Drag reduction on square-back vehicle using active flow control

Purpose This study aims to reduce the drag of a square-back vehicle which has poor aerodynamic performance due to its abrupt flow separation and large wake at the rear end. To reduce drag on a square-back vehicle, an innovative flow control system with a fan array on the vehicle’s rear side is installed. Design/methodology/approach The fan array positioned on the vehicle’s rear directs airflow (velocity with half of the vehicle speed) towards the vehicle’s backside to alter the pressure distribution. Findings The fan array located on the top rear portion of the vehicle creates a high-pressure zone that efficiently reduces the pressure difference and drag compared to a fan array positioned on the bottom rear portion of the vehicle. The fan array (covers around 15% of vehicles’ rear area, gap – 0.45% of the car’s length & airflow speed: 50% vehicle speed) positioned at 40% of vehicle height shows a maximum reduction in drag by 36% without affecting the downforce of the base vehicle. Research limitations/implications This study involved low-speed flow simulations on a 3D Ahmed body with a square back at 40 m/s. The infinitely thin fan was considered with the discontinuous pressure rise across the fan. Practical implications The maximum reduction in drag increases fuel efficiency, and the increase in downforce increases stability and speed during cornering. The optimum fan array design can be effectively used on bluff bodies, heavy vehicles, etc. for drag reduction. Originality/value The innovative fan array arrangement alters the pressure distribution on the square-back vehicle’s rear side and gives a lower drag force, with or without increasing the downforce.