Dynamic Stall Flow Control via a Trailing-Edge Flap

Effects of a moveable trailing-edge flap on the dynamic-load loops of an oscillating NACA 0015 airfoil were investigated at Re =1 .65 × × 10 5 . Both upward and downward flap deflections for different flap actuation start times, durations, and amplitudes were considered. Surface pressure measurements show that only upward flap deflections led to the reduction of nose-down pitching moment, and that the larger the flap deflection the more efficient the reduction mechanism was. The shorter the actuation duration the smaller the poststall lift loss. The reduction of the peak nose-down pitching moment was a consequence of the suction pressure appearing on the lower surface of the trailing-edge flap. The formation and detachment of the dynamic-stall vortex was not affected by the flap motion, whereas the low-pressure signature of the vortex was reduced by the upward flap deflection. The later the flap actuation during the upstroke, the greater the net torsional damping was. Optimum flap motion is also discussed.