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Pawel October 18, 2002 03:13

Porosity function

Have you ever heard about using so-called porosity function to describe boundary conditions in case when the physical boundary is not linear with the edges of the computational cells?

I know that the idea is based on implementing a function, with values between 0 and 1 (0 - a cell is filled with boundary, 1 - a cell is filled with fluid only, between 0 and 1 - a cell is partially filled with fluid and boundary. The same you do with the cell edges). You modify the equations of conservation by putting the values into them (just as it is done for porous media).

It is something I would like to do: to use the Cartesian mesh with objects on it, but the objects are not going to be rectangular at all - you may assume that they have a staircase geometry or use the porosity function or ....

Have anybody of you tried the technique? Or maybe you know another method for doing the same (the walls or objects are not "rectangular" but the mesh is) - it seems to me that some ideas from VOF may be adapted but I do not know too much about it. Maybe you know some references to that (Internet sites, papers, and so on)?

Best regards,


Wen Long October 21, 2002 12:47

Re: Porosity function
Hi, pawel:

please look at :

Surf Zobe dynamics simulated by a Boussinesq type Model. Part I. Model description and cross-shore motion of regular waves. By P.A.Madsen, O.R.Sorensen and H.A.Schaffer, Coastal Engineering, V32, 1997, pp255-287

It's a good simple approach for waves on a beach, but it needs necessary numerical filtering and some other tricks in the code.


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