Resolution of a paradox involving viscous dissipation and nonlinear drag in a porous medium

The modelling of viscous dissipation in a porous medium saturated by an inc ompressible fluid is discussed, for the case of Darcy, Forchheimer and Brin kman models. An apparent paradox relating to the effect of inertial effects on viscous dissipation is resolved, and some wider aspects of resistance t o flow (concerning quadratic drag and cubic drag) in a porous medium are di scussed. Criteria are given for the importance or otherwise of viscous diss ipation in various situations.