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

[Berta Beltran]

Hi, 

Thanks for your feedback Christopher. I have done as you suggested and I have defined my geometry as a bounding box where I subtract disks where the cylinders will plug. And then I define the cylinders as hollow tubes with no endcaps. Find attached my .geo file.





> On Dec 8, 2017, at 1:08 PM, Christophe Geuzaine <cgeuzaine at uliege.be> wrote:
> 
> 
> 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
> 
> Free software: http://gmsh.info | http://getdp.info | http://onelab.info
>