# Periodic mesh in gmsh

**URL:** <https://community.freefem.org/t/periodic-mesh-in-gmsh/754>\
**Category:** General Discussion\
**Created:** [January 23, 2021, 7:29am UTC](https://community.freefem.org/t/periodic-mesh-in-gmsh/754 "2021-01-23T07:29:40Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![chaimaa](https://avatars.discourse-cdn.com/v4/letter/c/c0e974/32.png) [@chaimaa](https://community.freefem.org/u/chaimaa)\
**Post date:** [January 23, 2021, 7:29am UTC](https://community.freefem.org/t/periodic-mesh-in-gmsh/754/1 "2021-01-23T07:29:40Z")

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Hi,  
I create the geometry file .stp by using CATIA and i import it to gmsh.  
when i set the function periodic surface in order to have similar meshes :

boundS13[] = Boundary{Surface {13};};  
boundS17[] = Boundary{Surface {17};};  
Periodic Surface 17 {boundS17[]} = 13 {boundS13[]};

i get this errors :

 ![image](https://canada1.discourse-cdn.com/flex030/uploads/freefem/original/1X/818e0d306ad1c3547d7795aa76a4f8f846fb2aac.png)

Could you please help me.

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<div class="post-metadata">

**Author:** ![prj](https://avatars.discourse-cdn.com/v4/letter/p/ecae2f/32.png) [@prj](https://community.freefem.org/u/prj)\
**Post date:** [January 23, 2021, 7:40am UTC](https://community.freefem.org/t/periodic-mesh-in-gmsh/754/2 "2021-01-23T07:40:42Z")

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Have you asked Gmsh people?

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<div class="post-metadata">

**Author:** ![chaimaa](https://avatars.discourse-cdn.com/v4/letter/c/c0e974/32.png) [@chaimaa](https://community.freefem.org/u/chaimaa)\
**Post date:** [January 23, 2021, 7:44am UTC](https://community.freefem.org/t/periodic-mesh-in-gmsh/754/3 "2021-01-23T07:44:22Z")

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I can’t find the community of gmsh