Effect of wall-slip on natural convection in a circular annulus

Abstract

Two-dimensional natural convection in an annulus enclosed by a hot inner cylinder and cold outer cylinder with air (Prandtl number, Pr=0.71) as the fluid is numerically investigated for Rayleigh number (Ra)= 5 × 104 using OpenFOAM. For a gap width to radius ratio (L/Ri ) of 1.6, the slip configurations are imposed by varying the Slip factor (SF) from 0 (no-slip) to 1 (full-slip) in steps of 0.2. The flow patterns and thermal fields for each slip factor are visualised using streamlines and isotherms and heat transfer is quantified by Nusselt number (Nu). It is observed that the natural convection patterns at full-slip boundary condition (SF=1) exhibit unique phenomena like vortex splitting, shrinkage in the thermally stagnant regions, and reduction in thermal boundary layer thickness. The heat transfer characteristics, in general, get enhanced with the increase in SF.