Plasma-Based Control of Transition on a Wing with Leading-Edge Excrescence

Abstract

Large-eddy simulations are carried out to investigate plasma-based flow control that is used to delay transition generated by excrescence on the leading edge of a wing. The wing airfoil section has a geometry that is representative of modern reconnaissance air vehicles and has an appreciable region of laminar flow at design conditions. Modification of the leading edge, which can be caused by the accumulation of debris, insect impacts, microscopic ice crystal formation, damage, or structural fatigue, may result in premature transition and an increase in drag. A dielectric barrier discharge plasma actuator, located downstream of the excrescence, is employed to mitigate transition, decrease drag, and increase energy efficiency. Numerical solutions are obtained to the Navier–Stokes equations that were augmented by source terms used to represent the body force imparted by the plasma actuator on the fluid. A simple phenomenological model provided this force resulting from the electric field generated by the plasma. The numerical method is based upon a high-fidelity numerical scheme and an implicit time-marching approach. An overset mesh system is employed to represent excrescence in the leading-edge region. Solutions are generated for both uniform and distributed excrescence geometries, as well as for the clean wing configuration without leading-edge modification. Results are obtained for two different values of the plasma field strength. Features of the computational flowfields are elucidated, and the effectiveness of control is quantified by comparison with baseline results without plasma actuation. It is found that plasma control can reestablish the laminar flow region lost to excrescence-generated transition and increase the lift-to-drag ratio by up to 8.7%.