Re: [mesa-users] calculate reaction flows

[Ian F. <ifo...@gm...>]

Hi,

Last year I spent quite a bit of time trying to find an intermediate sized
reaction net that would give simulations with accurate composition history
especially for stars 8Msun's and above. That meant trying to identify
isotopes and reactions that had the biggest impact. Part of the problem I
found (excluding my general lack of understanding) was that different
isotopes and reactions varied in importance at different temperatures and
compositions. Especially for stars that go through huge temperature changes
and densities, unless you have precise knowledge about the reaction, it
would be near impossible to isolate those that mattered. In some runs, even
including or omitting one reaction could make huge differences with the
effect only emerging at a specific temperature. On top of that our
knowledge of reaction rates still needs much research, so there can be
quite large differences in simulations depending on the rates chosen.

For now, I have resigned to just specifying the isotopes and let Mesa
identify all the reactions for larger stars otherwise my simulations can
produce unreliable results. For smaller stars however, the simpler reaction
nets supplied with mesa work pretty well because the temperature range and
density change is far less. Thus for the 1M pre_ms_to wd test suite
example, I was able to show that the o18_and_ne22 net (which has key
isotopes up to mg24) produced a result very similar to a net which had all
the reactions in a net with most of the isotopes up to mg24.

kind regards
ian

On 15 March 2017 at 15:43, Robert Farmer <rjf...@as...> wrote:

> Hi
>
> There is no direct way to do this, to work out the important reactions you
> could look at the abundances as well as adding
> add_reaction_categories to your profile columns to get a summary of the
> energy per reaction category (for example burn_fe shows the total energy
> from all fe based reactions)
>
> You could also look in the net/test code which does 1-zone burns which
> might be easier to get the flow rates and the individual forward/reverse
> rates
>
> Rob
>
> On Tue, Mar 14, 2017 at 8:20 PM, ertaoLee <ert...@gm...> wrote:
>
>> Dear MESA users,
>>
>> I am trying to find out which reactions are more important than others.
>> So, I need to calculate the reaction forward and reverse flows for each
>> reaction and draw a flow diagram.
>>
>> How do I do that?
>>
>> Thanks in advance for any help that you can offer!
>>
>>
>> ------------------------------
>> Er-Tao Li(李二涛)
>> Institute of Nuclear Technology，College of Physics & Energy, Shenzhen
>> University
>> Nanhai Ave 3688, Shenzhen, Guangdong, P.R.China, 518060
>> Tel: 86-755-26536232. Fax: 86-755-26534374
>>
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