On 11/27/18 9:02 PM, mrjonmatth...@gmail.com wrote:
> I'm working on a flux-pressure model using a Raviart-Thomas/DGQ FESystem. I'm
> using Dirichlet conditions on the RT (flux) elements on part of the domain
> and
> on the DGQ (pressure) elements on another part of the domain using the
> boundary_id's. I'm using VectorTools::interpolate_boundary_values to add the
> pressure BCs, but it doesn't appear to be adding rows to the ConstraintMatrix.
That's correct -- and it is because the DG elements have no degrees of freedom
on faces, they are all located in the interior of the cell.
In other words, you can't impose boundary conditions strongly on DG elements.
You need to impose them in your variational formulation, for example using a
penalty term in the same way as you are presumably adding penalty terms in the
interior of the domain. (Unless, of course, you use a formulation that has no
derivatives on the pressure variable at all -- in which case the Dirichlet
values on the pressure should show up in the bilinear form to begin with;
isn't this how step-20 does it?)
Best
W.
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Wolfgang Bangerth email: bange...@colostate.edu
www: http://www.math.colostate.edu/~bangerth/
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