Control of Unsteady Aerodynamic Loads Using Adaptive Blowing

Adaptive slot blowing was experimentally investigated on a NACA 0018 airfoil model as a method to minimize unsteady aerodynamic loads. Tests were conducted in a wind tunnel facility specifically designed to facilitate high amplitude wind speed fluctuations. Initially, the effect of steady blowing from a control slot located near the leading-edge was investigated under quasistatic conditions. At Reynolds numbers ranging from 1.5·10 to 5·10, a relative change in lift of ∆cl ≈ 0.5 was obtained over a wide range of angles of attack. Various dynamic test cases including a pitching motion, a sinusoidal variation of the wind tunnel speed and a combination of both were considered. The formation of the dynamic stall vortex was suppressed with blowing at moderate momentum coefficients. Dynamically adapting the momentum coefficient effectively counteracted the lift fluctuations resulting from the unsteady inflow conditions and virtually constant lift was obtained in all test cases. Furthermore, control significantly reduced the moment excursions in all dynamic pitching experiments.

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