[FLASH-USERS] (no subject)

[Dean Townsley]

Hi Michael,

I'm pretty sure the second to last column in SpeciesList.dat is the spin 
part of the nuclear partition function.  This is needed for equilibrium 
calculations and for computing inverse rates properly. I'm unsure about 
the last column, which is 0.5 for neutrons and protons and zero otherwise.

Nominally you can't just add species there.  You also have to include 
reactions.  The currently working nuclear reaction network in flash is 
"approx 13" (documented in "the flash paper" Fryxell et al 2000 
(2000ApJS..131..273F 
<http://adsabs.harvard.edu/abs/2000ApJS..131..273F>) ), which only 
treats the 13 nuclides He4, C12, O16, Ne20, Mg24, Si28, S32, Ar36, Ca40, 
Ti44, Cr48, Fe52, and Ni56.  These are connected by capture/release of 
an alpha particle (He4 nucleus), though the network uses approximate 
"effective" rates that account for other side-channel reactions.  This 
is the network used in CellularDetonation.  Very useful for explosive 
burning in supernovae, x-ray bursts, and other thermonuclear transient 
stellar phenomena.  Not so useful for deuterium/tritium fusion.

Dean


On 05/23/2013 01:12 AM, Michael Sabino wrote:
> Hi,
>
> I would like to introduce myself to this group. My name is Michael 
> Sabino, and I am drawn here due to my fascination of simulations of 
> fusion+hydro+grav+... on computers.
>
> First things first, and my first goal is to simulate something I can 
> understand, and then hopefully get across to others.
>
> I'd looked at SpeciesList.txt to add deuterium, tritium, and helium-4 
> to simulate detonation in those materials (primarily to familiarize 
> myself with some aspects of FLASH), and I believe I've added them 
> correctly, but I get some unexpected results.
>
> The main question is: What are the last and 2nd to last fields in the 
> SpeciesList.txt that are identified with "??" in the 
> Simulation_initSpecies.F90 comment? Are they important?
>
> The model I am using is a modified version of CellularDetonation, 
> where I added deuterium and tritium in place of carbon-12 and 
> attempted to detonate a 50:50 mixture of it.
>
> The spurious results I wasn't expecting were issues with the density 
> in the grid cells showing up as a very low number and erroring out to 
> stdout. So low, that it was below the smlrho and nuclearDensMin 
> settings. I had to lower those. The low values of density presumably 
> have something to do with the low temperature and density fusion 
> requirements of DT and DD, which I configured in my upstream 
> temperature and density profile in flash.par. After disabling 
> useShockBurn and doing the above, it seemed to be proceeding without 
> errors (albeit slowly, since it was evaluating the fusion routines a 
> lot more), but I'll keep you up-to-date.
>
>
> Thanks,
> Michael Sabino
> Michael.Rocco.Sabino at gmail.com <mailto:Michael.Rocco.Sabino at gmail.com>

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