  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.
