Separation Control by Plasma Actuators: Effects of Direct Momentum Injection and Vortex Generation

In this work, Dielectric Barrier Discharge actuators with triangular tips on their exposed electrodes are applied on a NACA 0015 airfoil and tested in the wind tunnel at an airspeed of 20 m/s (Re = 330k); the actuator set has been defined after previous laboratory studies. Steady and pulsed actuation are tested on all devices, including a straight DBD as reference. Force coefficients and electrical power are measured for every actuator, evaluating their performance in terms of aerodynamic coefficients changes with respect to the smooth airfoil and to the unpowered case, which is also characterized by means of surface visualizations. The influence of discharge length and tip spacing is studied by image processing techniques. The local field of motion is characterized by means of boundary layer velocity profiles, acquired with plasma off and on. Boundary layer thickness and momentum coefficients are determined at different spanwise locations for all the devices. The results are discussed evaluating the different impacts of streamwise momentum injection and vortex generation on the actuators performance, assuming these mechanisms as proper models for the data interpretation. In turn, this leads to outline possible design rules for this kind of DBD