Salt-finger convection in a stratified fluid layer induced by thermal and solutal capillary motion

Salt-finger convection in a double-diffusive system is a motion driven by the release of gravitational potential due to differential diffusion rates. The normal expectation is that, when the gravitational field is reduced, salt-finger convection together with other convective motions driven by buoyancy forces will be rapidly suppressed. However, because the destabilizing effect of the concentration gradient is amplified by the Lewis number, with values varying from 10² for aqueous salt solutions to 10⁴ for liquid metals, salt-finger convection may be generated at much reduced gravity levels. In the microgravity environment, the surface tension gradient assumes a dominant role in causing fluid motion. In this paper, we report some experimental results showing the generation of salt-finger convection due to capillary motion on the surface of a stratified fluid layer. A numerical simulation is presented to show the cause of salt-finger convection.