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Mesh becoming coarser during addLayers in sHM

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Old   December 13, 2010, 11:49
Default Mesh becoming coarser during addLayers in sHM
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Arne Stahlmann
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Hi,

I set up a test case for testing snappyHexMesh and especially the layer addition possibility.
I noticed that after the addLayers process, the surface mesh of my structure has become coarser, i.e. points and edges from the fine surface mesh (time 0.06) seem to have been used for the layer creation (time 0.09, vertical edges). Interestingly, this only happens on the cylinder part, not on the box part.

How can I stop this, as it is destroying my mesh in certain locations of the 'real' structure?

Pictures. left: after snapping procedure 0.06 right: after addLayers procedure 0.09.

The sHM dict is attached.
Attached Files
File Type: txt snappyHexMeshDict.txt (9.6 KB, 27 views)
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Old   December 14, 2010, 03:04
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Arne Stahlmann
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Ok, let's ask another question: Is this a 'normal' behaviour of sHM, i.e. does this happen in a similar way in your cases, or not?
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Old   January 21, 2011, 08:17
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Jim Knopf
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Do you have some pictures? I'm not sure about the phenomena you're describing

THX
jim
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Old   February 22, 2011, 06:44
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Shankar
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Hello Arnoldinho,
Your observation is right, i too have seen this strange behavior while generating boundary layer padding.
As of know i am also not aware of the real reason.
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Old   April 6, 2011, 12:20
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Eugene de Villiers
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The volume mesh isn't getting coarser. You are just observing a surface effect. Before the layers are added, SHM tries to merge all boundary faces in a cell that are close to co-planar to improve quality and reduce the number of added layer cells. The "coarsening" you are seeing on the cylinder is just this. Make a cutting plane normal to the cylinder and you will see. The reason you don't observe this on the box is because there much fewer same-cell co-planar faces on a coordinate aligned box.
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