Joel, Does the equation you want to solve for have multiple components? Otherwise it would not make sense to multiply in the right hand side something with a gradient. If you want to project the gradient into a vector valued finite element ansatz space, then the matrix you are assembling looks weird. In what you are doing you are also considering the coupling between all components.
You are calculating the gradient of your scalar finite element function correctly, but you need to find the correct component to use. For doing this you can use something like: const unsigned int component = fe.system_to_component_index(i).first; cell_rhs(i) += ((fe_values.shape_value (i, q_index) * fe_function_grad[q_index][component])* fe_values.JxW (q_index)); If you want to assemble a mass matrix for a vector-valued finite element, you have also to restrict assembling for the matrix to the case where the component for the ith and jth ansatz function are the same. You might want to have a look at step-8 [1] and the module "Handling vector valued problems"[2]. Best, Daniel [1] https://www.dealii.org/8.4.1/doxygen/deal.II/step_8.html#ElasticProblemassemble_system [2] https://www.dealii.org/8.4.1/doxygen/deal.II/group__vector__valued.html -- 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 dealii+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
