Capillary penetration of liquids between periodically corrugated plates

The capillary rise of a liquid between two sinusoidally corrugated plates in a gravitational field is considered in order to study the effect of geometrical variations perpendicular to the direction of penetration. The height of capillary rise of equilibrium is calculated over the cross section of the capillary using the method of local variations, and the effect of geometrical parameters is elucidated. It is found that the spatial variations in the rise height at the centerline are negligible while those at the capillary wall follow the variations in the capillary cross section. The centerline rise height is found to increase with the corrugation amplitude, particularly at small wavelengths. The relative enhancement in the centerline rise height compared with a parallel plate capillary is shown to be independent of the contact angle over the range of contact angles studied. Based on these theoretical predictions, it is concluded that the experimentally observed saturation front phenomenon in porous structures is probably of kinetic rather than thermodynamic origin.