Mesh Numbering / Orientation

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dsonntag
Posts: 1
Joined: Fri Jan 23, 2015 4:26 pm

Mesh Numbering / Orientation

Post by dsonntag »

Hi, I am trying to mesh a shell structure using hexaeder elements. Basically there will be a underlying, extruded surface and a thickness direction (perpendicular to the surface). Currently I am generating the geometry by extruding a curve to a surface (translate + extrude), then extruding the resulting surface to a volume (Offset+extrude), then meshing the volume.

In my FE-calculation the element definition is sensitive to the mesh numbering. So the first 4 nodes should be in the lower surface and the second 4 nodes in the upper surface. The problem is that the structured mesh generated by GiD is sometimes oriented in the plane of the shell instead of perpendicular to it (or in other words, each is Hexaeder is turned by 90°). Is there any way to get better control over the node numbering?

Cheers,
Daniel
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escolano
Posts: 1918
Joined: Sun Sep 05, 1982 10:51 pm

Re: Mesh Numbering / Orientation

Post by escolano »

I recommend to modify your code to not being so sensitive to node's numeration.

In your specific case:
a) if you are creating before the geometric points of the lower surface than the ones of the upper surface, then disabling the GiD renumeration, these nodes will be numbered before.

To disable the GiD numeration set the GiD variable 'RenumberMethod' to -1 , with

Code: Select all

escape escape escape Utilities Variables RenumberMethod -1 escape escape
2) you can mesh your volume semi-structured, and you can splicitly specify the 'extrussion direction' for this kind of mesh
Mesh->SemiStructured->Volumes
select the volumes and its number of divisions in the extrussion direction.
and in case of ambiguous direction, you can splicitly say it with:
Mesh->SemiStructured->Set->Structured direction (or alternatively the master surface)

And to have hexahedra instead of tetrahedra set this kind of elements to volumes (Mesh->Element type->Hexadedra)
and quadrilaterals to the surfaces.
Note that the top and bottom surface could be meshed with unstructur quadrilaterals, this feature is much more flexible that having to create a fully structured mesh.
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