Wingtip vortex modifications using alternating jets

The safe reduction of separation distance between airplanes can be achieved by modifying the wingtip vortices. Modifications in a near-field wake by using spanwise jets were studied on a NACA 0012 wing model. Experiments were conducted in the wind tunnel at 15 m/s and at an angle of attack of 7.5 degrees. Two chambers were integrated in the interior of the wing model with two angled jet slots in the wingtip. The jets pulsed at 10 Hz. The jet velocity distribution was quantified with the help of a hot-wire anemometry and 2D PIV. In order to investigate the evolution of wingtip vortex, the phase-locked 2D PIV measurements were conducted at 5 streamwise stations. Studies include the baseline case, steady and pulsed jet blowing on the pressure and suction sides, and alternating phase-shifted blowing of two jets. Spanwise blowing jets displace wingtip vortices upward and outward from the wing tip. Under the pulsed blowing, the vortex center oscillates along the line inclined to the horizontal. When advecting downstream, the vortex is moving in a spiral trajectory rotating in the direction of the baseline vortex rotation. Experiments revealed that the maximum circulation decreases and core size increases downstream under pulsed blowing.