Kinematic properties of monopolar vortices in a strain flow

The advection properties of monopolar vortices subjected to background strain were investigated both experimentally and numerically. Dye-visualization studies in a stratified fluid demonstrated the deformation of the vortex core and the shedding of passive tracers from the edge of the vortex. The main kinematic characteristics of the vortex evolution could be well captured by a simple model, in which the monopole was represented by a (strength-varying) point vortex surrounded by a contour of passive tracers. Full numerical simulations of the vortex evolution showed an excellent agreement with the observed tracer distributions and also revealed that the spatial distribution of vorticity must be taken into account in order to explain the final tearing of the laboratory vortex.