COLLAPSE INTERACTIONS OF FINITE-SIZED 2-DIMENSIONAL VORTICES

The point vortex model predicts that a certain configuration of three point vortices leads to a collapse of these vortices to one point. Num erical simulations have been performed to investigate the effect of a finite vortex size on this two-dimensional collapse interaction. The p aper presents results obtained with contour dynamics simulations of pa tches of uniform vorticity, and results obtained with finite differenc e simulations of vortices with continuous properties. In addition, the effect of viscosity and the presence of impermeable domain boundaries are investigated. The results show that the motion of finite-sized vo rtices is quite similar to the motion of point vortices as long as the mutual distance between the vortices is larger than their size. When the vortices are closer together their shapes start to deform and the subsequent evolution is different from that of the point vortices, and an actual collapse to one vortex does not take place. (C) 1997 Americ an Institute of Physics.