[petsc-users] Laplacian at infinity

[Jed Brown]

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).
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