[Users] AHFinderDirect?

[Erik Schnetter]

On Thu, Jul 19, 2012 at 12:37 AM, Bruno Giacomazzo
<bruno.giacomazzo at jila.colorado.edu> wrote:
> 2) What's going to happen with a 2 moving grids when apparent horizon was
> formed? Since I use maximum density tracking mechanism to track the
> positions of the NSs I want to switch the moving grids off after the
> formation of the apparent horizon and have only one centre of refinement at
> the origin.
>
>
> This behavior is also not controlled by AHFinderDirect, but by
> CarpetRegrid2. The only way I know to trigger grid changes like you describe
> is to write your own thorn which inherits from CarpetRegrid2 and changes its
> variables num_levels[i] as desired. Perhaps someone else can give better
> advice here.
>
>
> You do not need to switch off these additional grids, unless the
> greatly enlarge the fine grid you are evolving. Carpet combines the
> refined regions, and if you have three approximately equal regions,
> the combined region will work just fine. Is there a particular reason
> you want to switch them off?
>
>
> I think the problem in his case is that the grids follow the position of the
> maximum of the density. What we do with Whisky simulations of NS-NS mergers
> is to stop the movement of the grids after the merger (so you will end up
> having a set of fine grids fixed where the BH will form). If you don't do
> that, after the collapse to BH the positions of the grids would be quite
> "random". For example, if you are left with a disk outside the BH, then the
> centers of the grids will follow the position of the maximum density in the
> disk, which is not what you want usually.

Thorn CarpetRegrid2 can be "steered" at run time by modifying its grid
scalars (NOT its parameters!). You will then need to write a thorn to
e.g. set active[0] and active[1] to zero.

-erik

-- 
Erik Schnetter <schnetter at cct.lsu.edu>
http://www.perimeterinstitute.ca/personal/eschnetter/