[Mesa-users] Time step problems

[Shunyi Lan]

Dear Ebraheem:

Thanks for your reply.

The attachments are some selected profiles during the evolution. It should be noticed that this star is currently in a binary system and losing mass while the outer region is heated. The single star energy injection also tested, the timestep is also very small.

BTW, the " heat = " is not a typo, just indicate the heat is a free parameter.

Best regards,

Shunyi Lan

Sorry for not sending to the main thread. Please forgive me for my first MESA community inquiry.





-----原始邮件-----
发件人:"Ebraheem Farag" <ekfarag at asu.edu>
发送时间:2023-04-10 11:43:55 (星期一)
收件人: "兰顺义" <lanshunyi at ynao.ac.cn>
抄送: mesa-users at lists.mesastar.org
主题: Re: [Mesa-users] Time step problems


Hello 兰顺义,


Could you try making a plot of rho(k) vs T(k)?
also, " heat = " - Is this a typo?


-EbF 


On Sun, Apr 9, 2023 at 8:14 PM 兰顺义 <lanshunyi at ynao.ac.cn> wrote:


Dear MESA users and developers:




I'm using extra_energy hook to inject energy to stars. My MESA version is 10398. What I am encountering is, when the star is low mass star (0.5 Msun MS star, for example) and heating is relatively strong,(for example 10 times of luminosity of star) the time step will be very small. I tried to use control force_timestep_min_years to increase the timestep, e.g. 1d3 years, but it still can lower than this limit.

So my question is: how can I increase the timestep while securing the convergence at the same time? And how the exactly the force_timestep_min_years works?

Follow is part of my extra hook. All the variable have stated in right type and the hook works well (at least for other cases, e.g. inermediate mass MS stars, RG, etc.)

*****************************************

 heat = 

start = 0
s% extra_heat(:) = 0
tau_0 = 0.99
do k = 1, s% nz
if(s% tau(k)>tau_0) then
layer_max = k
exit
end if
end do

do k = 1, layer_max
      heat_current = heat*(s% tau(k+1) - s% tau(k) + &
      exp(-1.0*s% tau(k+1))-exp(-1.0*s% tau(k)))/ &
      (s% tau(layer_max)-1+exp(-1.0*s% tau(layer_max)))
      s% extra_heat(k) = heat_current/s% dm(k)
end do
*****************************************

Any suggestion would be very helpful!







Best regards,

Shunyi Lan

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