Stability of thermal convection in a salinity gradient due to lateral heating

Abstract

Experimental investigations have been conducted to study the behavior of the flow field induced by lateral heating in a stably stratified fluid of constant gradient. The experiments were carried out in a tank 5 × 7 case7 8 × 11 case3 4 in. high; two opposite walls were made of aluminum and kept at different but constant temperatures, while the other two were of plexiglass for flow observation. The governing parameter is shown to be the Rayleigh number based on the length scale which is the potential rise of a heated fluid element in a stably stratified surrounding. At subcritical Rayleigh numbers, the fluid rises, almost imperceptibly, parallel to the heated plate and the lateral transport of heat is entirely by conduction. At supercritical Rayleigh numbers, the flow becomes unstable and cellular convection results, which is clearly visible in a shadowgraph. The cells are of approximately equal size and they appear simultaneously all along the heated wall. They grow in the lateral direction and finally reach the opposite wall. The critical Rayleigh number above which cellular convection occurs has been experimentally determined to be 15000 ± 2500.