Experimental study on the structure and stability of a double-diffusive interface in a laterally heated enclosure

Abstract

Experiments are carried out to investigate the structure of a double diffusive interface separating two layers in a laterally heated enclosure. The main goal of this work is to study the structure of the interface and some of its instability characteristics. The velocity field at the vicinity of the interface is measured by a PIV system. Vertical concentration and temperature profiles are measured using a micro-scale conductivity/temperature instrument and the flow is visualized using the schlieren technique. Analysis of mean horizontal velocity profiles, obtained at different times during the experiment, illustrates the increasing tilt of the interface with time. Spectral analyses of velocity perturbations under unstable and stable conditions confirm the existence of the coherent vortices observed by the schlieren technique. The vortices above and below the interface are associated with different dominant frequencies due to the asymmetric character of the flow. Measurements show that the vortices are generated outside the region of the stabilizing concentration profile by a mechanism, which is essentially thermal and similar to Rayleigh-Bénard instability with weak shear.