[Gmsh] biperiodic conditions on a 3D non-extrudable geometry

demesy guillaume.demesy at fresnel.fr
Fri Feb 19 14:35:03 CET 2010

Ok, nervermind: Setting "nm = 1.;" instead of "nm = 1.e-9" at the very
first line of 'holes.geo' works fine.



On Thu, 18 Feb 2010 09:13:28 -0500, gdemesy at physics.utoronto.ca wrote:
> Dear Gmsh Users and Developers,
> I would need to impose biperiodic boundary conditions on two sets of  
> parallel surfaces in the attached geometry (respectively parallel to  
> zOx and zOy).
> Originally, I was planning to use identical unstructured mesh on these  
> surfaces, but as far as I understood, my only options consist in using  
> (i) an extrusion of surfaces or (ii) the Transfinite Algo which both  
> lead to structured surface mesh.
> I have considered these two last options:
> (i) I did not manage to extrude the mesh in both directions. Thus,  
> after extruding one surface in one direction (say Ox) and deleting all  
> the middle entries (as mentioned in  
> http://www.geuz.org/pipermail/gmsh/2009/004416.html), I still have to  
> extrude it in the Oy direction, which leads me to define some points  
> twice (?).
> (ii) I tried to use Transfinite Surfaces, like in the attached geo  
> file. I used MeshAdapt for the 2D part which generates proper 2D  
> meshes. Everything seems to be OK until the 3D meshing part:
> - Delaunay overwrites my identical surface mesh as mentioned in some  
> past mail.
> - Frontal leads to unexpected multiple "Error : Edge a - b multiple  
> times in surface mesh"
> Is there any workaround?
> Should I use Extrude instead?
> Eventually, I would like to end up with a fine mesh in the so-called  
> groove physical volume (n°6000), and ideally a mesh that goes  
> progressively coarser when reaching the top (resp. bottom) of the  
> physical region 5000=PML_top (resp. 1000=PML_bot). However, it seems  
> that Transfinite doesn't enjoy this kind of setting, e.g.  
> "paramaille_hol>paramaille". Would you have any solution in mind,  
> compatible with my earlier issue ?
> Thank you very much for your time.
> Best,
> Guillaume Demésy,
> Postdoc at University of Toronto.
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