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[ICEM] Mirror Mesh | Delete duplicate mesh

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Old   November 18, 2013, 09:13
Default Mirror Mesh | Delete duplicate mesh
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Dear all,

i want to simulate a set-up like shown below:



Therefore, i decided to mesh just this part of the geometry:



In the next step, i want to mirror this part which will result in a mesh which looks like this:



After this, i want to translate / copy this mesh a couple of times in order to get a mesh like shown above.

I generated a mesh for the very simple part (picture 2). As i want to mirror this mesh, i choose "Edit Mesh | Transform Mesh | Mirror Mesh". I worked with the options "Copy", "Merge Nodes" and "Delete duplicate elements" and i selected the whole mesh via frame-selection.

The green surface in my second picture is called "part_9", i think this names comes from my CAD-system (in this case CATIA). After mirroring the mesh, "part_9" still exists. With the options declared above, i would have been expected that this part of the mesh vanishes.

I have the same problems if i translate the mirrored mesh later on, which means that i have some kind of internal walls inside my mesh.

Please tell me where my mistake in thinking is.

Thanks in advance!


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Old   November 18, 2013, 09:42
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kad
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ICEM manual says:
"The deleting of elements during the automatic fix will remove one of the two duplicate ele-
ments, thus eliminating this error without creating a hole in the geometry."

E.g. if duplicate elements occur in surface region, deleting both would create a hole in the surface mesh. In your case the volume mesh is all in the same part. So you should be able to just delete those "interface" elementes without getting an error warning.

Furthermore I would not work with the frame selection when dealing with volume mesh. Displaying the whole mesh can easily crash ICEM on weaker computers. I prefer "select items in part" from the selection toolbar.
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Old   November 18, 2013, 10:12
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Sorry, maybe i don't understand the Help-Manual. Does this mean that i do not have to care about those "duplicate" elements or do i have to delete them manually after mirroring the mesh? How can those duplicate elements be deleted?

Thank you very much for your advice concerning the box-selection!
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Old   November 18, 2013, 10:54
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I think you use the term duplicate element wrong. A duplicate element is a cell face that shares all of its node with its neighbor face. So you have two cell faces that have exactly the same nodes and this is a mesh error. It is obvious that these kind of elements are created in the mirror plane. By fixing duplicate elements one of the two duplicate faces is deleted, the other one remains. Duplicate elements are not just "those elements in the mirror plane". There are two things you can do:

1) Define the mirror plane elements as internal walls in your solver.
2) Delete all shell elements in the mirror plane.

If you have to care for them, depends on your case. Mind that the mirror plane could also be a physical wall in other cases like yours. But in your case I would delete the elements because if think it's the easiest way.
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Old   November 18, 2013, 11:12
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Thank you for your fast reply! Maybe another option would be to exclude the shell elements in the mirror-plane from being mirrored?

Nevertheless i want to implement your suggestions, can you please explain me how to delete those shell-elements in the mirror-plane?
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Old   November 18, 2013, 11:54
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Right, that is another option. In your simple case this should be no problem. Nevertheless I always copy the mirror plane elements too, to avoid any uncovered faces or else.

There lots of different and simple ways of deleting the elements. The easiest would to turn on shells and only part_9 in Display tree and select visible. Btw. really great selection modes in ICEM are the floodfill selection up to an specified angle and the select elements inside closed curve loop. They make picking elements from screen very easy. So this would be another way. I guess you are so familiar with ICEM to find the delete elements function?
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Old   November 19, 2013, 08:35
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Hi kad, thank you very much fo your reply! Thanks to your help, i finally got my desired mesh!
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