MULTIPLE VORTEX CLUSTERING AND CHAOTIC ADVECTION IN 2 DIMENSIONS

Abstract

Multiple vortex clustering in a shear layer has been investigated by means of flow visualizations within the context of the two-dimensional Navier-Stokes equations. The study shows that as many as five vortices can cluster together to form a long-lived bound state. This clustering is shown to enhance the shear layer growth drastically. A bound state of six vortices, on the other hand, is difficult to observe when the individual vortices are evolved from the fundamental. In this case, chaotic advection of vortices takes place and destroys the individual vortical structures, which can be diagnosed in terms of a new criterion for structural stability, a C factor.