On Mon, 9 Jun 2014 11:10:12 +0200
Anders Logg <[email protected]> wrote:
> For vector elements, the jump() operator in UFL is defined as follows:
>
> dot(v('+'), n('+')) + dot(v('-'), n('-'))
>
> I'd like to argue that it should instead be implemented like so:
>
> outer(v('+'), n('+')) + outer(v('-'), n('-'))
This inconsistency has been already encountered by users
http://fenicsproject.org/qa/359/discontinuous-galerkin-jump-operators
Jan
>
> That would enable writing the natural term appearing in DG/Nitsche
> formulations for vector-valued problems as follows:
>
> inner(avg(grad(u)), jump(v, n))
>
> This would be analogous to the scalar case which is written
>
> dot(avg(grad(u)), jump(v, n))
>
> With the current implementation, the term for vector-elements must be
> implemented like this:
>
> dot(dot(avg(grad(u)), n('+')), jump(v))
>
> Is the current version of jump() for vector elements implemented as it
> is for a particular reason, or can we change it?
>
> --
> Anders
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