[Gmsh] [PROBLEM] Elements normals

[Xavier Mencaglia]

Dear,

I'm currently using the version 2.2.4 of GMSH to mesh a stp file which 
was created by Catia V5 R18.
When I check the normals of the surfaces of the step file, they are well 
oriented.
And then I mesh the step file (2D mesh - triangle elements only)  and I 
check the normals of the elements. I can see some normals that were 
inverted during the meshing operations. So some normals remain stable, 
pointing in the same direction as the normals in the step file and some 
normals are inverted.
It's a little bit problematic for me because I'm working with composites 
so I need to know and control the normals of the FE. The stacking 
sequence is strongly dependent on normals orientation especially if 
composites are not symmetric.

So I have 2 questions about that:

1/ Is this problem well known and is it linked to the way the mesh is 
performed ?
2/ If  this situation is normal, could you explain me why some normals 
are inverted ? What is the rule that pilots this mechanism ?

Thanks in advance for your answer,

Kind regards,

-- 
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*Ir Xavier Mencaglia
Research Engineer
Multiscale Materials Modeling Group
Cenaero - Research Center
Building Eole, 2nd floor
Rue des Frères Wright, 29
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