Modeling Multiphase Flow Through and Around Multiscale Deformable Porous Materials

Abstract: Detailed understanding of the coupling between fluid flow and solid deformation in porous media is crucial for the development biomedical devices and novel energy technologies relating to a wide range of geological and biological processes. Well established models based on poroelasticity theory exist for describing coupled fluid-solid mechanics. However, these models are not adapted to describe systems with multiple fluid phases or 'hybrid-scale' systems containing both solid-free regions and porous matrices. To address this problem, we present a novel computational fluid dynamics approach based on a unique set of volume-averaged partial differential equations that asymptotically approach the Navier-Stokes Volume-of-Fluid equations in solid-free-regions and Biot's Poroelasticity Theory in porous regions. Unlike existing multiscale multiphase solvers, it can match analytical predictions of capillary, relative permeability, and gravitational effects at both the pore and Darcy scales. Through careful consideration of interfacial dynamics and extensive benchmarking, we show that our model accurately captures the strong two-way coupling that is often exhibited between multiple fluids and deformable porous media during processes such as swelling, compression, and fracturing. The versatility of the approach is illustrated through studies that 1) quantified the effects of microporosity on sedimentary rock permeability, 2) identified the governing non-dimensional parameters that predict capillary and viscous fracturing in porous media, 3) characterised the effects of cracking on hydraulic fracture formation, and 4) described wave absorption and propagation in poroelastic coastal barriers. The approach's open-source numerical implementation 'hybridBiotInterFoam', marks the extension of computational fluid dynamics simulation packages into deformable, multi-phase, multiscale porous systems.