Transient and steady natural convection from a heat source embedded in thermally stratified porous layer

Numerical results are presented for transient and steady natural convection from a heat source buried in a saturated, porous layer. The porous layer is thermally stratified with a negative temperature gradient but its corresponding Rayleigh number is not greater than that of the critical value (Rac = 40). The effects of the size of the heat source and its buried depth are also investigated. The results, which include the buoyancy-induced flow patterns and temperature profiles, as well as the heat transfer coefficient in terms of the Nusselt number, are presented for a wide range of Rayleigh number and stratification parameter. The results thus obtained have important implications for applications in geothermal energy and underground disposal of nuclear wastes.