Influence of particulate geometry on permeability of porous materials

The durability of porous materials - especially when exposed to deleterious environs - depend on their permeability. This paper takes a closer look at the governing equations of fluid flow in porous media, and examines the role of particulate geometry on liquid water permeability of porous materials. A three dimensional (3D) micro-structural model is used to generate 3D microstructures of the materials. Microstructures featuring particulates with single or binary combination of geometries (i.e., spherical, cubical/cuboidal, cylindrical, and irregular), and a wide range of porosities and particulate numbers, are evaluated to elucidate their influence on permeability. A numerical model based on the lattice Boltzmann method (LBM) is used to calculate permeability of porous materials using their 3D microstructures as inputs. Results obtained from the LBM simulations show that permeability is significantly affected by geometry of the particulates - especially when the porosity is low and/or the number of particulates in the microstructure is small (e.g., <<100). High-aspect ratio particles (e.g., cylinders) - on account of their very low sphericity and superior ability to disrupt fluid flow - consistently produce lower permeability compared to equivalent-volume particulates (e.g., spheres) that have higher sphericity. The dependency of permeability on particulate geometry decreases at higher porosities and with increasing number of particulates in the microstructure. By clarifying the dependency of permeability on particulate geometry, outcomes of this study aid in quantification of errors - in permeability estimations - that arise on account of geometric (e.g., spherical) assumptions made in various microstructural models. (C) 2019 Elsevier B.V. All rights reserved.