[Gmsh] Hexa mesh with extruded mesh

[Ruth V. Sabariego]

Hi Umut,

For a surface, meshed with triangles:
If you extrude without Recombine, you get tetrahedra.
If you  extrude with Recombine, you get prisms.

For a surface, meshed with quadrangles (use first lines of your code):
If you extrude without Recombine, no 3D mesh is generated. A little bug? 
We'll have a look.
If you  extrude with Recombine, you get hexaedra.

Ruth

Umut Tabak wrote:
> Dear all,
>
> In a hexahedral mesh generation, I can do the tetrahedral meshing 
> without problems with the below piece of code. But uncommenting the 
> commented lines results in this problem : My surface is extruded, 
> however the surfaces in the direction of the extrusion are meshed with 
> quadrangles and the others with triangles and (I guess) as a result, I 
> can not get a hexahedral mesh for a simple box geometry.  I am sure I 
> am missing sth simple from the manual and your help is appreciated.
>
> P.S. I think I can define 8 corners of my box, define lines and 
> surfaces with transfinite to end up with the hexa mesh. But I wondered 
> the correct usage of extruded mesh option if I understood correctly 
> from the manual with the code below(lines uncommented).
>
> Thanks for the replies in advance. Attached also the include file.
>
> Umut
>
>    11 Include "truck3d_1r.geo";
>    12
>    13 // Transfinite Line{1} = 21 ;
>    14 // Transfinite Line{2,4} = 11;
>    15 // Transfinite Line{3} = 21;
>    16 // Transfinite Surface{10} = {1,2,3,4};
>    17 // Recombine Surface { 10 };
>    18 // Physical Surface(4) = {10};
>    19 // vol[]=Extrude {0.0,0.0,0.5}{   
> Surface{10};Layers{10};Recombine; };
>    20 // vol[]=Extrude {0.0,0.0,0.5}{ Surface{10};Layers{10}; };
>    21 vol[]=Extrude {0.0,0.0,0.5}{ Surface{10}; Layers{5}; };
>    22 //Transfinite Volume {11} = vol[1] ;
>    23 Physical Volume (11) = { vol[1] } ;
>    24 // binary format
>    25 // Mesh.MshBinary = 1 ;  // GMSH 2.2.4
>    26 // Mesh.Binary = 1 ;         // GMSH 2.2.5 changed to this
>    27 // color
>    28 // Mesh.Color.Quadrangles ;
>    29 // Nastran bdf format : option value is 31 for BDF output
>    30 // Mesh.Format = 31 ;
>
>
> ------------------------------------------------------------------------
>
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-- 
Dr. Ir. Ruth V. Sabariego
University of Liege, Institut Montefiore,
Dept. of Electrical Engineering & Computer Science, 
Applied & Computational Electromagnetics (ACE),
Sart Tilman Campus, Grande Traverse, 10 (B28), B-4000 LIEGE, Belgium
phone: +32-4-3663737 -- fax: +32-4-3662910 -- http://elap.montefiore.ulg.ac.be/

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