Automotive Application of Vortex Generators in Ground Effect

Abstract

Vortex generators (VG) are widely used in the aerospace industry, mainly to control boundary layer transition and to delay flow separations. A different type of VG is used on race cars for manipulating the flow over and under the vehicle, mainly to generate downforce (which is needed for better performance). Contrary to the VGs used on airplanes' wings, the VGs discussed here are much taller than the local boundary layer thickness and are not intended to control laminar to turbulent flow transition. Although, the effect of such VGs was studied in the past, not all features of the flow fields were documented. For example, the shape of the vortex wake behind a VG, the wake rollup and the resulting pressure signature is still not well understood. Consequently, this study investigates the above questions by using experimental methods. A generic model with several VGs was tested in a low speed wind tunnel and in addition to the lift and drag the surface pressure distribution and the trailing vortex signature behind the VGs were studied. In order to demonstrate the incremental effect of the vortex wake, airfoil shaped VGs were also tested, mainly to quantify the “blockage effectâ€‌ between the plate and the ground plane. The effect of rake (vehicle's angle of attack), which was not documented in previous work, was also investigated here. The results of this study provide quantitative information on the expected loads and pressure distribution behind such largescale VGs; data needed for the successful application of such devices to actual vehicles.