[Gmsh] How to generate periodic grids when importing step geometry ?

[Christophe Geuzaine]

> On 10 Oct 2017, at 13:16, Benedikt Oswald <benedikt.oswald at lspr.swiss> wrote:
> 
> Dear gmsh,
> 
> assume I have created a geometry in FreeCAD,
> 
> exported it as a STEP file and imported
> 
> into gmsh.

If you use FreeCAD, import directly the .brep file in Gmsh - it's much more efficient than STEP, and you will avoid all translation errors (as .brep is the native OpenCASCADE format, used directly by both FreeCAD and Gmsh).

> 
> How do I ensure conformal boundary meshes
> 
> for periodic analysis when I generate the mesh
> 
> in gmsh ?
> 

Just as you would do it for a "normal" Gmsh geometry, i.e., with "Periodic Surface" constraints.

For example if the periodic faces 1 and 2 are translated by 3 in the z direction, your geo file could look something like this:

Merge "file.brep";
Periodic Surface {1} = {2} Translate {0,0,3};

PS : with recent versions of Gmsh you can also directly create quite complicated geometries directly in Gmsh, with SetFactory("OpenCASCADE"). Or you can modify geometries created w.g. with FreeCAD. See gmsh/demos/boolean for examples, in particular demos/boolean/import.geo.



> Thanks for some hints,
> 
> Benedikt
> 
> 
> -- 
> ----------------------------------------------------------------------------------------------------------------------
> Dr. sc. techn. Benedikt Oswald - first engineer - LSPR AG - phone +41 43 366 90 74
> Grubenstrasse 9, CH-8045 Zürich, benedikt.oswald at lspr.swiss
> ----------------------------------------------------------------------------------------------------------------------
> 
> 
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-- 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine

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