International audienceThe velocity boundary condition that must be imposed at an interface between a porous medium anda free fluid is investigated. A heterogeneous transition zone characterized by rapidly varying properties is introducedbetween the two homogeneous porous and free fluid regions. The problem is solved using the method of matchedasymptotic expansions and boundary conditions between the two homogeneous regions are obtained. The continuityof the velocity is recovered and a jump in the stress built using the viscosity (and not the effective viscosity) appears.This result also provides an explicit dependence of the stress jump coefficient to the internal structure of the transitionzone and its sensitivity to this micro structure is recovere
