Effects of enclosure geometry and thermal boundary condition on Rayleigh-Bénard convection of cold water near its maximum density

Abstract

A series of three-dimensional numerical simulations on Rayleigh-Bénard convection of cold water with the density inversion phenomenon in different enclosed containers with two thermal boundary conditions on the sidewalls are performed by using the finite volume method. Rayleigh number ranges from 2 × 103 to 3 × 105. The effects of density inversion parameter, aspect ratio, geometrical shape of the enclosure and thermal boundary conditions are discussed in detail. Results indicate that the density inversion phenomenon and the aspect ratio have a significant influence on the flow pattern and heat transfer. At a large Rayleigh number, the period oscillatory R-B flow is observed in the rectangular container with conducting sidewalls. However, the unsteady R-B flow in the cylindrical container with insulating sidewalls behaves as the single period, multi-period and chaotic flow characteristics with the increase of Rayleigh number. The heat transfer ability is enhanced by increasing Rayleigh number and the aspect ratio, while it's weakened with the increase of the density inversion parameter. The average Nusselt number of Rayleigh-Bénard convection of cold water in the rectangular container is larger than that in the cylindrical container, but nearly the same for the insulating and conducting sidewalls.