Re: [Libmesh-users] Jacobian Free BC's?

[Derek G. <fri...@gm...>]

On Jun 2, 2008, at 8:15 AM, John Peterson wrote:

> Hey Derek,
>
> I'm sure you already have it, but I just wanted to say: be sure to
> multiply by the test function (in Libmesh "phi_face[i]" or
> "phi_side[i]").  I just remembered we had forgotten to do this once
> before in the Laplace-Young application :-)

Hehe... yes... thanks for the reminder.  I had already made sure that  
was the case here!  Didn't want to make that mistake twice....

> If "u-BC" differs appreciably from zero, the residual
> contributions from this term will be large.  We typically use a value
> on the order of 10^10.  What value are you using?

Right now I've settled on 10^5... but I might revisit that.

> I don't *think* the penalty should affect the convergence rate
> strongly.  But I don't have a lot of experience with the matrix-free
> Newton-Krylov techniques so I can't say for sure.

It's weird... it's not really affecting the _rate_ as much as it's  
actually affecting the convergence itself... ie the problem isn't  
fully converged when SNES says it is.  Maybe I just need to play with  
the convergence tolerances some more...

Thanks for your help!  As it is now... the code is working, I just  
have an unsatisfactory constant in there (1e5)...

Derek