Abstract

Transitory control and regulation of the aerodynamic loads on a static and dynamically pitching VR-12 airfoil is investigated in wind tunnel experiments. Actuation is enabled by a spanwise array of integrated combustion-based actuators that are triggered intermittently relative to the airfoil’s motion, producing high-impulse actuation jets on characteristic time scales that are an order of magnitude shorter than the airfoil’s convective time scale. Poststall transitory actuation leads to a momentary reattachment of the flow over the airfoil, and the effects of sequencing of actuation pulses on the aerodynamic characteristics of the airfoil are assessed using time-resolved measurements of the lift force and pitching moment coupled with particle image velocimetry that is acquired phased-locked to the airfoil motion. The present investigations show that the aerodynamic loading can be significantly altered by a number of actuation programs using strategically timed bursts during the pitch cycle. While actuation during the upstroke primarily affects the formation, evolution, and advection of the dynamic stall vortex, actuation during the downstroke accelerates flow reattachment. Superposition of such actuation programs can lead to enhancement of cycle lift and pitch stability, and reduced cycle hysteresis.

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