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Problems with volume defining

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Old   December 16, 2015, 11:54
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Tudor Miron
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Vangelis,

What would you suggest for volume mesh quality improvement and making sure that such problems don't appear? May be freasing sym plane before improving quality? May be I should frease surface mesh (as it was done in external aero tutorial) before creating layers/volume mesh?

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Ted
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Old   December 16, 2015, 20:38
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Hi Vangelis,
One more question... or 2 questions actually.

When I import mesh (outputted to fluent .msh format) into CFX than there's a couple of strange things:

First - all the baffle (zero thickness) walls appear with duplicate entities. For example Ė 4th from the top in the list (left side of screenshot) Ė FrontBumper_buffle and after - FrontBumper_buffle Shadow.

Another problem is that in ANSA I have PIDís (as you suggested) for heat exchangers (that I want to model as porous media) Ė Radiator_upstream and radiator_downstream with INTERNAL type. In CFX they appear as single entity (I canít separate them) and this cause problem with interface definition.


Iím a bit lost.


Thanks
Ted



PS: Is there a way to output in native CFX format (.gtm, ,cfx)? Don't know if it will help with above problems. Saving it in .cfx5 format didn't help.
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Old   December 18, 2015, 08:29
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Vangelis Skaperdas
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Hi Ted,

Yes you could Freeze the symmetry plane prior to Fix Qual.
For this, you should de-activate the Fix Quality settings in batch mesh
of layers and volume, so that you do this step manually after batch mesh.

I am not sure how CFX treats baffles.
From ANSA we output them as single surfaces and when Fluent
reads this mesh it automatically generates Shadow PIDs, copies
of the original baffles, so that in the end you have duplicate shells there.
This is how Fluent wants to work and I assume CFX is similar.

I am not sure why CFX merges the interior type faces. You should probably refer to CFX experts.

While in ANSA have you checked in Fluent Deck that in the property list
you have assigned correctly the BC Types in the property list (wall, interior, symmetry etc?)

What happens when you read in CFX a mesh that was output from ANSA in CFX5 format? It does not read it? What messages does it give?
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Old   December 18, 2015, 10:15
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Hi Vangelis,

Thanks for your help.

"I am not sure how CFX treats baffles.
From ANSA we output them as single surfaces and when Fluent
reads this mesh it automatically generates Shadow PIDs, copies
of the original baffles, so that in the end you have duplicate shells there.
This is how Fluent wants to work and I assume CFX is similar."

Is there any way to avoid this generating of duplicate surfaces? Thing is that if single surface is outputed from ICEM for example than in CFX there are no copies of original baffles.

Main problem is that in solution results air is penetrating all those baffles/zero thickness walls! Despite them having wall property! If a mesh is generated and imported from ICEM than zero thicknes walls are imported in CFX with no "shadow" copy/duplicate meshed surface, so it doesn't appear to be CFX problem but output problem. In fact I'm sure it is not really a problem - there should be an easy solution for this issue...

Thanks
Ted
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Old   December 21, 2015, 10:53
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Vangelis Skaperdas
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Dear Ted,

I am sorry but I cannot help you with CFX to that level.
I understand the problem is that CFX does not handle zero-thickness walls
as the mesh is read in but sees all as interior transparent to the flow boundaries. You need to ask probably to a CFX forum.
If you find the answer, do let me know please, I would like to know

Best regards

Vangelis
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Old   December 29, 2015, 05:44
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Hi Ted

Did you sort the problem with baffles in CFX?

Vangelis
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Old   December 29, 2015, 08:39
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Quote:
Originally Posted by vangelis View Post
Hi Ted

Did you sort the problem with baffles in CFX?

Vangelis

Hi Vangelis!

Unfortunately I could not. I had to get back to cad level - ad thickness to surfaces (major pita with complex surfaces) and now I'm about to start meshing new model.

Thanks
Ted
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Old   December 29, 2015, 09:22
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I think you should take the chance and ask the question in the ANSYS CFX forum before putting this effort in CAD
Vangelis
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Old   December 29, 2015, 09:50
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Quote:
Originally Posted by vangelis View Post
I think you should take the chance and ask the question in the ANSYS CFX forum before putting this effort in CAD
Vangelis
I will do it now.

Wish you the very best Holidays!

Thanks
Ted
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Old   December 29, 2015, 09:59
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Thank you, you, too!
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