Effect of Side Taper on Aerodynamics Drag of a Simple Body Shape with Diffuser and without Diffuser

There are different techniques to reduce aerodynamic drag of a vehicle. Side tapering or boat-tailing is one of the methods to reduce drag of a vehicle. In this study instead of using very simple shape of a model, a more relevant simple car like shape resembling a hatchback vehicle is utilized. This shape of a simple car body has 10^o diffuser angle. This hatchback model is modified digitally to give side tapering to it. The boat-tailing is restricted to sides of a vehicle and tapering is applied along the whole height of a vehicle. First a correlation study is performed between numerically predicted drag values and wind tunnel tested values. Effect of tapering with and without diffuser is also studied. An unexpected behavior is observed when removing a diffuser on base model caused reduction in drag values. Best tapering angles in both with and without diffuser cases are reported. Detailed post processing is performed to understand wake behavior and variation of different parameters in all different analysis cases.