[mesa-users] New approx21 in MESA

[Bill Paxton]

On Jun 18, 2014, at 1:40 PM, Manos Chatzopoulos wrote:

> Hi Bill,
> 
>  Thanks - that's very useful. So basically just use 
> 
>  ! 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
> 
> in my inlist exactly as you indicated in your last e-mail.



Yes --- and that's been part of inlist_massive_defaults for a long time.

You should try turning it off by commenting out the setting for sig_min_factor_for_high_Tcenter.

See what happens during core si burning without the mixing limits.

-B




> 
> Best,
> 
> Manos
>> Damn --- last second screwup in my previous message.   I got ahead of myself in the last comment.   We DO still need the limits on mixing at high T.   I'm looking at getting rid of that requirement and my fingers wrote that we'd already reached that goal.  not yet.   
>> 
>> So we no longer need the limits on reaction rates at high T but we do need the limits on mixing.  
>> 
>> Hope that helps.
>> 
>> -B
>> 
>> 
>> Begin forwarded message:
>> 
>>> From: Bill Paxton <paxton at kitp.ucsb.edu>
>>> Date: June 18, 2014 1:34:23 PM PDT
>>> To: Manos Chatzopoulos <manolis at flash.uchicago.edu>
>>> Cc: mesa-users at lists.sourceforge.net
>>> Subject: Re: [mesa-users] New approx21 in MESA
>>> 
>>> 
>>> 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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