Traveling plumes generated within a double-diffusive interface between counter shear flows

A two-layer, salt-stratified NaCl-H2O system destabilized and mixed by late ral heating and cooling is considered in this paper. Flow visualizations ar e performed to examine the structure of the diffusive interface that separa tes the convection layers. Simultaneous temperature measurement and flow vi sualization technique reveal the existence of a regular, three-dimensional flow structure consisting of time-periodic buoyant plumes within the interf ace, which are due to instabilities of diffusive type. The plumes aligned i n the spanwise direction travel toward the hot wall above the interface and toward the cold wall below the interface, respectively, and there is a pha se shift of a half plume spacing between the upper and lower ones. Conseque ntly, temperature and concentration oscillations are periodically observed in the paths of plumes. (C) 2000 American Institute of Physics. [S1070-6631 (00)50511-X].