[FLASH-USERS] EOS for guard cells

[Alan Calder]

Hi Maksim,

I had a similar problem once that may be what you are seeing. Does this
happen right after the mesh has refined?

I was working with a relativistic hydro solver. The problem was that when
the mesh refined, new guard cells were created but not filled. Thus no
values were set for the variables. Some of the sweeps included guard cells,
but as the new block just had some random gibberish in the guard cells, the
requirement that |v| < c was not always satisfied and the code would stop.

You could try adding a call to guard cell filling just before you call the
EOS to be sure you have "fresh" values in the guard cells.

Hope this helps!

Alan

On Sat, Jun 26, 2021 at 7:58 AM Maksim Kozlov <maksim.kozlov at nu.edu.kz>
wrote:

> Dear flash users,
> I would really appreciate it if somebody helps me with the following issue.
> I am experimenting with the equation of state (EOS). Don't ask me how it
> is possible but my pressure becomes negative sometimes. To make sure that
> sound speed is real, after calculating Gamma=Cs^2*rho/P (Gamma is GAMC, P
> is pressure, rho is density, Cs is sound speed). I am checking if  Gamma*P
> is positive (density is always positive). And  Gamma*P   is always positive
> in subroutine EOS. However  I receive an error  message from subroutine
> hy_uhd_shockDetec because Gamma*P/rho becomes negative so sound speed
> becomes imaginary. What I know is that it happens in guard cells only.
> However I do not understand how it can happen. Somewhere on the way from
> subroutine EOS to subroutine hy_uhd_shockDetect  Gamma*P in guard cells
> becomes negative yet as far as I understand both Gamma and P are calculated
> only in EOS.
> Many thanks!
> MAksim
>
>
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-- 
Alan C. Calder
Department of Physics and Astronomy
State University of New York at Stony Brook
Stony Brook, NY 11794-3800

office: ESS 438
phone:  (631) 632-1176
fax:  (631) 632-1745
web: http://www.astro.sunysb.edu/acalder
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