[Users] problem using McLachlan with a NS-BH system

[Wolfgang Kastaun]

Hi Bruno,

Not sure if related, but I vaguely recall that the gamma-driver shift
gauge condition can become unstable if the timestep exceeds a critical
value related to the damping constant eta in the driver. This might
happen with 9 levels if the timestep is also increasing by a factor 2
with each level. The solution I remember was to use the same timestep
for the few coarsest levels. Do you know if the first occurrence of NANs
in the shift happens on the coarsest level?

Cheers,
Wolfgang.

On 11/27/19 12:36 PM, Bruno Giacomazzo wrote:
> Dear All,
>   a student of mine (Giulia Crotti) is having issues running a NS-BH
> simulation with GRHydro and McLachlan (parfile attached). The problem we
> are having is with the metric evolution (see attached image for the
> lapse produced just before the crash) and I don't think I ever saw such
> a problem. Does any of you have any suggestio?
> 
> Approximately around 2000 iterations the simulation crashes with the
> following error:
> 
> ERROR from host r168c12s01.marconi.cineca.it
> <http://r168c12s01.marconi.cineca.it> process 0
> 
>   while executing schedule bin CCTK_EVOL, routine
> PunctureTracker::PunctureTracker_Track
> 
>   in thorn PunctureTracker, file
> /marconi/home/userexternal/gcrotti0/EinsteinToolkit/ET_2018_09/Cactus/arrangements/EinsteinAnalysis/PunctureTracker/src/puncture_tracker.cc:204:
> 
>   -> Shift at puncture #0 is (-nan,-nan,-nan).  This likely indicates an
> error in the simulation.
> 
> 
> Something is wrong with the metric; indeed the lapse function gets
> larger than 1. We have 9 refinement levels on the black hole, with a
> resolution of 0.045 on the finest grid. The initial data have been
> computed as to get a mass ratio = 3; so the black hole mass is ~4 solar
> masses. The black hole is non-spinning.
> 
> 
> Thanks,
> 
> Bruno
> 
> 
> -- 
> 
> Prof. Bruno Giacomazzo
> Department of Physics
> University of Milano-Bicocca
> Piazza della Scienza 3
> 20126 Milano
> Italy
> 
> email: bruno.giacomazzo at unimib.it <mailto:bruno.giacomazzo at unimib.it>
> phone: (+39) 02 6448 2321
> web: http://www.brunogiacomazzo.org <http://www.brunogiacomazzo.org/>
> 
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