[Mesa-users] Questions about (step)Overshooting

[Matheus Bernini]

Hi Nathan,

It makes sense... Let me see if I understood correctly: The exponential
function of the overshooting begin to decay at the f0, and the f gives how
fast this decay happens. Thus, when the starting point of the decay, f0,
begin more inward (e.g. 0.035), the function will have a smaller value at
some point out of the convection region than if f0 were closer to the
border (e.g. 0.030).

1) Sorry, in the inslists I sent the exponential overshooting were disabled
(because I'd run without exponential later), but when I ran they were
active for both cases (0.135-0.035 and 0.130-0.030).
2) Yes, the f0 for all elements core/shell have the same values

I guess it helped, Thanks!


Em sex, 28 de set de 2018 às 10:17, Nathan Grin <nathgrin at gmail.com>
escreveu:

> Hi Matheus,
>
> Indeed, for step overshooting, f0 is just a trick
> my guess is that the differences you see are due to applying exponential
> on the h/he shells during post-core-H phases, for exp overshooting f0 does
> make a difference
>
> what i don't understand is:
> in the current inlists, you are applying step overshooting to the h/he
> shells, not exponential (but i guess you change em for each run?), do you
> also see differences when only applying step?
> are you changing all the f0s simultaneously? i.e. f0_above_burn_h_core ==
> f0_above_burn_h_shell ==  f0_above_burn_he_core == f0_above_burn_he_shell
>
> hope this helps,
> cheers,
> nathan
>
>
> On Fri, 28 Sep 2018 at 01:40, Matheus Bernini via Mesa-users <
> mesa-users at lists.mesastar.org> wrote:
>
>> Hello,
>>
>> I'm an undergraduate student and I'm studying evolution of massive stars
>> using MESA.
>>
>> I was "playing around" with step overshooting initial values (
>> overshoot_f0_...) for hydrogen helium and nonburn core/shell and I noticed
>> that slightly changes on f0 (but always keeping f - f0 = 0.1) caused great
>> changes on the post-MS phases [figure].
>>
>>
>>     overshoot_f0_above_burn_h_core = 0.035
>>     step_overshoot_f_above_burn_h_core = 0.135
>>
>> vs.
>>
>>     overshoot_f0_above_burn_h_core = 0.030
>>     step_overshoot_f_above_burn_h_core = 0.130
>>
>> *For completeness, there was also an exponential overshooting on all of
>> the models of 0.001 on helium and hydrogen core/shell
>>
>> If I understood correctly, the f0 is the starting point for the overshoot
>> inward the region (core or shell) because the mixing coefficient is 0 on
>> the edge of the region, not allowing the computations to happen. So, if f0
>> is just a "trick" to allow the computation of the overshoot, why changing
>> it a little causes important changes on the evolution?
>>
>> Thanks :)
>>
>> -----------------------------------------------------------------
>> *Matheus Bernini Peron*
>>
>>
>> * Undergraduate student Observatório do Valongo,Universidade Federal do
>> Rio de Janeiro*
>>
>>
>>
>> *Ladeira do Pedro Antônio, 43 - SaúdeRio de Janeiro - RJ - CEP
>> 20080-090Brasil*
>> ___________________________________________________________
>> Evolution 32Msun, no rotation, Z_init = 0.014, Y_init = 0.266
>> red: 0.135 - 0.035
>> blue: 0.130 - 0.030
>> gray: GENEC (Ekstrom+2012)
>> [image: image.png]
>> _______________________________________________
>> mesa-users at lists.mesastar.org
>> https://lists.mesastar.org/mailman/listinfo/mesa-users
>>
>>
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