GMG: support prescribed values in parts of domain

Author: tjhei

source/simulator/core.cc

@@ -799,12 +799,11 @@ namespace aspect
     if (parameters.include_melt_transport)
       melt_handler->add_current_constraints (new_current_constraints);
 
-    // Finally update and let the prescribed solution plugins constrain parts of the solution
+    // Update and let the prescribed solution plugins constrain parts of the solution:
     prescribed_solution_manager.update();
     prescribed_solution_manager.constrain_solution(new_current_constraints);
 
-    // let plugins add more constraints if they so choose, then close the
-    // constraints object
+    // Finally, let plugins add more constraints if they so choose:
     signals.post_constraints_creation(*this, new_current_constraints);
 
     new_current_constraints.close();

source/simulator/solver/stokes_matrix_free_local_smoothing.cc

@@ -1610,13 +1610,18 @@ namespace aspect
       sim.compute_initial_velocity_boundary_constraints(constraints_v);
       sim.compute_current_velocity_boundary_constraints(constraints_v);
 
-
       VectorTools::compute_no_normal_flux_constraints (dof_handler_v,
                                                        /* first_vector_component= */
                                                        0,
                                                        this->get_boundary_velocity_manager().get_tangential_boundary_velocity_indicators(),
                                                        constraints_v,
                                                        this->get_mapping());
+
+      sim.prescribed_solution_manager.constrain_solution(constraints_v);
+
+      // Let plugins add more constraints if they so choose:
+      sim.signals.post_constraints_creation(*this, constraints_v);
+
       constraints_v.close ();
     }