On 2/11/19 12:20 AM, [email protected] wrote: > Dear Prof. Bangerth: > > Thank you very much for your quick reply! > > When I apply hanging node constraints to my matrix, as the step-6 > says: https://www.dealii.org/developer/doxygen/deal.II/step_6.html > I make 4 steps: > 1.Create a Constraints Class: > | > ConstraintMatrix constraints; > | > > 2.Fill this object using the function > DoFTools::make_hanging_node_constraints() to ensure continuity of the > elements > of the finite element space. > | > DoFTools::make_hanging_node_constraints (dof_handler, > constraints); > | > > 3.Copy the local contributions to the matrix and right hand side into > the > global objects: > | > constraints.distribute_local_to_global (cell_matrix, > cell_rhs, > local_dof_indices, > system_matrix, > system_rhs); > constraints.distribute_local_to_global (cell_volume_matrix, > local_dof_indices, > volume_matrix); > constraints.distribute_local_to_global (cell_gradient_matrix, > local_dof_indices, > gradient_matrix); > | > > > 4.Make sure that the degrees of "freedom" located on hanging nodes get > their correct (constrained) value: > | > constraints.distribute (solution); > |
Constraints are funny and sometimes require deep thought about what exactly they mean. What happens if you don't apply constraints to the cell_volume_matrix and cell_gradient_matrix -- i.e., you copy the elements 1:1 into the matrix, without the 'constraints' object? (Like in step-4.) Alternatively, you could do as you show above and after calling 'constraint.distribute(solution)' you manually set all constrained degrees of freedom in the solution vector to zero. That's not what you want to use for visualization, error estimation, ... but it might work for the operation you're trying here. I'm pretty sure that both of these solutions should work individually (but not in combination). But explaining why this is so would take a page or two, I'm afraid. Best W. -- ------------------------------------------------------------------------ Wolfgang Bangerth email: [email protected] www: http://www.math.colostate.edu/~bangerth/ -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
