Aerodynamic Behavior of Formula Student Open-Wheel Race Car Model with Regard to Head Restraint/Rear Wing Interaction

A realistic open-wheel race car model is investigated experimentally by means of surface flow visualization using UV active tufts, wall pressure as well as force measurements. The head restraint size is varied and crosswind conditions are reproduced inside a closed test section with a non-moving ground. An assessment of the aerodynamic components determines the contributions of front wing, rear wing and side wings with respect to the performance of the race car. Maximum downforce of the order of c_L ≈  −0.35 (front wing only), c_L ≈  −1.4 (front wing and rear wing combined) and c_L ≈  −1.5 (complete aero package) are found at a neutral yaw angle. By means of flow visualization and image subtraction techniques, regions of highly turbulent flow on the rear wing are identified. They are shown to grow in size when the largest head restraint is installed. As a result, the pressure distribution for this configuration exhibits a consistent decrease in magnitude. In the case of the smaller investigated head restraints, only marginal deviations are detected. The disadvantage of the largest head restraint, however, becomes less pronounced at small yaw angles, reaching a maximum in downforce at |β| ≈ 6°. Nonetheless, the application of a head restraint with a size exceeding a certain threshold is accompanied with a significant loss in downforce performance of the order of Δc_L ≈ 5.5%, as we are able to show in this article.