Investigation of oscillating airfoil shock phenomena

(Received 13 May 1991, revised 15 October 1991, accepted 17 October 1991)

Abstract
Fundamental experiments were performed in an unsteady flow water table facility to investigate and quantify the unsteady aerodynamics of a biconvex airfoil executing torsion mode oscillations at realistic reduced frequencies. A computer-based image enhancement system was used to measure the oscillating supersonic and transonic shock flow phenomena. By utilizing the hydraulic analogy to compare experimental results with a linear theoretical prediction, magnitude and phase relationships for the bow shock were determined to be relatively independent of Mach number while the magnitude of oscillation of the shock is a strong function of the reduced frequency. The supersonic bow shock is in phase with the airfoil motion at low reduced frequencies, lagging the airfoil motion as the reduced frequency is increased.