Неустойчивость двойной диффузии при сонаправленной диффузии растворенных компонент

Abstract

Diffusion can have a destabilizing effect on the development of convective flows in multicomponent liquid mixtures with different diffusion rates of components. The movement that arises in this case, which is generally called double (or differential) diffusive instability, is an important mechanism for intensifying mass and heat transfer in many natural and technological systems. As components that affect the overall density distribution in a liquid medium, heat and a dissolved substance or two dissolved substances can act. In the latter, isothermal case, the standard formulation of the problem includes the study of the stability of a two-layer system under counter diffusion of components dissolved in adjacent layers. The possibility of developing instability during co-directional diffusion of components having a different sign of the concentration dependence of density and initially dissolved in one of the layers was experimentally investigated for the first time. Such a statement of the problem is closest to a number of oceanological applications, where the development of instability is due to the uneven distribution of temperature and salinity of sea water. In present work, the development of double diffusive instability was found and it was shown that the structure of the resulting convective flow is determined by the ratios of the density increments due to the dissolution of the components and the diffusion coefficients. Based on the research results, a set of dimensionless parameters is proposed and a map of the regimes of the observed convective flows is constructed, which allows us to systematize the experimental data.