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Old   May 4, 2012, 19:50
Default Grid interface issue
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Caroline Vandame
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Hi guys,

I'm studying the bagless filter that you can see in the attached picture.
After many days of research, I figured out that to avoid high skewness cells, I should create 3 separate volumes: the top part of the cylinder, the bottom of the cylinder part, and the middle part +the inlet (as one volume).
I have 4 interfaces BCs where the meshes "meet" (in yellow), that are not exactly similar since the one from the middle volume also have the inlet part.

I used tmerge to create one mesh out of those three (you could do the same by opening multiple meshes in Fluent, but it didn't seem to change anything)

Here is where I'm stuck: I think I'm supposed to define my mesh interfaces in Fluent, which should work for overlapping non-conformal faces if I believe the help.
However, when I do that, it creates 2 wall BCs, that seem to be empty. And it seems I have no way to say that the common part should become interior, but the part that only belongs to one face should become a wall.

Is there something I should do first? Like merge/fuse zones (I'm not sure what those do)?
I don't think I have a periodic interface, nor a coupled one (all zones are fluid, and in the end, it should act like one volume)

I looked in previous threads, but couldn't find the answer.
Thanks for your help!
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Old   May 4, 2012, 23:16
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Lucky Tran
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Sounds like you are trying to define it as an interior interface. Are you sure you can't specify it that way? Just don't choose any of the options, they are optional.
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Old   May 4, 2012, 23:22
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Caroline Vandame
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So for each interface pair, one face is bigger than the other one. The common part should be defined as interior and the other part as wall.
Is that possible? How do you set the mesh interface as interior?
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Old   May 5, 2012, 09:21
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duri
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I hope fluent takes it that way. Interfaces are always interior you need not to specify any where.
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Old   May 5, 2012, 10:48
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Caroline Vandame
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In the picture, you can see what I want to do (taken from Fluent help guide)

But right now, when I create the grid interface, Fluent creates 2 walls, and when I try to draw them or to change them, I have the following error message
"zone-surface: cannot create surface from sliding interface zone. Creating empty surface."

I'm not trying to define a sliding interface zone...I just want my interior and my wall...
Any idea?
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Old   May 5, 2012, 14:25
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Lucky Tran
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Quote:
Originally Posted by CaroVandame View Post
But right now, when I create the grid interface, Fluent creates 2 walls, and when I try to draw them or to change them, I have the following error message
"zone-surface: cannot create surface from sliding interface zone. Creating empty surface."
Please give details on how you are creating the interface. I believe you are doing something wrong and making some mechanical error. This should be a straightforward task. List the GUI/TUI commands.
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Old   May 5, 2012, 14:37
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Caroline Vandame
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Ok here are the few steps I'm following, and it seems to work now:
- read the three meshes
- scale them
- merge the fluid zones
- merge the default.interior zones
- merge the outside wall boundaries
- create the grid interfaces by specifying the name, and the two faces that are involved (bottom face of the top mesh + top face of the middle mesh for ex). nothing else is specified since I don't have a coupled wall (it's a fluid-fluid interface -> interior face) or a periodic boundary
- initialize
- run

Fluent still creates these empty surfaces wall boundaries. but they don't seem to matter. The simulation seems to be running fine...

Hopefully it's not luck and I am following the right steps...
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