Three dimensional simulation of fluid flow in X‐ray CT images of porous media

Abstract

SUMMARYA numerical scheme is developed in order to simulate fluid flow in three dimensional (3-D) microstructures. The governing equations for steady incompressible flow are solved using the semi-implicit method for pressure-linked equations (SIMPLE) finite difference scheme within a non-staggered grid system that represents the 3-D microstructure. This system allows solving the governing equations using only one computational cell. The numerical scheme is verified through simulating fluid flow in idealized 3-D microstructures with known closed form solutions for permeability. The numerical factors affecting the solution in terms of convergence and accuracy are also discussed. These factors include the resolution of the analysed microstructure and the truncation criterion. Fluid flow in 2-D X-ray computed tomography (CT) images of real porous media microstructure is also simulated using this numerical model. These real microstructures include field cores of asphalt mixes, laboratory linear kneading compactor (LKC) specimens, and laboratory Superpave gyratory compactor (SGC) specimens. The numerical results for the permeability of the real microstructures are compared with the results from closed form solutions.

Discrete particle simulation of shock wave propagation in a binary Ni+Al powder mixture

“…For example, x-ray tomographs of asphalt mix have been used to simulate three-dimensional fluid flow and estimate permeability in pavements. 29 The results indicated that the prior notions of a direct relationship between void volume fraction and permeability were incorrect. Microstructure-based simulations have also been used to determine the effect of processing on the thermal conductivity of thermal barrier coatings.…”

Fluid flow and effective conductivity calculations on numerical images of bentonite microstructure

“…According to Adler et al (1990);Al-Omari and Masad (2004) and Masad et al (2000), the discrepancy between 2D and 3D computations can be attributed to the inherent limitation of a 2D computation in capturing the real 3D flow path in a highly heterogeneous material such as sand or clay, as well as to the difference in specific surface area between the discretized contours of the pore space and the real microstructure. Therefore, 2D computations can be improved by increasing the resolution of the images in order to capture the real specific surface.…”

“…In recent studies (Adler et al, 1990;Al-Omari and Masad, 2004;Blunt et al, 2013;Masad et al, 2000) the effective permeability of various porous materials (natural sandstones, carbonate reservoirs, asphalt pavements, sands, glass beads) was determined by solving the local equations of fluid flow. The microstructure was obtained directly from the sample by image processing, or idealized by utilizing statistical characteristics.…”

“…Blunt et al (2013) applied network modelling at larger scales to extract a topologically representative network consisting of pores and throats from the image, and the flow and transport properties were described semi-analytically. In (Adler et al, 1990;Al-Omari and Masad, 2004;Masad et al, 2000), the computed velocity field was driven by the pressure difference prescribed between the inlet and the outlet of the microstructure. Periodic boundary conditions were imposed for the velocity components, Darcy's law was written at the macroscopic scale and the effective permeability tensor was simply defined as the ratio between the average fluid velocity vector and the known pressure gradient.…”

Studying the effect of microstructural properties on the mechanical degradation of asphalt mixtures

“…Undoubtedly, interconnectivity is an important property of the air void phase in HMA mixture. However, previous studies have shown that the tortuosity of connected void paths in full dense mixtures is in a range of 3.16 and 4.94 [19]. Therefore, it is realistic to assume that the number of long connected paths within a 2-D slide of a mixture is negligible.…”