Interfacial breakdown of double-diffusive convective layers by a horizontal temperature gradient

A two-layer, salt-stratified system destabilized and mixed by lateral heati ng and cooling is studied experimentally using three different enclosures. The following conditions are considered: thermal Rayleigh number Ra-T = 2 x 10(7)-7 x 10(8) and initial buoyancy ratio N-i = 0.441-0.882. Kelvin-Helmh oltz vortices occur, in the initial stages before mixing, within the interf ace that separates the top and bottom convective layers due to shear instab ilities. After that, the interface is significantly tilted and is rolled up near the hot and cold walls, while following the downward migration of the interface at the cold wall, the fluid in the bottom layer penetrates into the top layer along the hot wall, indicating the onset of mixing. These mix ing processes depend on the thermal Rayleigh number and initial buoyancy ra tio. Finally we propose a correlation for the dimensionless mixing time, va lid for initial buoyancy ratios less than unity. (C) 1998 Elsevier Science Ltd. All rights reserved.