Flutter and Stall Flutter of a Rectangular Wing in a Wind Tunnel

Abstract

The aeroelastic behavior of a rectangular wing with pitch and plunge degrees of freedom was observed experimentally using pressure, acceleration, and particle image velocimetry measurements. The wing was set at different static angles of attack and wind-tunnel airspeeds. The wing’s dynamic behavior was governed by a twoparameter bifurcation from steady to limit cycle oscillations, with the two parameters being the airspeed and the static angle of attack. At the lowest static angle, the wing underwent a classical flutter phenomenon that was transformed into a supercriticalHopf bifurcation at higher angles. The latterwas combinedwith a fold bifurcation at intermediate angles of attack. All limit cycle oscillations observed were either low-amplitude oscillations with timevarying amplitude or high-amplitude oscillations with nearly steady amplitude. They were caused by two different types of dynamic stall phenomena. During low-amplitude limit cycle oscillations the periodically stalled flow covered only the rear part of the wing. During high-amplitude limit cycle oscillations, trailing-edge and leading-edge separation occurred. Trailing-edge separation was characterized by a significant amount of unsteadiness, varying visibly from cycle to cycle. The occurrence of leading-edge separation was muchmore regular and had the tendency to stabilize the amplitude of the limit cycle oscillation motion.