“…For low Darcy and particle Reynolds numbers, the viscous drag and inertia terms in the governing equations can be neglected (Bejan and Kraus 2003;Ingham and Pop 2005;Nield and Bejan 2006). Under these assumptions, the continuity, Darcy and energy equations for unsteady natural convection flow in a square cavity filled with an isotropic and homogenous porous medium can be expressed as [Bejan and Kraus (2003), Ingham and Pop (2005), Nield and Bejan (2006), Saeid and Pop (2004)]…”