INTERACTION OF SPANWISE VORTICES WITH A BOUNDARY-LAYER

The interaction of a spanwise vortex with a boundary layer has been nu merically simulated using a fractional-step method. The incompressible Navier-Stokes equations are solved to accurately predict the strong v iscous-inviscid interaction between a vortex either near or embedded w ithin a boundary layer of comparable size. A strong vortex induces an eruption and the production of a secondary vortex. The secondary vorte x causes the primary vortex to rebound, a response observed in many pr evious experiments and numerical simulations. However, weaker vortices as well do not follow the inviscid trajectory despite the absence of a secondary vortex. Rather than creating vorticity at the wall, a weak er vortex mainly redistributes the vorticity of the boundary layer, pu lling it away from the wall. The redistributed vorticity alters the pa th of the vortex. In the laminar cases studied the decay of the vortex is not significantly altered by the boundary layer. (C) 1995 American Institute of Physics.