[Mesa-users] Angular momentum mixing error

[Pablo Marchant]

Hi Andriy,

can't say much about the correctness of the jdot term you're implementing,
but the source of your issues is solely because you are doing a very large
torque on a tiny amount of mass. You have a 1 Msun star for which you do a
do-loop to find the first convective cell starting from the surface, and
apply all your torque only on those outer layers. The model can't handle
this enormous change, as that outermost radiative region has miniscule
mass, ~10^-9 solar masses. Your runs with solid body rotation simply
overcome this by distributing all that extra angular momentum to the entire
star. Moreover, you don't have any mechanism for angular momentum transport
included (other than a uniform am_nu_rot when you use that).

The attached run_star_extras together with your inlists let me ran a model
all the way to TAMS. Note that I used 12778 instead. The only change I did
was to replace
k_end=j_cz
with
k_end=j_con
you use j_cz to store the inner edge of the very outermost radiative
region. You use j_con to store the bottom of the convective envelope. This
switch is enough to make things go through. If you mean to use j_cz, I'm
not sure your model is physically sound.

When doing these types of changes be sure to verify that the profile for
extra_jdot makes sense. You can include it as output for the profile files,
and that should help you identify issues like this one.

Cheers

On Wed, Jun 3, 2020 at 5:44 PM Razinkov, Andriy Vasylhovych (1313xxx) <
andriy.razinkov at edu.uni-graz.at> wrote:

> Hi Pablo
>
> Thank you for your answer and apologies for the faulty hook. I attach the
> corrected run_star_extras/inlist with the outdated hook removed.
>
> The wind driven angular momentum (jdot) is simplification based on the equation
> 10 of Kawaler (1988).
>
> Best regards
> Andriy​​
>
>
> ------------------------------
> *From:* Pablo Marchant <pamarca at gmail.com>
> *Sent:* Wednesday, June 3, 2020 1:53 PM
> *To:* Razinkov, Andriy Vasylhovych (1313xxx)
> *Cc:* mesa-users at lists.mesastar.org
> *Subject:* Re: [Mesa-users] Angular momentum mixing error
>
> Hi Andriy,
>
> I can't manage to compile your code, apparently because your
> run_star_extras includes
>
> s% other_am_mixing => my_mixing
>
> but there's no my_mixing subroutine. It would also be useful if you
> specify more clearly where the equations you use come from (specific
> references to equation numbers in papers are ideal). For instance, I can't
> find the source of this equation
>
> jdot = s% x_ctrl(3) * 1.1265d47 * s%omega(1) * s%omega(1) * s%omega(1)
>
> Cheers.
>
> On Tue, May 26, 2020 at 9:11 PM Razinkov, Andriy Vasylhovych (1313xxx) <
> andriy.razinkov at edu.uni-graz.at> wrote:
>
>> ​​Dear MESA community
>>
>> I am writing with a question regarding the implementation of rotation in
>> MESA (version 12115). I am trying to reproduce the spin-down of
>> main-sequence stars, following Gallet et al (2013).
>>
>> So far I have implemented a disk-locking phase and wind loss following
>> Kawaler (1988). The model can reproduce the spin down if solid body
>> rotation is assumed and starting from a 1Myr 1Mo model, with up to 10 times
>> the current solar rotation rate.
>>
>> However, when in this setup the star is allowed to rotate non-uniformly
>> using "set_uniform_am_nu_non_rot = .false.”, MESA stops with the error
>> message "failed in mixing angular momentum“.
>>
>> I would be grateful if someone could give me some suggestions on how to
>> better understand this error message and how solve this problem in my
>> models.
>>
>> For further reference, I attach the inlists and run_star_extra for my
>> project
>>
>> Best Regards
>> Andriy​
>> _______________________________________________
>> mesa-users at lists.mesastar.org
>> https://lists.mesastar.org/mailman/listinfo/mesa-users
>>
>>
>
> --
> Pablo Marchant Campos
> M.Sc on Astrophysics, Universidad Católica de Chile
> PhD on Astrophysics, Argelander-Institut für Astronomie, Universität Bonn
>


-- 
Pablo Marchant Campos
M.Sc on Astrophysics, Universidad Católica de Chile
PhD on Astrophysics, Argelander-Institut für Astronomie, Universität Bonn
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