Hi all
I'm trying to implement periodic boundary conditions on pairs of opposite faces
of a cube in 3D. The problem is mixed in that each element has vectorial
(continuous) displacements, and (discontinuous) pressures and dilatation as
unknowns. I wish to impose periodicity between the displacement degrees of
freedom only.
I've adapted a 2d periodic boundary conditions algorithm. I've sorted the faces
of the element on the opposite sides based on the position of the centroid of
the elements face. The problem is now to match degrees of freedom on opposite
faces. I can determine if they are associated with the displacements and to
which local support point they correspond but this does not give me a geometric
measure to order the dof.
I can't restrict the problem to only Q_1 elements for the displacement but it
will always be Q_something.
Is there any way to use a function like DoFTools::map_dofs_to_support_points
but to restrict its operation to only certain components? Or, if I know a dof
index (local or global) can I determine the position of the support point? In
other words, is there a function like DoFTools::map_dofs_to_support_point that
only works with one dof at a time.
I would appreciate any suggestions as I'm sure I'm not the first to do this
Thanks as ever
andrew
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