A numerical study on the thermal capillary-buoyancy convection of a binary mixture driven by rotation and surface-tension gradient in a shallow annular pool

Abstract

The thermal capillary-buoyancy convection with the Soret effect in a rotating annular pool was investigated by a series of three-dimensional numerical simulations. The annular pool is heated at the outer cylinder, cooled at the inner cylinder and filled with the n-decane/n-hexane binary mixture with an initial mass fraction of 50%. The present investigation focuses on the effects of the Taylor number and aspect ratio on the flow stability and flow patterns of the thermal capillary-buoyancy convection. The results show that the critical thermal capillary Reynolds number increases with the increase of the Taylor number, while decreases with the increase of the aspect ratio. Once the thermal capillary Reynolds number exceeds the critical value, the basic flow bifurcates to the flow pattern composed by the slender spiral waves and hydrothermal waves at a relatively small aspect ratio. In addition, the slender spiral waves are gradually suppressed with the increase of the aspect ratio. The basic flow transits to the hydrothermal waves at a relatively large aspect ratio. With the increasing Taylor number, the hydrothermal waves usually develop to the coexistence of the hydrothermal waves and internal oscillatory flow, which is created by the rotating vortex contained in the basic flow. Moreover, the Soret effect creates the concentration gradient opposite to temperature gradient, which enhances the thermal capillary-buoyancy convection in the binary mixture.