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Old   September 10, 2012, 01:11
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Hamid
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Dear zaynah


Let me to explain two different boundary conditions:

1) Porous media
2) Porous jump

If you want to use porous media boundary condition it means that you have a volume have been filled with porous material. For this modeling you should know these items: a viscous loss term and an inertial loss term. It means that in your modeling you have different volumes but one of these volumes is porous media. In gambit you should separate this volume from the other volumes. I mean that you should insert the different name for this specific volume. Notice, if this specific volume has some walls that they are joining to the other volume you should set them as an "interior" in the boundary condition. Then you export the model in fluent and set the values for a viscous loss term and an inertial loss term in define\boundary condition\your specific name for your specific volume with TYPE: Fluid. You should check the porous zone in this part.
If you want to use the porous jump boundary condition, it means that you didn't want to model the porous volume. I mean it is not necessary for your project to know the pressure drop through this volume. In this case you know the thickness of the porous media and pressure jump and permeability of the face. Therefore in gambit, you set the "Interior" boundary condition for this face and in fluent you select the porous jump in define\boundary condition part. It should be noted that your face have to be located in the middle of model. I mean the outer boundary couldn't set as a porous jump boundary condition (Please see the Akim679 comment)
By means of this process you wouldn't have any problem. Please inform me if you try this process or not.
Good luck
Hamid
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Old   September 10, 2012, 02:46
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zaynah K.
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Dear Hamid thank you for such prompt reply.

I want to use a porous square in 2D to observe how the air enter the porous square and how it goes out.I mean i want to observe how my velocity changes after passing through the porous square.

but i Do not know how to proceed.. as each time i put Porous_jump In gambit when export to fluent it refuse to acknowledge it..

Thanks
zaynah
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Old   September 10, 2012, 05:35
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According to your explanation (I mean I want to observe how my velocity changes after passing through the porous square.), you couldn't achieve to the result (velocity behavior through porous square) by means of using porous jump boundary condition. You can extend your 2D model into 3D. Set the third dimension value to 1 m. then you have a volume (porous media). In fact you have a cube with 2D dimension values and the third dimension is 1 m.



Now, I have a question from you: does your inlet flow has distance from one side of the square? if not you should extrude left and right side of your cube for producing the inlet and outlet sections. I mean you couldn't set inlet and outlet boundary condition for the right and left side of the preliminary cube. You should extend the desired sides for setting the inlet and outlet boundary condition. (If you don't know the length of the extension, this value for inlet is 5 * hydraulic diameter of the inlet surface. I mean the distance between inlet surface and inlet side of the cube. The distance between outlet boundary and the outside of the cube is 10 or 8 * hydraulic diameter of the outlet surface.)



Now, by means of this procedure you have 3 volumes. (Left, middle and right) As I said before, you should set the surfaces joining to the left and right volumes to "INTERIOR".
In gambit, in zone section\Specifying continuum type, you should have one volume for porous and 2 other volume for your fluid.

Try it please
Good luck
Hamid
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Old   September 13, 2012, 15:20
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zaynah K.
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dear Hamid
Sorry for late reply i was in fact trying it.

but in my Gambit in the specify continuum i have only fluid or solid

That is why i was asking about the job of porous_jump in gambit.


zaynah
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Old   September 15, 2012, 02:55
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Hi Zaynah

Yes, in the specify continuum in gambit we have just fluid or solid. You should set your specific volume (porous media) as a fluid and then go to fluent. (Please insert the specific name for your porous media such as "POROUS SECTION") Read your case and check model's mesh. Now after your desired setting for model and material in "define" option. Then in the Define\boundary condition, you see the window divided into two parts, "Zone and Type".



Now you should find your specific volume in the Zone part (remember I set your porous volume as "POROUS SECTION"). Notice your volume property is "fluid" in Type part. Now click on "Setů"and put a check mark on "porous zone".

Good luck
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Old   March 7, 2013, 11:37
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Hi All,

How can I define a membrane be permeable to air only? I have defined the membrane as a Porous Jump. And I have a mixture of air and water and I want this membrane to be permeable to air only. But I'm not sure how to set this. Could anyone help me?

