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October 17, 2013, 23:32 |
Porosity and permeability in PorousInterFoam
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#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, |
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October 21, 2013, 09:04 |
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#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, |
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October 24, 2013, 05:00 |
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#4 | |
Senior Member
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Quote:
i think this PDF will be helpful. http://www.tfd.chalmers.se/~hani/kur...ukurReport.pdf GOOD LUCK |
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October 24, 2013, 11:39 |
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#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. |
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December 10, 2014, 05:18 |
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#6 |
New Member
otadol
Join Date: Nov 2014
Posts: 14
Rep Power: 12 |
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 |
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December 30, 2014, 07:48 |
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#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 |
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December 30, 2014, 11:46 |
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#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, |
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January 7, 2015, 04:45 |
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#9 |
New Member
otadol
Join Date: Nov 2014
Posts: 14
Rep Power: 12 |
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 10:01. |
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January 8, 2015, 11:50 |
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#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. |
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January 8, 2015, 15:16 |
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#11 |
Senior Member
Andrea Ferrari
Join Date: Dec 2010
Posts: 319
Rep Power: 17 |
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 |
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January 9, 2015, 05:10 |
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#12 |
New Member
otadol
Join Date: Nov 2014
Posts: 14
Rep Power: 12 |
hello Oruzeaz !
This is not a stupid question ! Iīm using OpenFOAM since September ! So I know how complicated it is to try to understand all the little tricks of this Software. And not everything is clear ! So itīs a pleasure to try to help you. about F, Iīve never touch it, Itīs might be for really special cases. about D, if you check it is in m^-2 so it looks like 1/permeability (because of permeability is in mē of course) about the question of introducing the porosity, if you check the porousInterFoam solver, this latter dont support the "porosity" parameter. As said the devellopers here : http://openfoam.org/mantisbt/view.php?id=477 Just saying : find it how to set up by your self! lol Here Jeferson tried to introduce the porosity into D by doing : D = porosity/permeability and it seems itīs work, I did it by my self and the results are similar to PAM-RTM (for me about resin injection) not exactly perfect but really near to!! As said Andrea, permeability is a Tensor, because the permeability can be different depends on the direction of the fluid. It means in your porous media, your fluid can move faster in X than in Y or Z direction. Just depends the settings of your porous media. Then to Quote Andrea : If your porous media is isotropic the x-y-z entries are equal, for anisotropic media they are not. I hope what I said was helpful for you! Good luck about your work! |
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January 14, 2015, 04:22 |
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#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 |
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January 14, 2015, 05:06 |
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#14 |
Senior Member
Andrea Ferrari
Join Date: Dec 2010
Posts: 319
Rep Power: 17 |
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 |
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August 12, 2015, 05:16 |
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#15 |
New Member
saeed rashidzade
Join Date: Jun 2015
Posts: 4
Rep Power: 11 |
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 |
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Tags |
permeability, porosity, porousinterfoam |
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