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Flow in Porous Materials

FLOW-3D example of modeling porous media

Numerical modeling of the transport of fluid in porous media can be a challenge, but FLOW-3D includes many valuable features for the solution of problems involving porous media flows. The FAVOR™ technique contains necessary porosity variables to enable the user to represent a continuous porous media. FLOW-3D allows users to simulate both saturated and unsaturated flow conditions. A power law relation allows users to model the non-linear relationship between capillary pressure and saturation in the unsaturated flow conditions.

Separate filling and draining curves can be used to model the phenomenon of hysteresis. Different porosity, permeability and wettability properties can be assigned to different obstacles, even when in direct contact with one another. Permeability can be specified based on flow direction, enabling the user to model anisotropic behavior of porous media. Heat transfer between fluid and the porous media may be taken into account.

Capillary Absorption

 CFD simulation of capillary absorption using FLOW-3D
Capillary absorption
benchmark comparing fluid
level to contact angle

Capillary absorption into the pore of a solid substance occurs because of adhesion between the liquid and the solid. A simple, yet useful, test of absorption is shown here. The test pore consists of a 1.0 μm wide, two-dimensional channel connected to an expanding throat whose side walls are circular arcs with 1.0 μm radii. In the absence of body forces, surface tension and wall adhesion pull liquid into the channel to a level that depends on the static contact angle between the liquid and solid. The accompanying figures show that FLOW-3D correctly computes the filling level (fluid is red) for any given contact angle.

Thanks to Martti Toivakka of Abo Akademi University in Finland for contributions to this article.