Non-isothermal flow in low permeable porous media: a comparison of Richards’ and two-phase flow approaches

Abstract

The present work compares the performance of two alternative flow models for the simulation of thermal-hydraulic coupled processes in low permeable porous media: non- isothermal Richards' and two-phase flow concepts. Both models take vaporization processes into account: however, the Richards' model neglects dynamic pressure variations and bulk flow of the gaseous phase. For the comparison of the two approaches first published data from a laboratory experiment is studied involving thermally driven moisture flow in a partially saturated bentonite sample. Then a benchmark test of longer-term thermal-hydraulic behavior in the engineered barrier system of a geological nuclear waste repository is analyzed (DECOVALEX project). It was found that both models can be used to reproduce the vaporization process if the intrinsic permeability is relative high. However, when a thermalhydraulic coupled problem has the same low intrinsic permeability for both the liquid and the gas phase, only the two-phase flow approach provides reasonable results.

Reactive transport codes for subsurface environmental simulation

“…OGS has a built-in random-walk particle tracking method for Euler-Lagrange simulations [97] and can simulate incompressible and compressible flow [98], densitydependent flow [99], unsaturated flow [100], two-phase flow [101,102], and overland flow [103]. All flow model components are available for non-isothermal conditions and for deformable porous media.…”

Implementation of the Barcelona Basic Model into TOUGH–FLAC for simulations of the geomechanical behavior of unsaturated soils

“…The slight disagreement that can be observed in Figure 7 can be attributed to differences in the modeling approach. Indeed, ROCMAS is a finite element code for fully coupled THM analysis under single phase unsaturated flow conditions, whereas TOUGH-FLAC is based on the sequential coupling of a finite volume fluid flow code to a finite difference geomechanical code, but with full multiphase flow capability-see Wang et al, (2010), for a recent discussion on singleversus-multiphase fluid flow modeling approaches for this type of problem). The results in Figure 7 are also in general agreement with simulation results of other numerical models for the same DECOVALEX bench-mark test presented in Rutqvist et al (2008Rutqvist et al ( , 2009).…”

黄土土柱加热加速蒸发的试验模拟研究

“…The water and gas flow are described by the extended Darcy's law for unsaturated porous medium. The relative permeabilities for both water and gas phases are considered and have the following form (Wang et al, 2011):…”