A fully implicit coupled pore-network/free-flow model for the pore-scale simulation of drying processes

Abstract

We present a fully coupled pore-network/free-flow model providing pore-scale insight into drying processes. We solve the Navier–Stokes equations with component transport in the free-flow region, coupled to a dynamic two-phase, two-component pore-network model (PNM) in the porous domain. The dynamic multi-physics model allows to temporally resolve drying processes in-between capillary equilibrium states. All simulations are non-isothermal and use pressure- and temperature-depended fluid properties. Carefully chosen coupling conditions and a monolithic solver ensure local conservation of mass, momentum, and energy fluxes, in particular at the interface between both model domains. We solve for wetting and non-wetting fluid pressure fields and consider advective gas transport in the network. Numerical examples demonstrate that the coupled model is able to cover a wide range of physical processes relevant for drying and show the mutual interaction of the two subregions. The model is implemented in the modular open-source framework DuMu${}^{\mathrm{x}}$ such that extensions are straight-forward.

Keywords:

• Dynamic pore-network model
• multi-physics simulation
• two-phase flow in porous media
• evaporation and drying
• pore-network Navier–Stokes coupling

Acknowledgments

We thank the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) for supporting this work by funding SFB 1313, Project Number 327154368.

Disclosure of interest statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the article.

Code availability

A module containing the source code used to produce the numerical results is publicly available at https://git.iws.uni-stuttgart.de/dumux-pub/weishaupt2021a.

Additional information

Funding

This work was supported by Deutsche Forschungsgemeinschaft (DFG, German Research Foundation, SFB 1313), Project Number 327154368.