Ground effect diffusers have become a prominent aerodynamic device on open-wheeled race cars and sports cars, typically used to generate downforce for better traction. The characteristics and physics that determines downforce generation and its application in automobile and racing industry needs an in-depth analysis to develop a systematic understanding. The amount of downforce generated is dependent of geometrical parameters like ride height, relative length of diffuser to that of the vehicle and the ramp angle. This paper explains the performance of ground effect diffusers and details a numerical investigation of the effects of geometrical parameters in order to find optimum downforce and efficiency for the inverted Ahmed model adapted as a vehicle diffuser bluff body. A short and long diffuser with relative lengths of 0.1 and 0.35 are studied. The short diffuser produced less maximum downforce and efficiency compared to the longer diffuser. Different diffuser ramp angles were found to correspond to different ride heights to achieve optimum efficiency and downforce.

Keywords : Ground-Effect, Aerodynamics, Diffuser, Downforce, Efficiency