Numerical investigation of plasma actuator configurations for flow separation control at multiple angles of attack

The objective of this study was to analyze the effectiveness of aerodynamic plasma actuators as a means of active flow control over an airfoil at multiple angles of attack under low Reynolds number conditions. Each angle of attack corresponded to two different flow separation mechanisms (i.e., laminar separation bubble (LSB) and fully turbulent flow separation at stall conditions). Detailed parametric studies based on steady and unsteady Reynolds Averaged Navier-Stokes simulations were performed for a NACA 0012 airfoil at a chord Reynolds number of 105 to investigate the influence of the number, the location, the imposed body force magnitude, and steady vs. unsteady operation of plasma actuators on flow control effectiveness. For LSB control, as much as a 50% improvement in the lift to drag ratio was observed. Results also show that the same improvement was achieved using unsteady or multiple actuators, which can require as much as 75% less time averaged body force compared to a single, steady actuator. For the stalled airfoil case, significant recovery in aerodynamic performance was observed for a single, steady actuator. However, for the stall conditions considered in this study, unsteady and multiple actuator configurations do not provide the same enhancement as a single, steady actuator, which may be due to the nature of the flow separation (turbulent, trailing edge separation). The results of both cases show that the optimum location of a plasma actuator would be just upstream of the separation location for maximum effectiveness. This highlights the usefulness of multiple actuator systems for flow control over a range of operating conditions as the separation location may be dynamic.