Experiments On the Identification of the Onset of Buoyancy-Driven Convection in High Aspect Ratio Top Open Cavities

Abstract

Abstract Experimental analysis of the onset of buoyancy-driven convection in atop facing high aspect ratio cavity is reported. Bottom surface of the cavity is heated, with its two vertical side walls being insulated. Thermal field in the cavity has been non-intrusively mapped using a Mach-Zehnder interferometer. The cavity has been subjected to two different temperature differences, ?T= 3oC (Ra?300) and ?T=15oC (Ra? 1400). Sudden change in the heat transfer coefficient, as well as the formation of thermally stratified layers at the bottom part of the cavity, were not observed for the applied cavity temperature differences, which in turn, indicates that there is no such phenomenon of onset of buoyancy-driven convection in high aspect ratio cavities. Corner flow, induced due to the temperature difference between the atmosphere and the cavity, is the dominant flow inside the cavity. Almost identical profiles of flow in both the cases of the applied temperature potential signify that the flow profile is independent of the Rayleigh number or the temperature differences. These observations have been supported by whole field temperature distribution profiles, spatial distributions of local Nusselt number and non-dimensional temperature at different positions of the cavity.