I have a non-linear form of the Poisson equation where the "diffusion" coefficient depends on the derivatives of the state variable (see image). There are no Dirichlet-type boundary conditions (i.e. no ebcs) so I really need to specify a good initial guess at the solution.
My questions are:
1) How are initial guesses passed to the solver? From the documentation, it doesn't seem like initial guesses can be directly passed to the nls.newton solver as an argument (though they are an argument of the subroutine __call__).
2) In what form should the initial guess vector/array be written? Can a function be passed? Do numerical values have be be specified at the mesh nodes?
Thanks for any help on this matter.