Vortex stripping and the erosion of coherent structures in two-dimensional flows

Abstract

This paper studies the erosion of a monotonically distributed vortex by the joint action of inviscid stripping, induced by an externally imposed adverse shear, and viscous diffusion, either in the form of Newtonian viscosity or hyperviscosity. It is shown that vortex erosion is greatly amplified by the presence of diffusion; abrupt vortex breakup or gradual quasi-equilibrium evolution depend crucially on the strain to peak vorticity ratio and on the Reynolds number. Peculiar, unexpected effects are observed when hyperviscosity is used in place of Newtonian viscosity.