Going With the Flow

Implementation of parallel processing in computational fluid dynamics (CFD) is shortening the time required to design products and systems, and is bringing once-elusive problems under a new measure of control. Parallel processing, which is making ever larger models practical, is based on an idea called domain decomposition. The software divides the flow domain into segments of roughly equal computational work. The technology is influencing automotive and aerospace testing by getting more and more work out of the wind tunnel and onto a computer, where it costs less to perform. DaimlerChrysler in Stuttgart, Germany, explored the aerodynamics of its Mercedes E-class sedan with a 10 million cell model. Besides saving time and money by parallel processing, CFD simulation permits review of arbitrary locations in a flow field, including particle tracking, and can rapidly highlight areas of concern about heat build-up. There are several factors that can inhibit a high degree of parallel scaling. Domain decomposition algorithms affect the load balancing between processors. Imbalances slow the system because the solution isn't in until the last processor is finished