[Users] question about MHD tests for GRHydro

[Bruno Giacomazzo]

Hi Hee Il,
	
On Oct 17, 2011, at 11:10 PM, Hee Il Kim wrote:

> I'm doing the BNS test with magnetic fields but it's just in the
> beginning stage. I don't know whether other people or the MHD
> developers have done the test for the BNS. The BNS simulations with
> the ET requires somewhat different setup from Whisky+BSSN_MoL.

	I imagine you are using McLachlan for the Einstein equations, but what are the other differences? I presume you are also using PPM+HLLE. There is a  difference between C2P in GRHydro and Whisky, but the rest should be similar I presume.

> I'm
> using a private thorn of Frank for the AMR. For the initial data, I
> modified the public bns reader, Meudon_Bin_NS.

	OK. If I were to do a comparison with Whisky I would use my thorns for ID and AMR.

> Currently, I have little information on the best parameter setup for
> the MHD. Please let me know if there's any special  treatment required
> for the MHD. Also I'd like to hear from Bruno on the initial B-field
> data. Do I need anything more than I can expect from the initial
> vector potential you used in the literatures?

	the vector potential I used in my simulations is exactly the one that is mentioned in my papers (Giacomazzo et al 2009 and Giacomazzo et al 2011). Other people have used slightly different versions (Anderson et al 2008, Liu et al 2008). The vector potential I used for the initial data has the property of having also the first derivative of the magnetic field (B) going to zero when B goes to zero (i.e., it is more smooth than the one used in the other papers).

Cheers,
Bruno

> Thanks in advance,
> 
> Hee Il
> 
> 2011/10/18 Bruno Giacomazzo <bruno.giacomazzo at jila.colorado.edu>:
>> Hi,
>> I have some questions about the MHD version of GRHydro. Today I had a
>> business meeting at the time of the telecon, otherwise I'd have asked them
>> during the telecon.
>> It is my understanding that the next release of the ET will happen next week
>> and it will contain MHD. Did you do already some tests in GR? Did you try
>> the evolution of BNS with magnetic fields? I'd like to try to run the code
>> with magnetized BNS and see how it compares with Whisky. As some of you know
>> in the past I had problems with divergence cleaning (DC) when evolving BNS
>> (strong violations of divB after the merger when the BH and the torus are
>> formed when using AMR) and so I'm curious to see if the implementation of DC
>> in GRHydro is more robust than the one I have in Whisky.
>> Thanks,
>> Bruno
>> P.S.: I will try to join the next ET telecon, so that I can get an update
>> before coming to LSU.
>> Dr. Bruno Giacomazzo
>> JILA - University of Colorado
>> 440 UCB
>> Boulder, CO 80309
>> USA
>> Tel.  : +1 303-492-0389
>> Fax  : +1 303-492-5235
>> email : bruno.giacomazzo at jila.colorado.edu
>> web: 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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Dr. Bruno Giacomazzo
JILA - University of Colorado
440 UCB
Boulder, CO 80309
USA

Tel.  : +1 303-492-0389
Fax  : +1 303-492-5235
email : bruno.giacomazzo at jila.colorado.edu
web: 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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