Vortex rings descending in a stratified fluid

Experimental and numerical results are presented of a laminar vortex ring descending in a linearly stratified fluid. It is observed that the ring shrinks in size as it penetrates the stratified environment and has nearly disappeared when it comes to a stop. This behavior is similar to what was observed by Maxworthy [J. Fluid Mech. 81, 465 (1977)] for a turbulent vortex ring in a stratified environment. The ring position and size collapse on a single curve when appropriately scaled. It is shown that baroclinic vorticity production of opposite sign and cross diffusion is the cause for the disappearance of the ring. The instantaneous ring Froude number is always ⩾1 and, therefore, no internal waves are generated.