Ring vortex collisions

A research question I am working on is the simulation of the head-on collision of two ring vortices, to study the turbulent cascade. Two counter-rotating rings colliding head-on disintegrate into smoke in a matter of miliseconds. This experiment can be thought of as a canonical system for studying the fast formation of minute (turbulent) structures from relatively smooth initial conditions. Experiments find it hard to measure everything that is going on, but simulations have a hard time figuring out which are the correct initial conditions to use: very smooth initial conditions can produce very different physics to conditions with a degree of noise, and different noises produce very different results due to turbulence's inherent chaotic behaviour.

High-speed visualization techniques have provided us with a new method to study these collisions. In this video we submitted in 2017 to the Gallery of Fluid Motion we have shown indications of an iterative mechanism which transfers energy across scales, similar to a turbulent cascade. We further quantified it in a recent article. Tubes have shown to be better for making higher Reynolds number simulations, and in the video submitted in 2018 we developed the previous analysis up to the asymptotic limits.

In my group, we are currently trying to better understand these mechanisms including how a ring collides against different sorts of walls, and how that applies to jellyfish, and whales.

Relevant articles

  • Cascade Leading to the Emergence of Small Structures in Vortex Ring Collisions R. McKeown, R. Ostilla-Mónico, A. Pumir, M. P. Brenner, S. M. Rubinstein Phys. Rev. Fluids, 3, 124702 [PRF][arXiv]