[jasouza1974]

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,

[Ahmed Khattab]

hi,

a difinition of porous zone and f,d is introduced in source file of porous zon

[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,

[Ahmed Khattab]

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

[jasouza1974]

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.

[cramsdead]

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 It´s quite wrong if you do D = porosity/permeability?

It´s not better to do : D = 1/(permeability*porosity) ?

Thanks for your reply.

Cheers

[jasouza1974]

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

[Cyp]

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,

[cramsdead]

Hello Jeferson,

I tested your trick on OF 2.2 and :
IT´s WORKING !

I don´t 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 !

[oreszti87]

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.

[Andrea_85]

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

[cramsdead]

hello Oruzeaz !
This is not a stupid question !

I´m 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 it´s a pleasure to try to help you.

about F, I´ve never touch it, It´s 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 m² 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 it´s 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!

[oreszti87]

Hallo Andrea,

thank you for your answer, it was helpful. I have another question. How can I calculate f?
When I use it?

Eszter

[Andrea_85]

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

[mordab]

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