[FLASH-USERS] Checkerboard structure in magnetic field using USM solver

[Rukmani Vijayaraghavan]

Hi Dongwook,

I'm using cfl=0.8. I've used first, second, and third order 
reconstruction with no luck. These are 3D simulations, the figures I 
attached are 2D slices through the central plane.

Thanks,

Rukmani


On 10/09/2017 12:07 AM, Dongwook Lee wrote:
> Dear Rukmani,
>
> It looks to me that they may come from numerical instability, although 
> it could be an issue related to the use of AMR. What reconstruction 
> scheme and CFL number are you using? Is this 2D or 3D?
>
> Best,
> Dongwook
>
> On Sun, Oct 8, 2017 at 12:59 PM, Rukmani Vijayaraghavan 
> <rukmani at virginia.edu <mailto:rukmani at virginia.edu>> wrote:
>
>     Hi everyone,
>
>     I get a strange, unphysical feature in the magnetic field
>     structure with the USM solver, seen in the attached slices of B_z
>     and the magnetic pressure. These features, as you can see, track
>     the block boundaries and look like a checkerboard of varying
>     magnetic field strength (and sign?) in individual grid cells. I've
>     tried modifying every possible USM solver switch, including the
>     Riemann solver, order, slope limiter, prolongation method,
>     steepening, etc. Using Riemann Solver = HLLC instead of HLLD makes
>     things a little better, since HLLC is more diffusive, but the
>     feature still eventually appears. Any advice on solving this or
>     even minimizing its effects would be helpful!
>
>     Thanks,
>
>     Rukmani
>
>     -- 
>     Rukmani Vijayaraghavan
>     NSF Astronomy & Astrophysics Postdoctoral Fellow
>     University of Virginia
>     rukmani at virginia.edu <mailto:rukmani at virginia.edu>
>
>
>
>
> -- 
>
> =========================================
> 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/ 
> <https://users.soe.ucsc.edu/%7Edongwook/>
>

-- 
Rukmani Vijayaraghavan
NSF Astronomy & Astrophysics Postdoctoral Fellow
University of Virginia
rukmani at virginia.edu

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