Shear-driven flushing of dense fluid from a canyon

The mechanics of shear-driven flushing of a dense fluid from a canyon is considered through a series of laboratory experiments. Experiments are presented for a range of canyon aspect ratios and flow Richardson numbers. The dynamics of the mixing is discussed qualitatively and four separate flow regimes are identified. The flow regime observed is shown to be dependent on both the canyon aspect ratio and the flow Richardson number. For taller, narrower canyons and higher Richardson numbers a two-layer stratification is observed throughout the flushing process. For wider canyons and intermediate Richardson numbers the canyon remains stably stratified but no distinct layers are observed. For low Richardson numbers and wide canyons, the canyon is relatively well mixed during the whole flushing process. A regime diagram showing the flow observed in Richardson number-aspect ratio space is presented.