Influence of solutal buoyancy on heat and mass transfer in mixed convection flow at constant thermal buoyancy: A 3D numerical study

The heat and mass transfer in the buoyancy-driven flow is mutually affected by the existence of temperature and concentration gradients in the mixed convection flow in several applications, like salinity in dissolved liquid or mixing concentration in liquid. The propagation of such combinations can be expedited by the presence of a rotating cylinder and moving lid. In this study, the mutual effect between concentration and temperature is coupled by including Soret and Dufour terms in the concentration and energy equations respectively. A three-dimensional numerical analysis of heat and mass transfer is presented by varying solutal buoyancy force at fixed thermal buoyancy in the flow with induced forced convection by moving top-wall and rotating cylinder with aspect ratio of 2.5. The heat and mass transfer (double diffusion flow) solver is framed in the open-source computational fluid dynamics tool OpenFOAM 5.0. The Reynolds number is kept the same for both the sources (rotating cylinder and moving top-wall) to induce forced convection and hence mixed convection in the domain. The thermal Rayleigh number and Richardson number are fixed for all the cases, and the buoyancy ratio (concentration buoyancy to thermal buoyancy) in the flow is altered by the fixed thermal Rayleigh number. The configuration of forced convection in the flow is varied by adjusting the angular rotational direction of the cylinder (clockwise and counter clockwise) and the direction of the moving top-wall (positive and negative x -direction). The clockwise direction and positive x -direction of the moving top-wall show 27% more mass transfer than other cases, and heat transfer is 37% more compared to other cases. The relevant quantities such as streamlines, isotherms, iso-concentration contours, average Nusselt number, and average Sherwood number have also significantly changed while the buoyancy ratios were varied.