By Pamela J. Waterman

You’ve heard the ads: a desperate person is on the phone to a GPS service, begging for assistance in choosing a wide-screen TV. How does one begin to decide about HDTV? LCD?  LCOS? That same feeling might dominate a current search for CFD (computational fluid dynamics) software. Cruising the websites of more than 50 companies that sell CFD-related programs feels like walking into a CFD big-box store and not knowing which aisle to start browsing.

Wander aimlessly no longer: The following primer is for purchasing the right CFD software for your application. We went to the intrepid experts at a variety of software companies for guidance.

First, Know Your Needs

You’re a design engineer with some FEA (finite element analysis)  experience. According to John Chawner, president of Pointwise—a grid-generation/preprocessing software company—your opening question should cut to the chase. “Can the CFD software solve your particular problem?” he asks. “Get proofs through benchmarking,  or examples that the vendor provides, or an evaluation copy to try.”  You might even ask the company to solve a sample problem for you.

Many software packages claim to model and solve a wide array of fluid dynamics problems, ranging from electronics thermal cooling to glacial runoff flows. General-purpose software may be just the ticket to cover both current and future projects, as well as such high-end situations as incompressible fluids and fluid-structure interactions. On the other hand, specialized products may be faster to learn or use, be highly integrated with your CAD system, and have menu tasks tightly tailored to your problem’s parameters.

Chris Reid, vice president and GM of the fluids business unit at ANSYS, Inc., points out that knowing the level of analysis needed is critical. “Do they need the type of CFD capability that warrants using one of the comprehensive Tier One ]top three or four] suppliers?  That would suggest they want to do some pretty sophisticated CFD, and their requirements for accuracy, for robustness, for the types of physics analysis they want to do, can only be achieved with one of those suppliers.” Reid says it is in the user’s best interest to understand just what’s possible in a full-blown versus entry-level package.

Another way to look at this issue is to determine what distinguishes a product from its competition. What are product X’s strengths and weaknesses? Can it simulate operation at different altitudes? Can it handle hypersonic flow? Can it compare and contrast designs? These questions might appear to put a company on the spot, but you should get solid answers.

When vendors tell a potential buyer how many customers they have, Mark Landon, president of Optimal Solutions, a developer of model-optimization software, says a useful follow-up question should be: “How many of your users are doing my same problem?” Read reviews and go through the grapevine to find out what others are saying. If you look at applications on a website, find out how long it took to set up and solve each problem. A sensational picture with a million-dollar price tag might not be a viable solution.

“CFD technology combined with desktop compute power has advanced rapidly over the last five years and it has finally become practical to perform many classes of basic and advanced flow simulations within the budget and time schedule of a typical new product development program,” concurred Don Tolle, marketing director for UGS Digital Simulation. “The need to create more innovative designs and to minimize physical prototyping is driving the need for engineers to use CFD tools to understand and validate the system level performance of their designs early and throughout the development cycle in order to meet design requirements related to flow, thermal and even combined flow/thermal behavior.”

Up to Speed

Another key factor is the level of CAD integration. According to Kevin O’Shea, VP of sales at BRNI, the essential questions are: “Is the CAD integration native, with no translation? And is there a bidirectional hook for updating the original model?”

If CFD functionality is available directly in the CAD environment,  users will see menus and specification trees in the style of the host package, which may speed up the learning process and simplify usage. Some packages even offer a wizard-style approach that prompts users to fill in values, and won’t proceed if certain conditions are not met.

An important issue often overlooked is matching the user to the software. Jim Spann, VP for North American marketing at BRNI, explains that of the 200,000 or so US mechanical engineers, half work at an OEM with fewer than 100 employees, and most of the work is done in small groups. “The vast majority of users will never afford traditional CFD, and they don’t have two days to learn how to build a mesh. Ask how long it will take for a person to get up to speed.”

Paul Bemis, vice president of product management at Fluent, goes a step further: “The code has to be easy to use and easy to remember. A lot of people will talk about ease of use, but easy to remember is really important. These people tend to be periodic users—they only use it once in a while, and they have to come back up this learning curve really quickly.”

How Much Support

Pointwise’s Chawner champions a variation of the classic real-estate mantra: “Support, support, support,” he says. “If I get stuck, are you going to be there to help me, and in what form?” Support is important for any software, but CFD is still new enough for many users to warrant extensive backup.

Find out what type of support is available and what it costs. “Ask about keystroke-specific tutorials, an HTML user’s guide,  distance-learning Web courses and webcasts, classroom seminars,  customized training, and a user forum,” suggests Bob Williams,  product manager at ALGOR. Is local training and local support important to you? Are field engineers available by phone, on an unlimited basis,  and how experienced are they?

Can you try before you buy? Find out if you can test a trial version, for 30 or 60 days, with field engineering support. According to Mike Harrison, president of Nika Fluid Solutions, “Trying the software gives you a chance to sample their technical support and set a standard for their performance; the support probably won’t get better after you buy.”

Pointing out a practical corollary to the support issue, Suchit Jain,  vice president of Analysis Products at SRAC, suggests you also ask about updates. “How often is the software updated? Is the release cycle 10 to 12 months or 24 to 36 months? Are the bug fixes provided in service packs?”