Thanks,
Leram
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Old   July 9, 2013, 11:45
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Tanjina Afrin
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Hi all,

Could you please tell me how can I calculate "face permeability" for porous jump BC when My model is a porous pipe submerged in water. I made the model in 2D, so pipe is just a line of 6 m. Any help will be really appreciated .
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Old   November 3, 2013, 11:13
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hi hamid:

dear hamid your experience and guidance are so useful ...
i want to know that did you use porous media in openfoam ?because i should solve my problem in this solver with porousInterFoam and when i export my case to openfoam, this solver can not find the porous media..
would you mind please help me to make my boundary condition in right way?
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Old   November 5, 2013, 00:36
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Quote:
Originally Posted by hesamgh View Post
hi hamid:

dear hamid your experience and guidance are so useful ...
i want to know that did you use porous media in openfoam ?because i should solve my problem in this solver with porousInterFoam and when i export my case to openfoam, this solver can not find the porous media..
would you mind please help me to make my boundary condition in right way?

Dear Hesam,

I'm awfully sorry. I have not any experience about openfaom. sorry again

regards
Hamid
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Old   November 18, 2013, 22:03
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Hi all
I have a proplem. In the VARTM process simulation in fluent. I use porous boundary condition.
I prepared the same geometry with my media.
- Prepared a rectangular surface body as add material (active body).
- Prepared all the baffles as rectangular surface body as frozen.
- Total-2 surface: 1-flow media, 2-fiber
inlet is "pressure inlet", outlet is "pressure outlet". but results are not as analytical and experimental. (time filling).
If someone were simulated and the results properly, please help me
thank!
dinhgiap
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Old   June 20, 2014, 07:20
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SAIKRISHNA N
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Hello, Hamid
I want to simulate flow through a rectangular porous section with inlet on leftside and outlet on right side with other two as walls in FLUENT. I have tried it by taking 'porous zone' in 'fluid' dialog box and given 'porosity' and left other things default. in the BCs for the interior surface i have chosen 'interior'. I have successfully completed simulation. Is it solving 'continuity and momentum equations in porous media'?
One more doubt is I found in user manual "porous jump" gives fast covergence for 2D models. How can I use porous jump. it is actually for an edge (in 2D), but I am having a surface here. how can I give this boundary condition?

Thank you
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Old   June 21, 2014, 00:28
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Quote:
Originally Posted by SS17 View Post
Hello, Hamid
I want to simulate flow through a rectangular porous section with inlet on leftside and outlet on right side with other two as walls in FLUENT. I have tried it by taking 'porous zone' in 'fluid' dialog box and given 'porosity' and left other things default. in the BCs for the interior surface i have chosen 'interior'. I have successfully completed simulation. Is it solving 'continuity and momentum equations in porous media'?
One more doubt is I found in user manual "porous jump" gives fast covergence for 2D models. How can I use porous jump. it is actually for an edge (in 2D), but I am having a surface here. how can I give this boundary condition?

Thank you

Hi SS17

about your first question: Yes, it solves continuity and momentum equations in porous media.
the second question: if you model your porous media as a volume and you want to see the viscus resistance and inertia resistance in the porous volume you should select the media as the porous zone and set required data.
but if your goal is not studying detail behavior of fluid in the volume you can use porous jump BC. if you want to model your geometry in 2D, you should draw a rectangle. split the rectangle via a edge in two parts. Now select the edge as a pressure jump BC. you should insert the permiability, thickness and pressure jump coefficient for this edge.

Good Luck
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Old   October 22, 2014, 03:45
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[QUOTE=Leram;412342]Hi All,

How can I define a membrane be permeable to air only? I have defined the membrane as a Porous Jump. And I have a mixture of air and water and I want this membrane to be permeable to air only. But I'm not sure how to set this. Could anyone help me?

Thanks,
Leram[/QU
Hi. my problem is like to your problem. so for your simulation and speak about work: asareh.p@gmail.com.
thanks
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