[petsc-users] Boundary conditions using DMComplex

[Matthew Knepley]

On Fri, Sep 21, 2012 at 2:20 PM, Subramanya G <subramanya.g at gmail.com>wrote:

> I have  a small question about using DMComplex.
>  How does one keep track of external boundaries. I found no methods to
> check if  a particular node/face belonged to a particular external
> edge set.
>

First you want to distinguish between

a) Topological boundaries

For this you use Labels, so you can mark parts of the mesh using
DMCcomplexSetLabelValue()

b) Algebraic Boundary Conditions

These are specified in the PetscSection using
PetscSectionSetConstraintDof() and
PetscSectionSetConstraintIndices(). To construct these, you typically use
the information
in the mesh labels.


> Also, Is it possible to set up a problem over a part of the mesh
> instead of the entire mesh?
>

This is very easy. Just create a PetscSection that only has unknowns over
part of the mesh.

   Matt


> Thanks
>
>
> Subramanya G Sadasiva,
>
> Graduate Research Assistant,
> Hierarchical Design and Characterization Laboratory,
> School of Mechanical Engineering,
> Purdue University.
>
> "The art of structure is where to put the holes"
> Robert Le Ricolais, 1894-1977
>



-- 
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
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