2-PHASE CONVECTION IN A POROUS-MEDIUM

The conditions for the onset of convection and the characteristics of the convection at the onset of instability are determined for a porous medium containing either a saturated liquid or a steam-water mixture. Convection is driven by a phase change instability mechanism. If steam and water are always in thermodynamic equilibrium, then temperature perturbations are directly responsible for pressure variations, which tend to move the fluid against the frictional resistance of the medium to flow. Mass conservation insures that any horizontal divergence of fluid is balanced by an appropriate vertical motion, while condensation and boiling occur to achieve a balance of forces in the vertical. These results are relevant to geothermal phenomena.