[mesa-users] Diffusion coefficient

[Masanobu Kunitomo]

Dear Bill,

Thank you very much for the prompt and kind reply and I am sorry for the late reply. I understand that D in the profile data is NOT multiplied by mix_factor. I have finally succeeded in the plot of D*mix_factor.

Thank you very much for your help!

Cheers,
Masanobu





> On Jun 20, 2015, at 01:42, Bill Paxton <paxton at kitp.ucsb.edu> wrote:
> 
> Hi Masanobu,
> 
> 
> On Jun 18, 2015, at 11:20 PM, Masanobu Kunitomo wrote:
> 
>> Dear Pablo,
>> 
>> Thanks for the prompt comments. 
>>> If you only have convection I can imagine not much happens unless you use a much stronger reduction, as convection is extremely fast.
>>> 
>> 
>> I am sorry for the insufficient explanation. I am focusing on fully-convective stars and I want to change the diffusion coefficient in the convective region which is determined by mlt as D = conv_vel*Lambda/3.
>> 
>> 
>> I know the mix_factor can handle the artificially decreased diffusion, but I found that in the output files “profile##.data”, "log_D_mix" or “log_mlt_D_mix” do not change even if mix_factor is decreased by a factor of 1d6.
> 
> The profile data is for the "normal" value of D without the mix_factor.
> 
>> Thus, I would like to know (1) how to change the diffusion coefficient in the mlt subroutine (in mlt.f). 
> 
> You can use the "hook" other_mlt to first call the standard MLT routine and then modify the results as desired before they are returned to the caller in star.
> 
>> If it is not possible, I would like to know (2) how the mix_factor works.
> 
> The mix_factor is applied in subroutine get_convection_sigmas in star/private/mix_info.f90 --
> the lagrangian diffusion coefficient sigma(k) at cell boundary k is set to mix_factor*D*(4*pi*r(k)^2*rho_face(k))^2
> Note that the value of D is not changed -- it is just used as a term in calculating sigma.
> 
> Good luck,
> Bill
> 
> 
> 
> 
> 
>> 
>> Cheers,
>> Masanobu
>> 
>> 
>> 
>>> On Jun 18, 2015, at 23:33, Pablo Marchant <pamarca at gmail.com <mailto:pamarca at gmail.com>> wrote:
>>> 
>>> You should just set mix_factor = 1d-2 in your inlist. If you only have convection I can imagine not much happens unless you use a much stronger reduction, as convection is extremely fast.
>>> 
>>> Am 18.06.2015 4:28 nachm. schrieb "Masanobu Kunitomo" <kunitomo.masanobu at c.mbox.nagoya-u.ac.jp <mailto:kunitomo.masanobu at c.mbox.nagoya-u.ac.jp>>:
>>> Dear all,
>>> 
>>> I am trying a test with the artificially decreased diffusion coefficient. Although I know it is possible with the “mix_factor” in controls, I did not understand how this works.
>>> 
>>> Instead of “mix_factor”, I tried a test with the modified “mlt.f” in the directory mesa/mlt/private. In the case of 100 times decreased diffusion coefficient, I multiplied a factor of 1d-2 as below:
>>> 	D = conv_vel*Lambda/3  *1d-2
>>> However, the calculated evolution was not changed.
>>> 
>>> Thus, today I would like to ask (1) whether it is possible to artificially change the diffusion coefficient in the file “mlt.f" or not and (2) how “mix_factor” works.
>>> 
>>> I am using version 6596 and I attached my mlt.f. Rotation has not been considered in our calculation. Thanks in advance for your any help!
>>> 
>>> Sincerely,
>>> Masanobu Kunitomo
>>> 
>>> --
>>> Masanobu Kunitomo, Ph.D.
>>> Laboratory for Theoretical Astronomy & Astrophysics (TA-Lab)
>>> Department of Physics, Nagoya University
>>> Furo-cho, Chikusa-ku, Nagoya, Aichi, Japan 464-8602
>>> Email: kunitomo.masanobu at c.mbox.nagoya-u.ac.jp <mailto:kunitomo.masanobu at c.mbox.nagoya-u.ac.jp>
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
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