[FLASH-USERS] Growing error in magnetic field when updating fluid variables in wind tunnel simulation

[Sean Couch]

Hi Rukmani,

I’ve seen something similar with the field loop advection test.  Have you tried setting E_modification and E_upwind to .TRUE. in your flash.par?

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 <mailto:couch at pa.msu.edu>




> On Feb 17, 2016, at 9:22 PM, Rukmani Vijayaraghavan <rukmani at virginia.edu> wrote:
> 
> Hi everyone,
> 
> I've come across an error when updating fluid variables at the inflow edge of a wind tunnel simulation. I'm running a simulation of a galaxy (with active dark matter particles, gas, and passive particles) in a box, whose fluid is initialized to be identical to the incoming wind (with vx, vy, vz = 600 km/s, 0, 0). There is a small error (on the order of 1%) when updating grid cells near the inflow boundary (with both USM and PPM solvers), and this error is spatially correlated with  block boundaries. While this error itself is tolerable as far as the density and pressure go, this has bad consequences for the magnetic field which grows as the wind propagates through the box (see attached figure, xl_boundary). This figure shows slices of Bx at two timesteps (annotated with block boundaries and magnetic field vectors). The dynamic range of Bx in this image has been reduced to highlight these discontinuities. At the timesteps shown in the attached image, the fluctuations in Bx are ~1%, but grow with time up to order unity. I've tried a variety of Riemann solvers (HLLC, HLLD, Roe, Hybrid), slope limiters (mc, minmod, etc.), interpolation orders, prolongation methods, turning on and off specific USM switches, but nothing seems to solve this issue so far. Has anybody else dealt with and/or successfully solved this issue?
> 
> Thanks,
> Rukmani
> 
> -- 
> Rukmani Vijayaraghavan
> NSF Astronomy & Astrophysics Postdoctoral Fellow
> University of Virginia
> rukmani at virginia.edu
> 
> <magxslc_discontinuity.png>

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