THE INTERACTION OF A VORTEX WITH A BOUNDARY-LAYER

The three-dimensional vortex/boundary layer interaction of a type whic h may occur on a high-lift aerofoil has been studied. The experimental configuration simulates the trailing vortex system generated by two d ifferentially-deflected slats which interact with an otherwise two-dim ensional boundary layer developed on the wing surface under a nominal zero pressure gradient. The mean and turbulent flowfields are measured by a triple hot-wire system. The measurements show that the trailing vortex system includes the vortex sheets shed from the slats and the s ingle vortex formed at the discontinuity between them. The single vort ex moves sideways and interacts with the boundary layer as it develops downstream. During the interaction with the boundary layer, the low m omentum, high turbulent-kinetic energy flow carrying negative longitud inal vorticity is entrained from the boundary layer and rolled into th e vortex at the line of lateral convergence on the test surface. Likew ise, at the line of lateral divergence, the high momentum, low turbule nt kinetic energy flow carried by the vortex impinges on the boundary layer, suppressing the turbulent energy level and the growth of the bo undary layer.