Contour Dynamics for the Euler Equations in Two Dimensions

We present a contour dynamics algorithm for the Euler equations of fluid dynamics in two dimensions. This is applied to regions of piecewise-constant vorticity withinfinite-area-vortexregions (FAVRs). Essentially, this reduces the dimensionality by one and we are treating the interaction of closed polygonal contours whose nodes are advected by the total fluid motion computed self-consistently. A leapfrog centered scheme is used for temporal advancement. Computer simulation results are given for two and four like-signed interacting FAVRs. In all cases wavelike surface deformations are observed. If the distance between FAVRs is comparable to their extent (“diameter”), these surface deformations are large. They play an essential role in the observed coalescence of FAVRs.