Natural convection heat transfer with anisotropic thermal diffusion for tilted two-dimensional cavities

Abstract

The effects of a domain tilt (counterclockwise, γ=00,300and600) and an anisotropic thermal diffusion on the natural convection heat transfer inside a square or rectangular cavity are investigated. The multiple relaxation time Lattice Boltzmann method with a double distribution function is used. The simulations are performed for a range of Rayleigh number (Ra=104to108). It is observed that the number of eddies is reduced due to the counterclockwise inclination of the cavity for a given Rayleigh number. The flow reversal is observed with a change in γ and anisotropic thermal diffusion ratio (β). Further, the stretching and merging of the inner core eddy with changes in γ and β are discussed. The spatially averaged Nusselt number along the hot wall (Nu¯h) is calculated to study the heat transfer rate and characteristics. It shows that the rate of heat transfer increases with an increase in the inclination and the thermal diffusivity ratio. For Ra=107and108 the observed flow structures are unsteady. The heat transfer in this type of unsteady flow and corresponding thermal plume dynamics are studied by computing Nu¯h at each non-dimensional timestep.