Calculating tortuosity in quasi-random anisotropic packings

Relating the micro-structural characteristics of porous media to their through-flow properties remains an interesting challenge for the paper coating community. The research presented herein attempts to address this challenge through computational science for complex quasi-random anisotropic plate-like particle packings. In plate-like packings comprising monodisperse plates of equal aspect ratios, tortuosity is seen to decrease as a function of porosity. However, tortuosity is concurrently found to increase as a function of increasing particle aspect ratio, even though the porosities of such packings are higher. Dimensional and rotational characteristics of plate-like packings are therefore seen to be more influential to tortuosity than volume fractions of pore space. When comparing tortuosity to mean tracer velocities, the generic trend is one of inverse proportionality, with higher levels of scatter existing at lower tracer velocities. It is postulated that nesting sites within the particle microstructure accounts for the lower velocities by effectively trapping the flow of fluid for discrete time periods, and reducing the total distances travelled through the packing. As a function of the mean spatial rotations, tortuosity is taken to be 2(nd) order. Inverse linear proportionality is found to exist between tortuosity and the D'Arcy permeability calculated for the packed media. Porosity tends to increase as a function of Euclidean spatial particle rotations.