[petsc-users] DMPlex and Boundary facets

[Matthew Knepley]

On Tue, May 18, 2021 at 8:18 AM Karin&NiKo <niko.karin at gmail.com> wrote:

> Dear PETSc team,
>
> I have tried to load a test mesh available in Gmsh' s demos directory
>  (share/doc/gmsh/demos/simple_geo/filter.geo, attached to this email) as a
> DMPlex.
> So I produced a msh4 file by doing :
>         gmsh -3 filter.geo -o /tmp/test.msh4
> Then I used src/dm/impls/plex/tutorials/ex2.c to load the mesh by doing :
>         ./ex2 -filename /tmp/test.msh4
>
> Unfortunately I get the error :
>
> [0]PETSC ERROR: --------------------- Error Message
> --------------------------------------------------------------
> [0]PETSC ERROR: No support for this operation for this object type
> [0]PETSC ERROR: Could not determine Plex facet for Gmsh element 1268 (Plex
> cell 12681)
>
> The error seems to come from the fact that the msh file contains
> tets *and* facets *only on the Physical entities* (aka parts of the mesh
> boundary where
> the user will assign Dirichlet or Neuman conditions).
> If I suppress these facets by commenting  the "Physical Surface" lines in
> the geo file and regenerating the mesh, everything is fine.
>
> But the use of these "Physical" stuff is very common in lots of finite
> element codes in order to assign boundary conditions.
> How should I do to keep  these boundary groups of 2D elements (with
> corresponding names) ?
>

Can you also send the *.msh file? I do not have Gmsh on this machine.

  Thanks,

     Matt


> Thanks for your help,
> Nicolas
>
>
>

-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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