Porous media setup issues in Fluent
 

Hi everyone,

I am using ANSYS workbench 12.1, academic licence. I am trying to model a very simple problem in FLUENT but have issues setting it up as I am not familiar with workbench. I hope someone can help me.

Set up:
-model a pipe (rectangular shape) with a porous media piece inside. The flow is going in the pipe, going through the porous media and getting out at the outlet of the same pipe.

STEP 1:
Using Design Modeler, I tried 2 methods:
-sketch the cross section and extrude (2 sketches, 1 for the pipe without porous media, 1 for the pipe that has the porous media inside)
-build 3 boxes (1 for the inlet part, 1 for the media part, 1 for the outlet part)
In both cases, I use the function FREEZE so that the software does not fuse the pieces together as 1 big piece automatically, as the 3 pieces are in contact on the whole cross section area.
I set all the pieces to liquid.

STEP 2:
Using Meshing 12.1:
-I need to use a sweep method which I implemented successfully
-I use the function "Create Named Selection" to set up the inlet, outlet, and symmetry
Now, here is the beginning of all my issues.
-The software set contacts automatically, and I choose "No Separation - fluid to fluid" and I think that the contact between the porous media and the non porous media is where my problem is. I tried all the contact types that are available to me, but it is not working.

STEP 3:
Fluent:
-When exporting to Fluent, the interface between the porous media boundary and the non porous media (on the cross section) is considered as a wall, where I believe, it shouldn't.
-When I try to go back to STEP 2 and create the "Named Selection" of those interfaces to "interior", to force Fluent to consider those surfaces as interior and not walls, an error message appear when importing it on Fluent saying:
"Model information file is not compatible with mesh"
and a similar message on the workbench window.

I am confident setting up the porous media then on Fluent, but the issue I have is during the set up of the mesh/geometry model.
I am aware that my issue is concerning the interface, contact between my porous media and my fluid inlet and outlet medias.
How can I solve that issue ?
I tried to look around and couldn't find any details for solutions for this simple issue.

Maybe it has changed or I am not doing it the right way, but I believe that the porous media interface has to be set to interior and NOT wall or fluent will consider it as a barrier when it is a porous media where fluid can go through it.

I am looking for help and input using workbench 12.1 before I switch back to Gambit/Fluent old days.

Thank you very much everyone for your help,

Bernard,

Have you try to set interface BC in your connection. Then create interface mesh in the interface side.

I am not familiar with the new interface and using workbench.

Do I have to set the interface BC using the modeler (not too sure, the modeler seems pretty basic) or meshing ? In Meshing, I tried to set up some contact conditions but none of them worked.

Hello Bernard,

I have read your thread, and found out I am facing same problem.

I have a rectangular section in which there is a porous media. I have prepared the rectangular section, made a surface as an active material (surface body - solid). Then I prepared the porous section as a rectangle again and made a surface frozen (surface body - fluid).

During meshing, I just defined "Inlet", "oulet" and "well"

When I imported this to FLUENT, it does the same problem as yours. It creates a contact between fluid and porous media as a wall which I don't want. It should be as an interior.

So, can you please tell me how to get rid of this?

Regards,

Sabrina

I can give you solution to your problem in GAMBIT modeler.


You can go for volume split for 3D/face split for 2D, option to establish connectivity between porous and nonporus zone. If you do that and export to FLUENT you will you will get a shadow face ensuring the connectivity between porous and non porous zone.

My friend using ANSYS says that you can use 'slice volume' option to establish connectivity in the design modeler of ANSYS.

Try it out.

Porous wall
 

Hi,

I am trying to model a wall as a "Porous wall", is there a way to specify that using GAMBIT and FLUENT?

Thanks,
Akim

porous wall
 

Porous media modelling is used for modelling two different phases of volume zone. I dont get about porous wall. could you eloborate.

Porous Jump
 

Hi,

Thanks for your reply. I have a 3D rectangular geometry, and I am trying to set the boundary condition of the bottom wall as a Porous jump in GAMBIT. However, when I read the mesh in FLUENT I get an error saying:
"Cannot change porous to porous-jump because
there is only one adjacent cell thread". I am not sure what this means or what I am doing wrong. Any help is appreciated.

Thanks,
Akim

@ Akim679,

Have you resolved this problem? How did you manage to do so, if you have?

Thanks

Hi akim, the reason your model isnt working is because you need the face that you define as a porous jump to be connected to both volumes, you have probably only connected it to one volume...many people make/have made this error inlcuding myself...hope this helps

I have done a similor case a few days ago. In addition to the named selection inlet and outlet faces I also created a names selections for the geometry of porous zone and the fluid zone. Hope this helps

help
 

hi,

Anyone can send me his fluent project in order to compare the results of flow in porous media ?

