The trapping and escape of buoyant vortex rings in sharply stratified fluids

TL;DR

This study investigates how buoyant vortex rings behave in sharply stratified fluids, revealing phenomena like trapping, partial trapping, and fissioning, through experiments and simulations.

Contribution

It combines experimental observations with numerical simulations to analyze vortex ring dynamics in stratified fluids, identifying critical behaviors based on key parameters.

Findings

Vortex rings can be completely trapped, partially trapped, or fission into smaller vortices.

Entrained fluid affects the buoyancy and dynamics of the vortex rings.

Critical behaviors depend on parameters like fluid densities and vortex travel distance.

Abstract

In this fluid dynamics video we study the dynamics of miscible vortex rings falling in ambient strongly (near two-layer) stratified fluid. Experiments and direct numerical simulations using the variable density Navier-Stokes (VARDEN) solver are presented and compared. Critical phenomena are identified depending upon the key parameters of the experiment (fluid and ring densities, upper layer vortex travel distance, etc) in which the descending dense vortex ring may experience complete trapping, partial trapping, or fissioning into a cascade of smaller vortices. The interaction of the vortex ring with the upper layer fluids leads to viscous entrainment which alters the effective buoyancy of the ring. Upon impinging on a density transition, the entrained fluid imparts different dynamics as it attempts to regain equilibrium leading to the critical behaviors.