[Gmsh] Problems for creating ruled surfaces belonging to a cylinder

[David Colignon]

On 26/12/09 20:58, Durufle marc wrote:
> Hello,
> your help has been very useful for the problem of the cavity, thanks
> very much. I have another problem with
> the geo file attached. I want that "ruled surfaces" 36, 38, 40, 46, 48
> and 50 are part of a cylinder, so I tried to
> construct nurbs which are belonging the cylinder, but the generated
> ruled surfaces are not part of the cylinder :(

Hi Marc,

the mesh seems fine here. How do you have verified that these ruled surfaces are not part of the cylinder ?


> Do you know a way to generate those surfaces correctly ?

We have an option to force the mesh on the surface of a sphere, but not on a cylinder...

http://geuz.org/gmsh/doc/texinfo/gmsh.html#Surfaces

Ruled Surface ( expression ) = { expression-list } < In Sphere { expression } >;
     Creates a ruled surface, i.e., a surface that can be interpolated using transfinite interpolation. The expression 
inside the parentheses is the ruled surface's identification number; the first expression-list on the right hand side 
should the identification number of a line loop composed of either three or four elementary lines. The optional In 
Sphere argument forces the surface to be a spherical patch (the extra parameter gives the identification number of the 
center of the sphere).


Is it possible
> (or soon possible) to specify directly
> a nurb surface in gmsh (not only a nurb curve), so that I could
> approximate the cylinder with nurb patches ?


I don't think we will add nurbs surfaces support natively in Gmsh ( Christophe, Jean-François, a comment ? )

You could/should generate these critical nurbs surfaces in a real CAD software/Solid Modeler
( Salome http://www.salome-platform.org/ is free and based on the same CAD engine as Gmsh, OpenCascade),
  export it in the STEP  format, import in Gmsh, finalize the geometry and mesh ...

Regards,

Dave

--
David Colignon, Ph.D.
Collaborateur Logistique du F.R.S.-FNRS
CÉCI - Consortium des Équipements de Calcul Intensif
ACE - Applied & Computational Electromagnetics
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Université de Liège
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