Thanks

cuipdon_77@hotmail.com

hi did anyone finally resolved that issue?

when i subtract the face which i want to be porous and define it as porous from my domain, and export to fluent i get the error messge,..

then i not subtract the face rather i just define it as porous_jump, but in fluent it is taking it as an entity..:(

please any help is more than welcome
zaynah

hi 4 u
 

you have to create your geometry without declaring any thing but in fluent creat an udf in which you declare the porosity of the media. it's very very easy. i always use it in modeling catalytic reactors with catalytic porous zone. cordialy

Hai,
For creating a porous zone inside a volume, you can split zone inside fluent and that becomes an interior zone where you can apply the condition of porous.

For creating a porous jump, you need to create the volumes on either side of the wall and specify that as an wall and when defining you can use porous jump. Since porous jump uses darcys law to compute pressure loss, it requires cells on either side of the wall.

Try and let me know

with regards,
Byron

Incline perforated plate
 

Does anyone have an idea of how I can model an inclined perforated plate using the porous jump B.C in FLUENT?

I am modelling a tube through which mixture of air and water passes and there is an air permeable membrane around the internal wall of the tube which is permeable to air only. I should model this as VOF in Fluent.

First, I need to set this wall boundary as Porous Jump in Gambit. I did the following steps in Gambit:

1) created a cylinder as volume
2) meshed it
3) set the boundaries as inflow, outflow, and porous jump (for the face around the cylinder)
4) set one fluid zone for the entire volume
5) export the mesh to Fluent

and when importing the mesh into Fluent, I got the Error Message : "Cannot change porous to porous-jump because there is only one adjacent cell thread".

Therefore, I tried the following procedure :

I created and two cylinders, one inside the other, and then define the surface of the inside cylinder as porous jump and the surface of the other as wall. But when exporting to Fluent, I just have one wall boundary in boundary conditions that are imported in Fluent. That is, Porous jump is missed!

I was wondering if you could help me define this problem? Much appriciated!

Thanks,
Leram

Hai
In Gambit set the interior wall also as wall and export the mesh to Fluent. In fluent you can define the interior wall as porous jump. Try this and post your response

regards
Byron Smith

Hi Bryon,

Thanks for your Reply.

My problem is when I define this interior as wall, I cannot see Porous Jump in Type of BCs in Fluent infront of Wall Zone.



Leram

I have the similar problem at the moment, when I succeed I will let you know, if someone knows the solution please tell us

tryh the following: two zones one fluid one porous with inlet outlet and the wall boundaries do not try to define explicetly the contact. I guess you are working with multibody part (Merge all parts in DM into one) and name the selections in Meshing

Porous jump error at mesh checking
 

Hi every one,

I had getting error in pororus jump error

Checking boundary types:
Error: jump zone 7 has wrong types of cell zones (cell and cell).

Zone & is comng under in My PEMFC as Inter of anode CC in boundary conditions type as porous jump

I dont know how to rectify it...

Help me solve this

Thanks Bryon for your suggestion,
my problem is from the initial stage. I am simulating the catalytic converter and have modeled in CATIA with two substrate(substrates here act as a porous media where reactions are taken place and have hexagonal cells) inside it. I have simply assembled those two substrates. Now should i mesh the substrate as well as fluid body at a time(if so then the meshing will not be completely done) or separately(if so the substrate will be meshed twice)? OR shall I create only external cover while modeling(meshing as well) and while giving bc's in fluent i shall create a block mention bc's as
porous.
please help me since I am novice in this domain
Regards
Umesh K

Hi every body
I don't know how determine initial velocity for the flow in porous media.
Thank you for time and consideration.
Best regards

do you have a mass flow?
In the porous domain definition there is something to define the solid to fluid ratio. So if it was 0.5, your velocity would be twice as if there was no solid domain. In front and after the porous domain you would have to define a fluid domain. If nothing is known, take entrainment inlet and mass flow rate. Then it works out the velocities inside and outside the porosity.
Its just a guess, no idea, what you want to do.

Hi Mr.Steffen,

Many thanks for your response.

I want to model the solid porous media with flow in it but there is not any fluid zone In front and after the porous domain. I really appreciate if you tell me how can I set initial velocity for the flow in porous media.

just put a mass flow in instead and it will work out the velocity

0 porosity
 

Hi,
Need urgent help!!

I have set porosity zero in a 3D cell zone inside a pipe, using a UDF. But there is still a flow through the pipe. I have checked the output of the UDF and there is no problem in that...

Don't know what to do now. It is like this-

porosity=0.0 (working fine)
after some time,
porosity=1.0 (working fine)
after some time,
porosity=0.0 (not working)

Porous jump definition
 

Hi guys,
I'm new in using Ansys Fluent, I would like to know how to set a "porous jump" surface. I create two fluid zone and I have properly defined the interface but, in the "boundary conditions", the contact region is defined as "interface" and that is the only option which appears in the drop down menù.
Why I can't set this surface as "porous jump"?
May I need to create a solid surface in the design modeler and make it recognized by ansys as a surface solid zone?
I well understand how to set a porous medium but my goal is to set just a porous jump surface.

Thank you in advance!

what do you mean by porous jump? Velocity jumps up when it enters the porous media, you can make a section through it in post.
https://www.cfd-online.com/Forums/fl...-boundary.html
maybe its a 2d thing?