[FLASH-USERS] Checkboard of Magnetic Monopoles

[dongwook at flash.uchicago.edu]

Hi Aaron again,

Have you tried running the same OrszagTang problem WITHOUT including your
cool module?

In case you still see the monopoles without it, did you need to implement
any other custom files other than the cool unit?

Best,
Dongwook

=========================================
Dongwook Lee, Ph.D., Research Scientist
The Flash Center for Computational Science
The University of Chicago
5747 S. Ellis Ave., Room 319
Chicago, IL 60637
(773) 834-6830

> Hi Mark,
>
> I have been able to recreate the checkboarding problem on the OrszagTang
> example using the USM solver.  I have included the necessary changes,
> which just involve including a modified cooling module to reduce the local
> internal energy by a small factor each time step.  I have included plots
> of divB at the first checkpoint for two cases: one with a static AMR and
> the internal energy dropping by a factor of 1e-6 each time step, the other
> with a dynamic AMR and the internal energy dropping by a factor of 1e-3
> each time step.  The monopoles always appear on the borders of 8x8
> squares.
>
> Thanks,
> Aaron
> ________________________________________
> From: Mark L Richardson [Mark.L.Richardson at asu.edu]
> Sent: Thursday, April 12, 2012 4:20 PM
> To: Aaron Froese
> Cc: flash-users at flash.uchicago.edu
> Subject: Re: [FLASH-USERS] Checkboard of Magnetic Monopoles
>
> Hi Aaron,
>   Are you able to overlay the grid so we can see how these features relate
> to the blocksize?
>
> Cheers,
>   -Mark
>
> On Thu, Apr 12, 2012 at 3:54 PM, Aaron Froese
> <aaron.froese at generalfusion.com<mailto:aaron.froese at generalfusion.com>>
> wrote:
> I am using the USM MHD solver with flash3 and I noticed that I am getting
> very large magnetic monopoles appearing in my solution, of the same order
> as the magnetic fields.  The monopoles appear in a somewhat random
> checkboard-like pattern, which I believe has something to do with the
> block-structure of the mesh.  I have attached two plots which show the
> magnitude of divb and posted copies online in case the mailing list does
> not allow file attachments.
>
> Cylindrical Shell Compression 2D - abs(divb)
> http://oi40.tinypic.com/1zeihbp.jpg
>
> Spherical Shell Compression 3D - abs(divb)
> http://oi39.tinypic.com/34grldv.jpg
>
> The central circle where the checkboard pattern appears is the only volume
> that is magnetized.  I am using a static AMR mesh with a uniform
> resolution across the magnetized volume, and less refinement in the
> surrounding non-magnetized fluid.  Has anyone observed similar behaviour?
> It is definitely numerical in nature, but I do not know what part of the
> code is responsible.
>
> Thanks,
> Aaron
>
>
>
> --
> Mark Richardson,
> Mark.L.Richardson at asu.edu<mailto:Mark.L.Richardson at asu.edu>
> Ph.D. Candidate: Astrophysics
> PSF 271
> School of Earth and Space Exploration
> Arizona State University
> 480 318-4449
> www.public.asu.edu/~mlricha4<http://www.public.asu.edu/~mlricha4>
>
>