[Mesa-users] Does it need to consider convection when relaxing entropy?

[Rob Farmer]

Hi,
>At the end of the relaxing composition, the age_yr is increased to 4d47
yrs. Is this reasonable?

Are you sure the relaxation process completed successfully? It sounds like
the model did not successfully finish the entropy relax process leaving the
star in an inconsistent state.

You could run your model as

./rn | tee run.log

to save the terminal output to look back and see if things finish properly.

>And during relaxing entropy, the luminosity profile appeared strange so I
try to figout why.

That is not enough information, what is strange about it? Show a plot.
Though in general you should only worry if the luminosity profile looking
"strange" after the entropy relaxation process has finished, not during the
relax process.

>This seems to be inconsistent with the description of relax entropy in the
mesa document (maybe my understanding is wrong).

Nothing in appendix B of paxton+ 2018 suggests a star can not be convective
to relax the entropy, the only requirement is model should be in
hydrostatic equilibrium. But it is also always useful to explicitly point
to where you read something (certain file, published paper etc) so we can
see if it is a misunderstanding or an out of date document.

> I found when mixing_length_alpha = 0.0 or min_T_for_acceleration_limited_conv_velocity
= 0d0 is set in the inlist, these strange place in the luminosity profile
disappears.

Again there is not enough information to identify what "strange place in
the luminosity profile" even is. Show a plot.

Rob


On Thu, 3 Sep 2020 at 09:52, 曾耀田 <zengyaotian at ynao.ac.cn> wrote:

> Dear all,
>
>     I‘m trying to import a 3D He star model which was obtained from an SPH
> simulation into MESA. Like said in the MESA IV paper (Appendix B), I'm
> trying to use the relaxation process to achieve this purpose. I'm using the
> latest version of MESA (r12778). When relaxing composition I found it can
> work only num_steps_to_relax_composition = 500 . At the end of the relaxing
> composition, the age_yr is increased to 4d47 yrs. Is this reasonable? And
> during relaxing entropy, the luminosity profile appeared strange so I try
> to figout why.  I found when mixing_length_alpha = 0.0 or min_T_for_acceleration_limited_conv_velocity
> = 0d0 is set in the inlist, these strange place in the luminosity profile
> disappears. it seems the convection exists during the relaxing entropy.
> This seems to be inconsistent with the description of relax entropy in the
> mesa document (maybe my understanding is wrong). So now, I’m not sure
> whether or not the convection should be considered during relaxing entropy.
> Is there anyone who can help?
>
>
> With best wishes,
>
> Yaotian Zeng
>
>
> The  inlist I used is shown below.
>
>
> ! inlist_relax
>
> &star_job
>
>
>     set_initial_dt = .true.
>     years_for_initial_dt = 1d-4
>
>
>     show_log_description_at_start = .true.
>     show_net_species_info = .true.
>
>     set_initial_cumulative_energy_error = .true.
>     new_cumulative_energy_error = 0d0
>
>
>     ! Relaxes composition
>     relax_initial_composition = .true.
>     num_steps_to_relax_composition = 500
>     relax_composition_filename = "composition.dat"
>
>     relax_initial_entropy = .true.
>     max_steps_to_relax_entropy = 1000
>     timescale_for_relax_entropy = 1d-9 ! in years
>     max_dt_for_relax_entropy = 1d-9 ! in years
>     num_timescales_for_relax_entropy = 300
>     relax_entropy_filename = "entropy.dat"
>     get_entropy_for_relax_from_eos = 'eosDE'
>
>
>     save_model_when_terminate = .true.
>     save_model_filename = 'relaxed.mod'
>
>
>     save_pgstar_files_when_terminate = .true.
>     pgstar_flag = .true.
>
>
> / ! end of star_job namelist
>
>
> &controls
>
>     !min_T_for_acceleration_limited_conv_velocity = 0d0
>
>     initial_mass = 1.232d0
>
>     !use_ledoux_criterion = .true.
>     !mixing_length_alpha = 1.8
>     !mixing_length_alpha = 0.0
>
>     max_num_profile_models = 10
>     profile_interval = 1
>     history_interval = 1
>     terminal_interval = 1
>     write_header_frequency = 1
>
>
>   ! stop when the center mass fraction of h1 drops below this limit
>     ! max_age = 1d1
>     xa_central_lower_limit_species(1) = 'he4'
>     xa_central_lower_limit(1) = 1d-4
>
>
> / ! end of controls namelist
>
>
> &pgstar
>
>
>
> / ! end of pgstar namelist
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.mesastar.org/pipermail/mesa-users/attachments/20200903/0b48b369/attachment.htm>