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[Gerard Awanou <question158115@xxxxxxxxxxxxxxxxxxxxx>]

New question #158115 on DOLFIN:
https://answers.launchpad.net/dolfin/+question/158115

I am running the Fenics demo written for C^0 Discontinuous Galerkin
method for the biharmonic equation. I understood that the demo is for
the boundary condition \Delta u =0. For a boundary condition \partial
u/\partial b =0, it seems that one should use the formulation in

C0 Interior Penalty Methods for Fourth Order Elliptic Boundary Value
Problems on Polygonal Domains by Brenner and Sung

To do this I need to compute n'(D^2 u)n (p. 100 of the paper).
I tried n[i]*( grad(grad(v))[i,j]*n[j]) without success.
How do you compute \partial^2 u/\partial n^2  where n is the unit 
outward normal to an edge?

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