[Gmsh] Error : Self intersecting surface mesh, computing intersections

[Christophe Geuzaine]

Dear Berta,

Your surface meshes intersect (see attached picture) because your geometry is incorrect : the end of the cylinders overlap with the rectangular faces. Either define the rectangular faces with circular) holes, or use the new OpenCASCADE kernel to intersect the solids.

Christophe

> On 7 Dec 2017, at 20:00, Berta Beltran <beltran at ualberta.ca> wrote:
> 
> Hi  all, 
> 
> I am trying to emulate this results (see attached figure)  from some previous simulations done with COSMOL Multiphysics for the electric potential of our device. I am creating the geometry and meshing it with Gmsh and then I will use Elmer to calculate the potential and electric fields. 
> 
> 
> 
> <Untitled.pdf>
> 
> 
> I have programed a file called small_cell.geo (attached) with a bounding box and 3 perpendicular wires inside. I want to have mirror conditions along the 4 long sides of the box as I will be periodically repeating this cell to make a bigger detector and therefore I need the wires to touch the walls. 
> 
> The geometry file seems to be ok if I look at it with Gmsh (see attached file) 
> 
> <small_cell_geo.pdf>
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> But when I try to mesh this geometry by doing in the command line 
> 
> #gmsh small_cell.geo -3 -order 2 
> 
> I get the following error 
> 
> Error   : Self intersecting surface mesh, computing intersections (this could take a while)
> 
> 
> 
> Error   : ------------------------------
> Error   : Mesh generation error summary
> Error   :     0 warnings
> Error   :     1 error
> Error   : Check the full log for details
> Error   : ------------------------------
> 
> 
> 
> 
> If I have a look at the  intersect.pos  file with Gmsh I see that the points where the wires touch the bounding box walls are the problems (see attached figure) 
> 
> <intersect.pdf>
> 
> 
> 
> But as I have mentioned I want the wires to touch the walls so that I can have mirror conditions when I calculate the electric field with Elmer. 
> 
> Any suggestion of how can I get right of this error ? 
> All my geometry files are attached to this email. 
> 
> Thanks in advance 
> 
> Berta 
> 
> 
> 
> <gf_cylinder.geo>
> <gf_rectangle.geo>
> <gf_x_cylinder.geo>
> <intersect.pos>
> <small_cell.geo>
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-- 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine

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