[Mesa-users] Equivalents to use_zero_dLdm_outer_BC in newer MESA releases

[Benjamin Herfray]

Hi Ebraheem,

Thank you for your help. If I understand correctly, the use_other_surface_PT hook requires us to impose a fixed outer temperature and pressure boundary condition, which in my specific case I do not want to do. Though please correct me if I am wrong and there is a way to implement the hook without fixing T and p. If not, do you know if this can be achieved with any other hooks that allow for more freedom---i.e. , not requiring us to fix T and p?

Thanks,
Benjamin
________________________________
From: Ebraheem Farag <ekfarag at asu.edu>
Sent: Tuesday, 9 July 2024 17:17
To: Benjamin Herfray <benjamin.herfray at mail.mcgill.ca>
Cc: mesa-users at lists.mesastar.org <mesa-users at lists.mesastar.org>
Subject: Re: [Mesa-users] Equivalents to use_zero_dLdm_outer_BC in newer MESA releases

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Hi Benjamin,

This boundary condition was probably removed during some pruning (from r15140 -> r21.12.1, one of the biggest internal clean ups of the code base since its inception) as it was not being used. You can probably reimplement it using a use_other_surface_PT hook in the run_star_extras.f90 similar to how the boundary conditions on the conductive flame test suite are implemented, see https://docs.mesastar.org/en/release-r24.03.1/test_suite/conductive_flame.html.

You just need to look into "./private/hydro_eqns.f90" in r15140, find "subroutine set_zero_dL_dm_BC" and paste it into your use_other_surface_PT hook in the run_star_extras.f90 and tweak accordingly.

I hope this helps. If you feel this outer boundary condition is important and should be reimplemented into the code base as a default option, I suggest opening an issue thread on the MESA github https://github.com/MESAHub/mesa/issues to make your case :).

-EbF

On Tue, Jul 9, 2024 at 9:34 AM Benjamin Herfray via Mesa-users <mesa-users at lists.mesastar.org<mailto:mesa-users at lists.mesastar.org>> wrote:
Hello MESA users,

I've been trying to run simulations of stellar winds during type-I X-ray bursts using version r24.03.1. In order to try to counter problems with density inversions developing near the outer layers of the atmosphere I would like to impose boundary conditions on the luminosity—specifically, I would like to impose dL/dm = 0 at the outer boundary.​ This is similar to the methods described in Yu & Weinberg, 2018 (https://doi.org/10.3847/1538-4357/aad045<https://urldefense.com/v3/__https://doi.org/10.3847/1538-4357/aad045__;!!IKRxdwAv5BmarQ!bk6TKa_fsuOzH32gDnHkWkhQLjQmM6bCZbZybr_JO604FPuhKJvQSzGk7VrTAHXCwIi75agxEARks4mV3G_dXHZLO6M0iw$>) and Guichandut & Cumming, 2021 (https://doi.org/10.3847/1538-4357/ace43c<https://urldefense.com/v3/__https://doi.org/10.3847/1538-4357/ace43c__;!!IKRxdwAv5BmarQ!bk6TKa_fsuOzH32gDnHkWkhQLjQmM6bCZbZybr_JO604FPuhKJvQSzGk7VrTAHXCwIi75agxEARks4mV3G_dXHaJQJjRnA$>) who used older versions of MESA.

Older versions of MESA (I believe up to r15140) have the control use_zero_dLdm_outer_BC to impose L(1) = L(2), however this was removed in subsequent versions with no explanation of the change in the changelog.

Does anyone know why this was removed, and is there a combination of controls present in the current version of MESA that I can use to have the equivalent effect as use_zero_dLdm_outer_BC? Or would I have to implement this as a custom condition through run_star_extras?

Thank you,
Benjamin Herfray
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