Rapid Design of a SUV by Combining Wind Tunnel Development and CFD Simulations

While wind tunnels often serve as the standard tool for aerodynamic development of vehicles they do not routinely and feasibly offer detailed information into the fundamental fluid structures in and around the vehicle. It is up to the insight and experience of the aerodynamicist to determine what flow features are present and suggest improvements to the design. This is one of the reasons that the aerodynamic development of a vehicle can become a long iterative process. One tool for gaining more information about the flow is Computational Fluid Dynamics (CFD) simulations, but these methods are not infallible. By combining the fluid behavior information gained from CFD with the trusted measurements from wind tunnel experiments throughout the design process, it is possible to reduce the total time of a development project and produce a more robust and improved design. Discussed in this paper is an example case for a new production SUV. Through a combined use of transient and adjoint optimization simulations, key areas for improvement were identified and studied. From these results parts for wind tunnel testing were developed and tested. With a day of wind tunnel testing, improvements were made to the vehicle to reduce the drag beyond the desired requirements. Furthermore an additional round of CFD verification of the improvements showed good agreement with the wind tunnel results. Customer full scale wind tunnel testing is also conducted to determine final performance levels.