Direct modification of the matrix (in general) to apply such a constraint will need consideration of the basis type and order, and how these map to the dofs. I am not sure this will be that easy to do, but I might be wrong.
Vikram Garg vikramvgarg.github.io/ On Sun, Jun 27, 2021 at 9:00 PM Renato Poli <rebp...@gmail.com> wrote: > I see your point. I was resisting to use the penalty while looking for a > more elegant solution. > > Just to get a feeling from your side: I thought on adding master-slave > constraints through constrain rows, before system assembly. Does that sound > reasonable? > > Thanks, > Renato > > Em dom., 27 de jun. de 2021 22:44, Vikram Garg <vikram.v.g...@gmail.com> > escreveu: > >> Hi Renato, >> I was suggesting that you use the scalar variable as the >> unknown uniform displacement on the boundary. I think it should be okay to >> add it as a variable that exists on the entire domain, as long as you >> specify the penalization only on the boundary. >> >> It looks like the penalty method has already been used to apply such >> constraints on the displacements, see page 21 here: >> https://www.osti.gov/servlets/purl/1463026 >> >> Thanks. >> Vikram Garg >> >> vikramvgarg.github.io/ >> >> >> On Sun, Jun 27, 2021 at 7:19 PM Renato Poli <rebp...@gmail.com> wrote: >> >>> Hi, thanks for the answer: >>> >>> @edgar: it is a FORCE (Neumann) while DISPLACEMENTS (primary variables) >>> must be tied together. (I am trying to solve Mandel's problem in >>> poroelasticity). Please let me know if it is clear. >>> >>> @Vikram: I did not get exactly the use of the SCALAR variable. It is a >>> single value in the whole domain, is that correct? Should I add this >>> variable _only_ in the boundary domain? I am digging into the >>> systems_of_equations_ex3, let's see if it gets clearer in the next few >>> days. >>> >>> Thanks, >>> Renato >>> >>> On Sun, Jun 27, 2021 at 8:38 PM Vikram Garg <vikram.v.g...@gmail.com> >>> wrote: >>> >>>> You might need a Lagrange multiplier formulation that sets a state >>>> variable >>>> in an entire subdomain or boundary to a single unknown scalar. Example >>>> 3 in >>>> systems of equations might help, it shows how SCALAR variables can be >>>> used. >>>> You could incorporate the scalar variable into the weak form via a >>>> penalty >>>> method. >>>> >>>> Vikram Garg >>>> >>>> vikramvgarg.github.io/ >>>> >>>> >>>> On Sun, Jun 27, 2021 at 6:10 PM edgar <edgar...@cryptolab.net> wrote: >>>> >>>> > On 2021-06-27 23:01, Renato Poli wrote: >>>> > > I'd like to add a force to a whole boundary. The constraint is that >>>> the >>>> > > whole boundary must have the same displacement. >>>> > > ---8<--- snip >>>> > >>>> > For the sake of disambiguation: do you want to impose displacement or >>>> > force? The displacement of a boundary is not only dependent on the >>>> force >>>> > it receives. >>>> > >>>> > I am guessing that the developers (regular user here! hi!) would like >>>> to >>>> > know. >>>> > >>>> > >>>> > _______________________________________________ >>>> > Libmesh-users mailing list >>>> > Libmesh-users@lists.sourceforge.net >>>> > https://lists.sourceforge.net/lists/listinfo/libmesh-users >>>> > >>>> >>>> _______________________________________________ >>>> Libmesh-users mailing list >>>> Libmesh-users@lists.sourceforge.net >>>> https://lists.sourceforge.net/lists/listinfo/libmesh-users >>>> >>> _______________________________________________ Libmesh-users mailing list Libmesh-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libmesh-users
