Self-induced vortex ring dynamics in subsonic rectangular jets

This is the authors' abstract. We don't add key points for this paper.

The development in space and time of vortex rings in low aspect-ratio (AR) rectangular jets is investigated. By design, the present studies isolate the self-induced ring dynamics from effects of unsteady events otherwise present upstream and downstream of the rings in developed jets. The simulations show that the vortex rings undergo quite regular self-induced nonplanar deformations, approximately recovering their shape and flatness with axis rotated with respect to their initial configuration. The axis-rotation periods are in good agreement with previously reported data for pseudoelliptic rings, and exhibit nearly linear growth rate as a function of AR. For the larger aspect-ratio case studied (AR=4), bifurcation of the ring due to vortex reconnection into roughly round rings is observed, followed by collision of the split rings and a new reconnection process, suggesting pathways for transition to turbulence based on self-induced vortex deformations and reconnections.