Coupled free-flow and porous media flow: a numerical and experimental investigation

Abstract

Modelling situations containing a freeflow region and adjacent porous medium is challenging due to the different model concepts in both domains. The interface can be described as either a sharp surface or a thin layer with complex properties using a pore-network model. In this study, the first step is taken by coupling a freeflow model with a pore-network model. Additionally, the interface is investigated experimentally using confocal microscopy. The velocity field is determined using particle tracking. Both single-phase and two-phase flow have been considered in the pore-network model. In the case of two-phase flow, the freeflow domain is occupied by the non-wetting phase. The single-phase model is able to recreate the flow patterns found in the experiments. However, the exact setup could not be recreated in the model, because of the large pore sizes of the micromodel. This leads to large flow velocities at the interface and creates problems for the Stokes model. The two-phase is not able to simulate the conditions of the experiments, because in the experiments, flow of water occurs without invasion of the pore-network by the non-wetting phase. For future work, the pore-network is to be coupled to a macroscopic porous medium model. For this purpose, additional boundary conditions have to be defined for the two-phase pore-network model. Furthermore, the model can be extended to include heat and component transport.