[mesa-users] noisy Brunt near convective boundary

[Santiago A. T. <re...@gm...>]

Hello mesa-users,

I'm trying to get the proper softening + mesh resolution settings to
smooth out things near the bottom convective boundary in a
shell-burning RGB star of about 1.2 M_sun. A symptom of the problem is
reflected on the noisy Brunt-Vaisala frequency (figure attached). This
not good for calculating pulsation frequencies through e.g. gyre,
there is a bit too much variation from time step to time step.

I'm including softening and additional resolution near the convective
boundary by settting

      xtra_coef_czb_full_on = 1
      xtra_coef_czb_full_off = 1

      xtra_dist_a_l_nb_czb = 2
      xtra_coef_a_l_nb_czb = 1d-1
      xtra_dist_b_l_nb_czb = 2
      xtra_coef_b_l_nb_czb = 1d-1

      conv_bdy_mix_softening_f  = 0.001
      conv_bdy_mix_softening_f0 = 0.003
      conv_bdy_mix_softening_min_D_mix = 0

I attach figures showing the mixing type, composition, gradr_sub_grada
all as function of radius around the zone in question. I'm using the
astero module, inlists also attached.

I have tried already a number of things like small overshooting,
semiconvection and diffusion but the results were not much better.

Any advice? I have the feeling that I'm not using the settings
properly... Many thanks in advance for any help!

Santiago