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-   -   Mistype in Darcy-Forchheimer porosity model description (https://www.cfd-online.com/Forums/openfoam-programming-development/69942-mistype-darcy-forchheimer-porosity-model-description.html)

 makaveli_lcf November 10, 2009 04:27

Mistype in Darcy-Forchheimer porosity model description

Hi all!

I noticed a mistype in description of Darcy-Forchheimer model at
http://foam.sourceforge.net/doc/Doxy...ce.html#l00036

it is

S = - (mu*d*U + rho*|U|*f/2) * U

but should be

S = - (mu*d + rho*|U|*f/2) * U

(according to the literature and source code implementation).

 calim_cfd August 5, 2011 13:09

acordingo to the header porousZone.H it has been fixed, if there was this problem in first place:
*************************************8
Implemented porosity models:

powerLaw (\e C0 and \e C1 parameters)
\f[
S = - \rho C_0 |U|^{(C_1 - 1)/2} U
\f]

Darcy-Forchheimer (@e d and \e f parameters)
\f[
S = - (\mu \, d + \frac{\rho |U|}{2} \, f) U
\f]
**************************************************

 makaveli_lcf August 5, 2011 16:26

Yeah, I posted this 2 years before)))

 calim_cfd August 6, 2011 12:16

hi maka!,glad to see you're still around! i'm new to OP and i'm trying to use the porosity solver and i bumped into ur post :P

since u've dealt with this topic b4 i'm taking this chance and i'll ask you.. do you know how to apply a permeability using in a cylindrical CS? i got a filter in a shape of a tube and i need to set its permeability in the radial direction.. any clues??

i found a few topics in the forums but the ones that seem to fit my need seemed to indicate some major changes in the codes and that's a lengthy path... do you know any shortcuts??

thanks a lot!!

 makaveli_lcf August 8, 2011 02:25

Hi!

Don't know what do you really need, but you can use e.g. a source term in your momentum equation and adjust it accordin to the local radial direction (just calculate some vector field field at the beginning). But that is apart of porous class. You can also hack it to meet your needs.

 calim_cfd August 8, 2011 07:56

Hello again Maka!

I'll try to be clearer. I want to model a porous zone. To achieve so, i need to set resistences in space, at all directions. Thing is, how do i "pick" a radial direction? i need a cylindrical coordinate system so that i can, lets say, set a vector similar to (100 1e7 1e7) representing a small resistence in direction e1=er and infinite in the others, i. e., e2(etheta)=e3(ez). I guess, It all boils down to: can i, and if so, how do i build a Cylindrical CS in OP.... so that i can set sth like:

coordinateSystem cylindrical_123;
// porosity 0.781;
Darcy
{
d d [0 -2 0 0 0] (x y z);
f f [0 -1 0 0 0] ( a b c);
}

thanks a lot :P

***********************

i found this post with the link and i guess i may have found what i needed.. it has a whole lof of other things..it's worth checking it out :)

http://www.cfd-online.com/Forums/ope...tml#post319310

 hchen December 11, 2014 17:07

Hi Mauricio:

I know it was a post long time ago...
But I am wondering if you manage to introduce a cylindrical coordinate into porous media? Since I am doing that right now!

Thanks!

Best regards
Hao
Quote:
 Originally Posted by calim_cfd (Post 319299) Hello again Maka! I'll try to be clearer. I want to model a porous zone. To achieve so, i need to set resistences in space, at all directions. Thing is, how do i "pick" a radial direction? i need a cylindrical coordinate system so that i can, lets say, set a vector similar to (100 1e7 1e7) representing a small resistence in direction e1=er and infinite in the others, i. e., e2(etheta)=e3(ez). I guess, It all boils down to: can i, and if so, how do i build a Cylindrical CS in OP.... so that i can set sth like: coordinateSystem cylindrical_123; // porosity 0.781; Darcy { d d [0 -2 0 0 0] (x y z); f f [0 -1 0 0 0] ( a b c); } http://imageshack.us/photo/my-images...radeteladn.pnghttp://imageshack.us/photo/my-images...radeteladn.png thanks a lot :P *********************** i found this post with the link and i guess i may have found what i needed.. it has a whole lof of other things..it's worth checking it out :) http://www.cfd-online.com/Forums/ope...tml#post319310

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