Factors Affecting the Significance of Gravity on the Infiltration of a Liquid into a Porous Solid

A mathematical model is formulated to illustrate the significance of gravity on the infiltration of a liquid in a porous solid. The result indicates that the relative significance of gravity on the infiltration depth depends on the infiltration time as well as the properties of the permeating liquid and the porous solid. The effect of gravity can be neglected for a short infiltration time, and for infiltration systems with the infiltrating liquid having a large value of surface energy, a small value of wetting angle on the solid, and a low density, and the porous solid having a small equivalent capillary radius and a small tortuosity.