Laminar-Separation-BubblesFlow Control over Airfoil Using SDBD Plasma Actuator

This experimental study is focused on the plasma active flow control over a 16% elliptic airfoil. Two Alternating-Current Surface-Dielectric-Barrier-Discharge (AC-SDBD) plasma actuators are installed on suction surface of the airfoil. The study is performed using AC-SDBD plasma actuator combined with the duty-cycle technique. In this study,the main purposes are to find the best fit way to eliminate or decrease the laminar separation bubble and to improve the lift and drag characteristics of the elliptic airfoil, especially improve the nonlinearities of the lift curve at the range of small angles of attack. The experiments are carried out in a 0.4 ×1.0 m low-turbulence low-speed wind tunnel at -2.5° to 13.5° angles of attack. The Reynolds number based on the chord of the airfoil are (1.4, 2.2) ×105. Lift and pitching moment were calculated from the surface pressure distributions and the total drag from the wake velocity profiles. The results consist different modes of controls: baseline, trip, plasma-off, three different steady plasma actuation and five different duty-cycle plasma actuation. For the duty-cycle, the frequencies are calculated by Strouhal number(St=0.167,0.5,1,1.33,1.83)for Re = 1.4 ×105. The pressure distributions, lift and drag curves with and without plasma actuation and with trip over the airfoil are used to compare. Significant increases in aerodynamic efficiency are achieved for certain electric parameters and locations of the actuator. The slope of lift coefficient curve at small angle of attack is closer to 2π with the adaptive duty-cycled plasma actuation.