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[Andreas Naumann <question155668@xxxxxxxxxxxxxxxxxxxxx>]

New question #155668 on DOLFIN:
https://answers.launchpad.net/dolfin/+question/155668

Hi @all,

i try to solve a non-linear stokes problem with a matrix valued factor similiar to

(inner( mu( inner(gamma, gamma) )*nabla u, v) - inner( p, div(v) ))*dx + .... =  ....

and gamma is given with a formula similar to:

gamma = gamma + dt * (gamma - nabla u)

How should I implement this problem with DOLFIN in Python? C++ is an option too :)

The simple way 
 (u, p) = TrialFunctions(...)
 gamma =grad(u)
 a= (inner( mu( inner(gamma, gamma) )*nabla u, v) - inner( p, div(v) ))*dx 

 gamma = gamma + dt * (gamma - nabla u)
 will not work. 
 something like 
a.gamma = gamma + dt * (gamma - nabla u)
does not work too, because the form does not have an attribute  gamma. 

 swap = gamma + dt * (gamma - nabla u)
 gamma.assign(swap)

does not work, because the gradient (type?, expression?) does not have the attribute (member function?) assign.

Is there any way to solve such a problem with Dolfin? If yes.. how does it look like?

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