Pore Scale Modeling of Colloid Transport in Unsaturated Porous Media with COMSOL

COMSOL Multiphysics was used to simulate the transport of inert colloidal particles at the pore scale within an unsaturated micromodel consisting of sand grains and air bubbles. The unsaturated soil pore was modeled as four adjoining grains with an air bubble trapped at the center. Colloids were assumed to behave passively in the flow field since mass effects, size effects, and interfacial forces were not considered in the present analysis. A significant fraction of colloids were found to be retained within the porous media, but this occurred because those colloids were caught in stagnation zones of the flow field. Based on our result we conclude that COMSOL MP3.2 will be a valuable tool for numerically simulating colloid behavior at the micrometer scale.