Wake-vortex alleviation flowfield studies

Wake-vortex-alleviation research was conducted in the far-field vortex wake of a generic wing-tail aircraft model. The goals were to achieve accelerated vortex strength reduction and to map the conditions at which this reduction would occur. The wing-tail model was run in a water tow tank to generate a pair of unequal-strength counter-rotating vortices on each side of centerline. Dye flow visualization provided physical insight into the nature of the vortex interactions, and three-component particle image velocimetry allowed quantification of key characteristics of the flowfield, including circulation, vorticity, vortex trajectory, and induced rolling moments. Experiments were conducted for a variety of model angles of attack, tail incidence angles, and tail spans. The results showed that with high tail/wing circulation ratios (high tail downloads) the tail and wing vortices interacted strongly, leaving substantially weakened vortices after a distance of about 60 to 70 spans downstream of the model. A longitudinal static stability analysis identified the moderate-to-high static margins required to achieve such circulation ratios.