[Mesa-users] resolution issues

Sun Aug 5 02:22:29 EDT 2018

please cc mesa-users on replies so that everyone may potentially benefit.

there are several types of processes that mix chemical elements,
convection being but one, angular momentum being another. you may
want to peruse the mesa instrument papers.

a test suite inlist is a good place to start a convergence study, 
but it is sometimes/often only the beginning. in order to draw
valid conclusions, convergence studies need care and an understanding 
of the model to be sure apples are being compared to apples. 

attached are 1) minimalist modifications of your inlist to better 
ensure an apples to apples comparison and 2) a plot showing chi-by-eye 
convergence of the radius with time when angular momentum mixing is active.
best wishes on carrying your project forward!

fxt

> On Aug 3, 2018, at 11:15 AM, Forrest Bullard <fbullard at mail.csuchico.edu> wrote:
> 
> I was under the impression that these controls are what turn on mixing,
> 
>       am_nu_visc_factor = 0
>       am_D_mix_factor = 0.0333333333333333d0
>       D_DSI_factor = 0
>       D_SH_factor = 1
>       D_SSI_factor = 1
>       D_ES_factor = 1
>       D_GSF_factor = 1
>       D_ST_factor = 1
> 
> and that these controls affected the wind scheme.
> 
>       cool_wind_full_on_T = 9.99d9
>       hot_wind_full_on_T = 1d10 
>       cool_wind_RGB_scheme = 'Reimers'
>       cool_wind_AGB_scheme = 'Blocker'
>       RGB_to_AGB_wind_switch = 1d-4
>       Reimers_scaling_factor = 0.7d0  
>       Blocker_scaling_factor = 0.7d0  
> 
> Though it is good to know that some amount of mixing is always on. Perhaps drastic is not the most appropriate word to use in this case as I am mostly concerned with the fact that I am not seeing convergence with higher temporal resolution when those specified mixing factors are turned on, and in fact I don't seem to be getting convergence with higher spacial resolutions either. My biggest concern is that I am some how messing up the numerics by altering the resolutions, and was also wondering if for some reason spacial and temporal resolutions needed to be altered in unison. My final study will be an attempt to understand chaos in the stellar evolution model and I would like for this chaos to come as much from the equations and as little from my inappropriate choice of controls as possible. I chose these specific controls because they were in the star defaults pre main sequence to white dwarf model and I was hoping they would be appropriate for my study but perhaps it is best if I just leave the control defaults as they are.
> 
> Again any insight is great and if I can clarify anything further as to what I am attempting to do feel free to ask.
> 
> Thank you,
> Forrest Bullard
> 
> On Fri, Aug 3, 2018 at 2:47 AM, Francis Timmes <fxt44 at mac.com> wrote:
> i applaud your testing of convergence in mesa models.
> with var_control this is a temporal convergence study,
> which is distinct from but related to a mass/spatial 
> resolution exploration. 
> 
> > I only get such a drastic difference when I have mixing on.
> 
> i'm unsure what is meant here on several fronts. do the differences 
> refer to the evolutionary age or radius in your plots? why are the 
> differences considered "drastic"? mixing of chemical elements, 
> in a broad sense, is always on. does "mixing" refer to the 
> D_omega_flag, convective_bdy_weight or something else in the inlist?
> 
> fxt
> 
> 
> 
> 
> > On Aug 2, 2018, at 10:47 AM, Forrest Bullard via Mesa-users <mesa-users at lists.mesastar.org> wrote:
> > 
> > Hello everyone,
> > 
> > I am currently trying to do a resolution study for some summer research that I am doing and I seem to be having a slight issue with varcontrol_target and was wondering if someone might be able to provide some insight. I seem to be getting sizeable difference in the time it takes to reach the end of main sequence when I turn up the resolution on this control. I have ran this control at 1d-3, 1d-4, and 5d-5 and have notice that I only get such a drastic difference when I have mixing on.
> > 
> > I was wondering if perhaps I am not running at a high enough resolution to see convergence yet or if there is anything else I should be thinking about? I have provided some graphs of the data I collected, one with mixing on and winds on and one without, and the inlist I am using for these parameters on the later is the same just with these controls commented out.
> > 
> > Thank you,
> > Forrest Bullard
> > <time_resolution.png><time_resolution_(mixing_on,_winds_on).png><inlist_1.0>_______________________________________________
> > mesa-users at lists.mesastar.org
> > https://lists.mesastar.org/mailman/listinfo/mesa-users

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