Transonic deep stall of a free-to-pitch rigid wing

Abstract

This work presents a combined numerical and experimental investigation of a rigid wing free to pitch in a transonic flow at Mach 0.8. The wing exhibits small-amplitude oscillations around an equilibrium point in deep stall, where a large separation region develops on the suction side. Fluid–structure interaction simulations suggest that the oscillation frequency originates from the unsteady motion of the juncture vortex that forms between the wind tunnel sidewall and the wing. The measured oscillation frequency is approximately 350 Hz, while the numerical prediction yields a value of 290 Hz. Additionally, a simplified criterion is proposed to estimate the juncture vortex oscillation frequency as the ratio between the mean vortex circulation and the product of the chord and the average vortex diameter.