[Mesa-users] AGB convergence issue

[Champagne, Arthur E]

Hi all,
     I’m fairly new to MESA - I’m running r10108 and various test models run fine. I’ve constructed a 5 M_sun, Z=1e-4 model, which evolves in a reasonable way to the start of the AGB. The first 2 pulses look good, but it bogs down on the 3rd pulse, which occurs after the He shall narrows. The problem is “hydro_newton_step failed to accept” and debugging indicates that the problem is occurring in the zones that include the edges of the He shell. No surprise. I’ve tried various approaches to improving resolution and convergence, without success. These have come from the inlists on the web page as well as the agb and 13C pocket models in the test suite. The most recent attempt included (from the agb model):

mesh_dlog_pp_dlogP_extra = 0.25
mesh_dlog_cno_dlogP_extra = 0.25

mesh_dlog_3alf_dlogP_extra = 0.225
mesh_dlog_burn_c_dlogP_extra = 0.225
mesh_dlog_burn_n_dlogP_extra = 0.225
mesh_dlog_burn_o_dlogP_extra = 0.225

mesh_logX_species(1) = 'h1'
mesh_logX_min_for_extra(1) = -6
mesh_dlogX_dlogP_extra(1) = 0.25

mesh_logX_species(1) = 'he4'
mesh_logX_min_for_extra(1) = -6
mesh_dlogX_dlogP_extra(1) = 0.25

xtra_coef_os_above_nonburn = 0.5
xtra_coef_os_below_nonburn = 0.25

xtra_coef_os_above_burn_h = 0.25
xtra_coef_os_below_burn_h = 0.15

xtra_coef_os_above_burn_he = 0.25
xtra_coef_os_below_burn_he = 0.25

xtra_coef_os_above_burn_z = 0.25
xtra_coef_os_below_burn_z = 0.25

xtra_dist_os_above_nonburn = 0.1
xtra_dist_os_below_nonburn = 0.2

xtra_dist_os_above_burn_h = 0.2
xtra_dist_os_below_burn_h = 0.2

xtra_dist_os_above_burn_he = 0.2
xtra_dist_os_below_burn_he = 0.2

xtra_dist_os_above_burn_z = 0.2
xtra_dist_os_below_burn_z = 0.2

    I have tried playing with the parameters some, but I don’t have a good intuition yet for what they’re doing. So I was wondering if someone who has encountered this problem might have some advice on how to proceed?
    Many thanks,
    Art Champagne


_________________________________________________________________

Yeah, he filled his head with notions, seemingly (George Harrison)
_________________________________________________________________
A.E. Champagne
Class of 1989 William C. Friday Professor of Physics
Dept. of Physics and Astronomy, Univ. of North Carolina
Office: Phillips 230, (919) 962-7205
and Director, Triangle Universities Nuclear Laboratory, Duke Univ.
Office: TUNL 414, (919) 660-2607
aec at tunl.duke.edu<mailto:aec at tunl.duke.edu> or artc at physics.unc.edu<mailto:artc at physics.unc.edu>
_________________________________________________________________





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