Hi Ben,
the diffusion problem with Neumann BC is in the strong formulation:
\nabla (M \cdot \nabla V) = 0 in \Omega n \cdot M \cdot \nabla V = v^N on \Gamma^N (Neumann),
but the weak form is:
\int\Omega (M \cdot \nabla V) \cdot \nabla p = \int{\Gamma^N} v^N
Do you really need that term? It is not implemented in Sfepy, there is only the evaluation term d_surface_flux:
\int_{\Gamma^N} n M \cdot \nabla V
but I'm not sure it is correct, the problem is probably with accuracy of the boundary derivative. I'm currently working on some tests.
Regards Vladimir
On 03/29/2013 03:35 PM, Ben Derrett wrote:
Hello,
In the weak formulation of my problem (a 2D diffusion problem), I have the term
\int_{\Gamma^N} p\nabla V\cdot M n
where \Gamma^N is region where Neumann BC is applied, p is a test function, V is the unknown function, M is a 2x2 matrix and n is the normal vector. Has an SfePy term been written corresponding to this?
Alternatively, is there a SfePy term corresponding to the integral
\int_{\Gamma^N} p\nabla V\cdot q,
where q is a vector? I saw the term dw_surface_lcouple, but it doesn't seem to support the weak evaluation mode.
Thanks, Ben
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