[FLASH-USERS] ensuring div B = 0 when adjusting evolution
Slavin, Jonathan
jslavin at cfa.harvard.edu
Fri Jun 9 12:19:32 EDT 2017
Hi Dongwook,
I was using HLLD. However my problem was solved when I set the initial
time step after the second explosion to dtinit, which is a very small
value. So I think it was related to the large pressure gradients present
when the second explosion is initiated. As far as I can tell, the problem
was between fine resolution pixels, not at a fine-coarse boundary.
Jon
On Thu, Jun 8, 2017 at 7:05 PM, Dongwook Lee <dongwook at flash.uchicago.edu>
wrote:
> Hi Jon,
>
> Do you see large B fluctuations aligned with the fine-coarse block
> boundaries; and they get larger over time?
>
> Just to add one quick suggestion: what Riemann solver you've been using?
> If HLLD, can you try to switch to HLLC or HLL and see if the fluctuations
> still persist?
>
> Cheers,
> Dongwook
>
> On Fri, May 26, 2017 at 1:38 PM, Slavin, Jonathan <jslavin at cfa.harvard.edu
> > wrote:
>
>> 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?bibco
>>> de=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
>>>
>>>
>>> _______________________________________________
>>> flash-users mailing list
>>> flash-users at flash.uchicago.edu
>>> http://flash.uchicago.edu/mailman/listinfo/flash-users
>>>
>> --
>> ________________________________________________________
>> 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
>> ________________________________________________________
>>
>>
>
>
> --
>
> =========================================
> Dongwook Lee, Ph.D., Assistant Professor
> Applied Mathematics and Statistics
> University of California, Santa Cruz
> Baskin Engineering, Room 353C
> 1156 High Street, Santa Cruz, CA 95064
> https://users.soe.ucsc.edu/~dongwook/
>
>
--
________________________________________________________
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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