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BLEED CONTROL OF PITCHING AIRFOIL AERODYNAMICS BY VORTICITY FLUX MODIFICATION

John M. Kearney
Woodruff School of Mechanical Engineering Georgia Institute of Technology Atlanta, Georgia, USA 30332-0405

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

要約

Distributed active bleed driven by pressure differences across a pitching airfoil is used to regulate the vorticity flux over the airfoil's surface and thereby to control aerodynamic loads in wind tunnel experiments. The range of pitch angles is varied beyond the static stall margin (14° < α < 22°) of the 2-D VR-7 airfoil at reduced pitching rates up to k = 0.42. Bleed is regulated dynamically using piezoelectric louvers between the model's pressure side near the trailing edge and the suction surface near the leading edge. The time-dependent interactions of the bleed with the cross flow and its effects on the production, accumulation, and advection of vorticity concentrations during the pitch cycle are measured using phase-locked PIV. These interactions mitigate the impact of abrupt transitions between attachment and separation by reducing the peak lift and moment loads that can lead to pitch instabilities. As a result, the stability of the pitch cycle can be improved (negative damping reduced) by as much as ΔEα = 1.21 (at k ɢ.25).