[FLASH-USERS] [EXT] Re: Computed hydro dt is not positive

[Acharya, Nitish]

Hi Klaus,

Some months ago, you emailed me on how gamc is computed per component per material in FLASH as follows:

  eosData(gamc+i) = eosData(tempToUse+i)/eosData(dens+i) * &
                             eosData(dpt+i)**2 /  eosData(det+i) &
                           + eosData(dens+i) * eosData(dpd+i)

where dpt represent d Pres / d T, det represents d E / d T, and dpd
represents d Pres / d rho.  Each of those derivative terms in computed
from finite differences of values from Pres(T,rho) and E(T,rho) tables.

But how are gamc for each component (ele, ion, rad) initialized in the simulation? I might be able to figure out the earlier issue if I can understand this part ie initialization of per component gamma values (both for tabulated and gamma law EOS).

Thanks,
Nitish
________________________________
From: flash-users-bounces at flash.uchicago.edu <flash-users-bounces at flash.uchicago.edu> on behalf of Acharya, Nitish <nachary2 at ur.rochester.edu>
Sent: Tuesday, September 22, 2020 5:09 PM
To: Klaus Weide <klaus at flash.uchicago.edu>; flash-users at flash.uchicago.edu <flash-users at flash.uchicago.edu>
Subject: Re: [FLASH-USERS] [EXT] Re: Computed hydro dt is not positive

Hi Klaus,

Thank you for your suggestions.

I checked my EOS file which I have attached here. The data (species #2) looks just fine but I am still getting the same error right during driver initialization. I have tried reducing the time step and tried to tune couple more runtime params but the error persists. It's just hard to know at this point what's causing this error.

I would really appreciate your help,

Thanks,
Nitish
________________________________
From: flash-users-bounces at flash.uchicago.edu <flash-users-bounces at flash.uchicago.edu> on behalf of Klaus Weide <klaus at flash.uchicago.edu>
Sent: Thursday, September 17, 2020 2:34 PM
To: flash-users at flash.uchicago.edu <flash-users at flash.uchicago.edu>
Subject: [EXT] Re: [FLASH-USERS] Computed hydro dt is not positive

On Thu, 17 Sep 2020, Acharya, Nitish wrote:

> I have been applying the analytical ideal gas EOS to simulate my
> material for a LaserSlab based problem. Recently, instead of using an
> equation, I used the same ideal gas model and built a tabulated IONMIX
> EOS. However, as I use the tabulated EOS for the simulation, I've been
> repeatedly getting an error during driver initialization

FLASH should generate a file EOS_printout_tables.txt when it starts up.
The first thing I would do is carefully check that file:

*  Do all the data make sense?
*  Are all values positive that physically should be positive
   (energies, pressures)?
*  Are all pressures and energies monotonically increasing with increasing
   temperature?
*  You should have a nonzero Z(T,density) function (shown under the
   heading IONIZATION DATA in the printout file); it should be constant
   if your EOS table file is meant to exactly represent a (3T) Gamma Eos.

Klaus
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