[Users] evolving a BH hole with Kerr-Schild ID in ET

[Erik Schnetter]

Roland

Here is an old parameter file that I'm sure used to work at some
point. I think we cleaned up McLachlan parameters a few years ago, so
this parameter file might output warnings or errors (with suggestions
for correcting them, if all goes as intended).

-erik


On Thu, Apr 25, 2019 at 12:57 PM Haas, Roland <rhaas at illinois.edu> wrote:
>
> Hello Zach,
>
> > I generally suggest shifting the grid so that the closest gridpoint
> > to the origin is (dx/2, dy/2, dz/2), where dx,dy,dz are the
> > resolutions on the finest grid. I've used this trick many times to
> > stabilize evolutions. Also you may want to try the ShiftedKerrSchild
> > thorn (in the ETK), which enables a radial offset that shrinks the BH
> > coordinate size but at the same time kills off enormous constraint
> > violations near r=0. Unlike the existing KerrSchild thorn(s), this
> > one uses the standard Kerr-Schild metric written in spherical
> > coordinates and does the basis xform.
> Right, I had completely forgotten about that one. Thank you. So
> ShifterKerrSchild is actually different from Exact with its
> Kerr_KerrSchild__epsilon parameter (ie it would do proper coordinate
> transformation r -> r+r0 rather than just add r0 in some of the 1/r
> terms)?
>
> Note that the goal is use it only as ID and not to reset the metric at
> each time so I will have to modify ShifterKerrSchild a bit.
>
> Yours,
> Roland
>
> --
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-- 
Erik Schnetter <schnetter at gmail.com>
http://www.perimeterinstitute.ca/personal/eschnetter/
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