The stratification phenomena in the thermal and solutal fields of double-diffusive convection in a circular cylinder

Abstract

The structure of double diffusive convection in a circular cylinder cavity has been numerically studied. The numerical results exhibit some new characters of non-horizontal stratifications of thermal and solutal fields: in the stratification state, the isothermal lines near the sidewall are higher than that near the symmetry axis, while the isoconcentration lines near the symmetry axis are relatively high. The mechanism of these non-horizontal stratifications is illustrated by comparing double-diffusive convection with natural convection driven by thermal buoyancy or solutal buoyancy alone. The effects of Lewis number Le and buoyancy ratio N on the non-horizontal stratifications of thermal and solutal fields are also investigated. The results show that: at a given time (t = 0.2), with an increase in Le (Le = 0–15), the area influenced by solute diffusion decreases; for isothermal line, the gradients of it initially increase, but it tends to be horizontal at the top of the cavity when the Lewis number is higher than 10. When N varies from 0 to 2, the isoconcentration lines tend to be horizontal while the gradients of isothermal line increase.