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

[Sean Couch]

Hi Andrea,

I have used the 2.5D UHD approach and it seems to work for me.  Behavior is as expected, though I guess I have not done an extremely thorough job of testing the angular momentum conservation.  Do you have a simple test problem that could be used?

Sean


-----------------------------------------------------------
Sean M. Couch
Theoretical Astrophysics Including Relativity
California Institute of Technology
Mail Code 350-17
Pasadena, CA  91125
(626) 395-4282
www.tapir.caltech.edu/~smc <http://www.tapir.caltech.edu/~smc>
> On Apr 13, 2015, at 12:42 PM, Andrea Derdzinski <aderdzinski at astro.columbia.edu <mailto:aderdzinski at astro.columbia.edu>> wrote:
> 
> 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 <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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