Time-dependent inviscid vortices in three-dimensional boundary layers

We address the inviscid stability problem for time-dependent Görtler vortices within a three-dimensional boundary layer. As the crossflow component is increased the Görtler vortex is found to suffer a change in structure to either that of a crossflow instability or to a vortex which is trapped in a thin zone within the boundary layer. These results are natural counterparts to those found by Bassom and Hall (19) who were concerned with stationary inviscid and viscous Görtler vortices. We investigate the two forms into which the vortex may evolve with increasing crossflow and in particular we obtain an asymptotic description of the high wavenumber inviscid modes. Significantly, we demonstrate how the properties of these latter modes may be matched to the time-dependent viscous vortices of Bassom and Hall (19) and how the frequency of the disturbance crucially affects its characteristics.