Thermal instabilities in a fluid saturated porous medium

This chapter contains a review of the thermoconvective instabilities that may occur in a fluid saturated porous medium. Reference is made to a horizontal porous layer. The macroscopic description of the fluid flow in a porous medium is outlined. Then, the mass, momentum and energy balance equations for porous media are described and discussed. As a first basic example of convective instabilities, the classical Darcy-Bénard problem is studied in order to highlight the main characteristics of the linear stability analysis. Extensions of the Darcy-Bénard problem based on the Forchheimer model and on the Brinkman model of momentum flow are analysed. Moreover, the effects of either a horizontal or a vertical throughflow in the layer are discussed. The contribution of the effect of viscous dissipation is investigated as a possible cause of convective instabilities.