Design for Performance through Simulation

Exa’s technology and products are catalyzing a disruptive change in how manufacturers design, engineer, and optimize their products. Simulation-driven design enabled by PowerFLOW makes predictive information available earlier in the design process, permitting deeper exploration of the design space. Rapid iterations between analysis and design can provide essential insight into how new design concepts will perform, and enable engineers to propose changes that improve the performance, yet satisfy the design aethetics.



Automobile sales have always been driven in large part by the exterior design, and this trend is rapidly moving into other sectors of the ground transportation industry including commercial vehicles. Consumers and operators want vehicles that not only perform well, but look great and reflect their self-image. In addition, fuel economy and emissions control is now central to the sale of vehicles. Fuel economy and emissions are heavily influenced by aerodynamic drag, which in turn is influenced by tiny geometric details and very subtle changes in exterior surface design.


In the past, the studio has been able to design the exterior at the concept stage with minimal awareness of the aerodynamic, thermal, and aeroacoustic performance of the vehicle. It has been up to engineering to try to engineer in the performance after the fact, with very little ability to change the key exterior design parameters, thus limiting their ability to optimize the design for performance. Leading manufacturers now recognize that in order to compete globally, the separation between studio and engineering must be eliminated. Designers need to know in the earliest stages of concept development what the performance of their designs will be so the designs will be efficient from the start. Similarly, engineering teams must be able to communicate aerodynamic effects and propose changes to the design that will be acceptable to the designers.



Comparison of alternative designs (note differences in wake structure produced by subtle changes in geometry)



One of the biggest barriers to collaboration has been that it simply takes too long for engineering to provide feedback on the performance of the design. At the concept stage, the design can be in the form of sketches, photos, free-form curves, or clay models. However, engineering needs complete 3D geometry of the vehicle in order to perform analysis. The process of producing analysis-quality geometry from early stage conceptual design data has been very slow, requiring building surfaces with specialized tools that often takes weeks. By the time engineering has done the analysis, the design team has moved on and the analysis has limited value. A different process is required.


Engineering often struggles to effectively communicate proposed changes to the design for two reasons. First, the tools typically available to engineering to change the design modify the surfaces in ways that are unacceptable to the designers, and the changes are simply rejected out of hand. Second, engineering typically communicates using numbers and flat-shaded images, which make it very difficult for designers to understand what the proposed shape change is. Effective communication to designers must use the “language” of design — photorealistic images and animations.


Real time morphing with Exa Software.



Exa has a solution for highly productive collaboration between design and engineering. Exa has developed a process methodology and has tools to produce analysis-ready, fully detailed vehicle geometry from sketches or curves within a few days. Exa’s PowerCLAY uses patented lattice transformation methods to morph mesh models in real time, while respecting the curvatures of the surfaces, improving the likelihood that the shape change will be acceptable to designers. in addition, PowerCLAY can merge a carryover, fully detailed underbody with new upper surfaces in the space of a few hours. PowerFLOW’s patented Lattice Boltzmann simulation technology does not require the engineer to create a fluid mesh, so once the vehicle surface mesh is prepared, the simulation results are available in hours. Performance feedback can be available in days instead weeks.


Once the initial analysis has been performed, PowerCLAY is used by engineering to rapidly morph the design to address performance issues. Because PowerCLAY can morph in real time and respects surface curvatures, engineers and designers can sit in the same room and perform live exploration of the design change possibilities. Designers can tell engineers how the design can be changed without violating the design intent. Images of the vehicle are presented photo-realistically with analysis results overlaid using RTT DeltaGen or a similar tool. This dramatically improves the communication process because it uses the “language” of designers.




Exa has developed methods to rapidly characterize the design space very early in the design process. A series of simulation runs are performed in which the key design parameters are modified over a range. The resulting response surface can then be used to predict what the performance might be at a combination of parameters that has never been tested before. This is extremely useful information for the design team to be able to predict a priori what impact a design change will have on performance. Exa has developed significant expertise in and methods for performing design characterization using adaptive response surface models. This approach enables design characterization to occur with significantly fewer simulation runs than traditional approaches, making the approach much faster.


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