Dear David, dear all, It seems like the issue is much more involved than I initially thought. Some updates since I started going into this issue <https://github.com/dealii/dealii/issues/7970>.
1. I could solve the problem for lowest order RaviartThomas Elements (RT). This is already good. 2. The fix does not work for lowest order BDM elements. 3. The fix does not work for higher order elements, neither BDM nor RT elements Suspected reason: For shape functions of higher order elements (whose normal components) are supported on a face flipping the sign on a flipped face is not enough since the flipped face changes/reverts the ordering of the face dofs hence the translation of local to global numbering of degrees of freedom changes for cells with flipped faces. I am not sure but at least I suspect that. Is this being taken care of by Deal.II somewhere? I will go on chasing the bug and hopefully come up with a merge request soon. Best, Konrad On Wednesday, December 9, 2020 at 3:44:58 PM UTC+1 Konrad Simon wrote: > Hi David, > > Many thanks for the hint. After some research I believe I stumbled over this > issue#7970 <https://github.com/dealii/dealii/issues/7970>? Let's see what > I can do. > > Best, > Konrad > On Tuesday, December 8, 2020 at 10:56:44 PM UTC+1 Wells, David wrote: > >> Hi Konrad, >> >> This isn't a very satisfying answer but, to the best of my knowledge, >> these Hdiv elements weren't written with general unstructured 3D meshes in >> mind. I suspect, without looking more closely, that this is a problem on >> our side. >> >> We document this for the FE_RaviartThomasNodal class but for >> FE_RaviartThomas this is just a comment in the source file. Would you be >> willing to write a patch explaining things better for the other Hdiv >> classes? >> >> Best, >> David >> ------------------------------ >> *From:* dea...@googlegroups.com <dea...@googlegroups.com> on behalf of >> Konrad Simon <ksimo...@gmail.com> >> *Sent:* Monday, December 7, 2020 12:48 PM >> *To:* deal.II User Group <dea...@googlegroups.com> >> *Subject:* [deal.II] Div-conforming elements in 3D >> >> Dear Deal.ii community, >> >> Sorry for spamming the mailing list again. I posted some of the below >> stuff already in another post but that might have been with too many >> unnecessary details and confusing ideas from my side. >> >> I am not sure if I stumbled over something and would like to report on >> that. >> >> Goal is to project a given function onto a finite element space over a >> certain mesh. The focus here shall be on H(div)-conforming elements such as >> Raviart-Thomas and Brezzi-Douglas-Marini Elements. >> >> I do so with several different meshes and I noticed an inconsistency in >> the projection on meshes with, say, not so simple topology (e.g., holes and >> voids). >> >> Observations: >> 1. The problematic meshes do have faces with non-standard orientation. My >> first thought was this was not carried over to the mapping of the >> H(div)-basis but I was wrong. The mesh orientation is consistent (as far as >> I can tell). A cube, for example, is not problematic. Please see two >> example plots below. >> >> 2. The issue arises with both Raviart-Thomas and Brezzi-Douglas-Marini >> Elements. >> >> 3. The issue arises in 3D only. >> >> Any ideas what I ran into? >> >> Best, >> Konrad[image: plate_with_hole.png][image: hyper_shell.png] >> >> -- >> 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/fa304b41-f83f-4c96-a2f7-c4e9e813553fn%40googlegroups.com >> >> <https://groups.google.com/d/msgid/dealii/fa304b41-f83f-4c96-a2f7-c4e9e813553fn%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/883fee09-6fba-4d38-914d-869e2e7058adn%40googlegroups.com.
