[FLASH-USERS] 2D Spherical and Cartesian Geometry

[Michiel Bustraan]

Klaus,

I set the geometr to 2d spherical in the setup command, as you can see below, as well as in the flash.par file.
Here is the information you asked for, from the logfile of the failed simulation:

Version:         FLASH 4.3_release   
  
Setup syntax:    /home/mbust/FLASH4.3/bin/setup.py MySimulation -2d -auto +spherical -objdir sphersimulation species=h1 ManualSpeciesDirectives=True +parallelio +uhd -maxblocks=10000 -gridinterpolation=monotonic

ymax                        =                 0.180E+03 [CHANGED]
ymin                        =                 0.000E+00

xl_boundary_type            = reflect                        [CHANGED]
xr_boundary_type            = outflow                        [CHANGED]
yl_boundary_type            = reflect                        [CHANGED]
yr_boundary_type            = reflect                        [CHANGED]


I'm not sure if these boundaries are relevant, but I was using them in a previous simulation and forgot to remove them:
diff_eleflmode              = fl_none                       
diff_elexlboundarytype      = outflow                       
diff_elexrboundarytype      = outflow                       
diff_eleylboundarytype      = outflow                       
diff_eleyrboundarytype      = outflow                       
diff_elezlboundarytype      = outflow                       
diff_elezrboundarytype      = outflow                       
diff_ionflmode              = fl_none                       
diff_ionxlboundarytype      = outflow                       
diff_ionxrboundarytype      = outflow                       
diff_ionylboundarytype      = outflow                       
diff_ionyrboundarytype      = outflow                       
diff_ionzlboundarytype      = outflow                       
diff_ionzrboundarytype      = outflow  

For the Hydro, this is from the flash.par file:

# Hydro
useHydro                       = .true.
cfl                            = 0.1 #6
interpol_order                 = 2 #2
updateHydroFluxes              = .TRUE.
eintSwitch		       = 1e-4
ppm_modifystates	       = .FALSE.
use_cma_advection	       = .FALSE.

##  SWITCHES SPECIFIC TO THE UNSPLIT HYDRO SOLVER               ##
#       I. INTERPOLATION SCHEME:
order           = 5          # Interpolation order (first/second/third/fifth order)
slopeLimiter    = "mc"   # Slope limiters (minmod*, mc, vanLeer, hybrid, limited)
LimitedSlopeBeta= 1.         # Slope parameter for the "limited" slope by Toro
charLimiting    = .true.     # Characteristic limiting vs.Primitive limiting
transorder	= 3

use_avisc       = .true.     # use artificial viscosity (originally for PPM)
cvisc           =  0.1       # coefficient for artificial viscosity
use_flattening  = .true.     # use flattening (dissipative) (originally for PPM)
use_steepening  = .false.    # use contact steepening (originally for PPM)
use_upwindTVD   = .false.    # use upwind biased TVD slope for PPM (need nguard=6)
flux_correct    = .true.
EOSforRiemann   = .true. #*
transOrder      = 1
use_auxEintEqn  = .TRUE.
hydroComputeDtOption = -1
hy_fPresInMomFlux = 0.0 

#       II. RIEMANN SOLVERS: 
RiemannSolver   = "HLLC"   # Roe, HLL*, HLLC, LLF, Marquina
entropy         = .true.     # Entropy fix for the Roe solver

#       III. STRONG SHOCK HANDELING SCHEME:
shockDetect     = .true.    # Shock Detect for numerical stability
shockLowerCFL	= .true.
## -------------------------------------------------------------##

I tried changing these in various ways, but nothing seemed to help.

- Michiel
________________________________________
From: Klaus Weide <klaus at flash.uchicago.edu>
Sent: Friday, September 23, 2016 3:29 PM
To: Michiel Bustraan
Cc: flash-users at flash.uchicago.edu
Subject: Re: [FLASH-USERS] 2D Spherical and Cartesian Geometry

On Fri, 23 Sep 2016, Michiel Bustraan wrote:

> Firstly, I've been trying to run a simulation in 2D with a spherical geometry, but a few steps after starting the simulation the code crashes due to a negative dt.
>
> I set the density and temperature constant in the simulation, and the velocity to 0, so nothing should be happening (just as a test case).
>
> I'm attaching a plot of the density just before the crash. I'm guessing the problem lies in the grid somewhere, but I have no idea how to fix it.?
>
>
> Have any of you encountered something like this before?

Michiel,

It is not so unusual to see some sort of instabilities developing close to
the axis in 2D spherical coordinates, but FLASH should be able to do
better than THAT.

Wee need more information to understand what may be going on. To start
with, are you using the latest release version of FLASH? Which hydro
solver are you using? What was your setup command?

How have you set the geometry to 2D spherical? How have you set related
runtime parameters, in particular, ymin, ymax, and all boundary
conditions?

Klaus