Optimal actuator selection for airfoil separation control

Many active flow control strategies have been developed to mitigate flow separation and improve aerodynamic performance. Most studies have focused on optimizing the control action for a given actuator configuration; however, actuator placement is intimately tied to achievable performance. In this paper, we formulate a systematic approach for determining the optimal actuator location for separation control from numerical and experimental fluids data for both stable and unstable systems. High-fidelity numerical fluids simulations have been performed to compute the lift and separation-angle responses to a pulse of localized body-force actuation applied at six distinct locations on the upper surface of the airfoil. These pulse response data are then used to determine the actuator location among the set that can drive the system output to an arbitrary value with the minimum amount of input energy. The results of this study indicate that the optimal actuator locations for controlling lift and separation angle are not identical.