[petsc-users] Laplacian at infinity

[Matthew Knepley]

On Mon, Sep 22, 2014 at 9:08 AM, Jed Brown <jed at jedbrown.org> wrote:

> Matthew Knepley <knepley at gmail.com> writes:
>
> > On Mon, Sep 22, 2014 at 7:36 AM, John Alletto <4bikerboyjohn at gmail.com>
> > wrote:
> >
> >> All,
> >>
> >> I am try to match some E&M problems with analytical solutions.
> >> How do I deal with infinity when using a uniform grid ?
> >>
> >
> > It depends on your problem. Keep making it bigger and see if you get
> > convergence.
>
> This is a way to assess error caused by the finite grid, but you can
> also use an analytic solution for that.  Using an asymptotic expansion
> for the boundary condition can be useful (esp. when there is nonzero
> charge in the domain, for example).  For wave propagation, look at
> perfectly matched layers (PML).
>

PML is the best option, although many codes simply use attenuation.

   Matt

-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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