[Users] Resolving two BH

Peter Diener diener at cct.lsu.edu
Tue Jun 7 09:13:11 CDT 2016


This issue is discussed for example in


where a non-constant damping in the gamma driver shift is presented to
handle unequal mass binaries. As far as I remember there may also be 
later papers with further improvements to the method.



On Tuesday 2016-06-07 01:00, Frank Loeffler wrote:

>Date: Tue, 7 Jun 2016 01:00:59
>From: Frank Loeffler <knarf at cct.lsu.edu>
>To: rahul kashyap <rahulkashyap411 at gmail.com>
>Cc: Einstein Toolkit Users <users at einsteintoolkit.org>
>Subject: Re: [Users] Resolving two BH
> On Mon, Jun 06, 2016 at 06:50:04PM -0400, rahul kashyap wrote:
>> Thanks for the reply. My apologies that I'm not completely familiar many of
>> the physical and numerical issues while simulating bbh. I have experience
>> in AMR astrophysical simulations.
> No need to apologize.
>> When I do the bbh simulation of ratio around 1, it evolves perfectly fine.
>> With higher mass ratio, the smaller BH just becomes bigger and blows up.
>> I'm assuming this as a problem of refinement.
> It is not. It looks like what I described earlier: your gauge
> conditions, in particular the shift condition, isn't well suited for the
> small black hole. Grid points are "falling in", making it appear growing
> on the computational grid. You may try to play with the values such that
> the small black hole evolves fine (you can try that with a simulation of
> only a small black hole of that size), but then you might find that the
> large black hole "vanishes from the grid" because grid points there are
> pushed out too much. If this is the case, you might need
> position-dependent values.
> Frank

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