Compressible and viscous two-phase flow in porous media based on mixture theory formulation

The purpose of this work is to carry out investigations of a generalized two-phase model for porous media flow. The momentum balance equations account for fluid-rock resistance forces as well as fluid-fluid drag force effects,
in addition, to internal viscosity through a Brinkmann type viscous term. We carry out detailed investigations of a onedimensional version of the general model. Various a priori estimates are derived that give rise to an existence
result. More precisely, we rely on the energy method and use compressibility in combination with the structure of the viscous term to obtain H1-estimates as well upper and lower uniform bounds of mass variables. These a priori estimates imply existence of solutions in a suitable functional space for a global time T > 0. We also derive discrete schemes both for the incompressible and compressible case to explore the role of the viscosity term (Brinkmann type) as well as the incompressible versus the compressible case. We demonstrate similarities and differences between a formulation that is based, respectively, on interstitial velocity and Darcy velocity in the viscous term. The investigations may suggest that interstitial velocity seems more natural to use in the formulation of momentum balance than Darcy velocity.