On the dynamics of gravity current motion in a stratified ambient

Abstract

This study presents LES results of lock-release propagating gravity current (GC) at the base of a linearly stratified ambient. The focus of the study is to investigate the effect of ambient stratification on GC motion for both subcritical and supercritical regimes. The effects of Reynolds number and the ratio of the fluid depth in the lock to the total ambient fluid depth on GC front velocity are also examined. Also, the effect of stratification strength on mixing is evaluated. It is found that both subcritical and supercritical GCs have a constant-velocity phase. This phase terminates due to the current interaction with the internal waves (IWs) for the former, while for the latter, it is due to the decay of the head buoyancy. The duration of the constant-velocity phase increases with increasing stratification strength when the current is supercritical. For weak stratification the turbulence is considerable, while it is suppressed with stronger stratification. Mixing is more intense for supercritical GCs; however, mixing efficiency is much higher for subcritical GCs.