[FLASH-USERS] ensuring div B = 0 when adjusting evolution

Fri May 26 16:38:51 EDT 2017

To answer Sean and Ernesto's questions:
I am using the USM solver and AMR.  I have now determined that div B is
still 0 after the second explosion, which is not too surprising since, for
this run, I have not changed the magnetic field and include div B cleaning
(killdivb = .true.). So the problem is not with non-zero div B but with the
large B fluctuations that are initiated. I noticed that there are small
scale fluctuations in the region where the second explosion is initiated
before the explosion, though the field is weak ~ 0.01 muG.  The
fluctuations after the explosion go from ~ -1000 muG - +1000 muG.  I do
expect amplification of B field fluctuations at the shock, but not to that
extent.

The way I'm initiating the second explosion is (almost) the same way I
initiate the first one - I set the pressure of parcels within a given
radius to a value such that the sum of the energy in those parcels is equal
to the value I want for the explosion (1.E51 ergs).  I set the density to a
value so as to have the mass total to 8 solar masses.  So all the energy is
thermal at first.  I'll see about calling the EOS unit, since I haven't
done that.  Any additional info on how to do that would be appreciated.

Thanks,
Jon

On Fri, May 26, 2017 at 1:00 PM, <flash-users-request at flash.uchicago.edu>
wrote:
>
> ---------- Forwarded message ----------
> From: ERNESTO ZURBRIGGEN <ezurbriggen at unc.edu.ar>
> To: flash-users at flash.uchicago.edu
> Cc:
> Bcc:
> Date: Fri, 26 May 2017 10:56:45 -0300
> Subject: Re: [FLASH-USERS] ensuring div B = 0 when adjusting evolution
> Hi Jon!
>
> Have you tried to set off a less intense second supernova explosion? Have
> you observed the same problems in that case? The second explotion might be
> much too intense.
>
> On the other hand, how do you set the later explotion? I mean, applying
> the explotion, are you consistently modifying the thermodynamical
> variables? For example, if you instantaneously modify the density and the
> temperature, then you also should call the Eos unit to keep the
> consistence. I have experimented situations in which just modifying
> velocities and keeping the thermodynamics unaltered, I also had to call the
> Eos unit in order to maintain consistence
>
> Some runtime parameter that might help being on are 'shockDetect' and
> 'shockLowerCFL' (this last one I think is just in realease 4.4).
>
>
> Best!
>
> --
> *Ernesto Zurbriggen*
>
> *Instituto de Astronomía Teórica y Experimental (IATE). *
> *Observatorio Astronómico de Córdoba (OAC), **Universidad Nacional de
> Córdoba **(UNC)**. *
> *Teléfono: +54 0351 4331064-5, interno 222. *
> *Córdoba, Argentina.*
>
>
> ---------- Forwarded message ----------
> From: "Sean M. Couch" <couch at pa.msu.edu>
> To: "Slavin, Jonathan" <jslavin at cfa.harvard.edu>, flash-users <
> flash-users at flash.uchicago.edu>
> Cc:
> Bcc:
> Date: Fri, 26 May 2017 14:07:22 +0000
> Subject: Re: [FLASH-USERS] ensuring div B = 0 when adjusting evolution
> Hi Jon,
>
> Can you give a little more info? Are you using the USM solver? Are you
> using AMR? Have you actually checked that divB>0 in the output data? A log
> file from a representative run would be useful.
>
> In my experience, the USM solver in cylindrical R-Z coordinates with AMR
> can be….touchy. But it should work and maintain divB=0! (See, e.g.,
> http://adsabs.harvard.edu/cgi-bin/nph-data_query?
> bibcode=2013ApJ...773..136J&link_type=EJOURNAL).
>
> Cheers,
> Sean
>
>
> ------------------------------------------------------------
> ----------------------------------------------
> Sean M. Couch
> Assistant Professor
> Department of Physics and Astronomy
> Department of Computational Mathematics, Science, and Engineering
> National Superconducting Cyclotron Laboratory/Facility for Rare Isotope
> Beams
> Michigan State University
> 567 Wilson Rd, 3250 BPS
> East Lansing, MI  48824
> (517) 884-5035    ——    couch at pa.msu.edu    ——    www.pa.msu.edu/~couch
>
>
>
>
> On May 25, 2017 at 4:41:45 PM, Slavin, Jonathan (jslavin at cfa.harvard.edu)
> wrote:
>
> Hi all,
>
> I'm running MHD simulations where I set off a second supernova explosion
> within a pre-existing remnant.  I'm using Simulation_adjustEvolution for
> this.  However, I'm running into a problem with the magnetic field just
> after initiating the second explosion.  I'm getting very large
> pixel-to-pixel variations in Bx and By at the edge of the new expanding
> blast wave.  I'm thinking that it could be because of non-zero div B in the
> region in which the explosion is generated. So my question is, does anyone
> have a suggestion for div B cleaning at the point that the explosion is
> started, i.e. within Simulation_adjustEvolution, to prevent the problems
> I'm having? I don't really expect the B field to be dynamically important
> inside the remnant (beta >> 1), so accuracy of the B field is probably not
> important there.  I should add that I'm doing these calculations in 2D
> cylindrical symmetry (R-Z).  Thanks in advance for any help.
>
> Regards,
> Jon
>
>
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-- 
________________________________________________________
Jonathan D. Slavin                 Harvard-Smithsonian CfA
jslavin at cfa.harvard.edu       60 Garden Street, MS 83
phone: (617) 496-7981       Cambridge, MA 02138-1516
cell: (781) 363-0035             USA
________________________________________________________
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