Drag reduction of ahmed body using surface dimples: A computational approach

Automobile Engineers have been trying to introduce the application of using dimples to reduce the drag of both road and air vehicles. Developments in automobile industry have led to increased fuel consumption, thereby increasing the need to reduce the fuel consumption. About 60 percentage of the total drag created due to the relative motion between vehicle and air is created at the rear end of the vehicle due to the formation of wake. The major means of drag experienced by a bluff body is the pressure or form drag. Whereas, the main cause of drag for a streamlined body is the skin friction drag which is due to the resistance offered by the friction on the vehicle skin. The present work intends to describe the variations in coefficient of drag of Ahmed body by modifying the top surface of the body using surface dimples of constant diameter 10 mm, constant dimple ratio (ratio of depth of dimple to diameter of dimple) and varying the number of dimples. To accomplish this, the Ahmed body was designed in CATIA@ and the CFD analysis was carried out using ANSYS Fluent@ solver. The drag reduces and also increases for specific patterns of dimples. The results obtained show that the minimum reduction of drag has been obtained for 1 and 5 dimples which is 2.05 percentage and a maximum reduction of drag has been obtained for 3 dimples which is 3.42 percentage. The drag increased gradually if the number of dimples increased beyond 5. The outcomes are validated with different research works in existence and significant conclusions are obtained.