Cost and Flexibility

Most vendors agree that cost should not be the first consideration,  primarily because it may not show the whole picture. Stephen Ferguson of CD-adapco, proposes that “cost, although often seen as a deciding factor, should be compared against the potential savings that CFD can provide by eliminating unnecessary design iterations and prototypes.” As CFD analysis has become more responsive to development cycles, when used properly, it will usually save many times its purchase price.

Prices run the gamut from free tools (with no support) to CAE packages that can solve any physics you can imagine; software that was $25,000 a few years ago might now be $10,000. But even so, Akshai Runchal,  president of ACRI, cautions, “The cost of software can pale in comparison with the cost of training.”

On a practical level, does the software run on the hardware you have available, perhaps a simple desktop system? Mike Peery, president of Tecplot observes, “Many of our users still use single-CPU machines;  however, I’m seeing a migration to dual-CPU Windows and Linux systems.”

Beyond the hardware, think about whether your hardware-software configuration allows for growth. The software should not only work with your other CAE tools, but should also handle both current and future needs. Fluent’s Bemis calls it having “headroom;” simple codes with simple functionality might not be able to tackle more complex problems down the road, so an expandable approach might be important.

Make It Work

You expect sales staff at the big-box stores not only to know their products but also to suggest different options for getting a job done. Nika’s Harrison believes this is an important role for the vendor. “Are they willing to discuss the impact of relevant fluid dynamics on your work?” he asks. “Can they identify potential benefits? See what industry knowledge they have of your engineering and prototyping process; it’s all about bringing CFD upstream to optimize the design, so see if they can help you avoid some pain.”

ACRI’s Runchal turns the situation around a bit. “It’s increasingly important to understand that the uncertainties are no longer in the computer and in the math,” he points out, “the uncertainties are now in the physics, and you must evaluate which parts of the physics are well understood, which are partly understood, and which are not understood at all.” In other words, back to square one: Know your problem.

For an initial project, you might want to hire a consultant. Then,  it’s time to shop for yourself. Right aisle, right shelf, right product—with a little homework, your CFD purchase will be the best fit for your pocket, your project, and your schedule.

Contributing editor Pamela J. Waterman is an electrical engineer and a freelance technical writer based in Arizona. You can contact her about this article by sending an e-mail c/o DE‘s Editors.

Why Now for CFD?

CFD has more users because it’s becoming practical,” notes Fluent’s Paul Bemis. “In terms of computer models, five years ago, you could only do simple representations. Now, it’s usable in a reasonable amount of time, by someone with a reasonable amount of expertise.” The earlier roadblocks of price (for software and expert staff), complicated usage, and a steep entry path are now going away.

“CFD software usage is about where FEA was 10 years ago,” comments BRNI’s O’Shea. “The industry is maturing, and we’re putting easier-to-use, high-value software on the desks of mechanical engineers (not analysts).”

Investigate just how CFD will benefit your company. As Kevin Duffy, VP of engineering at Maya Heat Transfer Technology suggests, consider whether the market success and performance of your product is significantly driven by your ability to predict and optimize its fluid flow characteristics, or flow-thermal performance. Chances are, the answer is yes. Thus, he adds, “If you’re not using CFD today,  you’re really missing out on a vital technology.”—PW

CFD Information Resources

Try TenLinks.com Ultimate CAE Directory, an engineering website that takes its name from ranking sites for a particular sub-topic. Click here to see its range of CFD sites. Two examples: efluids.com has several handy tools for both students and professionals, and cfd-online.com includes news, books, company lists,  and an event calendar.

A CFD community site that includes lots of news items is CFDReview.com, and another source known more for its FEA information, but which now includes CFD is NAFEMS in the UK. Take its Working Group survey to help identify international needs in CFD guidance, training, communication, and standards by clicking here.—PW

Company Information

ACRI, Inc.
Bel Air, CA

ACUSIM Software
Mountain View, CA

Adaptive Research Corp.
Alhambra, CA

ADINA R&D
Watertown, MA

ALGOR,  Inc.
Pittsburgh, PA

ANSYS,  Inc.
Canonsburg, PA

BRNI,  Inc. (CFdesign)
Charlottesville, VA

CD-adapco
London, UK

CHAM,  Ltd.
Concentration Heat & Momentum
London, UK

CEI—Computational Engineering Int’l
Apex,NC

Daat Research Corp.
Lebanon, NH

EMRC
Troy, MI

ESI-CFDRC
Huntsville, AL

Exa Corp.
Burlington, MA

Flomerics, Inc.
Marlborough, MA

Flow Science, Inc.
Santa Fe, NM

Fluent,  Inc.
Lebanon, NH

Harvard Thermal
Harvard, MA

Intelligent Light, Inc.
Rutherford, NJ

Maya Heat Transfer Technology, Ltd.
Montreal, QUE

Metacomp Technologies, Inc.
Agoura Hills, CA

NIKA Fluid Solutions
Colfax, CA

NUMECA International
Brussels, Belgium

Optimal Solutions Software, LLC
Idaho Falls, ID

Pointwise, Inc.
Fort Worth, TX

Software Cradle
Osaka, Japan

SRAC Corp.
Los Angeles, CA

Technalysis, Inc.
Indianapolis, IN

Tecplot, Inc.
Bellevue, WA

UGS Corp.
Plano, TX

XYZ Scientific
Livermore, CA