[Mesa-users] Relaxing angle-averaged model from hydro simulation

Pablo Marchant pamarca at gmail.com
Tue Feb 6 18:16:24 EST 2018

Hi Manos,

can you share your terminal output to get an idea?

we are doing some work to stabilize the relax routines, can't give you an
ETA on that though. In particular with rotation I found that the current
implementation of the calculation of FP and FT (the correction factors to
the pressure and temperature equations) can experience some large changes
which make convergence hard.

I have some unfinished work now trying to integrate these factors for the
case of a point mass Roche potential. This is a good approximation for most
stellar purposes, and it allows constructing a simple fit to the integrated
values rather than having to recompute it in MESA. Attached is a simple
example of this implementation, it's mostly using a couple of by-eye-fits I
made (see the attached plot showing the factors as a function of the volume
equivalent radius). Can you try this out and see if it improves things at
all? Goes in star/private/. Not promising anything though.

Another option is to increase the steps for relaxation, for instance:

  num_steps_to_relax_composition = 300

in star_job


On Tue, Feb 6, 2018 at 4:23 PM, Manos Chatzopoulos <
chatzopoulos at phys.lsu.edu> wrote:

> Dear mesa-users,
> We are using our 3D hydro code (OctoTiger) to simulate the stellar merger
> of an 1Msun star within the envelope of a larger (~14 Msun) star. We then
> extract the angle-averaged data in the format required by the MESA (v.
> 10108) relaxation routines (as set in the relax_composition_j_entropy
> test_suite setup and described in the star/defaults/star_job.defaults). I
> attach plots of our entropy_new.dat, angular_momentum_new.dat and
> composition_new.dat inputs showing the models we import into MESA starting
> with the inlist_relax_composition_j_entropy (attached). I also attach
> *png plots showing comparison between these profiles (only for H/He in
> composition) and the original profiles used in the test_suite problem. As
> you can see we are setting the mass of the desired relaxed model equal to
> the mass coming out from our simulation.
> We are having issues getting a converged/relaxed model, especially when we
> turn on relaxation for the angular momentum profile (Which we need,
> ultimately). Any help/input would be greatly appreciated on how to move
> forward.
> Best regards,
> --
> Dr. Manos Chatzopoulos
> Assistant Professor
> Department of Physics & Astronomy
> Louisiana State University
> Nicholson #275
> Office # 225-578-2907
> Baton Rouge, LA 70803
> United States of America
> http://www.lsu.edu/physics/people/faculty/chatzopoulos.php
> _______________________________________________
> mesa-users at lists.mesastar.org
> https://lists.mesastar.org/mailman/listinfo/mesa-users

Pablo Marchant Campos
M.Sc on Astrophysics, Universidad Católica de Chile
PhD on Astrophysics, Argelander-Institut für Astronomie, Universität Bonn
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