Search Results

Important vehicle performance parameters such as, fuel economy and high speed stability are directly influenced by its aerodynamic drag and lift. Wind tunnel testing to asses these parameters requires heavy investment especially when test wind tunnel is not available in the country where vehicle development center is present. Hence to save cost and to compress development time, it is essential to asses and optimize parameters of a vehicle in very early stages of development. Using numerical flow simulations optimization runs can be carried out digitally. Industry demands prediction of aerodynamic drag and lift coefficients (CD,CL) within an accuracy of a few counts, consuming minimal HPC resources and in a short turnaround time. Different OEMs deploy different testing methods and different softwares for numerical simulations.

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 10o 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.