The use of a Bluff Body Wake Generator for Wind Tunnel Studies of NASCAR Drafting Aerodynamics

It is well documented that the aerodynamic downforce that is developed by a NASCAR race car is degraded when closely following another car. This may lead to handling imbalance and a reduced overtaking capability. Although wind tunnel studies have been performed to investigate this race situation those investigations have frequently been compromised in order to accommodate two or more test vehicles or models within the confines of the wind tunnel's working section. 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 maximize the test length available to the test model. Data and analysis are presented that identify and quantify the key three-dimensional characteristics of the wake structure of a NASCAR race car and 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 60%. It is clearly demonstrated that a simple, bluff body wake generator is an effective tool that allows detailed drafting studies to be performed in existing facilities and without the need to reduce the scale of the test models.