Percolation Around Structurally Disordered Sand Grains: A Dynamical Infiltration Study

Percolation transitions, marking the boundary between configurations which admit the fluid or charge flow and those which are impermeable on large scales are salient phenomena for transport through porous materials where flow is through irregular spaces around impenetrable grains instead of well-defined linear channels. Using dynamical infiltration simulations involving virtual tracers moving in void regions, we calculate critical grain densities per unit volume where the inclusions are positionally and orientationally disordered. In addition, as a novel element, we also consider varying degrees of structural disorder, in which the shapes of grains are subject to random variation. In the case of ellipsoids, tetrahedrons, and rectangular solids we find that if expressed in units of the mean grain volume, the critical concentration is remarkably robust, with little variation for light to moderate disorder in the inclusion shapes. We also discuss scenarios in which in random variations in facet plane distances for solids such as dodecahedrons eventually yield non-dodecahedral fragments; with large scale dynamical infiltration simulations we seek to determine if percolation thresholds remain robust with increasing diversity in types of grain shapes or instead undergo a shift.