[Gmsh] Problem with periodic boundary condition for a volume extruded using wire

[Christophe Geuzaine]

> On 29 Jun 2018, at 13:52, Changwei ZHOU <changwei.zhou at ifsttar.fr> wrote:
> 
> Dear Sir,
> 
> I have a problem with periodic boundary condition.
> 
> The model concerns a helix obtained by extuding using wire under OpenCASCADE Kernel (because in my final application, I need to use Boolean operation). 
> 
> Gmsh failed to apply periodic boundary condition with correct affine transform matrix of translation-rotation
> 
> Please find attached the helix.geo files with a lot of comments which give a better explanation of my problem.
> 

The start/end surfaces of the pipe probably does not (exactly) match the explicit rotation - increasing the tolerance (-tol) will indeed allow the periodic matcher to find its counterparts, but for values that are far too large to be usable.

I would try first on a simpler case where you can explicitly check the angle. It might also be worth it to investigate the different modes for OpenCASCADE pipes (see the comments in Geo/GModelIO_OCC.cpp), as well as putting the spine in different locations.

Christophe



> Thanks for your clarification.
> 
> Changwei ZHOU
> 
> IFSTTAR Nantes
> 
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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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