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

A two-layer, salt-stratified NaCl-H₂O system destabilized and mixed by lateral heating and cooling is considered in this paper. Flow visualizations are performed to examine the structure of the diffusive interface that separates the convection layers. Simultaneous temperature measurement and flow visualization technique reveal the existence of a regular, three-dimensional flow structure consisting of time-periodic buoyant plumes within the interface, which are due to instabilities of diffusive type. The plumes aligned in the spanwise direction travel toward the hot wall above the interface and toward the cold wall below the interface, respectively, and there is a phase shift of a half plume spacing between the upper and lower ones. Consequently, temperature and concentration oscillations are periodically observed in the paths of plumes. (C) 2000 American Institute of Physics.