[Gmsh] Strange behavior meshing / exporting

[Andreas Puettmann]

Hi all!

I have been experiencing weird problems with some GMSH generated tetra 
meshes. After some testing I was able to boil it down to the following 
strange behavior:

I create a cylinder with a very simple .geo file. For meshing and 
exporting of the mesh in ASCII format via the GUI I tried different 
approaches:

Meshing:
First option: Click only the "3D" button
Second option: Click "1D" "2D" "3D" successively

Saving:
First option: "File->Save Mesh"
Second option: "File->Save as" + "save all (ignore physical groups)" 
activated
Third option: "File->Save as" + "save all (ignore physical groups)" not 
activated

The funny thing is that any of the 6 possible combinations produce a 
different .msh file, i.e. different numbers of nodes and elements. Is 
really neither of these 6 supposed to result in identical files?

So, I would really appreciate some info on the differences between the 
different approaches. Especially:
What exactly is the difference between the two meshing options? Doesn't 
clicking "3D" just do the same as 1D-2D-3D?
And what is the difference between the first and the third saving 
option? I would think they should be just the same...

I am attaching the .geo file, and the 6 mesh files. Their file names may 
be read as:
_3D : meshing option 1
_123: meshing option 2

_SM: saving option 1 (save mesh)
_SA_ig: saving option 2 (save as + ignore phys. gr.)
_SA: saving option 3 (save as + do not ignore phys. gr.)

Thanks for any help!
Andreas

-- 
Dipl.-Ing. Andreas Puettmann

German Research School for
Simulation Sciences GmbH
c/o Institute of Bio- and Geosciences 1
52425 Jülich | Germany

Tel +49 2461 61 5541
Fax +49 2461 61 3870
Web www.grs-sim.de

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