Hi Alex
I had to contend with a similar issue that arose in gradient crystal
plasticity where the nodal unknowns are the displacement and the
plastic slip. I wish to impose periodicity on only the displacement.
I assume you are using the PeriodicConstraints class that has been
posted previously to impose periodic constraints. As you say, you
first match up the nodes. In the method void
PeriodicConstraints::recursive_constraint_search
I simply added the following line after:
for (unsigned int i = 0; i < dofs_per_face; ++i) {
if (face1-
>get_dof_handler().get_fe().system_to_base_index(i).first.first == U) {
where U is a enumeration for 0 (i.e. a displacement) and Gamma an
enumeration for slips.
I have setup the fe class so that the displacements and slips are
interpolated independently
fe(FE_Q<deal_II_dimension>(pOrderIn), deal_II_dimension, //
displacement degrees of freedom
FE_Q<deal_II_dimension>(pOrderIn),
crystal_in.get_no_slip_systems()), // slip degrees of freedom ...
and reordered my dofs component wise as follows:
// displacements -> 0 slips -> 1
std::vector<unsigned int> block_component(deal_II_dimension +
pcrystal->get_no_slip_systems(), Gamma);
for (unsigned int ii = 0; ii < deal_II_dimension; ii++)
block_component[ii] = U;
// reorder the dof component wise
DoFRenumbering::component_wise(dof_handler, block_component);
I hope this helps.
Andrew
On 17 Aug 2009, at 11:48 PM, Giavaras Alexandros wrote:
Hi everyone
I am trying to impose periodic boundary conditions for a flow problem
using Stokes-Brikman equations. I need to impose periodicity
parallel to
the pressure drom and normal to it. And this may be a bit tricky.I am
able to get the dofs for the two periodic faces and match
them.However,
I think I must find a way to exclude the pessure dof from the vertices
and from the imposition of periodicity.Either way, does anyone know
how
I can do that?Currently, I am using a command of the form
Face->get_dof_indices(vector<unsigned> dofs);
Which gives me all the dofs indices on the face.Are these dofs meant
to
be ordered in the sense: first say velocity and then pressure?or the
indices are arbitrary?When intiallizing the FESystem object I first
intialize the velocity approximation and then the pressure if this
has
anything to do.
All the best
Alex
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