[Gmsh] How to make a rotationally periodic 3D mesh

[Christophe Geuzaine]

> On 24 Jun 2018, at 14:41, Zuheyr Alsalihi <alsalihi at vki.ac.be> wrote:
> 
> Hello,
> 
> I just needed to better explain my previous question:
> 
> I need to make a triangular cake slice shaped 3d solid mesh using gmsh 3.0.6 where the 2nd side is the rotational periodic surface of the first side surface of the mesh. The rotation angle is 2*Pi/N where N is the number of slices.
> 
> To make it visually clear, if N=1, left periodic surface would be close on itself and the rotation angle would be 2*Pi.
> 
> The geometry is imported through a step file and all I have to force is to make gmsh generate a rotationally periodic mesh on the periodic surfaces.
> 
> I just cannot succeed to find the correct syntax to the statement
> 
> //Periodic Surface { expression-list } = { expression-list } Rotate { expression-list } ;
> 
> To tell gmsh that gthe mesh on the left periodic surface, master, is going to be rotated by an angle 2*Pi/N to make the mesh on the other slave periodic surface.
> 

I've clarified the doc and added a rotation example in 

https://gitlab.onelab.info/gmsh/gmsh/blob/master/demos/boolean/periodic.geo <https://gitlab.onelab.info/gmsh/gmsh/blob/master/demos/boolean/periodic.geo>

Note that if your whole geometry is rotation-invariant, you should probably just 

- import the 2D slice 

- extrude+rotate the 2D slice, together with the mesh.

(See e.g. https://gitlab.onelab.info/gmsh/gmsh/blob/master/demos/boolean/revolve2.geo <https://gitlab.onelab.info/gmsh/gmsh/blob/master/demos/boolean/revolve2.geo>)

This way you won't have to specify periodicity - the mesh will automatically be periodic.

Christophe



> I must have some conceptual problem. Thank you for reading.
> 
> Best regards.
> 
> 
> -- 
> Dr. Zuheyr Alsalihi
> Senior Research Engineer
> Turbomachinery and Propulsion and
> Aeronautics and Aerospace Departments
> von Karman Institute for Fluid Dynamics
> Waterloosesteenweg 72, B-1640 Sint-Genesius-Rode, Belgium
> Direct Line: +32 (0)2 359 98 65
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> E-mail: alsalihi at vki.ac.be
> http://www.vki.ac.be
> 
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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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