SINKING PATCHES OF SALT WATER ON A SLOPE OF BOTTOM SURROUNDED BY FRESH WATER: DYNAMICS AND STRUCTURAL FEATURES OF DENSITY FRONT PROPAGATION UP THE SLOPE

Abstract

The study of the dynamics of two small volumes of water with negative buoyancy (patches of salt water), imitated a sinking of dense water into an underlying water, was carried out. These volumes usually appear in the process of surface water cooling during seasonal convection in the coastal zone of the sea. The main tools of investigation were laboratory and numerical experiments. The main stages of motion of patches were identified: sinking, contact, and spreading along a bottom slope. The process of interaction of the water patches during their movement up the bottom slope was detailed in laboratory experiments. Patches of salt water retained unmixed long time, that confirm the laminar character of the appearing flows. Distributions of tracers obtained in the calculations was analyzed with the aim to identify the characteristic stages of the flow of patches up the slope. Three stages were suggested: initial contact, diving, wrapping and breaking. For the first time dense water flow up the slope, which occur as a result of sinking of small volumes of salt water, was described. The results allow us to notice the intensification of mixing of water dense than underlying waters in the process of surface water cooling in coastal zone of the sea.