Hi all,
I am considering Periodic Boundary Condition for a problem which is very
simillar to step-25. Before applying periodic condition, I considered
homogeneous Newmann Boundary condition in external surfaces by simply
omitting Neumann term in week formulation (v , n.grad(u) )=0. However,
since Neumann BC has meaning when we have external surface and now I have
periodicity condition, It seems I can not have both periodic and neumann BC
simultaneously. Therefore I am going to eliminate Neumann condition by
keeping the term (v, n.grad(u)) in my right hand side as a generalized
force term. I added the following in my assembly to do so
for (unsigned int face_number=0;
face_number<GeometryInfo<dim>::faces_per_cell; ++face_number)
if (cell->face(face_number)->at_boundary())
{
fe_face_values_eta.reinit (cell, face_number);
fe_face_values_eta.get_function_gradients(old_solution_eta,
solution_eta_gradients);
for (unsigned int q_point=0; q_point<n_q_points_f;
++q_point)
{
for (unsigned int i=0; i<dofs_per_cell_eta; ++i)
{
const double neumann_value
= (solution_eta_gradients[q_point] *
fe_face_values_eta.normal_vector(q_point));
cell_nl_term(i) += (neumann_value *
fe_face_values_eta.shape_value(i,q_point) *
fe_face_values_eta.JxW(q_point));
}
}
}
But the solver doesn't converge after this change. I was wondering If I am
addressing the problem rightly.
Best,
Hamed
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