[Gmsh] periodic mesh

Josefin Ahlkrona josefin.ahlkrona at it.uu.se
Wed Feb 3 18:06:15 CET 2016

```Hi,

Thank you for the answer. Is there a way to make structured meshes
periodic? Since it's structured of course the nodes match, but I would
like the edges to match eachother too!

Best Regards,

Josefin

On 02/03/2016 06:02 PM, Christophe Geuzaine wrote:
>> On 02 Feb 2016, at 20:59, Josefin Ahlkrona <josefin.ahlkrona at it.uu.se> wrote:
>>
>> Hi,
>>
>> I have a cuboid (x,y,z) domain for which i have created tetrahedral, structured mesh.  Now, I want to apply periodic boundary conditions in x, and y direction and in order to do that I need the mesh to be identical for the x=0 and x=xmax surfaces, as well as for the y=0 and y=ymax surfaces. It is not sufficient for only the nodes to match but I also want the edges to match!
>>
>> I have tried to use the "Periodic Surface" command without success. I have seen several posts on using the "Periodic Surface" commands without finding a solution for my problem.
>>
> The Periodic meshing command only apply to unstructured grids. In your case the grid is set structured (meshed by extrusion with the "Layers" option).
>
>
>> Could anyone help me?
>>
>> My geofile looks like this:
>>
>> cl=1.0;
>> //cuboid which is 8000,8000,1000 big
>>
>> Point(1) = {0,0,0,cl};
>> Extrude {8000,0,0} {
>>   Point{1}; Layers{10};
>> }
>> Extrude {0,8000,0} {
>>   Line{1}; Layers{10};
>> }
>> Extrude {0,0,1000} {
>>   Surface{5}; Layers{5};
>> }
>>
>>
>> boundMaster[] = Boundary{26};
>> boundSlave[] = Boundary{-8}; //tried plus and minus sign here..
>> boundMaster2[] = Boundary{22};
>> boundSlave2[] = Boundary{-14};  //tried plus and minus sign here..
>>
>> Periodic Surface 18 {boundSlave[]} = 26 {boundMaster[]};
>> Periodic Surface 14 {boundSlave2[]} = 22 {boundMaster2[]};
>>
>> Physical Surface(28) = {14};   //y=y0
>> Physical Surface(29) = {18};   //x=xmax
>> Physical Surface(30) = {22};   //y=ymax
>> Physical Surface(31) = {26};   //x=x0
>> Physical Surface(32) = {5};    //top
>> Physical Surface(33) = {27};   //bottom
>>
>> Physical Volume(34) = {1};
>>
>> Best,
>>
>> Josefin
>>
>>
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--

Josefin Ahlkrona
PhD Student
Division of Scientific Computing
Department of Information Technology
Uppsala University
Box 337
SE-751 05 Uppsala
Sweden

Email: josefin.ahlkrona at it.uu.se
Webpage: http://www.it.uu.se/katalog/josah992
Ph: +46-18-4712980
Fax: +46 18 523049, +46 18 511925

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