On Fri, 27 Jan 2017, John Peterson wrote: > On Fri, Jan 27, 2017 at 8:34 AM, Manav Bhatia <[email protected]> wrote: > >> What I have in mind is a two-phase fluid problem with some interface >> boundary that is evolving with time. Then, if I choose to use XFEM or >> Lagrange multipliers at the interface, then the nodes/elements where these >> extra dofs will be defined will change with time.
So each dof would have support only on a single element or at most a patch of element around a node? >> How easy/difficult would it be to do this with libMesh? > > Addition/deletion of dofs happens all the time during adaptive > refinement/coarsening, so in principle I think this should be possible. Indeed. If you don't want to modify the mesh by actually splitting interface elements, you could try adding a per-subdomain variable and then adding or removing elements from that subdomain as the interface passes into or out of them. > One thing that isn't really possible is adding/removing _variables_ to a > system once it has been initialized, This is true, and it's only halfway easy to change. We could probably support *adding* variables midsimulation without too many bugfixes, but I suspect that *removing* variables midsimulation would trash assumptions in a number of places. > so e.g. representing the Lagrange multipliers as SCALAR variables > and changing the number of said variables frequently would not work > well. In the case of SCALAR variables there's a workaround, I believe: you can change the *order* of a SCALAR variable on the fly, and as the order changes so does the number of scalar dofs it involves. I don't think we have this in test coverage so I wouldn't swear it's not broken, but I bet it would be easy to fix. --- Roy ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
