[mesa-users] bad angular_momentum_j

[Pablo Marchant]

Also, be sure you are getting your units right. That's an easy way to
create absurdly large jdots (been there). For the process you are
considering, what's the decay timescale for Jorb (ie. Jorb/Jdot)? If that
is absurdly tiny then I'd worry.

On Thu, Aug 4, 2016 at 4:50 AM, Pablo Marchant <pamarca at gmail.com> wrote:

> Kenny, I'd recommend you to manually adjust the timestep, this is
> something we discussed here in mesa-users a while ago, copy from Rob
> Farmer's answer to create a hard timestep limit
>
> (Untested)
>
> In extras_startup:
> s%xtra1=0.d0
>
> extras_finish_step:
> s%xtra1=s%log_R
>
> extras_check_model:
>
> if( abs( 10**s%xtra1_old - 10**s%log_R) > EPS) then
>     extras_check_model = retry
>     s% dt = s%dt * SOME_SCALE_FACTOR
> end if
>
> And to create a soft timestep limit:
>
> (also untested)
>
> if( abs( 10**s%xtra1_old - 10**s%log_R) > EPS) then
>     s% dt_next = min(s% dt_next, s%dt * SOME_SCALE_FACTOR)
> end if
>
> If the first timestep is the issue, then set a smaller initial timestep.
> Check this from defaults/star_job.defaults
>
>  435          !### set_initial_dt
>  436          !### years_for_initial_dt
>  437          !### seconds_for_initial_dt
>  438          ! if true, set initial timestep, dt, in years
>  439
>  440       set_initial_dt = .false.
>  441       years_for_initial_dt = 0
>  442       seconds_for_initial_dt = 0
>
> On Wed, Aug 3, 2016 at 4:56 PM, Kenny Van <kvan at ualberta.ca> wrote:
>
>> Hi,
>>
>> I'm currently working on adapting additional magnetic braking terms into
>> MESA using the run_binary_extras.f file. I'm currently running into an
>> issue where the amount of angular momentum being removed is too great in a
>> single timestep and causing the simulation to break. Looking at the code it
>> seems like the MESA binary evolution dies immediately if the angular
>> momentum loss is too great instead of retrying with a smaller timestep. Is
>> there a way to get MESA to retry with a smaller timestep when it encounters
>> this issue?
>>
>> Thanks
>>
>>
>> ------------------------------------------------------------------------------
>>
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>>
>>
>
>
> --
> Pablo Marchant Campos
> M.Sc on Astrophysics, Universidad Católica de Chile
> PhD student, Argelander-Institut für Astronomie
>



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