VORTEX BREAKDOWN OVER A DELTA-WING WITH OSCILLATING LEADING-EDGE FLAPS

The effects of oscillating leading-edge flaps on leading-edge vortices and vortex breakdown were investigated for a delta wing with upward-d eflected flaps. The variation of breakdown location revealed hysteresi s loops. The time-averaged breakdown location over one cycle may move upstream or downstream compared to the quasi-steady case, depending on the amplitude of flap oscillations and angle of attack. Measurements of the phase-averaged velocity upstream of breakdown did not reveal an y correlation to the response of breakdown location. The effect of osc illating flaps is largest when the breakdown location is near the trai ling-edge region in the static case.