Transport of gas bubbles by vortex rings

Multiphase vortex rings are commonly observed in environmental and industrial settings. Interactions between vortex rings and bubbles allow bubbles to be entrained and accumulate in the vortex core and subsequently transported over a distance. Our study aims to investigate the behaviours of gas bubbles that are fed into vortex rings at different stages.

Novel experimental setups are used to measure the size distribution of bubbles entrained, transported and detrained at various locations. The vortex ring’s evolving ability to carry various sized bubbles, as well as the volume of bubbles that remain in the vortex rings, can then be concluded. A computational model has been implemented to quantitatively study the bubbles’ Lagrangian trajectories. Results from both simulations and experiments indicate that bubbles are preferentially entrapped in the vortex core, suggesting that a similar mechanism could facilitate long-distance transport of bubbles by ocean currents. Furthermore, the vorticity distributions in vortex ring flows are modified due to the presence of bubbles, and a numerical simulation model is developed to study the effects of microbubbles on the vortex ring structures, highlighting the two-way interactions between bubbles and the carrier flow.