company has had discussions with one organization which spent a great deal of money for a well-known commercial software package, only to discover that it could not model all the physics relevant to their product. Don't let your organization make the same mistake..

  • Are the underlying algorithms well-suited for your problems? Even if CFD codes have the capability to model the physics of a particular problem, you should consider whether or not the basic algorithms being used are good choices for your applications. For example, density-based CFD codes can often be made to solve low Mach number flows, but they are not really the best choice if that is going to be your dominant application. A pressure-based code would probably do a better job for you.

  • Who else uses the code? How healthy is the company? It will do you no good to spend a large sum to acquire a commercial CFD code if the company goes out of business the next month. Make sure that the software provider is well managed and has a good customer base. Also, it would be a good idea to talk to some of their other customers about using the code. Are they happy with their investment? Would they do it again?

  • What support options are available? Is any local support available? There is nothing like having a local office where you can go to ask questions face to face. Often, just knowing that you could come down and visit in person seems to encourage the staff to go the extra mile. I'm not saying they will ignore you otherwise, but don't discount the value of having support nearby. The availability of ongoing support from the software provider is, as I see it, one of the two main advantages of commercial CFD codes, so make sure the package you acquire comes with the right support for your organization.

  • Do you have any in-house experience-base with the code? No matter how friendly the user interface is (and friendly interfaces are a second big reason to look at commercial codes), all CFD codes have a learning curve. If you have personnel who already have experience with one package or another, it can greatly speed up the process of bringing the package into production use. All other things being equal, go with the package you have the most experience with.

  • Get a trial license. I have never yet met a sales person for a CFD firm that I have caught in a deliberate lie. My experiences with sales staff have generally been very pleasant, and everyone has tried to be helpful, honest, and informative. However, no one understands your situation like you do. Fluid dynamics is non-linear, and what seems like it should be a simple extension to problems that have been successfully addressed previously doesn't always turn out so simple.

    By getting a trial license, you can apply a code on your problems to ensure that you can get the quality of results you need. It also lets you verify that your organization can fit the code into your computing infrastructure productively. I know one case where a code is gradually being phased out of a company just because the requirements it makes on the computing environment are not really compatible with their setup.

  • What sort of training is available? If you are bringing in a completely new system to your organization, it is probably worth the investment of time and money to obtain formal training for at least some of the personnel that you expect to use the code. Most vendors are willing to work with you to get you started with their products. After all, successful customers are repeat customers, and without training, your chances of success with their products are much less. Try to get the vendor to present the training at your own facilities, or see if there are classes co-located with some event (such as a technical conference) where you might be sending personnel anyway.

  • Should you look at a customized "expert system"? If your applications consistently fall in a very narrow range (i.e. the geometry and/or the results you need from your CFD solutions are just variations on the same theme), then you should probably be looking at the possibility of a tailored CFD package for your specific problems. Not all vendors can create such systems, but many do, and when they work, expert systems can really enhance your engineering processes.

    The most elaborate of these systems provide a "wrapper" (typically in the form of a graphical user interface), which allows the line engineer (or designer) to modify specific parameters to generate a new variation of some class of problem (whether that's a new geometry, different flow conditions, or both). The system then "automatically" creates a computational mesh, runs the flow solver, and computes specific desired quantities (e.g. heat transfer, lift, drag, moments, etc.).

    If your CFD needs are compatible with this approach, it can bring the power of CFD right to the heart of design and production. Be careful with these systems, however, because if a user strays too far from the original configurations around which the system was designed, the system fidelity is likely to degrade significantly, and there may be no warning that anything has gone wrong.

So, which companies should you look at? I have put together a short discussion of several that I have some familiarity with but the list is by no means exhaustive.

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