Momentum injection-based active flow control of a simplified automotive body

With the advent of high-speed vehicles, it is necessary to redesign the vehicles with due consideration to exterior aerodynamics. The present study explores an active flow control technique for aerodynamic drag reduction to achieve reduced energy consumption for a simplified automotive body. To this end, detailed computational fluid dynamics (CFD) simulations are performed to resolve the turbulent flow features around the vehicle body by employing improved delayed detached eddy simulation (IDDES). The present modeling strategy is validated against the experimental aerodynamics data of an Ahmed body with 25° slant angle. This is a well-known benchmark problem for studying the wake dynamics of ground vehicles. An active flow control strategy is designed to investigate the efficacy of momentum injection control by means of a single rotating cylinder. Three distinct control cylinders of different sizes are chosen to study the influence of momentum injection control. Among the cases numerically investigated with constant actuation speeds, a maximum drag reduction of 11.6% is observed. To assess the net energy savings, a cost function is formulated and minimized for various conditions. Furthermore, within the active flow control framework, three distinct closed-loop feedback control strategies are incorporated to various input conditions and the quantum of actuation as dictated by the control algorithm. The efficacy of these closed-loop feedback controls are assessed by applying on–off control to the actuator.