Boundary conditions at a fluid–porous interface: An a priori estimation of the stress jump coefficients

The momentum transfer at the interface between a porous medium and an adjacent free fluid is investigated by introducing three different levels of description of the problem. This study focuses mainly on the up-scaling from the mesoscopic to the macroscopic level of description. An explicit relation between the jump parameters, the location of the discontinuous interface (macroscopic description) and the structure of the transition region (mesoscopic description) is obtained. This relation allows to explain the large sensitivity of the jump parameters to the location of the discontinuous interface observed in previous studies. It is shown that it is crucial to conserve exactly the forces in the up-scaling analysis.