Bursting of a Swirling Jet Stemming from a Localized Perturbation

Abstract

The present study is aimed at understanding the mechanisms which lead coherent vortex structures to burst, as observed in fully turbulent flows [2]. A single structure is considered here, modeled by a Batchelor-vortex flow. The linear and nonlinear evolution of an initially localized perturbation is followed by DNS. As already known [5], the flow is linearly unstable towards helicoidal disturbances. Vortical helices are found to arise from the saturation of this primary instability. At the same time, the vortex bursts in the neighborhood of the initial perturbation location, where numerous linear instability modes grow in place, the interaction of which is likely to cause rapid vortex dissipation.