Vehicle Aerodynamic Development Using a Novel Reduced Turn-Around Time Approach

Automotive manufacturers are under continuous pressure to satisfy changing consumer demands and regulatory requirements in an increasingly competitive landscape. This requires Aerodynamic departments to evaluate more design ideas in less development time. Aerodynamic departments are seeking to speed up their analysis in order to provide more feedback on performance to design and styling. Vehicle designers already leverage Computational Fluid Dynamics in order to quickly assess vehicle aerodynamic performance during product development. However, in order to meet modern development challenges, reducing simulation cost and turn-around-time is necessary. To that end, a novel approach to reducing simulation time of vehicle aerodynamics without sacrificing accuracy was tested in this paper. The methodology is called Transient Boundary Seeding, and enables the usage of a reduced simulation domain without the loss of information from the omitted region. As aerodynamic flow is transient in nature, replacing a reduced domain with an average value boundary condition is insufficient because the unsteady behavior of the flow is lost. With Transient Boundary Seeding, the turbulence and transient flow structures are fully captured and added at the boundary of the simulated sub-domain, maintaining the same level of accuracy as a full vehicle simulation. The paper includes the results of testing this methodology, which shows reduction of up to 66% in simulation time with no reduction in accuracy. The methodology was used to test the sensitivity of the vehicle performance to changes in rim designs, and adding or removing underbody panels. The accuracy of the trends was very well predicted with this methodology, as well as the impact of those changes on the vehicle drag. The flow structures around the vehicle are also very well predicted. With this methodology, simulation turn-around time can be significantly reduced for multiple design variants and thus, productivity and design processes can be improved.