[dune-pdelab] periodic boundary conditions

[Christian Engwer]

On Wed, Nov 02, 2011 at 02:16:41PM +0100, Oleh Krehel wrote:
> Thanks, Christian.
> It works now. But what exactly is the overlap?
> (Documentation says something like "overlap is overlap")

well, it is one of the basic concepts of the parallel dune interface,
thus it is not elaborated in the doxygen documentation. You should
have a look at the dune paper. It is the overlap, like you know it in
an overlapping domain decomposition approach. In our case, you should
think of periodicity as some kind of reference cell with overlap to
its neighbors, which coincide with the cell itself.

Christian

> 2011/11/2 Christian Engwer <christian.engwer at uni-muenster.de>:
> > On Wed, Nov 02, 2011 at 01:12:17PM +0100, Oleh Krehel wrote:
> >> 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.
> >
> > You asked for a grid without overlap
> >
> >> 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
> >> >> >
> >> >> >
> >> >>
> >> >
> >
> >> #define DUNE_DEVEL_MODE
> >> //#define NDEBUG
> >> #include "../config.h"
> >> #include <iostream>
> >> #include <dune/common/mpihelper.hh>
> >> #include <dune/common/exceptions.hh>
> >> #include <boost/exception/all.hpp>
> >> #include <dune/grid/yaspgrid.hh>
> >>
> >> template <class GV>
> >> void traverseGrid(const GV& gv){
> >>   typedef typename GV::template Codim<0>::Iterator element_iterator;
> >>   typedef typename GV::IntersectionIterator intersection_iterator;
> >>   element_iterator it=gv.template begin<0>(),
> >>                   end=gv.template end<0>();
> >>   for(;it!=end;++it){
> >>     Dune::GeometryType gt=it->type();
> >>     std::cout<<"\nvisiting leaf "<<gt
> >>              <<" with first vertex at "<<it->geometry().corner(0);
> >>     intersection_iterator is=gv.ibegin(*it),
> >>                        isend=gv.iend(*it);
> >>     for(;is!=isend;++is){
> >>       if(is->neighbor())
> >>         std::cout<<"\nneighbor";
> >>       if(is->boundary())
> >>         std::cout<<"\nboundary";
> >>     }
> >>   }
> >> }
> >>
> >> void dowork(int level){
> >>   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);
> >>   //grid.globalRefine(level);
> >>   typedef Dune::YaspGrid<d>::LeafGridView GV;
> >>   const GV& gv=grid.leafView();
> >>   traverseGrid(gv);
> >> }
> >>
> >> int main(int argc, char** argv)
> >>     try
> >>     {
> >>       Dune::MPIHelper::instance(argc,argv);
> >>       int level=2;
> >>       if(argc==2)
> >>         sscanf(argv[1],"%d",&level);
> >>       dowork(level);
> >>       std::cout<<"\n;\n";
> >>       return 0;
> >>     }
> >>     catch (Dune::Exception& e){
> >>       std::cerr << "Dune reported error: " << e << std::endl;
> >>     }
> >>     catch (boost::exception& e){
> >>       std::cerr << boost::diagnostic_information(e);
> >>     }
> >>     catch (...){
> >>       std::cerr << "Unknown exception thrown!" << std::endl;
> >>     }
> >
> >
> 
> _______________________________________________
> dune-pdelab mailing list
> dune-pdelab at dune-project.org
> http://lists.dune-project.org/mailman/listinfo/dune-pdelab
>