Of the many software technologies that have begun to move into mainstream by product development engineers, one emerging technology is computational fluid dynamics (CFD) software. CFD software is increasingly being put to use by product development engineers early in the design process to prove out proposed designs while still on the digital drawing board.
The advantages to the product development process, in terms of reducing both the overall design cycle time as well as the costs associated with traditional testing methods, are many. Engineers can design better products faster when allowed the luxury of running multiple "what if" type scenarios while designs are still fluid and easily changeable. Once metal or plastic parts are cut, subsequent design changes can bloat design budgets and derail schedules.
Still many engineers avoid using CFD tools because the legacy of conventional CFD tools still haunt them. These tools were infamously difficult to learn and use, compute-intensive, and often prohibitively expensive. Another issue is that few engineers can ill afford to spend a week learning a tool that they will use barely 10 percent to 15 percent of the time.
Today, many CFD tool vendors have identified product development engineers as a new potential market for their products. Typical CFD packages, however, were designed with the specialist in mind, making them unsuited for occasional use by engineers and difficult to incorporate into existing product design processes.
According to Dennis Nagy, an industry consultant who has held executive positions at MSC, Fluent Inc. and Engeneous, these high-end packages are designed for "the specialist who long ago paid the price of learning a hard-to-use CFD package so they can solve really complex and exotic problems, which in practice don't occur very often."
Some CFD software packages, however, are developed specifically for the average engineer. One such package is CFdesign from Blue Ridge Numerics. "What makes CFdesign unique is that it is amazingly well integrated with CAD systems, easy-to-use, streamlined, and offers great graphics for looking at results," says Nagy.
CFdesign is geared towards product development engineers who deal with geometry created in a myriad of CAD systems who want quick answers to "what if" inquiries so proposed designs can move forward rapidly and with greater confidence. "What Blue Ridge Numerics has addressed is this huge segment of industry, the majority really, that has a product in which flow is an issue but it's an issue in the context of some complicated geometry: a valve, a pump, a compressor, impellers, or electronic cooling in printed circuit boards with components stuck on them, like fans or heat sinks, inside the box," says Nagy. "The physics is straightforward; it's just heat and air, but the geometry is very complicated."
For designers ready to successfully ply CFD tools early in the product development effort, here are five key guidelines:
1. CFD must be closely integrated with MCAD systems.
Engineers working in product development know their CAD systems like the back of their hand. To facilitate the use of CFD software, several CFD packages now enable engineers to simulate fluid flow or heat transfer directly on their native MCAD geometry, eliminating the need for any data conversion using formats such as IGES, STEP, or STL. CFdesign offers full associativity with most leading MCAD software, so changes made to the original MCAD model are automatically reflected in the CFdesign simulation model.
After placing a purchase order for a higher-end CFD software package, Glenn Yamasaki, mechanical engineering manager at EDO Corp., a manufacturer of electronic intelligence equipment for military use, saw a demo of CFdesign at a user group meeting and quickly became a believer in the software's direct integration with his CAD software. "The interface with Pro/ENGINEER is almost like an extension of that software. The biggest advantage of CFdesign is its parametric interface to Pro/ENGINEER, which let us create extremely detailed models of what we're trying to analyze," says Yamasaki. "A lot of conventional CFD programs require you to simplify the model—take out a lot of details—but with CFdesign you don't have to do that."
2. CFD must be easy to use by existing engineering staff on an infrequent basis.
Since most product development engineers do not use CFD tools on a daily basis, the tools must be intuitive and easy to learn and use, even if infrequently.
"A product development engineer today wears many hats," says Nagy. "They have to do some structural analysis, flow analysis, kinematics, fatigue-related analysis, costing, supply chain management; they juggle all of these in their daily work so when they need to do a little flow analysis, they don't want to take a one-week training course every two months."
Stan Isbitsky, a senior engineering manager at Velan Valves, a Canadian manufacturer of valves, says that he was able to effectively use CFdesign software almost immediately after receiving it. "A little while after we got the software package and without any formal training, I was able to understand it, apply it, and make a number of runs," says Isbitsky. "Basically we were able to do a number of 'what if' scenarios out of box and substantially improve the design. When we tested the prototype and we were right on the money."
For EDO Corp.'s Yamasaki, CFdesign's supporting tutorials made it easy for him to learn the software and use it effectively each of the handful of times a year it's needed to prove out a proposed design. "We would do maybe four to five analyses a year. It's not like we've got a person just doing CFD all the time," says Yamasaki. "CFdesign was very easy to learn. The tutorials are excellent because they have a variety of samples on which you can base your own model, which was a huge help. With the other software package the entire documentation package was only 50 pages long and covered only the basics of the system."
