An Experimental Investigation of Trailing Vortices Behind a Wing with a Vortex Dissipator

Abstract

An experimental study was carried out on a rectangular wing in the NASA-Ames 7- by 10-Foot Wind Tunnel. Flow visualization studies were made using a tuft grid and smoke. Preliminary studies showed that the introduction of a bluff body into the trailing vortex downstream of the wing resulted in modification of the vortex. Further studies showed that a small vertical panel, termed a vortex dissipater, mounted on the wing upper surface near the wing tip also caused modification of the vortex. Both the smoke and tuft grid visualization studies indicated that the dissipater caused a significant reduction in the maximum tangential velocities in the trailing vortex. Additional studies using a hot wire anemometer showed significant reductions in the magnitude of the tangential velocities, increases in the cross-sectional dimensions of the core of the dissipated vortex and changes in the turbulence structure. Limited flight tests with a dissipater fitted to a Convair 990 wing tip and using a Lear jet aircraft as a probe indicated that the rolling acceleration and the degree of roll control required was less in the modified vortex than in the unmodified vortex.