[FLASH-USERS] EOS for guard cells

[Alan Calder]

And let me re-phrase that a little better- The problem was that when the
mesh refined, new blocks were created, but the guard cells were not filled.

On Sat, Jun 26, 2021 at 9:56 AM Alan Calder <alan.calder at stonybrook.edu>
wrote:

> 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
>


-- 
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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