[petsc-users] How to find a good initial guess for a BVP

[Ryan Yan]

Hi All,
Hopefully, this is not considered as an off-topic thread. Since I got snes
converged reason -6.

Can anyone please share some hints on how to find a good inital guess?

I am solving a nonlinear BVP(steady-states) extracted from a time-dependent
problem by setting d/dt=0. The equation is conservational law for mass,
momentum, internal energy, with an algebraic heating source. After all,
v(velocity), P(pressure), U(fluid internal energy), can be solved from this
coupled system. I am using Newton's method for this nonlinear system.
Frankly, I do not have a good initial guess for the solver. The only
information that I have is the inital condition for the time-dependent
problem, where the BVP comes from. I have tried my solver with different
inital guess for many times, but with no luck of a satisfying residual
reduction.

So, do I have to solve the time-dependent problem after a long time stepping
to get a steady solution? Or is there any better way of finding a good
initial guess?

Any suggestion is highly appreciated.

Yan
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