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-   -   Problem with pressure jump in 3d problem (http://www.cfd-online.com/Forums/fluent/102651-problem-pressure-jump-3d-problem.html)

paisano May 30, 2012 18:55

Problem with pressure jump in 3d problem
 
1 Attachment(s)
I have a divergence problem when i use porous jump condition in a 3d problem. I want to model wind passing over a windbreak.
The windbreak was modeled as a solid with 1 mm thickness and it was inserted in a huge control volume. The meshing has like 3 million elements and it was very difficult to mesh.
The control volume is attached

Can anybody help me?

Guava Wang May 30, 2012 22:50

hi paisano,
the porous model with 1mm thickness can be simplified as a surface, and set the surface as porous jump boundary condition. in this way, mesh will be easy. the main issue is that the surface sliced the solid for interior zone. hope this will help.

regards
Guava

paisano May 30, 2012 23:10

Thanks for the answer, but the porous jump model can only be applied to interior type zones, not to faces.
I donīt know too much of Fluent, but can I do Surfaces with interior Zones? I think not, but i`m not sure.

Guava Wang May 31, 2012 04:25

Quote:

Originally Posted by paisano (Post 363949)
Thanks for the answer, but the porous jump model can only be applied to interior type zones, not to faces.
I donīt know too much of Fluent, but can I do Surfaces with interior Zones? I think not, but i`m not sure.

you can do as follows. first divide the model into several parts, and then form a new part in ANSYS DM. the face amid two parts is an interior zone when you import model into FLUENT. that face is taken as the porous jump BC . you can try.

paisano May 31, 2012 14:33

Quote:

Originally Posted by Guava Wang (Post 363984)
you can do as follows. first divide the model into several parts, and then form a new part in ANSYS DM. the face amid two parts is an interior zone when you import model into FLUENT. that face is taken as the porous jump BC . you can try.

i wil try it, thanks a lot!!

paisano June 3, 2012 21:32

When it runs with the porous jump-condition, Fluent Crashes. And when i open the Setup again it appears:
Change zone type [3] (Failed)
Change zone type [4] (Failed)
Change zone type [5] (Failed).
Without the porous jump-condition the software doesn`t crash (with Interfaces and interface interior zone created).
I'm looking for the solution..

delaneyluke June 6, 2012 07:29

A porous jump is applied to 2D faces and appears under the Boundary Conditions tab
Here you only need to input 3 variables, inertial resistance coeff (pressure jump coeff C2), viscous resistance coeff (Face permeability) and medium thickness

A porous media is applied to a cellzone and allows you to input the same coefficients but in all 3 directions.

Regards
Luke

paisano June 6, 2012 10:14

Quote:

Originally Posted by delaneyluke (Post 365014)
A porous jump is applied to 2D faces and appears under the Boundary Conditions tab
Here you only need to input 3 variables, inertial resistance coeff (pressure jump coeff C2), viscous resistance coeff (Face permeability) and medium thickness

A porous media is applied to a cellzone and allows you to input the same coefficients but in all 3 directions.

Regards
Luke

In 3d problems you can also apply porous jump to interior zones (not to faces). I use porous jump because in the user guide says that has better convergence.

Regards.

paisano June 11, 2012 13:37

Problem almost solved! the problem that i had is that I couldn't run the model in parallel cores. When I run the problem with serial core nothing bad happens (but it takes too much!). I noted that, when I opened FLUENT and i had the following message:

Warning: Partition method "Metis" is not allowed for
autopartitioning for cases with nonconformal
interfaces before the interfaces are defined
and intersected, use "Principal Axes" instead.
You may use the "Metis" partition method
after the case is read in and the interfaces
are intersected.,

When i change the partition method (Principal Axes), FLUENT crashes...

Anybody know how to solve this?

Kamu November 28, 2012 04:20

Porous jump
 
Quote:

Originally Posted by delaneyluke (Post 365014)
A porous jump is applied to 2D faces and appears under the Boundary Conditions tab
Here you only need to input 3 variables, inertial resistance coeff (pressure jump coeff C2), viscous resistance coeff (Face permeability) and medium thickness

A porous media is applied to a cellzone and allows you to input the same coefficients but in all 3 directions.

Regards
Luke

Dear Luke

How does FLUENT treat an inclined surface when specified as a porous jump? I am analyzing heat transfer enhancement with inclined perforated plates?
Thanks in advance


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