The Effects of Solid Wall Wind Tunnel Blockage on Incremental Changes to Generic and Simplified Automotive Bodies

In the authors’ previous work, a database was generated documenting the effects of variable blockage ratios on the drag and lift of simplified and generic automotive bodies in solid wall wind tunnels. This database displays significant differences in the responses of different vehicle architectures to changes in wind tunnel blockage. What was not examined in this previous work was the effect of wind tunnel blockage on the incremental values of geometry changes to these generic models. This is critical knowledge related to the aerodynamic development process of automotive vehicles in wind tunnels. To complement that work, the present paper examines the effects of changes in solid wall blockage on the incremental force values of geometry changes on the simplified sedan geometry known as the Pilot Fastback, the Pilot Squareback and the Ford GTU pickup. It is intended that this information will give initial insight as to the degree in which solid wall wind tunnel blockage effects can influence the aerodynamic development process utilized in the automotive industry and bluff body research activities. It is also intended to further inform the documentation process of the SAE Road Vehicle Aerodynamics Forum Committee (RVAC) and the Subsonic Aerodynamic Testing Association combined activity, Commonized Automotive Aerodynamic Test Standards, or CAATS. As in previous work the study is conducted utilizing Computational Fluid Dynamics (CFD) employing the Lattice-Boltzmann method of simulating the fluid flows.