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

Mon Dec 2 04:49:15 CST 2019

Erik,

As for your first question, we are setting the following parameters:

ML_BSSN::harmonicN           = 1
ML_BSSN::harmonicF           = 2.0
ML_BSSN::ShiftGammaCoeff     = 0.75
ML_BSSN::BetaDriver          = 0.25   #  ~1/M_BH
ML_BSSN::advectLapse         = 1.0
ML_BSSN::advectShift         = 1.0

ML_BSSN::MinimumLapse        = 1.0e-8
ML_BSSN::initial_boundary_condition = "extrapolate-gammas"
ML_BSSN::rhs_boundary_condition     = "NewRad"

As you can see, we are not setting the lapse gauge driver parameter,
leaving it to be the default (which is 0). We choose to do this
because this was consistent with BNS simulations that Bruno did.

For your second question, I attach two plots of the BH position on the
xy plane and its coordinate radius.
Thanks again,

Giulia

Il giorno lun 2 dic 2019 alle ore 04:45 Erik Schnetter
<schnetter at cct.lsu.edu> ha scritto:
>
> Giulia
>
> Let me make a few more guesses:
>
> - How do the lapse gauge driver parameters look like? Did you rescale
> them as well?
> - How does the apparent horizon position / shape / coordinate radius
> behave before this happens?
>
> -erik
>
> On Fri, Nov 29, 2019 at 6:33 AM Giulia Crotti
> <g.crotti1 at campus.unimib.it> wrote:
> >
> > Dear all,
> > thanks for the suggestions. Indeed the problem seems to be occurring
> > on the finest grid, because the lapse is wrong on the finest level. We
> > did try changing the ML_BSSN::BetaDriver parameter from 0.71 to 0.25
> > (in order to make it ~1/M_BH), but the result was pretty much the
> > same.
> >
> > Cheers,
> > Giulia
> >
> > Il giorno mer 27 nov 2019 alle ore 16:27 Erik Schnetter
> > <schnetter at cct.lsu.edu> ha scritto:
> > >
> > > The issue with the time step size (see probably
> > > <https://arxiv.org/abs/1003.0859>) occurs on the coarsest levels only.
> > > If the error occurs near the puncture on the fine grid, then this is
> > > not the problem.
> > >
> > > Some of the gauge parameters have a dimension (e.g. 1/length). The
> > > "standard" settings are optimized for M=1. If your black hole mass is
> > > very different, then you might need to change them. If you have a
> > > total mass of M=4, then the gauge might try to act four times faster
> > > than usual, leading to an instability. The cure would then be
> > > increased resolution, or changing the respective parameters.
> > >
> > > -erik
> > >
> > >
> > >
> > > On Wed, Nov 27, 2019 at 8:52 AM Wolfgang Kastaun <physik at fangwolg.de> wrote:
> > > >
> > > > 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/>
> > > > >
> > > > > ----------------------------------------------------------------------
> > > > > There are only 10 types of people in the world:
> > > > > Those who understand binary, and those who don't
> > > > > ----------------------------------------------------------------------
> > > > >
> > > > >
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> > >
> > >
> > > --
> > > Erik Schnetter <schnetter at cct.lsu.edu>
> > > http://www.perimeterinstitute.ca/personal/eschnetter/
> > > _______________________________________________
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>
>
>
> --
> Erik Schnetter <schnetter at cct.lsu.edu>
> http://www.perimeterinstitute.ca/personal/eschnetter/
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