Liquid water transport model in hydrophilic granular media: Preliminary validation with drying rate of hierarchical granular material

A simple one-dimensional power law model was proposed based on the assumption that the product of the water permeability and the pressure gradient is proportional to the cube of the water saturation. This model is semi-quantitatively consistent with the experimental results and suggests that the role of small gradients in water saturation in the wet region can not be ignored in determining the transition point from a constant rate period (CRP) to a falling rate period (FRP) in evaporation rates.