Oscillating-Wing Tip Vortex with Passive Short-Span Trailing-Edge Flaps

Abstract

Tip vortex flow behind an oscillating NACA 0015 wing with passive short-span trailing-edge flaps was investigated experimentally at Re = 1.81 x 105. The spoiler was found to be very effective in diffusing the tip vortex, in terms of the reduction of peak tangential velocity ν θpeak and vortex strength, compared to a baseline wing, and also led to additional vertical upward displacement of the vortex center. No significant influence on the vortex size was observed, however. The spoiler-induced negative camber effects also translated into slightly reduced bound circulation, total lift, and lift-induced drag. For a tab, the dynamic increase-decrease in the vortex size and strength persisted and had values larger than for a baseline wing. No substantial change in ν θpeak , compared to that for a baseline wing, was noticed. The axial core velocity was always wakelike, and the vortex center was shifted relatively outboard and vertically downward below the baseline wing. The tab also led to an increase in the lift and drag forces. The symmetric flap provided a compromise in the critical vortex-flow quantities between the spoiler and tab cases.