Re: [Libmesh-users] Periodic BCs

[David K. <dknez@MIT.EDU>]

hah, it's always the way isn't it: you figure it out just after emailing 
the list...

I moved the adding of the periodic BC to after equation_systems.init() 
and added the aptly named function call:

  dof_map.create_dof_constraints(mesh);

and now it works!

Cheers,
Dave



David Knezevic wrote:
> Hi all,
>
> I'm trying to use libMesh's functionality for periodic boundary 
> conditions, but I can't quite figure it out... I looked it up in the 
> archives, but couldn't find any info.
>
> I'm trying to do a Navier-Stokes channel flow problem with periodic 
> BCs on the left and right boundaries; I added:
>
>   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);
>
>
> to the matrix assembly (before the element loop), and then (as usual) 
> I called
>
>   dof_map.constrain_element_matrix_and_vector (Ke, Fe, dof_indices);
>
> in order to impose the periodic constraint on the element matrices? I 
> guess I must be missing something, because this isn't giving me 
> periodicity?
>
> Thanks!
>
> Dave
>