CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Running, Solving & CFD

how to set correctly the porosity properties to use porousInterFoam?

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   December 3, 2014, 03:57
Default how to set correctly the porosity properties to use porousInterFoam?
  #1
New Member
 
otadol
Join Date: Nov 2014
Posts: 14
Rep Power: 8
cramsdead is on a distinguished road
Hello Foamers !

I would like to know how to set the porosity properties correctly.

Please someome can advise me? Explain me how to set correctly the porosity properties?

I would like a permeability of 5e-11 mē
and trying some different porosity on : like 0,3 0,5 0,8

Is it right?
into the line :

d d [0 -2 0 0 0 0 0] (X X X);
(X X X) is the porosity coefficient divided by the permeability coeff? (here the same in all directions)
Is it right?


Code:
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.2.1 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "constant";
object porosityProperties;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
porosity1
{
type DarcyForchheimer;
active yes;
cellZone porouszone;
porosity 0.5;
permeability 5e-11;
 
DarcyForchheimerCoeffs
{
mu mu;
d d [0 -2 0 0 0 0 0] (0.1e11 0.1e11 0.1e11); //0.5/5e-11=0.1e11
f f [0 -1 0 0 0 0 0] (0 0 0);
 
//coordinateSystem
//{
// e1 (0.70710678 0.70710678 0);
// e2 (0 0 1);
//}
 
}
}
 
************************************************************************* //
I know there is an other post about this but was only fonded about suppositions. I want to be sure!

Thanks a lot for considering my post.
cramsdead is offline   Reply With Quote

Old   December 4, 2014, 07:13
Default
  #2
New Member
 
otadol
Join Date: Nov 2014
Posts: 14
Rep Power: 8
cramsdead is on a distinguished road
please anyone?
cramsdead is offline   Reply With Quote

Old   December 4, 2014, 11:06
Default
  #3
Member
 
Hao Chen
Join Date: Aug 2014
Posts: 66
Rep Power: 0
hchen is on a distinguished road
Hi,

D is the porous resistance coefficient.

Darcy-Freidheim formula basically says S = d*u+F*mag(U)*U.

Best regards
Hao
hchen is offline   Reply With Quote

Old   December 8, 2014, 04:38
Default
  #4
New Member
 
otadol
Join Date: Nov 2014
Posts: 14
Rep Power: 8
cramsdead is on a distinguished road
ok I got it :

The permeability k is generally expressed in Darcy (D). Hao, I think you mean the porous resistance coeff right?
One Darcy is the permeability of a continuous, isotropic body through which a fluid of similar viscosity to that of water at 20 ° C flowing at a speed of 1 cm · s-1 when subjected to a pressure of 1 atm, which corresponds to the dimension of a surface. 1 D = 0.97 Ũ 10-12 mē

The term hydraulic conductivity (K or permeability coefficient) is the ratio between the permeability and the viscosity of the fluid (the fluid is usually water). More a environement is permeable, more the fluid will flow quickly.
Hydraulic conductivity is expressed in m⋅s-1

So here into the d d [0 -2 0 0 0 0 0] (X X X);
X is the "k" permeability coefficient. This is just so weird OpenFoam ask d in m^-2 and not in mē...

So my last question is : for a permeability of 5e-11 I have to set X=5e11 OR X=0,2e11?

I donīt think we need to set the porosity coefficient here. This is 2 things really different.

thank you for your reply.
cramsdead is offline   Reply With Quote

Old   December 8, 2014, 16:56
Default
  #5
Member
 
Hao Chen
Join Date: Aug 2014
Posts: 66
Rep Power: 0
hchen is on a distinguished road
I am sorry that I am not an expert in hydraulics, but somehow you are right that permeability is expressed as D and F. However when you consider Darcy law, you need to put it into NS equation and the additional term S should have the same dimension with original NS equation. That is why D and F has that dimension. I remember that I read some paper describing relation between D and k, but I can not remember. You can check some papers on porous media.

Porosity does not have anything to do with D and F. It does not occur in openfoam native porous media library.

Best regards
Hao
hchen is offline   Reply With Quote

Old   December 10, 2014, 03:43
Default
  #6
New Member
 
otadol
Join Date: Nov 2014
Posts: 14
Rep Power: 8
cramsdead is on a distinguished road
Hi Hao,

Thanks a lot for your reply, I was asking for that to be sure that "normally" porosity does have anything to do with D and F but it seems there is a little trick about it as explained in the following post :
http://www.cfd-online.com/Forums/ope...interfoam.html

So I think Iīm gonna try it into my simulations.

Well, my last question is : for a permeability of 5e-11 I have to set X=5e11 OR X=0,2e11?

Because I donīt want to do an easy mistake like this.

Thank you for your reply,

Cheers
cramsdead is offline   Reply With Quote

Reply

Tags
porosity

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
[ICEM] ICEM Scripting Issues tylerplowright ANSYS Meshing & Geometry 32 Today 18:38
[General] 2 datas on one plot Akuji ParaView 46 December 1, 2013 14:06
udf inlet velocity is not set correctly, why ? GaoGe FLUENT 0 June 17, 2008 08:33
Problems with installation jonititan OpenFOAM Installation 4 November 6, 2005 04:16
how correctly set up BC for compressible flows.... yann Phoenics 5 October 13, 2003 03:35


All times are GMT -4. The time now is 21:08.