[FLASH-USERS] noisiness in run with high ekin/eint

[Slavin, Jonathan]

Hi,

I've been doing runs in 1D spherical symmetry of supernova remnants
starting with fast cool ejecta.  This is one of those situations in which
the kinetic energy far exceeds the thermal energy (at least in the early
stages).

I know about eintSwitch which is supposed to help with numerical issues
that arise in such situations, but I've been finding that setting it lower
actually results in less noisiness, though the noisiness that remains is,
if nothing else, unsightly.  What happens is that the pressure develops
fairly large fluctuations that seem to be purely numerical since there
doesn't seem to be any other source for them.  The pressure is small in
those regions, relative to the kinetic energy, but still the noise seems to
affect the density.

So I'm wondering if others have found parameter settings or approaches that
work well in this sort of situation.  If so, I'd like to hear about them.
I should mention that I've been using split PPM.  I did try to use unsplit
hydro but it failed with the pressure dropping to the smallp value very
quickly.  I may try to investigate that some more.

Regards,
Jon

-- 
________________________________________________________
Jonathan D. Slavin                 Harvard-Smithsonian CfA
jslavin at cfa.harvard.edu       60 Garden Street, MS 83
phone: (617) 496-7981       Cambridge, MA 02138-1516
cell: (781) 363-0035             USA
________________________________________________________
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