[FLASH-USERS] Problems with 2.5D cylindrical disk using FLASH 4.2.2 unsplit solver

[Andrea Derdzinski]

Hi everyone,

I'm trying to simulate an isothermal disk with in 2.5D cylindrical geometry
(r,z) around a point mass (with the computational domain outside of the
origin). To my understanding I need to use the unsplit Hydro solver in
order to conserve angular momentum (
http://flash.uchicago.edu/pipermail/flash-users/2012-September/001163.html).


There is no viscosity, so this is essentially a rotating fluid. Initially I
want the fluid to be steady, with no radial velocity (v_r = 0) and no
vertical velocity (v_z = 0), only a rotational phi velocity. I solve for
the initial conditions analytically to ensure that there is both radial and
vertical support, but at the first time step there seems to be a lack of
vertical pressure support and the gas develops a negative vertical
velocity.

Analytically the gravitational force is balanced by the pressure gradient
force, but this doesn't seem to be the case in the simulation. The issue
does not go away with higher resolution. I've checked that the isothermal
condition is enforced in the EOS unit, and that the gravitational
acceleration is implemented correctly.

Has anyone had success running a simulation in 2.5D cylindrical geometry
using the unsplit solver? I'd appreciate hearing about any issues other
users have ran into or any advice.

The unsplit setup:
order = 3
slopeLimiter = "mc"
RiemannSolver = "HLLC"
conserveAngmom = .true.
use_gravhalfupdate = .true.
fluxcorrect = .true.



Thanks,
Andrea
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