[mesa-users] New approx21 in MESA

[Bill Paxton]

On Jun 18, 2014, at 12:58 PM, Manos Chatzopoulos wrote:

> Dear all,
> 
>  In the last release it was indicated that:
> 
> "re implement approx21 for better performance and numerical stability 
> using Frank's code as basis.
> introduce quad precision calculation of dydt"
> 
>  So, in principle just calling the star_job option
> 
> new_net_name = 'approx21.net'
> 
>  Will automatically allow the newly implemented and improved version of 
> the approx21 network to run right? Nothing
> else special flag options need to be turned on?

Correct.


> 
>  Is that supposed to enhance numerical performance toward the very late 
> stages of stellar evolution (past core Si/S burning?)

Note the following from release message:

Begin forwarded message:

> reimplement approx21 for better performance and numerical stability using Frank's code as basis.
> introduce quad precision calculation of dydt
> 
> remove high T reaction rate limits. 
> can now run fully coupled approx21 models to core collapse without it.
> but note that we still have high T limits on convective coeffs

The star test suite cases that run approx21 models to core collapse are no longer using T limits.
I'm working on the issue of limits on mixing at high T.
These were turned on by the following lines in inlist_massive_defaults; we no longer need them.

         ! high center T limit to avoid negative mass fractions
         sig_min_factor_for_high_Tcenter = 0.01
          ! inactive when >= 1d0
            ! if Tcenter >= Tcenter_min_for_sig_min_factor_full_on,
            ! then okay to reduce sig by as much as this factor
            ! as needed to prevent causing negative abundances
         Tcenter_min_for_sig_min_factor_full_on = 2d9
            ! if Tcenter >= this, factor = sig_min_factor_for_neg_abundances
            ! this should be > Tcenter_max_for_sig_min_factor_full_off.
         Tcenter_max_for_sig_min_factor_full_off = 1d9
            ! if Tcenter <= this, factor = 1, so has no effect
            ! this should be < Tcenter_min_for_sig_min_factor_full_on.
         ! for T > full_off and < full_on, factor changes linearly with Tcenter



-Bill

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