Modeling multiphase flow with a hybrid model based on the Pore-network and the lattice Boltzmann method

Eduard Puig Montellà,Antonio Gens,Chi Yuan ,Bruno Chareyre

doi:10.1051/e3sconf/202019502009

Abstract

Lattice Boltzmann method (LBM) simulations provide an excellent description of two-phase flow through porous media. However, such simulations require a significant computation time. In order to optimize the computation resources, we propose a hybrid model that combines the efficiency of the pore-network approach and the accuracy of the lattice Boltzmann method at the pore scale. The hybrid model is based on the decomposition of the granular assembly into small subsets, in which LBM simulations are performed to determine the main hydrostatic properties (entry capillary pressure, capillary pressure - liquid content relationship and liquid morphology for each pore throat). A primary drainage of a random packing of spheres is presented and contrasted to the results of the same problem fully resolved by the LBM. Liquid morphology and invasion paths are correctly reproduced by the hybrid method.

Highlights

The mechanical behavior of partially saturated granular systems is strongly influenced by the fluid flow
Even though 3D images from X-ray tomography are a useful and common tool to characterize the fluid morphology in the porous medium during the funicular regime [3], very few attempts have been carried out to obtain a geometrical description of the liquid distribution and morphology within the porous media [4, 5]
The macroscopic density and momentum variables are recovered from the distribution functions: Following the 2PFV-Discrete Element Method (DEM) scheme developed by [10] based on a three-dimensional triangulation method and DEM to study the hydro-mechanical behavior of unsaturated deformable granular materials, the hybrid model relies on the same triangulation to generate the pore-scale network

Summary

Introduction

The mechanical behavior of partially saturated granular systems is strongly influenced by the fluid flow. When the liquid content is increased, pendular bridges coalesce forming complex liquid morphologies. At this point, the pendular regime is replaced by the funicular regime. The hybrid method presented in this article follows the pore-scale approach referred as "two-phase pore-scale finite volume-discrete element method" (2PFV-DEM) [10]. In this method, the invasion of the non-wetting phase is controlled by the entry capillary pressure (pec). The hybrid model follows the decomposition scheme proposed by [12] Such technique leads to a discretization of the pore space as a set of connected throats.

Lattice Boltzmann Method

Fluid displacement

Numerical setup

Liquid morphology and preferential paths

Conclusions