Abstract
An overview of aspects of vehicle aerodynamics is presented, including the time-averaged and timevarying forces and pressures for commercial vehicles and passenger cars. A simplified generic shape (the Ahmed body) with varying rear slant angles is used to illustrate how the shape of the rear of a car influences the drag and wake flow. The wake velocity deficit (which gives insight into where following vehicles should be positioned to benefit from slipstreaming drag reductions) is shown to be very dependant on the rear slant angle. As a slant back angle of 30 degrees is approached, the velocity deficit regions in the wake move further apart, indicating that following vehicles obtain less drag reductions than if they were in the wake of a vehicle with a lower slant angle. However it is argued that much of the external body shape for cars is dictated by a combination of packaging requirements and consumer desires, thus is influenced by stylists rather than aerodynamicists. Internal cooling flows and the underbody can be influenced by aerodynamicists, as can minor details that influence aerodynamic noise. The relative merits of computational versus experimental methods are discussed for these areas and it argued that CFD works well for the prediction of time-averaged forces and cooling flows, but not for aeroacoustic predictions.
Keywords: Vehicle, Car, Aerodynamic, Review, Ground Simulation, ITS, CFD, EFD,