[FLASH-USERS] Numerical Effects in Spherical Coordinates

[Michiel Bustraan]

Klaus,

Modifying the Grid_ files to force refinement sound a like a significant improvement to fluctuations.
I will look into modifying those files.

Experimenting with the cfl couldn't hurt.
I will see what effect it has on the oscillations.

Thank you very much for the advice. I was wary about modifying the actual FLASH code, but it might be necessary at this point.

Kind Regards,
Michiel
________________________________________
From: Klaus Weide <klaus at flash.uchicago.edu>
Sent: Thursday, March 23, 2017 8:44 PM
To: Michiel Bustraan
Cc: flash-users at flash.uchicago.edu
Subject: Re: [FLASH-USERS] Numerical Effects in Spherical Coordinates

On Wed, 22 Mar 2017, Michiel Bustraan wrote:

> Dear FLASH Users,
>
>
> I've been running 2D simulations of shocks in spherical simulations.
>
> The initial conditions involve a high density around the origin.
>
>
> I had to introduce random temperature fluctuations in the inner region to ensure refinement.

Michiel,

1.)
You should not have to introduce artificial fluctuations in order to
ensure refinement.  A modified Grid_markRefineDerefine.F90 with an
appropriated  call to Grid_makeSpecialized added, should take care of that.
See the User's Guide if necessary, and you should be able to find
examples in existing simulations.

2.)
I suggest some experimentation to find out whether lowering the runtime
parameter cfl will make the oscillations go away (or suppress them
significantly).

Klaus