SALT-FINGER CONVECTION GENERATED BY LATERAL HEATING OF A SOLUTE GRADIENT

When a tank of fluid with a solute gradient is subjected to lateral he ating, a series of horizontal convection cells is generated when the c ritical condition is exceeded. This phenomenon has been observed exper imentally and simulated by two-dimensional numerical schemes by a numb er of previous investigators. In each of the convection cells, relativ ely warm and solute-rich fluid flows from the hot to the cold wall alo ng the top of the cell while the return of the relatively cool and sol ute-poor fluid is along the bottom of the cell. This situation is cond ucive to the onset of salt fingers. We recently performed a series of such experiments with salt-water and ethanol-water solutions. By using flow visualization techniques, salt fingers in longitudinal rolls typ ical of those occurring in shear flows were observed. Salt fingers wer e observed as soon as convection was initiated, and they advanced with the convection front. Experiments with an ethanol-water solution show ed that salt fingers can be generated by flows driven by a surface ten sion gradient and that the effect of solute concentration on surface t ension plays an important role in the process.