[Gmsh] Node ordering for quadratic elements

[Kris Van den Abeele]

Hi Christophe,

I verified the node ordering in the meshes I attached in my previous
email. The mesh for the sine bump (sineBumpHexaCurved3D.msh) has the
ordering you described. The mesh for the cilinder (halfcylinder_3D.msh)
has not. The nodes associated to the second and fourth face (1256 and
2367) are swapped, as well as the nodes associated to the third and
fifth face (1458 and 3478).

Best regards,
Kris


On Sun, 2008-02-24 at 18:56 +0100, Christophe Geuzaine wrote:
> Kris Van den Abeele wrote:
> > Hi,
> > 
> > My name is Kris Van den Abeele, I am a PhD student at VUB (research
> > group of Prof Lacor). I am working on the development high-order
> > Spectral Volume and Spectral Difference methods, which I implement in
> > the VKI COOLFluiD code. I've been using Gmsh (Version 2.0.8, on Linux)
> > as a mesh generator for a long time now and I am very happy with it.
> > 
> > Lately, I've been creating meshes consisting of quadratic (27 nodes)
> > hexahedral elements, and I've encountered a problem. On the website, I
> > have not found the order in which the nodes of such a quadratic
> > hexahedron are written to the mesh file. I have two different meshes,
> > and it seems that for two different meshes, the order in which the nodes
> > are outputted differs (more specifically for the nodes that lie in the
> > center of a face).
> 
> Hi Kris - The second order nodes are given in the following order: 
> first, the nodes associated with edges are given in the order of the 
> edges; then, the nodes associated with faces are given in the order of 
> the faces. The ordering of the edges and the faces is given here:
> 
> http://geuz.org/gmsh/doc/texinfo/gmsh_10.html#SEC71
> 
> Can you check if your meshes are consistent with the docs? If not, it's 
> a bug and we will fix it.
> 
> Take care,
> Christophe
> 
> 
> > 
> > In attachment, I have included the .geo and .msh (Version 1.0) files
> > corresponding to the two meshes.
> > 
> > Could you have a look at this, or maybe send me the order in which the
> > nodes are outputted?
> > 
> > Thanks in advance!
> > Best regards,
> > Kris Van den Abeele
> > 
> > 
> > 
> > 
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> 
> 
-- 
Ir. Kris Van den Abeele

FWO Research Engineer

Vrije Universiteit Brussel

Dept. of Mechanical Engineering
 
Fluid Mechanics and Thermodynamics Research Group
 
Pleinlaan 2, 1050 Brussels, Belgium
 
Tel. : 02/629.23.99
 
Fax : 02/629.28.80