Effect of apex flap length on leading edge vortex breakdown over delta wings

The effectiveness of the apex flaps to control the vortex breakdown on a 70° sweep angle delta wings was studied experimentally. The angle of attack was in a range of 30°C-50°C. The flap angles and its length were found to be two important factors in determining the position of vortex breakdown in steady flow. Flow visualization results reveal that a drooping apex flap, effectively lowering the angle of attack of the portion of the wing closest to the apex can delay vortex breakdown. The variation in the flap angle produces a nonlinear effect on the vortex breakdown location, and it can be seen that the biggest flap produces the most significant effectiveness. The effect of the combination of the two apex flaps is better than that of single flap at α=35°.