Poroelastic flow across a permeable interface: a Hamilton's principle approach and its finite element implementation

We consider fluid flow across a permeable interface within a deformable porous medium. We use mixture theory. The mixture’s constituents are assumed to be incompressible in their pure form. We use Hamilton’s principle to obtain the governing equations, and we propose a corresponding finite element implementation. The filtration velocity and the pore pressure are allowed to be discontinuous across the interface while some control of these discontinuities is built into the interfacial constitutive behavior. To facilitate the practical implementation of the formulation in a finite element scheme, we introduce a Lagrange multiplier field over the interface for the explicit enforcement of the jump condition of the balance of mass. Our formulation appears to recover some basic results from the literature. One element of novelty of the work is the formulation of an approach that can accommodate specific constitutive assumptions pertaining to the behavior of the interface that do not necessarily imply the continuity of the filtration velocity and/or of the pore pressure across it. Another new element is a practical strategy for transitioning from the variational statement produced by the application of Hamilton's principle to a corresponding finite element method implementation of our approach.