Fuel consumption is at an all-time high, with crude oil set to get depleted in the next two decades. Drag force is one of the major components responsible for decreasing mileage and thus increasing fuel consumption in vehicles. Using passive modifications such as spherical depressions on the body surface, aerodynamic drag experienced by passenger vehicles can be significantly reduced. Spherical depressions are designed to delay flow separation, following which the wake size is reduced, resulting in a decrease in drag force. In this study, computer-aided design (CAD) models of generalized lightweight vehicles are made with dimples at the sides of the car, having a diameter of 60 mm and a center-to-center distance of 90 mm. Several models are created having depression aspect ratios (ARs) of 2, 4, 6, and 8, and each model is simulated to velocities of 22 m/s, 24 m/s, 26 m/s, 28 m/s, and 30 m/s. Computational fluid dynamics (CFD) is used to study flow characteristics using parameters such as velocity vectors, pressure contours, and drag coefficient and compare models with depressions against those without. It is observed that an increase in AR leads to an increase in the coefficient of drag and that ARs of 6 and 8 exhibit drag values greater than for the car without depressions. A reduction in drag of up to 3.8% is observed from the study, using an AR of 2.
