[Mesa-users] Doubt on overshoot parameters

[anne.thoul at uliege.be]

Dear Pedro,


Your last example is the right way to do it.

>>     overshoot_f_above_burn_h_core = 0.018
>>     overshoot_f_above_burn_h_shell = 0.018
>>     overshoot_f_below_nonburn_shell = 0.018
>> 
>>     overshoot_f0_above_burn_h_core = 0.001
>>     overshoot_f0_above_burn_h_shell = 0.001
>>     overshoot_f0_below_nonburn_shell = 0.001

In case of doubt, you can always look at the examples in the test_suite. 
For example the inlist of the case « inlist_7M_prems_to_AGB"  has the following setup for overshooting to cover all situations:

      overshoot_f_above_nonburn_core = 0.014
      overshoot_f_above_nonburn_shell = 0.014
      overshoot_f_below_nonburn_shell = 0.014
      overshoot_f_above_burn_h_core = 0.014
      overshoot_f_above_burn_h_shell = 0.014
      overshoot_f_below_burn_h_shell = 0.014
      overshoot_f_above_burn_he_core = 0.014
      overshoot_f_above_burn_he_shell = 0.014
      overshoot_f_below_burn_he_shell = 0.014
      overshoot_f_above_burn_z_core = 0.014
      overshoot_f_above_burn_z_shell = 0.014
      overshoot_f_below_burn_z_shell = 0.014

      overshoot_f0_above_nonburn_core = 0.004
      overshoot_f0_above_nonburn_shell = 0.004
      overshoot_f0_below_nonburn_shell = 0.004
      overshoot_f0_above_burn_h_core = 0.004
      overshoot_f0_above_burn_h_shell = 0.004
      overshoot_f0_below_burn_h_shell = 0.004
      overshoot_f0_above_burn_he_core = 0.004
      overshoot_f0_above_burn_he_shell = 0.004
      overshoot_f0_below_burn_he_shell = 0.004
      overshoot_f0_above_burn_z_core = 0.004
      overshoot_f0_above_burn_z_shell = 0.004
      overshoot_f0_below_burn_z_shell = 0.004

Cheers

Anne



> Le 9 déc. 2018 à 14:04, Pedro Nuno David Gomes via Mesa-users <mesa-users at lists.mesastar.org> a écrit :
> 
> Dear MESA users,
> 
> I have a doubt on the overshoot parameters I was hoping you could help me clarify. I'm sure this is a very simple doubt, but I can't wrap my head around it.
> 
> I have an inlist of a previous MESA release (release 7456) with the following controls regarding the overshooting,
> 
>     overshoot_f_below_nonburn = 0.018
>     overshoot_f_above_burn_h = 0.018
>     overshoot_f_above_burn_he = 0.018
> 
> From what I understood, using these controls one establishes that overshoot occurs at a distance 0.018*H from the boundaries of convective regions, with H being the scale height. Right?
> 
> Now, I was trying to run the same controls in the latest MESA release but I got an error: "Fortran runtime error: Cannot match namelist object name overshoot_f_below_nonburn".
> 
> So, the previous controls changed with posterior releases. I'm having some doubts understanding how to implement these controls in the current release. At first I simply thought about replacing them directly with (what I think are) the updated controls,
> 
>     overshoot_f_above_burn_h_core = 0.018
>     overshoot_f_above_burn_h_shell = 0.018
>     overshoot_f_below_nonburn_shell = 0.018
> 
> (I'm not considering helium burning regions because I'm only interested in analysing the lower Red Giant Branch). But when I run MESA I get an error: "ERROR: when using overshooting above, must set f0_above > 0".
> 
> From what I read on the controls defaults, namely
> 
>     "The switch from convective mixing to overshooting happens at a distance f0*Hp into the convection zone
>     (...) where Hp is the pressure scale height at that location.",
> 
> I also have to define f0. So, given this explanation, what I thought I had to do was replace f with f0,
> 
>     overshoot_f0_above_burn_h_core = 0.018
>     overshoot_f0_above_burn_h_shell = 0.018
>     overshoot_f0_below_nonburn_shell = 0.018
> 
> And in this case MESA runs. However, I'm not sure if this is the way - from what I read after, namely
> 
>      "for example, if you want overshooting of 0.2 scale heights beyond the normal edge, you might want
>       to back up 0.05 scale heights to get the diffusion coeff from near the edge and then go out by 0.25
>       scale heights from there to reach 0.2 Hp beyond the old boundary. In the inlist this would mean setting
>       the “f0” to 0.05 and the “f” to 0.25."
> 
> I have to define in the inlist controls with f and f0 simultaneoulsy; so, from my understanding, this would mean writting, for instance,
> 
>     overshoot_f_above_burn_h_core = 0.018
>     overshoot_f_above_burn_h_shell = 0.018
>     overshoot_f_below_nonburn_shell = 0.018
> 
>     overshoot_f0_above_burn_h_core = 0.001
>     overshoot_f0_above_burn_h_shell = 0.001
>     overshoot_f0_below_nonburn_shell = 0.001
> 
> Is any of these the right way, or am I missing something? If this is the case, could you help me understand how to replace the previous controls with these values?
> 
> Thank you for your attention. Regards,
> 
> Pedro
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