[firedrake] Error - NonlinearVariationalSolver

[Lawrence Mitchell]

On 10 Nov 2014, at 18:37, Lawrence Mitchell <lawrence.mitchell at imperial.ac.uk> wrote:

> Dear Anna,
> 
> On 10 Nov 2014, at 18:13, Anna Kalogirou <a.kalogirou at leeds.ac.uk> wrote:
> 
>> Dear all,
>> 
>> I wrote the attached simple code to solve a shallow water problem with a nonlinear solver, but I get the following error (note that the linear problem works fine). Can someone help me and see what I am doing wrong? Thanks you very much!
> 
> 
> Your residual Fphi is written in terms of phi, however in your nonlinear problem, you ask to linearise around phi1.
> 
> Fphi = (gamma*phi + 0.5*mu*inner(grad(gamma),grad(phi))
>        - (gamma*phi0 + 0.5*mu*inner(grad(gamma),grad(phi0))
>        + dt*gamma*eta0))*dx
> phi_problem = NonlinearVariationalProblem(Fphi,phi1)
> 
> I think you probably want:
> 
> phi_problem = NonlinearVariationalProblem(Fphi, phi)
> 
> Note that, compared to the LinearVariationalProblem, where the solution is placed in a separate output Function, for the nonlinear problem, the solution variable must be the Function you want to solve for in the residual.
> 
> I think there are similar changes required for the eta and laplace solvers.
> 
> Cheers,
> 
> Lawrence

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