[FLASH-USERS] [External Sender] Negative Internal Energies in the 2D, AMR, Z-Pinch problem

Fri Nov 8 14:34:05 EST 2024

Hi Paul,

Since your errors seem to be coming from Heatexchange, the issue might be with the equilibration time.

For v4.8, we removed some redundant code and started using the subroutine PlasmaState_ieEquilTime. This routine calls PlasmaState_tau to get the electron-ion collision time and then rescales it to get the equilibration time. The problem is that we had implemented a floor on the average ionization state zbar inside PlasmaState_tau; this is useful for transport coefficients to avoid tau blowing up for small zbar. However, we should allow tau to be large for low zbar for the equilibration time.

We’re going to fix this in 4.8.1, but in the meantime, you can edit PlasmaState_ieEquilTime.F90. Remove the call to PlsmaState_tau and add:
tau = (3.*sqrt(pls_mele)*(pls_boltz*tele)**1.5) / &
           (4.*sqrt(2.*PI) * ll * pls_qele**4 * zbar**2 * nion)

Can’t guarantee this will solve your issue, but it’s worth a try.

--
Eddie Hansen
Applications Group Leader
Flash Center for Computational Science

From: flash-users <flash-users-bounces at flash.rochester.edu> on behalf of Paul Campbell <Paul.Campbell at zap.energy>
Date: Tuesday, November 5, 2024 at 7:37 PM
To: Sutcliffe, Graeme <sutcliffe2 at llnl.gov>
Cc: flash-users at flash.rochester.edu <flash-users at flash.rochester.edu>
Subject: Re: [FLASH-USERS] [External Sender] Negative Internal Energies in the 2D, AMR, Z-Pinch problem
Thanks for the advice, I’ve resubmitted a job with the extra parameters you’ve suggested.  So far the log files are still complaining about Negative internal energy but I will let it run over night and see how far it gets.  I should have included in my first email that I’m using version 4.8 (although for your suggestion I don’t think the difference in version matters).  For reference this is what the warning from the log files look like:

“
[ 11-04-2024  13:44:58.918 ] [Heatexchange] Warning: Negative internal energy detected
[ 11-04-2024  13:44:58.920 ] [Heatexchange] Correcting for this...
[ 11-04-2024  13:44:58.922 ] [Heatexchange] OLD EION/TION:  7.292804E+10 5.244171E+03
[ 11-04-2024  13:44:58.923 ] [Heatexchange] OLD EELE/TELE:  5.715019E+08 7.379651E+03
[ 11-04-2024  13:44:58.925 ] [Heatexchange] BAD EION/TION:  7.721564E+10 5.546998E+03
[ 11-04-2024  13:44:58.926 ] [Heatexchange] BAD EELE/TELE: -3.716098E+09 5.546998E+03
[ 11-04-2024  13:44:58.927 ] [Heatexchange] CORRECTED EION:  7.721564E+10
[ 11-04-2024  13:44:58.929 ] [Heatexchange] CORRECTED EELE:  2.116656E+08
[ 11-04-2024  13:44:58.930 ] [Heatexchange] FINAL EION:  7.329861E+10
[ 11-04-2024  13:44:58.931 ] [Heatexchange] FINAL EELE:  2.009281E+08
[ 11-04-2024  13:44:58.932 ]
 [ 11-04-2024  13:44:58.933 ] [Heatexchange] Note: Further warnings suppressed
[ 11-04-2024  16:00:05.980 ] Species  1: Lookup for T > Tmax(table): 35 times,first for (3.1052449E+08,1.0000000E+16),highest T was 2.3375415E+10

...... (lots of look ups for the 3 species here) …….

[ 11-04-2024  16:27:26.386 ] [hy_uhd_ragelike] Negative internal energies in 3T update
[ 11-04-2024  16:27:26.387 ]   Falling back to using internal energy ratios instead of pressure ratios
“
Paul Campbell

From: Sutcliffe, Graeme <sutcliffe2 at llnl.gov>
Sent: Tuesday, November 5, 2024 1:56 PM
To: Paul Campbell <Paul.Campbell at zap.energy>
Cc: flash-users at flash.rochester.edu
Subject: Re: [External Sender] [FLASH-USERS] Negative Internal Energies in the 2D, AMR, Z-Pinch problem

Hi Paul,

You can try the following par file options if you haven't already, which helped me to get some laserslab runs working back in FLASH4.7 (adjust accordingly if you're not doing a 3T sim):
dr_usePOSdefComputeDt = .true.
dr_posdefdtfactor = 0.1
dr_numPosdefVars = 3
dr_posdefVar_1 = "eele"
dr_posdefVar_2 = "eion"
dr_posdefVar_3 = "erad"

The dr_posdefdtfactor of 0.1 might be a bit aggressive (i.e. too small), I haven't played with it.

Graeme
________________________________
From: flash-users <flash-users-bounces at flash.rochester.edu<mailto:flash-users-bounces at flash.rochester.edu>> on behalf of Paul Campbell <Paul.Campbell at zap.energy<mailto:Paul.Campbell at zap.energy>>
Sent: Tuesday, November 5, 2024 1:37 PM
To: flash-users at flash.rochester.edu<mailto:flash-users at flash.rochester.edu> <flash-users at flash.rochester.edu<mailto:flash-users at flash.rochester.edu>>
Subject: [FLASH-USERS] Negative Internal Energies in the 2D, AMR, Z-Pinch problem

Hello,

I am attempting to get the 2D Z-pinch problem working with AMR but have been unable to get the sim to run without crashing .  From the logs, I appear to be running into many negative internal energy warnings.  It looks like both the electron and ion temperatures/energies need to be continuously corrected.  To try and address this issue, I have tried refining on density, electron, and ion temperatures but the warnings persist.  In terms of the AMR settings, I am using a 32x32 grid with 4x4 cells, a lrefine_max=4, and I have left the refinement cutoffs and filters unchanged from default.  My questions are:

  1.  Is this an issue with the AMR settings, would a finer grid fix this problem?
  2.  Should I be refining on different parameters?
  3.  Is this an issue with a non-AMR setting?

Paul Campbell

________________________________

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