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Fluent gets rid of interior boundaries

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Old   August 29, 2012, 12:26
Default Fluent gets rid of interior boundaries
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Michael Frank
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Hi,

I am relatively new to Ansys ICEM and Fluent so this might be an obvious question for some.

Basically I am trying to create two boxes (in 3D). The two boxes are of different sizes and the smaller one is placed inside of the larger one. To me this seems quite a straight forward task in icem. However, when FLUENT reads the exported file it only detects the outer box and completely disregards the inner one.

I have checked the .msh file produced by ICEM which does not include any information regarding the smaller, inner box, so I suppose the problem is during the exportation!

If anyone has a clue of what might be going on I would be very grateful.

Thanks in advance
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Old   August 29, 2012, 15:57
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Try to define the internal surfaces inside ICEM before exporting to Fluent.

Output -> Boundary conditions -> Surfaces -> Two-sided -> Create new -> interior
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Old   August 30, 2012, 04:58
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Hi yonchong and thank you very much for your reply.

So far I had the boundary condition as wall. I tried what you said (i.e. setting the interior boundary condition) but without any effect.

Any other ideas?

Thanks again
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Old   August 30, 2012, 05:06
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How if you generate two seperate boxes in ICEM and import the two meshes into the Fluent. Have you tried that?
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Old   August 30, 2012, 05:12
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Hi siara817 and thanks for your response

I haven't actually tried what you said. I sounds like a very good idea. I will try it out and let you know what happens.

However, as I am trying to familiarise myself with these pieces of software, it would be great if someone could still shine some light onto where I am messing things up
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Old   August 30, 2012, 05:16
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I look forward to seeing if it worked for you. I think the reason of removing the interior box is, that ICEM generates mesh for the main box and ignore small box. If you could determine in ICEM to generate mesh seperately for every box, then I think it will be solved.
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Old   August 30, 2012, 05:37
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Have in mind that when I do the same thing in 2D (i.e. square within a square) everything works fine!

By the way, how can I import two separate meshes in fluent?
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Old   August 30, 2012, 06:29
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Could you upload the file so I can have a look?

By the way, you did create a body for each boxes?
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Old   August 30, 2012, 06:59
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Which file would you like me to upload? the project file?

Yes I did add a body for both boxes.
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Old   August 30, 2012, 07:56
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Just the tin file.
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Old   August 30, 2012, 09:16
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I am attaching the .tin file for the mesh!

Thanks
Attached Files
File Type: zip boxes.tin.zip (22 Bytes, 9 views)
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Old   August 30, 2012, 09:21
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Nothing in the zip file.
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Old   August 30, 2012, 09:22
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Sorry about that... try again
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File Type: zip boxes.zip (1.9 KB, 5 views)
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Old   August 30, 2012, 09:47
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The grid is very coarse but I did no find any problem.

I created a volume and surface mesh together using Octree.

Output -> Boundary Conditions

and set the surfaces_heater as an interior (not interface).

Output -> Write input

to create fluent.msh.

Read into Fluent and it created a surface called "int_surfaces_heater".
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Old   August 30, 2012, 09:58
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Thanks again for your reply.

I haven't refined the mesh yet as I am first trying to get everything working but you are right! It needs a lot of work.

Regarding the problem, I have changed the boundary conditions to interior and wrote the output. However the problem persists! Did you manage to make it work?
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Old   August 30, 2012, 10:26
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I haven't touched a thing but it worked for me.
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Old   August 30, 2012, 10:57
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I must be doing something wrong when I output it for fluent then! I just select fluent v_6 for solver and then I write to output. Is there anything else I should be doing?
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Old   August 30, 2012, 11:29
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No. It will ask for uns file you want to use and will write out a fluent mesh file.

By the way, the interior surface will have name changed with prefix of "int_".
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Old   August 30, 2012, 11:38
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this is very strange! This is exactly what I am doing! In fluent I get an int_liquid, where liquid is the material point of the larger box, and surface_bath which is the large box itself!
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Old   August 30, 2012, 14:14
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I am posting a screenshot.

You can see the int_surface_heater which is the interior type boundary condition.
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