[dune-pdelab] Periodic Boundary Conditions in Sequential

[Steffen Müthing]

Hi Tim,

> Am 16.01.2017 um 13:06 schrieb Dodwell, Timothy <T.Dodwell at exeter.ac.uk>:
> 
> Dear All,
> 
> I have a post-doc modelling a 2D problem on a donut. We have implemented this in YaspGrid with Geometry Grid.
> 
> We clearly need to setup periodic boundary conditions.
> 
> I thought DUNE handled this much like parallel domain decomposition, so you have to set the overlap to one and tell the grid it is periodic (then that is it!)

yes, that’s how it’s done (at least with YaspGrid).

> 
> From the look of our solutions the periodic boundary conditions have not been implemented correctly
> 
> -    Does YaspGrid ignore the overlap if you run it in sequential mode?

No, the overlap is there (but I’m not sure if you need to have Dune compiled with MPI support, there might be shortcuts in the
code that prevent it from working correctly without MPI enabled).

> 
> -    Do you have to write a constraint space for periodic boundary conditions in sequential (all the examples of this are assembled elementwise which is not what we want for periodic boundary conditions!)

You have to use OverlappingConformingDirichletsConstraints for this to work, otherwise the constraints assembler will not put
any constraints on the periodic boundaries (which are recognized as processor boundaries in this case).

Steffen

> 
> Any help would be great! Thanks in advance!
> 
> Tim
> 
> 
> Dr Tim Dodwell
> Senior Lecturer in Engineering Mathematics
> Rm 221 - Harrison Building
> College of Engineering, Mathematics & Physical Sciences
> University of Exeter
> Exeter
> Devon
> EX4 4PY
> 
> mail: t.dodwell(at)exeter.ac.uk
> tel: +44 (0)1392 725899
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> web: http://emps.exeter.ac.uk/engineering/staff/td336
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> 
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