Momentum transfer at a fluid/porous interface
Momentum transport at a fluid/porous interface is modeled using a single-domain approach where the fluid and porous regions are treated as a continuum. This study deals with a quantitative comparison with the two-domain model where the fluid and the porous layer are considered separately. Numerical solutions associated to the single-domain formulation are compared to analytical and experimental results. When the porous material is homogeneous, the flow in the two regions is well described by both formulations. This is not the case for porous structures with continuous variations of the properties near the interface. A non-homogeneous analysis is performed to account for this situation, introducing a variable permeability layer between the homogeneous porous medium and the fluid region. Numerical results show that the stress jump condition proposed by Ochoa-Tapia and Whitaker (1995a,b) is not suited to represent momentum transport within the porous layer in the vicinity of the interface, since the jump coefficient does not explicity describe its structure. The numerical results allow for determining the thickness of the non homogeneous boundary layer, which is found to be on the order of the average pore size of the porous medium. Finally, a simple integration of the momentum equation upon the non-homogeneous boundary layer yields an explicit permeability-dependence of the jump coefficient.