[Mesa-users] inaccuracies from large mesh_delta_coeff and convergence helpers

[Simon Murphy]

Hi folks,

I'm supervising a student project to investigate systematic modelling uncertainties on pulsation frequencies of 1.5--2.0 Msun stars.

This involves evolving some models from very young ages (create_pre_main_sequence_model = .true.) to the late main sequence. A major difficulty is having models converge, because the solver eventually gives up with "hydro_failed" a lot of the time.

There are of course things that help. Having "Pextra_factor > 1", having "okay_to_reduce_gradT_excess = .true.", and, it seems, having larger "mesh_delta_coeff". I'm not sure why the latter helps, but it seems that it does. Would love to know why.

My question is this: if at some point in the evolution the run uses, say, Pextra_factor = 2 and mesh_delta_coeff = 1.0, is there any point in later using Pextra_factor = 1 and mesh_delta_coeff = 0.1? Or is that accuracy permanently lost?

The student or I would check ourselves, but we can't get anything to converge with Pextra_factor = 1 and mesh_delta_coeff = 0.1 all the way through.

Thanks,
Simon

-----------------------------------------
Dr Simon J. Murphy
Incoming ARC Future Fellow
School of Physics
University of Sydney
NSW 2006, Australia
tel: (+61) 0290365104
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