Experiments on interaction of a jet with a trailing vortex

A parametric study was performed to evaluate the effect of a cold jet on a single trailing vortex. Flow visualization and Particle Image Velocimetry (PIV) measurements were conducted in wind and water tunnels. The main parameters examined were the ratio of jet strength to vortex strength, the initial distance between the jet and the vortex, the jet inclination angle, the Reynolds number and the downstream distance from the trailing edge. It was shown that the jet turbulence is wrapped around the vortex and ingested into it with increasing streamwise distance. This turbulence ingestion takes place faster with decreasing jet-to-vortex distance and increasing jet strength. Both time-averaged and instantaneous flow fields showed that the effect of the jet on the vortex can be quite significant. The trailing vortex became diffused with its rotational velocity and vorticity levels reduced. The mechanism with which the jet interacts with the vortex is a combination of vortices shed by the jet and the turbulence. No noticeable differences were found within the Reynolds number range tested. The effect of jet on vortex is delayed when the jet is blowing at an angle to the free stream and away from the vortex such as during take-off. The results suggest that the engine jets might have favorable effects on wing vortices, in particular on flap-edge vortices.