Re: [mesa-users] tracing center_h1

[Max K. <max...@gm...>]

Ehsan,

As you may know, if you just enable "center h1" in your history_columns
file then you will get the central h1 mass fraction (center_h1, in the
terminology of star_data.inc) at each recorded model number.

With regard to the code, which allows you to fine-tune what number you're
actually observing, what you want to do is create an integer j that records
the species number in the network of your isotope (while the other modules
have functions that allow you to work with isotope names or abbreviations,
the array xa is indexed by species number in your network). You can use the
recommended code to automate this, e.g.

real :: center_h1_new
integer :: j

j = net_iso(h1) ! Assigns the isotope number in the network for h1 to the
integer j
center_h1_new = xa(j,s% nz) ! Records mass fraction of species j (h1) in
center cell



Or, you could make slightly more complicated averages of the innermost,
say, 10 cells:

real :: center_h1_avg
integer :: j, i

j = net_iso(h1)
center_h1_avg = 0.
do i = (s% nz) - 9, s% nz
  center_h1_avg = + center_h1_avg + xa(j,i)
end do
center_h1_avg = center_h1_avg / 10.



In any case, the xa_old and xa_older variables may be useful for internal
bookkeeping in the code but I do not think they will be helpful to you for
this purpose. Finally, the next trick would be to figure out how to output
your new variable in the standard history.data file (or, you could be less
tricky and just write to file as part of your above code, in
run_star_extras).

Max

On Mon, Aug 27, 2012 at 3:56 PM, Ehsan Moravveji <mor...@ia...>wrote:

> Hello all,
>
> I would like to trace center_h1 during the main sequence evolution, and
> make sure it is monotonically dropping. for this, I know that I must use
> the three star_info pointers: xa, xa_old and xa_older in star_data.dek
> (now star_data.inc in the new release):
>
>       ! composition variables: xa(j,k) holds mass fraction of species j
> for location k
>       ! j is an integer from 1 to s% species
>       ! chem_id(j) gives the iso identifier from chem_def
>       ! net_iso(chem_id(j)) = j
>       real(dp), pointer, dimension(:,:) :: xa, xa_old, xa_older
>
> However, I cannot understand what values to assign to j and k
> in e.g. xa(j,k).
>
> Can someone please help me with this?
>
> Best regards.
> Ehsan.
>
>
>
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