A diffuse interface method for the Navier–Stokes/Darcy equations

Abstract

We present a diffuse interface method for coupling free and porous-medium-type flows modeled by the Navier–Stokes and Darcy equations. Its essential component is a diffuse geometry model generated from the phase-field solution of a separate initial boundary value problem that is based on the Allen–Cahn equation. Phase-field approximations of the interface and its gradient are then employed to transfer all interface terms in the coupled variational flow formulation into volumetric terms. This eliminates the need for an explicit interface parametrization between the two flow regimes. We illustrate accuracy and convergence for a series of benchmark examples, using standard low-order stabilized finite element discretizations. Our diffuse interface method is particularly attractive for coupled flow analysis on imaging data with complex implicit interfaces, where procedures for deriving explicit surface parametrizations constitute a significant bottleneck. We demonstrate the potential of our method to establish seamless imaging-through-analysis workflows by computing a perfusion profile for a full-scale 3D human liver based on MRI scans.