Periodic intrusions in a stratified fluid

Abstract

When a salt-stratified body of fluid is heated from the side a series of almost horizontal convective layers can develop with well-mixed interiors. These layers can propagate into the interior of the stratified fluid. This behaviour is also observed with intrusions at fronts between stratified bodies of fluid where their composition varies. We look at a simplified model of intrusion growth where the mechanism behind the creation of their well-mixed interiors is neglected, and look at how a stack of such intrusions will propagate away from the wall or front. We find that there is a transition from a regime where the propagation is essentially inviscid and the intrusion length is proportional to time, to one where viscosity is important and the propagation rate slows down, with the length being proportional to the square-root of time.