Optimal amplification of the Crow instability

Abstract

A mechanism for promoting the Crow instability in a counter-rotating vortex pair is presented within the framework of linear dynamics. It consists of (i) the creation of a periodic array of vortex rings along the length of the vortices by stretching of vorticity at the leading hyperbolic point of the dipole, and (ii) the deformation of the vortices by the vortex rings leading to the Crow instability. A reduction of the characteristic time of the Crow instability by a factor of roughly 2 can be obtained by this mechanism.