A high-performing sawtooth plasma actuator with multi-electrodes

Abstract

The present study for the first time develops a high performing sawtooth plasma actuator (PA) that may produce large flow velocity u and streamwise vorticity ωx′ by means of increasing the number of electrodes. This improved performance is crucial for improving the post-stall airfoil aerodynamics. It is found that the high performing sawtooth PA with three encapsulated electrodes powered by +Vdc (hereafter called the optimum sawtooth PA) produces the maximum ωx′ and u of 650 s−1 and 6.83 m/s, respectively. The plasma-induced flow is linked to the acceleration of the negatively charged species in the streamwise direction caused by the +Vdc-powered encapsulated electrodes and is 26.5% larger than that produced by a standard sawtooth PA (with two sawtooth electrodes) under the same power consumption. At a chord Reynolds number Re=1.0×105, the optimum sawtooth PA under steady mode actuation postpones the stall angle-of-attack α of a NACA 4412 airfoil by 4° and increases the maximum lift coefficient CL by 8.1%; the former is appreciably larger than that (0°) achieved by the standard sawtooth PA. Furthermore, under the optimum burst mode actuation (non-dimensional burst frequency F+=1.4 and duty cycle DC=7%), the stall α and the maximum CL increase by 5° and 19.6%, respectively, along with a 93% power saving. The physical mechanisms behind the impressive performance are discussed.