[dune-pdelab] periodic boundary conditions

[Oleh Krehel]

Hi,

I tried this code:

  const int d=2;
  Dune::FieldVector<double,d> L(1);
  Dune::FieldVector<int,d> N(2);
  Dune::FieldVector<bool,d> periodic(true);
  int overlap=0;
  Dune::YaspGrid<d> grid(L,N,periodic,overlap);

Then when I traverse on the leafview the instersections of each element,
the sets of is->neighbor() and is->boundary() don't overlap, they're
just like the non-periodic ones.
Can someone please explain, maybe there's something I've missed?

regards,
Oleh





2011/10/31 Christian Engwer <christian.engwer at uni-muenster.de>:
> Hi!
>
> first you have to settle the question of the grid. I don't have a
> complete overview of the support of periodic boundaries of the
> different grid managers.
>
> I know:
> - YaspGrid handles what you want, but without inclusions
> - UG does have some kind of periodic support, but I don't know what
>  exactly is supported and you can't use easily fromm DUNE [patches
>  wellcome ;-)]
> - Alugrid from 1.23 on support periodic boundaries in 3D
>
> Depending on the grid you are using the periodicity is implemented
> similar to parallel coupling, which uses domain decomposition with
> overlap or ghosts. In this case you should use the periodic
> constraints. If the grid implements periodicity as periodicity in the
> topology of the grid, you don't have to change anything (not sure if
> any grid supports this).
>
> The last option is implement periodictity in PDELab without support of
> the grid. You should the write your own constraints-assembler
> local-operator, which adds dirichlet constraints on one side. There is
> no real tutorial on this. You will have to dive into it...
>
> Christian
>
>> I need a fully periodic cube: left-right, top-bottom in 2D,
>> and additionally front-back in 3D.
>> The cube has an arbitrarily shaped inclusion(like a circle or a sphere) inside,
>> with Dirichlet b.c.
>> I was looking at section 8.4 of the tutorial explaining constraints
>> for Dirichlet b.c.,
>> but the transformation matrix there is local, when I need the global one for the
>> periodic b.c.
>> Can you point me to the source file that does what you described above?
>>
>> regards,
>> Oleh
>>
>>
>>
>> 2011/10/31 Christian Engwer <christian.engwer at uni-muenster.de>:
>> > Dear Oleh,
>> >
>> >> I need to implement periodic boundary conditions for a transport problem.
>> >> Google shows that there's no such functionality in DUNE at the moment.
>> >> Perhaps someone can give me some pointers or suggestions on how
>> >> to implement periodic b.c. in a straightforward way.
>> >
>> > it depends on which BC you need.
>> >
>> > Straight forward: You have a mesh like this:
>> >
>> > o-x-x-x-o
>> > | | | | |
>> > o-x-x-x-o
>> > | | | | |
>> > o-x-x-x-o
>> >
>> > where the 'o' nodes are associated with each other. This kind of mesh
>> > is available with yaspgrid. It is implemented as a periodic mesh with
>> > overlap on the left and right side.
>> >
>> > If you need something more general it will get tricky and you should
>> > explain in detail what you want to achieve.
>> >
>> > Cheers
>> > Christian
>> >
>> >
>>
>
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