Re: [deal.II] Hanging node constraints for one component of a vector system

[Wolfgang Bangerth]

On 7/3/20 11:20 AM, Stephen wrote:
> I have an FE system object made of FE_TraceQ and FE_FaceQ and would like to
> apply hanging node (and zero boundary) constraints to only the first
> component. This is easy with zero boundary since the function
> DoFTools::make_zero_boundary_constraints can take a component mask as an
> argument but I see no such variant for
> DofTools::make_hanging_node_constraints; what would be the easiest way to do
> this practically?

Right. That's because make_hanging_node_constraints() in essence just enforces
a property of the finite element space, namely specific continuity
constraints. These properties are described by the finite element class.

If I understand you right, then you want an FE_FaceQ that does not require
continuity from a large face to its child faces -- in other words, you want it
to be discontinuous. I am curious why you need this? That's because the
continuity between cells of the same size is implicitly provided. Why do you
want to treat faces with hanging nodes differently?

(If that's what you really want, you need to come up with a different way to
describe the finite element space -- using a different class derived from
FiniteElement<dim> -- and I'm happy to walk you through the process. But I
don't understand why you would want to do that, and so am curious about the
underlying reason first.)

Best
W.


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Wolfgang Bangerth email: bang...@colostate.edu
www: http://www.math.colostate.edu/~bangerth/