You need to make sure you call System::reinit_constraints (
http://libmesh.github.io/doxygen/classlibMesh_1_1System.html#ad12672358a8e9796a42bd7f42888c54f)
after your update to update the Dirchlet boundary condition if it depends
on time.
On Fri, Jan 22, 2016 at 10:45 AM, Junchao Zhang <junchao.zh...@gmail.com>
wrote:
> I added DirichletBoundary to adaptivity_ex2, but I found I couldn't get
> correct Fe at time 1 (i.e, system.time = 0+dt). I am not sure it is a limit
> of libmesh, or my understanding is wrong.
> adaptivity_ex2 is a transient problem. "the initial condition will be taken
> as the exact solution at time 0, as will the Dirichlet boundary conditions
> at time t." The outline of the code is:
>
> 1. system.time = 0;
> 2. Create a DirichletBoundary object and add it to equation_system;
> 3. equation_systems.init (); // Init solution and Dirichlet constrains
> at time 0
> 4.
> 5. for each time step {
> 6. system.time += dt;
> 7. *system.old_local_solution = *system.current_local_solution;
> 8. for each refinement step {
> 9. Ke += ...
> 10. Fe += ...system.old_solution()... // Need solution computed at
> time 0
> 11. heterogenously_constrain_element_matrix_and_vector; // Uses
> constraints computed at time 0, but should use constraints computed at
> time
> 1
> 12. Add Ke, Fe to global matrix and vector;
> 13. Solve the system;
> 14. equation_systems.reinit ();
> 15. }
> 16. }
>
> Suppose the code runs straight from line 1 to line 11, at line 11, what we
> use are wrong constraints computed at time 0. Actually, we should use
> constraints
> of time 1, which are not computed yet.
> I tried to rearrange the code, but I found I could not make it, since I
> could not use solution of time 0 and constraints of time 1 at line 10 and
> 11 at the same time.
>
> Any thoughts?
>
>
> --Junchao Zhang
>
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