Hello Chong, you've set `dominate = true` for your `FE_Nothing` element. This means that your solution will be constrained to be continuous on interfaces with other elements. Since `FE_Nothing` represents the zero space, all DoFs on interfaces will be constrained to zero.
You can disable this behavior by setting `dominate = false` (the default value). Correct me if I'm wrong, but I think that's what you want to do. We've updated the documentation recently in this regard. Please see the `FE_Nothing in combination with other elements` section in the `Detailed Description` of FE_Nothing <https://www.dealii.org/developer/doxygen/deal.II/classFE__Nothing.html>. Currently, there are other issues with the `FE_Nothing` class in combination with `FE_System`. Let us know if the above does not fix your problem and you think your issue is connected to #1496 <https://github.com/dealii/dealii/issues/1496>. Best, Marc On Tuesday, May 4, 2021 at 8:34:04 PM UTC-6 liuch...@gmail.com wrote: > Dear Bruno > > > Thank you for your reply. > > > I think I did not express my problem well. To be clear, I used the > FE_Enriched for assigning these two finite elements and combined them using > FE_System: > > FE_Enriched<dim> fe_type_1(FE_Q<dim (1), FE_Nothing<dim>(1,true), > nullptr); > > FE_Enriched<dim> fe_type_2(FE_Q<dim (1), FE_Q<dim>(1), enriched_function); > > FESystem<dim> hp_FE(fe_type_1, fe_type_2). > > > I would like to use fe_type_2 with an enriched_function to approximate the > local behavior of materials. The local behavior can be captured by the > extra dofs created by fe_type_2 ( note that fe_type_1 just generates the > standard dofs since the FE_Nothing is used). However, *I found that the > extra dofs are constrained when I used the make_hanging_nodes_constraints() > function*. The reason why I used this function is the local refinement. > > > My questions are > > (1) Is there a way to keep the extra dofs introduced by fe_type_2 > unconstrained when applying the make_hanging_nodes_constraints() function? > > > (2) If the extra dofs require to constrain when the > make_hanging_nodes_constraints() function is utilized, can I remove these > extra dofs from the AffineConstraints container generated by the function? > > > Hope I express my problems clearly. Thank you for any suggestions. > > > Best wishes, > > Chong > > Bruno Turcksin <bruno.t...@gmail.com> 于2021年5月5日周三 上午2:21写道： > >> Chong Liu, >> >> On Tuesday, May 4, 2021 at 12:06:39 PM UTC-4 liuch...@gmail.com wrote: >> >>> >>> Question: >>> >>> *How can I only constrain the hanging nodes for fe_type_1*? >>> >> >> Why do you want to do that? If you don't constrain fe_type_2, the >> solution won't be continuous. If you have more dofs in one side of the edge >> than in the other side, you need to constrain some of the dofs. It doesn't >> matter if the reason you have more dofs is because the cell has been >> refined or if it's because the fe degree is higher. >> >> Best, >> >> Bruno >> >> -- >> 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+un...@googlegroups.com. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/dealii/f29a2020-7916-4d74-b9ed-aae271a5479fn%40googlegroups.com >> >> <https://groups.google.com/d/msgid/dealii/f29a2020-7916-4d74-b9ed-aae271a5479fn%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- 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. To view this discussion on the web visit https://groups.google.com/d/msgid/dealii/048f45bc-05d6-4f85-a789-455b86841573n%40googlegroups.com.
