[s3s4m]

Hi at all !

I have found this forum during my seemingly endless investigation of a solution to my problem in CFX. I hope there is someone here who can help.

I want to model the spreading of a liquid through a porous medium. Initially, there is air inside this porous medium. Than you inject some other liquid fluid in this p.m. The liquid spreads and the air is displaced.

So far, so good. I chose a multiphase approach, inhomogenous fluid model.
But the question is...how do I implement the capillary force, which acts on the gas-fluid interface ?
As a first step, I established a subdomain to the p.m. I can define a general momentum source there, when the volume fraction of the liquid exceeds a certain value. But this Source acts on both fluids, the air and the liquid. This is not physically correct, since the capillary force acts only on the liquid phase and "pulls" it towards the gaseous phase.

Basically, I should manipulate the term S_M,alpha of the phase alpha at the inhomogenous hydrodynamic equations for multiphase flow.
With S_M,alpha, I should be able to define the capillary force for the liquid at a certain position (i.e. the interface) as an external body force.
How do I do that ?

There is nothing described in the documentation to manipulate S_M,alpha

I would appreciate your help. And sorry for my rough english.

F.F.