On the effect of reversing the direction of convection in a two-component fluid

Abstract

The theoretical problem of convection in a two-component medium (for example, in salt water) after “switching on” the sources/sinks of heat and admixture on an infinite vertical boundary is considered. Generally speaking, the degree of influence of the two components on convection is different due to the difference in their diffusion velocities. We suppose that heat diffuses much faster than the admixture and then the heated/cooled region at the lateral boundary is much thicker than the region of propagation of the impurity concentration disturbance. Therefore, convection due to temperature deviations is less affected by viscosity than due to deviations in admixture concentration. As a result, even a relatively weak “thermal” source of buoyancy can determine the direction of convection for some time in spite of the action of a more intense “concentration” source of buoyancy of a different sign. But if a vertical layer of a medium of finite thickness is considered, then a stationary regime is established over time, in which the direction of convection is determined by the total source of buoyancy, so that the direction of convection can change sign.