3. CFD must consistently reduce project schedules and costs.
In the past, CFD was somewhat restricted to use by research specialists. But to be successfully incorporated into product development efforts, it must prove itself by enabling engineering teams to consistently cut project schedules and associated costs.
In the first design project in which they used CFdesign, engineers at Velan Valves sought to design a special forged globe valve for a customer on a tight schedule. By using CFdesign, Isbitsky says they were able to cut a number of "cut and try" or physical prototyping steps out of the process. "We had to make only two prototypes and our final product was basically identical to the second prototype," says Isbitsky. "We cut out at least three prototypes, which slashed six weeks from our design cycle time. CFdesign paid for and proved itself on this first job because the results were in such close agreement with the prediction."
As part of a kick-off for a new design project at Watts Regulator, an engineering team sought out ways to revamp their product development process and accelerate its design cycle. As part of this initiative, the team used CFdesign to design a new line of six specific-sized valves—ranging in size from a quarter-inch to two inches—for a line of small backflow prevention devices. After running a series of correlation studies to confirm the accuracy of the CFdesign simulation results, the team was able to quickly narrow in on optimized designs. "The first size that we had to do took us two runs in prototypes and we hit the other five on the first go-round," says Jeff Scilingo, R&D Engineering manager as Watts Regulator.
"In terms of prototyping costs and the front-end development expense, the savings was considerable. The valve involves brass castings, so we had pattern equipment to fabricate for each run cycle and we figure we probably saved—for each size—amounts in the ten thousand-dollar range. We know in tooling development alone we saved $50,000 but the biggest gain was in the development cycle," says Scilingo. "For each interaction, we were looking at four- to eight-week lag time between tests for a given version. By cutting out one or two cycles per design and having some of the overlapping accumulative effects we feel that we probably saved at least six months and maybe upwards of nine months in the development cycle. We recouped our initial expense of buying CFdesign in the very first project."
4. CFD must be integrated with CAE applications
CFdesign offers interoperability with many leading CAE applications. Simulation results are automatically prepared as an "input deck" that can be used by leading structural analysis software to calculate flow and thermal-induced stress and other important engineering concerns.
Mark Stocker, a senior project engineer in Corning's Precision Machine System Group, wanted a CFD tool that would let him import its thermal distribution simulation results into COSMOS/Motion, a motion simulation and kinematics software from SolidWorks Corp.
"One of the reasons I really wanted this software is that I can use it to calculate the thermal distribution across the model—both the fluids and the mechanics of the system—and then export that thermal distribution into a finite element mesh so I can calculate machine or component distortions using that thermal distribution information. We're really interested in how machines distort with fairly small temperature fluctuations or differentials. Temperature differentials are often the most significant source of machine error motion," says Stocker.
Stocker can't imagine tackling the design of any of Corning's multimillion dollar production equipment without the use of CFD and CAE software. "I wouldn't even try to guess how much longer it would have taken me without CFD; I just know that I would not even do a project without it," says Stocker. "I wouldn't want to guarantee to meet specifications without using these tools. In our business, the machines have to work right the first time."
5. CFD results must be easily shared with others.
CFdesign's Design Review Center provides a dynamic visualization environment in which engineering decision-makers can evaluate multiple designs. The software's Design Review Center enables users as well as nonusers within a company to clearly see the relationship between design changes and product performance, so design decisions can be made with confidence.
Chris Hayes, a project engineer in the CAE Group at Roush Engineering, used the software' Design Review Center to demonstrate to a customer the dynamics of what was happening inside a valve. Initially the customer wanted Hayes to e-mail him a report with images to show what was happening, but Hayes felt that static images would not be effective at communicating what was happening inside the valve.
"I told him that I could send him a hundred pictures but they wouldn't really show him what he wanted to see," says Hayes. "With the Design Review Center, I could show him the same thing in different views, then move things around, look at it in different areas and review all of the possible designs that way. They were really impressed by it. They saw the pressure relief valve and they could see the flow through it and what was happening in it. They didn't need to know the science behind it but they could see what was happening."
More information is available by contacting Blue Ridge Numerics, Inc., 3315 Berkmar Dr., Ste. 2B, Charlottesville VA 22901, calling at 434-977-2764, or visiting www.cfdesign.com.
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