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[mesh manipulation] StitchMesh creates non-orthogonal cells

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Old   March 22, 2017, 07:08
Default StitchMesh creates non-orthogonal cells
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Roger
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Dear users,

I am trying to stitch 2 parts of a mesh together. Both parts are created with hyperbolic extrusion and then converted to foam from a P3D -file. For the stitching i created a faceSet with topoSet and then a patch with createPatch. Until here, everything is well.
However when i use stitchmesh on the patches it gives a non-orthogonality of 87. When one looks at the mesh itself you see that the cells perfectly align. (see attached) Another part of the patches is stitched together correctly. Can anyone help me why this happens, or if there are other tools that can do this? I have tried to mess around with a toleranceDict but this does not seem to work.

Kind regards, Roger
Attached Images
File Type: png Patches.PNG (12.2 KB, 32 views)
File Type: png boundary-zoom.PNG (8.6 KB, 30 views)
File Type: png non-ortho-set.PNG (1.7 KB, 26 views)
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Old   October 4, 2017, 13:15
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Thomas Evans
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Orthogonality (in OpenFOAM, specifically checkMesh) is strictly a relation between cells. Specifically, it is the angle between the face vector and the cell center to cell center vector. Cells, therefore, have no orthogonality measure in themselves.

ignore >> At the inside corner, your cell center to cell center vector is nearly vertical, but the face vectors nearly horizontal. Hence the bad orthogonality result. << ignore

Okay, I didn't look closely enough. Thought I was looking at a 2d mesh, not part of a 3d mesh. Can't tell where/how stitched, but that should be where the cells don't line up well.

Also, the cells which connect may not be the obvious ones. If the cells are ever-so-slightly offset, there may be new faces created between cells that do not look connected.

Last edited by windscion; October 4, 2017 at 14:39.
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