SAE International The Aerodynamic Characteristics of a Race Car Wing Operating in a Wake 2008-01-0658

It is well documented that the aerodynamic performance of an open wheel race car is degraded when closely following another car. The greatest performance loss is usually experienced by the front-mounted wing leading to reduced aerodynamic downforce, handling imbalance and a reduced overtaking capability. Although previous wind tunnel studies have been performed to investigate this race situation the model scales have generally been compromised in order to achieve representative separation between the two test vehicles within the confines of the wind tunnel working section and particularly within the limited length of the moving ground plane. This study addresses that issue by using a very short, bluff body to create an accurate representation of the wake flow from the leading car in order to provide additional, effective test length ahead of the instrumented model. Data and analysis are presented that identify and quantify the key three-dimensional characteristics of the wake structure of a Formula One Racing car. It is shown that the wake structure is dominated by a trailing vortex pair coupled with turbulence intensities in excess of 40% and a velocity deficit that locally exceeds 50%. The effect of that wake structure upon a following vehicle and, in particular, its front wing is described and the relative significance of each of the primary characteristics of the wake is investigated independently. As the wake develops the effect of loss redistribution and reduced wake intensity suggest the wake influence reduces rapidly with increasing inter-vehicle spacing whilst the vortex structure is more persistent. As a consequence a following car experiences considerable local incidence variation and from the available evidence it could be argued that attempts to frame racing regulations to encourage overtaking should focus primarily on the reduction of the strength of the trailing vortex pair.