[Libmesh-users] Periodic Boundary Condition IDs

[Andrea H. <and...@gm...>]

Hello-

I'm attempting to implement some periodic boundary conditions. I'm
just wanting to work with a square QUAD mesh.

In looking at past posts it looks like the following should work (when
placed before the equation_systems:init()):

   PeriodicBoundary pbc;
   pbc.myboundary = inflow_ID;
   pbc.pairedboundary = outflow_ID;
   RealVectorValue boundary_translation(channel_length,0.,0.);
   pbc.translation_vector = boundary_translation;

   dof_map.add_periodic_boundary(pbc);

I'm wondering though, does the inflow_ID and ouflow_ID correspond to
the same numbers as the edges of an element are numbered? i.e. 0 for
the bottom, 1 for the right side, 2 for the top, and 3 for the left
side? So, should something like:

  PeriodicBoundary pbc1;
  pbc1.myboundary = 0;
  pbc1.pairedboundary = 2;
  RealVectorValue boundary_translation1(0.,ymax-ymin,0.);
  pbc1.translation_vector = boundary_translation1;

  PeriodicBoundary pbc2;
  pbc2.myboundary = 1;
  pbc2.pairedboundary = 3;
  RealVectorValue boundary_translation2(xmax-xmin,0.,0.);
  pbc1.translation_vector = boundary_translation2;

  system.get_dof_map().add_periodic_boundary(pbc1);
  system.get_dof_map().add_periodic_boundary(pbc2);

work for setting periodic boundary conditions for the top and bottom
and then the sides? Or are these id's corresponding to something that
would be inherent to the mesh?

I've tried the code above and get the following error:

Assertion `!_b' failed.
[0] /h1/ahawkins/LIBRARIES/LIBMESH/libmesh-r3801/include/parallel/threads.h,
line 64, compiled Apr 29 2010 at 12:08:34
terminate called after throwing an instance of 'libMesh::LogicError'
  what():  Error in libMesh internal logic

where the traceback is:
Stack frames: 10
0: print_trace(std::ostream&)
1: _ZN7Threads11BoolAcquireC9ERb
2: Threads::BoolAcquire::BoolAcquire(bool&)
3: void Threads::parallel_reduce<StoredRange<MeshBase::const_node_iterator,
Node const*>, (anonymous
namespace)::FindBBox>(StoredRange<MeshBase::const_node_iterator, Node
const*> const&, (anonymous namespace)::FindBBox&)
4: MeshTools::bounding_box(MeshBase const&)
5: PointLocatorTree::init(Trees::BuildType)
6: _ZN16PointLocatorTreeC9ERK8MeshBasePK16PointLocatorBase
7: PointLocatorTree::PointLocatorTree(MeshBase const&, PointLocatorBase const*)
8: PointLocatorBase::build(MeshEnums::PointLocatorType, MeshBase
const&, PointLocatorBase const*)
9: MeshBase::point_locator() const

Thanks in advance!
Andrea