Chapter 16 - Non-Darcy free and mixed convection boundary-layer flow in porous media

Abstract

This chapter discusses non-Darcy free and mixed convection boundary-layer flow in porous media. The non-Darcy flow situation prevails when the Reynolds number and characteristic fluid velocity of the medium becomes large. A great number of heat transfer applications in porous media are investigated with the help of a constant coefficient heat conduction model. The terms of Forchheimer and Brinkman, and a variable near wall porosity are added to the Darcy law model in order to account for inertia, boundary drag, and flow channeling phenomena, which occur at the higher pore velocities in porous media convection. When combined with heat transfer, a constant heat convection coefficient is not appropriate to describe the additional mechanical mixing of fluid particles with different temperatures that takes place at such velocities and it is observed that fluid velocity dependent thermal diffusivities are deemed to better describe these processes. There are several theoretical and empirical models, which describe the spreading of heat when it is being conducted through an isotropic homogeneous porous medium and simultaneously transported with a carrier fluid.