[Users] Only getting partial Waveform while running that parameter file in the gallery example for BBH GW150914

[Roland Haas]

Hello Vinod,

Yes, you will need to run the simulation until at least time=1400 to
see the merger that happened at time=900 at a detector located at r=500.

The expected_merger variable is, as far as I recall, only used to
"size" the domain so the exact value is not extremely critical but
should be about (and ideally not much smaller) than the actual merger
time (eg based on a post-Newtonian prediction).

If possible, please keep users at einsteintoolkit.org in the addressee
list so that ohters can find this resolution as well.

Yours,
Roland

On Mon, 10 Jul 2023 14:59:20 +0530
Vinod Pisharody <vinod.pisharody22 at gmail.com> wrote:

> Hello Roland ,
> Thank you for the response. I have only 1 output-0000 directory .
> However looking at your first response I wanted to clarify .
> In the .rpar file the "expected_merger " variable seems to take a
> value of 1000 .However in my .out file the merger seems to happen
> around 908 .Is this a discrepancy ?Also if I am understanding your
> answer correctly then even after the merger happpens at say time=900
> ,I need to let the simulation run till time=1400 for the wave to
> reach the detector at r =500 ?  I am attaching the last few lines of
> my .out file which shows the merger happpening around 908
> Thanks and regards,
> Vinod
> 
> On Fri, 7 Jul 2023 at 21:03, Roland Haas <rhaas at illinois.edu> wrote:
> 
> > Hello Vinod,
> >
> > Sorry for the long delay.
> >  
> > > I have been trying to run the simulation of GW150914 given in
> > > gallery  
> > .The  
> > > simulation ran succesfully .However I am only getting a partial
> > > waveform .The merger and the ringdown phase is not being captured
> > > .I am attaching both the waveform and a gnuplot showing the
> > > completing of merger . There  
> > is  
> > > also another doubt I have .In the gallery while creating the job
> > > for this simulation there is a command called --define N which
> > > is set to 28  
> > .Could  
> > > someone tell me whats the purpose of that and help me understand
> > > whats going wrong ?  
> >
> > I cannot tell for sure since I do not know how long you ran the
> > simulation. My first guess would be that the waveform has not yet
> > had time to travel to the location of  the detector at r=500. Since
> > the source is the black holes at about r=0 it will take the wave
> > about 500 time units to travel the distance of 500 space units
> > (speed of light is c=1 in the simulation).
> >
> > A second issue to consider is that if you have multiple output-NNNN
> > directories then you have to first concatenate the output data file
> > to have access to all data. Specialized analysis tools like kuibit,
> > SimulationTools and PostCactus (see
> > https://urldefense.com/v3/__https://docs.einsteintoolkit.org/et-docs/Analysis_and_post-processing__;!!DZ3fjg!637T4cXsHrwZerkMgVSFG2oZ_EyIQ2rG5tctRdYDnwbB7o9tud5Ub5xZum-5iQo3BHbZmGc-XLYt8NewPSGC4lHKDr8$
> > ) will usually do this automatically but if you use your own Python
> > or gnuplot code then you will have to do so yourself.
> >
> > Yours,
> > Roland
> >
> > --
> > My email is as private as my paper mail. I therefore support
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> >  .