Hi ZhiChao, One more note: The BNS simulation you performed was an equal-mass case. You should find that the amount of ejecta will be much larger if you chose a significantly unequal-mass system. You will want to adjust the AMR grid structure accordingly before proceeding on this front.
-Zach * * * Prof. Zachariah Etienne Physics & Astronomy Dept. West Virginia University http://astro.phys.wvu.edu/zetienne/ http://blackholesathome.net <https://blackholesathome.net> On Wed, Feb 12, 2020 at 11:14 PM Zach Etienne <[email protected]> wrote: > One quick clarification: > > When I said > > "[integrated measures of rest mass over a volume] can become completely > unreliable at the time of black hole formation" > > I meant that the conservative nature of GRMHD schemes can and do break > down inside black holes, so mass might be lost after it passes inside a > black hole horizon. This should have no ill effect outside the horizon, as > "what happens in the horizon stays in the horizon". Generally you'd want to > perform a surface integral to monitor the rest mass passing into the > horizon and combine it with a volume integral outside the horizon to > measure the total rest mass after black hole formation. > > -Zach > > * * * > Prof. Zachariah Etienne > Physics & Astronomy Dept. > West Virginia University > http://astro.phys.wvu.edu/zetienne/ > http://blackholesathome.net > <https://blackholesathome.net> > > > On Wed, Feb 12, 2020 at 11:05 PM Zach Etienne <[email protected]> wrote: > >> Hi ZhiChao, >> >> > The program runs without error, however there is no eject during the >> merge. >> >> Typical ejecta from BNS mergers amount to a very tiny fraction of the >> total initial mass, with values of 1e-3 Msun from BNS merger simulations >> being reported in the literature (https://arxiv.org/abs/1809.11161). >> This value is highly dependent on the equation of state however. Further >> most simulations reporting ejecta are not performed at multiple numerical >> resolutions, meaning that the values may be adjusted downwards with >> subsequent simulations. Indeed in most simulations I saw for which more >> than one resolution was performed in that paper, the higher resolution >> simulation has less ejecta (see Table 2)--sometimes significantly less >> (e.g., LS220_M140140_LK). >> >> Bottom line, I am not surprised you didn't see any ejecta. Ejecta >> measurements are often dominated by numerical error, and depend sensitively >> on equation of state. The very simple equation of state you chose (simple >> Gamma=2 polytrope) might not exhibit much, if any, ejecta in the limit of >> very high resolution. >> >> A recent update to IllinoisGRMHD supports more sophisticated (piecewise >> polytrope/"hybrid") equations of state. It exists within the IllinoisGRMHD >> subdirectory of https://github.com/zachetienne/nrpytutorial . You might >> have more luck getting ejecta from BNS initial data with >> piecewise-polytrope equations of state. >> >> > And "restmass. Init. IN sphere @ >> (0.000000e+00,0.000000e+00,0.000000e+00), r=2.708902e+02. Moves/Tracks AMR >> Centre -1/-1" is increasing. >> >> If I'm interpreting this correctly (I might not be), you are measuring >> total rest mass within 270.89 in code units. You seem to observe an >> increase of 0.06% over the course of the simulation. That's not much, and >> can happen due to interpolation errors at AMR refinement boundaries (matter >> crosses AMR refinement boundaries and tiny errors add up to a small boost >> in mass), or become completely unreliable at the time of black hole >> formation. Performing another simulation at higher or lower resolution and >> additional volume integral regions may help diagnose this measurement. I >> think you'd want to analyze the rest mass *outside* an interior volume to >> estimate ejecta anyway. >> >> A more sophisticated interpolation treatment at AMR refinement boundaries >> might help reduce this error, which amounts to a different prolongation >> type (e.g., ENO) being chosen for evolved GRMHD variables. >> >> Hope this helps. >> >> -Zach >> >> * * * >> Prof. Zachariah Etienne >> Physics & Astronomy Dept. >> West Virginia University >> http://astro.phys.wvu.edu/zetienne/ >> http://blackholesathome.net >> <https://blackholesathome.net> >> >> >> On Wed, Feb 12, 2020 at 9:25 PM ZhiChao Zhao <[email protected]> >> wrote: >> >>> Hello everyone, >>> >>> I am Zhi-Chao Zhao from Beijing Normal University, China. >>> I am using EinsteinToolkit and IllinoisGRMHD to simulate BNS merge. >>> >>> I use a par file modified from >>> https://bitbucket.org/zach_etienne/wvuthorns_diagnostics/src/master/NSNS_parameter_files/nsns_test.par >>> . >>> I just add one line >>> "VolumeIntegrals_GRMHD::volintegral_inside_sphere__radius[6] = >>> 270.89015422746235". >>> >>> The initial data is got from Zach Etienne. >>> >>> The program runs without error, however there is no eject during the >>> merge. >>> Two videos: >>> https://gogo.treenew.be/rho_b_movie.mpg >>> https://gogo.treenew.be/rho_b_log_movie.mpg >>> >>> >>> And "restmass. Init. IN sphere @ >>> (0.000000e+00,0.000000e+00,0.000000e+00), r=2.708902e+02. Moves/Tracks AMR >>> Centre -1/-1" is increasing. >>> One figure: >>> https://gogo.treenew.be/newplot.png >>> >>> I don't know where I went wrong. Can anyone help me? >>> >>> >>> _______________________________________________ >>> Users mailing list >>> [email protected] >>> http://lists.einsteintoolkit.org/mailman/listinfo/users >>> >>
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