Passive variable rear-wing aerodynamics of an open-wheel racing car

Abstract

A rear wing designed to improve motoring performance and enhance stability during cornering needs to generate a large downforce at a relatively low speed. If the angle of attack of the rear wing is large, then air resistance is increased during high-speed driving, and thus, fuel consumption is increased due to the large drag values. On the other hand, the performance on high-speed cornering will improve overall lap time with an increased angle of attack. To mitigate this disadvantage, we aimed to reduce the angle of attack during high-speed driving to reduce downforce and drag and thus to reduce fuel consumption. Meanwhile, during low-speed driving, for example in cornering, the angle of attack was increased and a large downforce generated to improve driving stability. In order to achieve both goals, we developed a passive-type variable rear wing. This rear wing was designed to have a three-step shape where the second step in the center was designed to swing. We first confirmed the behavior through both computer-aided engineering analysis and wind tunnel experiments, and then we constructed a full-size rear wing and measured the downforce on a student Formula SAE vehicle. The results showed that it is possible to generate a downforce of 80 N at a low speed of 30 km/h (8.3 m/s) and a downforce of 145 N at a high speed of 50 km/h (13.9 m/s).