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### Avoiding Subdivision of the edges when meshing a surface

Posted: Sun Mar 06, 2016 1:59 am
Hi all,

I'm currently having difficulties with meshing the interior of a tunnel (attached). In particular, 2 issues arise:

1. So far I have tried with unstructured meshes in case the is no way to structure the mesh. The problem is that after I input the points and lines and create a surface, at the time when I mesh the surface, the program automatically creates another node in the edge of the surface. I attach pictures. As you can see, the new extra node lies on one side of the lining, whilst on the other side there is no extra node.

Is it possible to avoid this? For my problem It is imperative that the mesh does not contain any nodes on the edges that are not original points. In other words, I would like to impose that the nodes at the edges be only the points of the geometry. Any help is appreciated.

2. Is it possible to obtain a structured mesh with this geometry? I have thought about it long time and I can't seem to be able to do it. Any guidance on subdivision or whatever method would be appreciated.

Regards.

### Re: Avoiding Subdivision of the edges when meshing a surface

Posted: Mon Mar 07, 2016 1:05 pm
Hello,

there is one restriction with the unstructured quadrilateral mesher in GiD: the sum of the line elements (of the mesh) enclosing a surface, must be even. This may be the reason why GiD is adding an aditional node in that line. To avoid this, you should ensure the number of lines contour of the surface is even too (in case you want one element per line). In that case, GiD will be able to generate the unstructured quadrilateral mesh.

Apart from this, structured meshes (in 2D) can only be generated from a 4-sided surface, although some cases can be meshed if GiD can (automatically) detect 4 sharp corners among all the contour lines.

### Re: Avoiding Subdivision of the edges when meshing a surface

Posted: Mon Mar 07, 2016 1:06 pm
About avoiding extra nodes in your lines, you must assign to these lines
Mesh->Structured->Lines->Assign number of cells
and set 1 division to your lines.

About structuring your surface, it is possible for example with this pattern of several surfaces:

structured_excavation.png (27.79 KiB) Viewed 3261 times

CI6910MallaInteriorv2Prueba2.zip
The GiD example modified to be meshed structured