Capillary Pressure in Porous Media#

Capillary pressure in porous media = {yes | no}

Description / Usage#

In partially saturated porous media, the capillary pressure is the difference between the gas and liquid pressures. This option only takes affect for POROUS_TWO_PHASE and POROUS_UNSATURATED media types (see Media Type card). This variable is called PC in the output EXODUS II file.

The permissible values for this postprocessing option are:


Calculate the capillary pressure and write to output EXODUS II file.


Do not calculate the capillary pressure.


This is a sample input card to activate calculation of capillary pressure:

Capillary pressure in porous media = yes

Technical Discussion#

The capillary pressure is a critical variable for partially saturated porous media, and is in fact the dependent variable for unsaturated (not two-phase) flows for which the gasphase pressure is taken as constant. It is simply defined as


As such, positive capillary pressures imply liquid phase pressure being greater than gas phase pressure. Because liquid phase saturation strongly correlates to capillary pressure, this current quantity is a good indicator of the level of liquid inventory in smaller pores in the skeleton relative to large pores. Contouring this quantity can give some indication of the level of suction exerted on the porous-skeleton, which is relevant when the skeleton is taken as deformable.


GT-009.3: GOMA’s Capabilities for Partially Saturated Flow in Porous Media, September 1, 2002, P. R. Schunk