Separation Control Using Plasma Actuator on an Elliptic Airfoil at Low Reynolds Numbers

Abstract

Detailed investigation of a 16% thickness elliptic airfoil is developed at a low turbulence wind tunnel. The purpose is to eliminate or decrease the nonlinearities of the lift curve at the range of small angles of attack for low Reynolds numbers. The baseline flow is characterized by four distinct regimes, depending on angle of attack, with each exhibiting unique flow behavior. To explain how the plasma actuation affects the laminar separation over the airfoil, the impact of boundary layer trip strip is explored. The results show that the Alternating-Current Single-Dielectric-Barrier-Discharge (AC-DBD) would energize the boundary layer, thereby delay separation and increase the circulation of airfoil, resulting in an increase of linear performance. The linear proportional control at small AOA range is achieved with the appropriate lift enhancement and reduction by using plasma actuation. The slope of the lift is 2π. The duty-cycled plasma actuation is more effectively than the steady actuation at lower Re. When the Reynolds numbers increase to Re=1.8×10 5 and 2.2×10 5 , the plasma actuation can no longer affects the separation. However, the AC-SDBD plasma actuator still can eliminate the bubble like a transition trip. Nomenclature c p = pressure coefficient c l = lift coefficient of airfoil c = chord α = angle of attack τ = fraction of time when actuator is activated over a duty-cycled period f = frequency of duty cycle f + = reduced frequency of duty cycle, fc / U∞ k = height of grit F = frequency of voltage source L = lift force