[mesa-users] Is there any way to solve min_time_step convergence problem?

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<DIV style="FONT-FAMILY: Dotum; FONT-SIZE: 10pt">Dear MESA users, 
<DIV><BR></DIV>
<DIV>I have faced on numerical problem during the simulation.</DIV>
<DIV>&nbsp;</DIV>
<DIV>When I try to make an iron core for very high mass star&nbsp;models(40M, 45M, 50M),</DIV>
<DIV>&nbsp;</DIV>
<DIV>it terminates with min time step convergence problem.</DIV>
<DIV>&nbsp;</DIV>
<DIV>For 50M case, it terminates with the output message "termination code: v_surf_div_v_kh_upper_limit".</DIV>
<DIV>&nbsp;</DIV>
<DIV>The inlist file is here(the only difference is the initial mass of the ZAMS)&nbsp;:<BR><BR>&amp;star_job</DIV>
<DIV>&nbsp;&nbsp;&nbsp;create_pre_main_sequence_model = .false.</DIV>
<DIV>&nbsp;&nbsp; change_initial_net = .true.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <BR>&nbsp;&nbsp; new_net_name = 'approx21.net'&nbsp;<BR>&nbsp;&nbsp;&nbsp;pgstar_flag = .true.</DIV>
<DIV>&nbsp;</DIV>
<DIV>/ !end of star_job namelist</DIV>
<DIV><BR>&amp;controls</DIV>
<DIV>&nbsp; ! starting specifications</DIV>
<DIV>&nbsp;&nbsp;zams_filename = 'zams_z2m2_y28.data'</DIV>
<DIV>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; initial_mass = 40<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; initial_z = 0.02d0<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Zbase = 0.02d0</DIV>
<DIV>&nbsp;</DIV>
<DIV>&nbsp;&nbsp;okay_to_reduce_gradT_excess = .true. <BR>&nbsp;&nbsp;varcontrol_target = 1.0d-3<BR>&nbsp;&nbsp;mesh_delta_coeff = 3<BR>&nbsp;&nbsp;min_timestep_limit = 1d-99<BR>&nbsp;&nbsp;fe_core_infall_limit = 1d8 ! cm/sec<BR>&nbsp;&nbsp;mixing_length_alpha = 2</DIV>
<DIV><BR>&nbsp;&nbsp;RGB_wind_scheme = 'Dutch' !string means no RGB wind<BR>&nbsp;&nbsp;AGB_wind_scheme = 'Dutch'! empty string means no AGB wind<BR>&nbsp;&nbsp;RGB_to_AGB_wind_switch = 1d-4<BR>&nbsp;&nbsp;Dutch_wind_eta = 1&nbsp;&nbsp;</DIV>
<DIV>&nbsp;</DIV>
<DIV>/ ! end of controls namelist</DIV>
<DIV>&nbsp;</DIV>
<DIV>I'm using the mesa version 6794 and mesa SDK version 20140715.</DIV>
<DIV>If you have any opinion, please notice me. It would be very helpful to me.</DIV>
<DIV>&nbsp;</DIV>
<DIV>-Sincerely yours, HYUN TAEK-</DIV></DIV></DIV><BR><BR>
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