Evolution analysis of the main mechanisms of the jet/vortex interaction

A new analysis method of the jet/vortex interaction is presented to better understand the effect of each vortical structure on the others composing the jet and even on itself. Vortical structures are isolated from each other and the velocity field they produce is calculated by means of the Biot–Savart law. The structure influence on each another is then distinguished from the others by using its velocity field in the calculation of the vorticity momentum equations. Based on 3D‐datafields provided by a large‐eddy‐simulation (LES) of the interaction between a Lamb–Oseen vortex and a turbulent round jet, a post‐processing tool educes the vortical structures and quantifies the different vorticity momentum equations terms. The study has been limited to the first steps of the interaction regime when there are still few vortical structures so that the subsequent analysis of the post‐process results remains simple enough to be performed. The present method confirmed the intensification of azimuthal structures as they roll up around the main vortex. Core disturbance of the latter was found to be initially caused by those structures and not by core dynamic instabilities, which become dominant with the appearance of non‐linear mechanisms. Copyright © 2010 John Wiley & Sons, Ltd.