Optimizing Rear Spoiler Angle for Enhanced Vehicle Braking Performance

The recent advancements in vehicle powertrain and aerodynamics have led to an increase in the production of faster passenger cars, where high-speed driving scenarios demand equally efficient and safe braking systems to ensure the safety of both passengers and surrounding vehicles and pedestrians. At high speeds, aerodynamics can significantly impact overall vehicle braking performance due to the interaction between downforces and lift forces, which, in turn, affects the vehicle’s overall dynamic weight, directly contributing to the maximum attainable deceleration or braking force. Accordingly, the braking performance can be maximized by generating more downforce by means of rear spoilers, while taking into consideration their inevitable drag, which adds to the total vehicle motion resistance. Therefore, this proposed work aims to investigate the effectiveness of employing an active rear spoiler to enhance the vehicle’s braking performance, without introducing remarkable drag that could impair the driving performance and its accompanying fuel consumption. For aerodynamics analysis, a two-dimensional computational fluid dynamics (CFD) model has been developed in ANSYS-Fluent®, and its results have been fed into an integrated 7-DOF vehicle body dynamics model equipped with a nonlinear pneumatic tire model developed in MATLAB®. The investigation has been conducted for different combinations of braking initial speed, tire–road adhesion, and rear spoiler angle. The findings show that the existence of the optimal angle of the rear spoiler remarkably enhances the overall braking performance and reduces the distance needed to make the car come to a complete stop. Ultimately, this shows the effectiveness and necessity of implementing an active rear spoiler to optimize the performance of both braking (reduction in the needed braking distance) and driving (reduction in the inevitable accompanying aerodynamic drag).