Bi-directional Control of the Aerodynamic Loads on an Airfoil at Low Angles of Attack using Fluidic Actuation

Controlled, bi-directional regulation of the aerodynamic loads on an airfoil at low angles of attack when the base flow is fully attached is investigated in wind tunnel experiments using fluidic actuation in the absence of moving control surfaces. Control is effected by inducing transitory vorticity concentrations on the suction and pressure surfaces using pulsed actuation on time scales that are significantly shorter than the airfoil’s convective time scale. Actuation is provided using individually-controlled spanwise arrays of miniature combustion-based actuators that are located near the leading edge and trailing edge of the suction and pressure surfaces. The effects of actuation are assessed using phase-locked measurements of the time-dependent aerodynamic loads and particle image velocimetry. Independent actuation on the suction or pressure surfaces near the airfoil’s trailing edge leads to momentary accumulation of vorticity and the concomitant, respective decrease or increase in lift is coupled with changes in the airfoil’s Kutta condition. Therefore, bursts of successive actuation pulses enable bi-directional control authority without the need for mechanical control surfaces, and with lower drag penalty.