[FLASH-USERS] Best practice for referencing Abar, Zbar

[Klaus Weide]

On Thu, 5 May 2011, Dean Townsley wrote:

> Hi Aaron,
> 
> Just looking at your code snippets, it appears that the unsplit hydro module
> is not quite fully compliant with multispecies.  Presumably this is because it
> has been tested mostly with one species (="no species") and with the ye/sumy
> scalars.

Dean,

I think the unsplit Hydro module IS compliant with Eos implementations 
that use Multispecies; it's just that such implementations do not require
the caller of Eos() to set eosData(EOS_ABAR) and eosData(EOS_ZBAR), but
do it themselves in Eos.F90.

As another remark, FLASH4-alpha has just added an interface for getting
abar and zbar without having to know whether a simulation uses Multispecies
or the sumy/ye mass scalars (or neither). See <URL:
http://flash.uchicago.edu/site/flashcode/user_support/robodoc-FLASH4_alpha/home.py?submit=docs/source/physics/Eos/Eos_getAbarZbar_F90.html >.

> The EOS modules that use the sumy/ye scalars are not in the public release, at
> least as of 3.3, though they are not complicated.  These are used when fluid
> properties such as abar and zbar are derived from some other dynamic value
> such as a reaction progress variable or something more general.  They can be
> used to represent fluid properties without resorting to a large number of
> species.
> 
> If you're interested in what this is used for, see:
> http://adsabs.harvard.edu/abs/2009ApJ...701.1582T
> particularly section 3 discussing the nuclear burning model.
> 
> On the error you are seeing:  you have to initialize the mass scalars on the
> grid, otherwise abar will be infinity.

Right - *If* a simulation defines those mass scalars, then it is also
responsible for initializing them in Simulation_initBlock.

Klaus