CFD Online Discussion Forums

CFD Online Discussion Forums (
-   Phoenics (
-   -   mass generation with porosity setting (

lily May 2, 2006 10:41

mass generation with porosity setting
Hi everyone:

My case is about porous media. I really want to know how to set my porous media with porosity=0.3 and gas generation rate of 1kg/M3*S.

I had set my object attributs with domin material and set its VPOR=0.3, and, use ------ PATCH (SOR ,VOLUME,2,0,0,0,0,0,1,1) COVAL (SOR ,P1 , FIXFLU, 1.0) ----- to set mass generation. But I think that's incorecte because the porosity is not 1,especially on Pressure results.

I need help. thanks

KALI SANJAY May 3, 2006 03:10

Re: mass generation with porosity setting
You can use CONPOR command to set porosity over any length of your domain.

for 1-Dimensional problem it can be


However you can also use VPOR and check polis for further info...

Your gas generation rate is in Kg/M3*sec... so your Volume in coval is fine....however check your other numbers after volume in patch for the domain you are interested in source term....


IXF is your first node in x direction and IXL is your last node in X direction. Similarly IYX and IYF are first and last nodes in Y direction....if you are solving for 1-Dimensional problem and say you have 10 nodes, the patch command will look like

PATCH(SOR, VOLUME, 1, 10, 1, 1, 1, 1, 1, 1)

I hope your problem is not transient...if it is make argument of patch to LSTEP

Refer Patch command in Polis



KALI SANJAY May 3, 2006 03:16

Re: mass generation with porosity setting
CONPOR(SOR,0.3,EAST,1,nx,1,1,1,1) use 'east' instead of 'cell' works for me and hope it will also for you....!

lily May 3, 2006 10:01

Re: mass generation with porosity setting
Thanks for your timely reply Sanjay:) Follow your advise,I changed my porosity setting to CONPOR(SOR,0.3,EAST,1,nx,1,1,1,1) ,and that do work for me:)

But, I am still confused by the mass generation term. As the porous media is not 100% open for flow, I think the result pressure should be diffrent with the situation that media is 30% open for flow. But through experimentations I find the porosity setting didn't affects the pressure results. I don't know why:(

Rami May 4, 2006 02:22

Re: mass generation with porosity setting

As far as I know, setting the conpor type to EAST rather than CELL is used for prescribing the east face porosity (EPOR) rather than the volume porosity (VPOR), meaning you are defining and solving a different problem.

Settings of porosity has no influence on the pressure unless you explicitly define a resistance model (e.g., Darcy law, Ergun model, etc.) relating the pressure gadient to the velocity. For an explanation of the latter refer to

lily May 8, 2006 07:36

Re: mass generation with porosity setting
Thanks rami

I have changed the term VPOR to diffrent values but I got same results, but EPOR worked , I don't know why. And, I am still puzzled by Generation source term setting with porous media. I always feel that this term sould be difrrent between situations there 'have' or 'no' porous media. I have define a resistance model, thanks again:)

Kali Sanjay May 9, 2006 12:37

Re: mass generation with porosity setting
CONPOR setting for 'EAST' from 1 to NX cells is same as 'EPOR'. CONPOR allows to specify porosity for a particular grids and EPOR is Whole-field store for East face porosity.

Kali Sanjay November 4, 2006 14:01

Re: mass generation with porosity setting
Dear Mike, I figured out my problem.....actually when I am giving the migration term as fluxes on east and west walls, I forgot to take in account of effective mobility (which is u/Tortuosity) at the porous/non-porous interface. That's why the flux calculated at the interface from porous side is not the same as flux calculated from non-porous side. This resulted in imbalance. However I would still like your expert coment on the CONPOR implementation. My doubt regarding the actual volume I hope is correct.

Now I want to calculate the velovity field. The problem here is to use superficial velocity. Actually I know the velocity in the porous media (The source of this velocity is due to electroosmosis, a sort of pump inside the porous media). I know the velocity field in the whole domain (actual velocity in the pores and in non-porous medium), I have pressure to atmosphere at the ends. The whole purpose of solving my pressure and velocity equations is to satisfy the continuity equation (as the velocity field I have is sort of function of x, varying). Do I just need to activate DARCY=T and solve the U1? I can just specify the U1 as source term and will solve the Pressure and U1 to satisfy continuity...will it be OK or do I need to do anything else.

Thank you in advance,


All times are GMT -4. The time now is 14:18.