[Gmsh] RE : stl and prism extrusion

[Hoessler, Julien]

Hi David,
Thanks for the quick answer. The stl importation crashes with the stl file or a msh file obtained from the stl, but I guess that's because my stl is too fine (214K elements), I'll try again with a coarser mesh. As far as the prism extrusion is concerned,it works well and after recombining, the prism look perfectly fine on a curved surface, except that I get errors telling me that the prisms are degenerated. Is it an unnecessary warning or should I be worried?
I also have a bonus question if you don't mind. When I generate the extrusion of the surfaces and put them on a list surf[], is it possible to access the edges and vertices of the top surfaces to define the volume above? I could extrude the edges and vertices too but it would mean that some entities would be duplicated.
Best regards
Julien
________________________________________
De : David Colignon [David.Colignon at ulg.ac.be]
Date d'envoi : vendredi 11 décembre 2009 14:40
À : Hoessler, Julien
Cc : gmsh at geuz.org
Objet : Re: [Gmsh] stl and prism extrusion

On 11/12/09 15:00, Hoessler, Julien wrote:
> Good afternoon all,
> First of all, thanks for writing this code, I'm using it a lot to generate 2D/3D meshes for DNS and stability analysis. I was wondering if it is possible to extrude a layer of prisms using the surface normals instead of a specific direction. I need to generate a layer of prisms out of a wall which is curved and there is more than 80 degrees of angular difference between the two extreme locations of the surface (it is smooth, but twists a bit like a sinh).


Hi Julien,

it is still experimental and quite hidden in the documentation
  ( http://www.geuz.org/gmsh/doc/texinfo/gmsh.html#Structured-grids ),
but you can try:

Extrude { Surface { expression-list }; layers }

which extrudes a boundary layer along the normals of the specified surfaces (if they are smooth and do not form acute
angles).

> My second question is about the stl importation. I have a stl file which is a 3D box that I can read and visualise without problems, but I'd like to remesh it

The undocumented "Compound Surface" command is also very experimental, but you can try the attached file (reparam.geo)
which here use a .msh file but should also work with a .stl file.


, mesh the volume inside  and split the box surface to assign different physical groups for boundary conditions (and add
a layer of prisms on one of the surfaces). Is it possible with Gmsh? I've searched through the questions in this mailing
list, do I need the opencascade support for this?


Regards,

Dave


--
David Colignon, Ph.D.
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