[Gmsh] How can I make this mesh such that it has periodic sides

[Christophe Geuzaine]

> On 4 Apr 2019, at 18:03, Abiti Adili <aadili1 at lsu.edu> wrote:
> 
> I have  a tetrahedral mesh over a unit box that has  two balls of different sizes inside the box. The geometry is created by geometrycloser.geo, and the physical  entities and such were created by importing geometrycloser.geo into  omnibuscloser.geo.
> 
> I have a periodicity condition to impose where I need to say that 
> 1) right side of the box is the same with left side
> 2) top side is the same with bottom side
> 3) front side is the same with the back side
> 
> When I tried to make the system matrices periodic using a function that has been tested on other examples, it did not work correctly and I  have concluded that either vertices or facets on the sides of the box may not have been aligned.
> 
> I am writing to ask if there is anyway that I can modify the geo files I provided so that I can integrate the periodicity condition into the mesh I make?  Thank you very much.
> 

You need to explicitly tell Gmsh that the meshes should be periodic. In your example, add

Periodic Surface{5} = {6} Translate {1,0,0};
Periodic Surface{2} = {4} Translate {0,1,0};
Periodic Surface{1} = {3} Translate {0,0,1};

at the end of the geo file.

Christophe

> 
> Adil<geometrycloser.geo><omnibuscloser.geo>_______________________________________________
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— 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine