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UNSTEADY SEPARATION CONTROL USING SPATIALLY-COMPACT PULSED ACTUATION

George Tak Kwong Woo
George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology 771 Ferst Drive, Atlanta, GA 30332, USA

Ari Glezer
George W. Woodruff School of Mechanical Engineering Georgia Institute of Technology 771 Ferst Drive, Atlanta, Georgia 30332, USA

Abstract

The dynamics of controlled 3-D transitory attachment of stalled flow over a static and dynamically pitching 2-D airfoil is investigated in wind tunnel experiments. Pulsed actuation is effected over a spanwise fraction of the separated domain on a time scale that is an order of magnitude shorter than the characteristic convective time scale using surface-integrated pulsed, combustion-driven actuator jets. The dynamics of vorticity concentrations over the airfoil and in its near wake is computed from high-resolution PIV measurements of the flow field that are obtained phase-locked to the actuation in multiple cross-stream planes. The present measurements show that transitory attachment spreads towards the outboard, unactuated flow domains and far exceeds the spanwise width of the actuator. The attachment is accompanied by the formation of 3-D vortical structures that are advected and shed into the near wake. It is shown that coupling of the pulsed actuation to the airfoil's motion enhances the control authority of 3-D unsteady separation and can significantly mitigate the adverse effects of dynamic stall on the unsteady lift and pitching moment.