[FLASH-USERS] value of Ye for single species runs

[Slavin, Jonathan]

​Hi Klaus,

As I understand it, if the runtime parameter eos_singleSpeciesZ is not set,
then it will have a value of 1.  I could set eos_singleSpeciesZ, but since
it isn't used in the equation of state for the single species gamma EOS (as
I found out from earlier e-mail exchanges with people in this group), I can
just as well absorb it into the diff_eleFlCoef runtime parameter, with is
supposed to limit the conductive flux.

I think the flux limiter is perfectly appropriate for the 1T case under the
assumption that there is fast equilibration of ​the electron and ion
temperatures.  There have been many calculations of cloud evaporation and,
as far as I can recall, they all make that assumption.  And since Cowie &
McKee (1977), it has been recognized that thermal conduction "saturates"
when it reaches a level at which the heat flux reaches the maximum that can
be carried by the electrons.  I'm trying to be careful about how I set the
diff_eleFlCoef so as to match the assumptions used in various of the 1D
steady flow calculations of cloud evaporation so as to be able to compare
the results.

Regards,
Jon

On Sat, Oct 3, 2015 at 1:00 PM, <flash-users-request at flash.uchicago.edu>
wrote:

> From: Klaus Weide <klaus at flash.uchicago.edu>
> To: John ZuHone <jzuhone at space.mit.edu>
> Cc: flash-users <flash-users at flash.uchicago.edu>
> Date: Fri, 2 Oct 2015 15:59:23 -0500 (CDT)
> Subject: Re: [FLASH-USERS] value of Ye for single species runs
> On Fri, 2 Oct 2015, John ZuHone wrote:
>
> > Just for reference, Jon and I have been discussing this off-list. The
> > single-species gamma-law EOS only has a stub for this subroutine.
>
> Hi John,
>
> That's not correct if with "this routine" you mean Eos_getAbarZbar.F90.
> The implementation of this routine (shared by the single-species gamma-law
> EOS implementation and other EOS implementations) is in
>   physics/Eos/EosMain/Eos_getAbarZbar.F90 .
> There are various #ifdef's, but in Jon's case as I understand it (no
> FLASH_MULTISPECIES defined, and SUMY_MSCALAR and YE_MSCALAR not both
> defined) the returned values should simply be what is set by the
> following lines:
>   if (present(abar)) abar = eos_singleSpeciesA
>   if (present(zbar)) zbar = eos_singleSpeciesZ
>   if (present(sumY)) sumY = 1.0/eos_singleSpeciesA
>   if (present(Ye))   Ye   = eos_singleSpeciesZ/eos_singleSpeciesA
>
> > I suggested copying the Eos_getAbarZbar stub to the simulation directory
> > and changing it to set the quantities to whatever he needs,
>
> That should also work, but why not just set runtime parameters
> eos_singleSpeciesZ / eos_singleSpeciesA appropriately.
>
> > but as I am
> > not familiar with this particular diffusion module I think someone with
> > more knowledge should comment if this is the right way to go.
>
> The source file physics/Diffuse/DiffuseMain/Unsplit/diff_advanceTherm.F90
> has mainly been developed for 3T situations; it is also supposed to work
> in a 1T context, but I don't know how appropriate the flux limiter is in
> that case.
>
> Klaus
>
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