[mesa-users] bad angular_momentum_j

[Pablo Marchant]

You should be able to do that in extras_binary_startup. Anyhow, I'd just go
for the simple approach of setting a small initial timestep, if its too
small it will grow quite fast.

On Fri, Aug 5, 2016 at 3:36 AM, Kenny Van <kvan at ualberta.ca> wrote:

> Yes, but I was also hoping to create an adaptive way for MESA to adjust
> the first step if necessary
>
> On 4 August 2016 at 17:00, Pablo Marchant <pamarca at gmail.com> wrote:
>
>> Are you running into these issues at the first timestep? If so, you need
>> to ensure the first step is small as well.
>>
>> On Thu, Aug 4, 2016 at 11:02 PM, Kenny Van <kvan at ualberta.ca> wrote:
>>
>>> Hi Everyone,
>>>
>>> So I've checked the units for Jdot and they seem fine, Jorb/Jdot is on
>>> the order of 1e12. The issue I'm currently running into is that the code
>>> doesn't quite seem to be doing what I think it should be doing.
>>> For extra checks I also included:
>>>
>>>          write(*,*) "starting modified MB"
>>>          if (b% angular_momentum_j <= 0) then
>>>             write(*,*), "angular_momentum_j <= 0", b% angular_momentum_j
>>>             b% s1% dt_next = min(b% s1% dt * 0.50, b% s1% dt_next)
>>>             extras_binary_startup = retry
>>>          end if
>>>
>>> to extra_binary_startup. Just to check if my initial timestep is
>>> sufficiently small and the MESA code doesn't seem to be triggering this. I
>>> have a similar portion of code in extras_binary_check_model,
>>> but I haven't reached a point where the simulation breaks to determine
>>> if this works or not. Does the file binary_evolve.f90 trigger and instantly
>>> kill the MESA simulation before the code checks the
>>> run_binary_extras.f file?
>>>
>>>
>>>
>>> On 3 August 2016 at 21:25, Kenny Van <kvan at ualberta.ca> wrote:
>>>
>>>> Hey Pablo,
>>>>
>>>> Thanks for the advice, I'll try out the time step adjustment to see how
>>>> it goes. I'll also double check the units to be 100% sure that I haven't
>>>> crated any jdots that are a few orders too big.
>>>>
>>>>
>>>> On 3 August 2016 at 20:53, Pablo Marchant <pamarca at gmail.com> wrote:
>>>>
>>>>> 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
>>>>>>>
>>>>>>> ------------------------------------------------------------
>>>>>>> ------------------
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> mesa-users mailing list
>>>>>>> mesa-users at lists.sourceforge.net
>>>>>>> https://lists.sourceforge.net/lists/listinfo/mesa-users
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> 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
>>>>>
>>>>
>>>>
>>>
>>
>>
>> --
>> 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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