[Gmsh] Mesh extrusion

[Antoine Dechaume]

Hello,

So far I used quite simple 10-points tetrahedral structured mesh  
created by a program I was given, which basically creates hexahedron  
and then split each one into 4 identical tetrahedron.

To check gmsh mesh, I ran a simulation for a test case. The results  
are globally ok, but some values deviate from the expected ones. It  
seems to me that the deviation comes from the fact that the mesh  
created by gmsh is not "symmetric" ( I'm not sure how to qualify  
this, though the deviated values lost symmetry in some sense ).

The mesh I used was created only by extrusion, the following small  
example is similar :

Point(1) = { 0, 0 , 0 , 1 };

Extrude { 1 , 0 , 0 }
{Point{ 1 };Layers{{ 1  },{ 1. }};}

Extrude { 0 , 1 , 0 }
{Line{ 1 };Layers{ 1 },{ 1. }};}

Extrude { 0 , 0 , 1 }
{Surface{ 5 };Layers{{ 1 },{ 1. }};}

Then meshing this cube with second order linear tetrahedron will  
create 6 elements which are not all identical, one point is also  
created at the centre of the cube. ( 4 identical elements and no  
centre point with the other meshing program ).

Strangely, meshing once more will change some of the elements !

Is there a way I can create a mesh such that this cube has 4  
identical tetrahedron ?

Thanks,
Antoine.