THE LIFE FORCE OF AN 2-D AIRFOIL IN UNSTEADY FREESTREAM

Ismet Gursul*, Hank Lin†, and Chih-Ming Ho‡

*Assistant Professor, Department of Mechanical, Industrial, and Nuclear Engineering, University of Cincinnati.

†Research assistant, Department of Aerospace Engineering, University of Southern California.

‡Professor, Mechanical, Aerospace, and Nuclear Engineering Department, University of California, Los Angeles.

Abstract

The response of a NACA 0012 airfoil in the poststall region was examined when the unsteady freestream velocity varied sinusoidally as a function of time. Several operational parameters, including the reduced frequency, the angle of attack, and the amplitude of the freestream oscillation were systematically varied over a large range of values. Lift measurements showed that under the optimum condition, the phase-averaged lift force becomes maximum. For the optimal case, flow visualization shows that the high aerodynamic loads are due to a large coherent vortex which sheds from the leading-edge and stays on the wing for an appreciable portion of the cycle.

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