[mesa-users] Core resolution: non-convergent behavior increasing mesh_delta_coeff

[Francis Timmes]

i’ll take this one offline and let you report back to the community when its resolved.

fxt


> On Jul 24, 2015, at 3:27 AM, Mathieu <mathren90 at gmail.com> wrote:
> 
> Hi everyone,
> 
> I am trying to run models of massive stars (15 <= M_zams/Msun <= 30) until oxygen depletion (X(o16)<0.04 in the center), but I am finding a problem with the spatial resolution (mesh gridding) of the inner regions, especially during and after neon burning. The problem is illustrated in the attached plots.
> 
> I compare 30 solar mass models computed starting on the ZAMS with the mesa_45.net nuclear reaction network. All models have the same physical settings (see attached inlists and run_star_extras.f), except for my varying mesh_delta_coeff. 
> 
> Increasing the mesh_delta_coeff produces qualitatively and quantitatively different tracks on the (central density,central temperature)-plane, and significantly different masses of the various (He, C/O) cores (see attached plots). The  number of cells at the end of each computation shown in the attached plots is, respectively:
>                      
>                             mesh_delta_coeff = 1     =>  nz = 31096
>                             mesh_delta_coeff = 0.5  =>  nz = 65763
>                             mesh_delta_coeff = 0.2  =>  nz = 142096
> 
> I also ran tests without my "customized" mass loss, mesh refinements and timestep controls, and different initial masses, both with the MESA release 6794 and 7624, and I have found that the discrepancies were worse than or comparable to what I am showing here. 
> Using my timestep controls (in the routine extras_finish_step) and mesh refinements (other_mesh_fcns_data) improves the behavior, but only up to neon burning. 
> 
> I have uploaded here  <http://www.tapir.caltech.edu/%7Emathren90/materials/MWE.tar.gz>a minimal working example with models and photos to restart the runs with mesh_delta_coeff=1 and mesh_delta_coeff=0.5, ready to be compiled and run (with the release 7624).
> 
> This non-convergent behavior when changing the resolution makes a detailed study of the core structure in late stages very questionable, and I would be grateful if you could help me constrain the mesh intelligently, so that the core structure does not depend so sensitively on the spatial resolution (provided that enough cells are used, of course).
> 
> Thanks,
> 
> Mathieu
> 
> 
> <30Msun_rhoc_Tc.png><run_star_extras.f><30Msun_ab_profiles_at_O_depl.png><inlist.txt><inlist_massive_defaults.txt><inlist_project.txt>------------------------------------------------------------------------------
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