DOLFIN

Derivatives over external facets

Asked by Douglas Brinkerhoff

I am trying to solve a free surface problem of reduced topological dimension, and I was wondering if there was a way to force the assembler to consider the problem to be of lower dimension e.g. to assemble over an external boundary with varying vertical coordinate as if that boundary was a 1D horizontal line. I've done this by manually mapping nodal values between a 2D mesh and a 1D mesh, but I can't imagine how this would work in parallel (How to copy parallel data from one mesh to another would be another question). I'd like to figure out how to do it with only one mesh. Does FEniCS have this capability?

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Anders Logg (logg) said : 		#1

On Tue, Aug 21, 2012 at 07:25:57PM -0000, Douglas Brinkerhoff wrote:
> New question #206442 on DOLFIN:
> https://answers.launchpad.net/dolfin/+question/206442
>
> I am trying to solve a free surface problem of reduced topological
> dimension, and I was wondering if there was a way to force the
> assembler to consider the problem to be of lower dimension e.g. to
> assemble over an external boundary with varying vertical coordinate
> as if that boundary was a 1D horizontal line. I've done this by
> manually mapping nodal values between a 2D mesh and a 1D mesh, but I
> can't imagine how this would work in parallel (How to copy parallel
> data from one mesh to another would be another question). I'd like
> to figure out how to do it with only one mesh. Does FEniCS have
> this capability?

I think it should be possible but the assembler would just ignore the
extra coordinate so you would need to introduce a mapping of some sort
as part of your variational problem.

--
Anders

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