# Porosity and permeability in PorousInterFoam

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 October 17, 2013, 22:32 Porosity and permeability in PorousInterFoam #1 New Member   Jeferson Souza Join Date: Jan 2012 Location: Brazil Posts: 19 Rep Power: 14 Dear all, I'm trying to understand how to set porosity and permeability in porousInterFoam solver. For example: - porosity = 0.8 - permeability = 1.e-9 m2 and defining D = 0.8/1.e-9 I'm using the following in the porousZones dictionary for a isotropic media. { note "Reinforced Media"; porosity 0.8; Darcy { d d [ 0 -2 0 0 0 0 0 ] ( -1 D -1 ); f f [ 0 -1 0 0 0 0 0 ] ( 0 0 0 ); } } Is this correct? Which is the mathematical formulation for continuity, momentum and volume fraction equations used in porousInterFoam? Does porosity appears in all equations? thanks, santoo_cfd likes this.

 October 18, 2013, 20:35 #2 Senior Member     ahmed Join Date: Feb 2010 Posts: 182 Blog Entries: 1 Rep Power: 16 hi, a difinition of porous zone and f,d is introduced in source file of porous zon

 October 21, 2013, 08:04 #3 New Member   Jeferson Souza Join Date: Jan 2012 Location: Brazil Posts: 19 Rep Power: 14 Hi Khattab, Thanks for your reply. I took a look at the porousZone.H file. In the definition of the the S (line 50), there is no reference for the porosity. It seems that if the media has a porosity different than one all you need to do is to explicitly specify it at the "constant/porousZones" dictionary, however I've been solving some problems with the porousInterFoam solver and I only get reasonable (actually corrected) results when I multiply S by the porosity. I'm getting the results I need, however this "little trick" is bothering me, since I'm not sure about the correct formulation and I may be doing something wrong. Did you have this problem (or something like this) before? Thanks,

October 24, 2013, 04:00
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ahmed
Join Date: Feb 2010
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Quote:
 Originally Posted by jasouza1974 Hi Khattab, Thanks for your reply. I took a look at the porousZone.H file. In the definition of the the S (line 50), there is no reference for the porosity. It seems that if the media has a porosity different than one all you need to do is to explicitly specify it at the "constant/porousZones" dictionary, however I've been solving some problems with the porousInterFoam solver and I only get reasonable (actually corrected) results when I multiply S by the porosity. I'm getting the results I need, however this "little trick" is bothering me, since I'm not sure about the correct formulation and I may be doing something wrong. Did you have this problem (or something like this) before? Thanks,
Hi,

i think this PDF will be helpful.

http://www.tfd.chalmers.se/~hani/kur...ukurReport.pdf

GOOD LUCK

 October 24, 2013, 10:39 #5 New Member   Jeferson Souza Join Date: Jan 2012 Location: Brazil Posts: 19 Rep Power: 14 Hi, thanks again for your reply. Actually, I've got the idea of multiplying the source term by the porosity when I was reading this tutorial for the first time. I saw in Eq. (1) of the tutorial that gamma (porosity) is used only for the transient term, than I did D = porosity/permeability instead of D = 1./permeability and got reasonable results (actually results are good). I understand that this is an approximation since all terms of the momentum equation should be multiplied by the porosity. Am I right? I can not understand why only the transient term is multiplied by the porosity in the porous media model.

 December 10, 2014, 04:18 #6 New Member   otadol Join Date: Nov 2014 Posts: 14 Rep Power: 11 Hello Jeferson, I have actually the same kind of Problem. Even if the porosity does not have anything to do with D and F. It does not occur in openfoam native porous media library. You had a good idea about your little trick, I have to test it. But are you sure about the formula : D = porosity/permeability? Because bigger is D, slower the fluid runs through the porouszone right? And technically smaller is the porosity, slower the fluid runs through the porouszone? So Itīs quite wrong if you do D = porosity/permeability? Itīs not better to do : D = 1/(permeability*porosity) ? Thanks for your reply. Cheers

 December 30, 2014, 06:48 #7 New Member   Jeferson Souza Join Date: Jan 2012 Location: Brazil Posts: 19 Rep Power: 14 Hi, I really never understood why my "trick" works. However, I have tested it many times and it works. At least in version 2.1.1 (also in older 2.* versions). I know that version 2.3 has a problem, and as long as I know, the porous media model does not work well in this version. I've tried to upgrade to version 2.3 once and had to return to the old 2.1.1. Thanks, Jeferson

 December 30, 2014, 10:46 #8 Senior Member   Cyprien Join Date: Feb 2010 Location: Stanford University Posts: 299 Rep Power: 18 Hi all, For real two-phase flow in porous media solver, you can have a look at this thread: http://www.cfd-online.com/Forums/ope...-openfoam.html And keep in mind that porousInterFoam can be used only when very strong assumptions are satisfied (no capillarity, sharp interface...)... Best,

 January 7, 2015, 03:45 #9 New Member   otadol Join Date: Nov 2014 Posts: 14 Rep Power: 11 Hello Jeferson, I tested your trick on OF 2.2 and : ITīs WORKING ! I donīt know why too but results still really similar with PAM RTM about resin injection. The problem still, I cant explain that. Well, thanks a lot for your messages. Best regards and Happy New Year ! Last edited by cramsdead; January 15, 2015 at 09:01.

 January 8, 2015, 10:50 #10 New Member   Oruzeaz Haufgr Join Date: Jul 2014 Posts: 2 Rep Power: 0 Dear All, I'm a new user of OpenFoam, I want to modelling water flow in porous media. Not clear for me how to calculate D and F numbers. D=porosity/permeability, am I right? But this is only 1 number. d (0 0 0) how can I calculate all three coordinates? Sorry for the stupid question. Thanks for your reply.

 January 8, 2015, 14:16 #11 Senior Member   Andrea Ferrari Join Date: Dec 2010 Posts: 319 Rep Power: 16 Hello, the permeability is a tensor. The 3 components that you have to specify go on the diagonal of the tensor D, have a look at the source code to see how D is constructed. If your porous media is isotropic the x-y-z entries are equal, for anisotropic media they are not. Hope this help! Andrea

 January 14, 2015, 03:22 #13 New Member   Oruzeaz Haufgr Join Date: Jul 2014 Posts: 2 Rep Power: 0 Hallo Andrea, thank you for your answer, it was helpful. I have another question. How can I calculate f? When I use it? Eszter

 January 14, 2015, 04:06 #14 Senior Member   Andrea Ferrari Join Date: Dec 2010 Posts: 319 Rep Power: 16 Hello, take a look at the source code: src/finiteVolume/cfdTools/general/porosityModel/DarcyForchheimer/DarcyForchheimer.H you 'll find a small description of the coefficients. f is the Forchheimer coefficient [1/m] and should be use when inertial effects are not negligible. Both d and f are case-dependent coefficients that are usually calculated from experimental data (or simulations), so you should know them for your case. Hope this help! Andrea

 August 12, 2015, 04:16 #15 New Member   saeed rashidzade Join Date: Jun 2015 Posts: 4 Rep Power: 10 hi foamers, i gonna set the darcy number 10e-5, but i don't know how to use d and f in porosityproperties, if anyone knows please help me! thanks

 Tags permeability, porosity, porousinterfoam