[mesa-users] BV frequency, gradients and mlt problems - bugs?

[Jakub Ostrowski]

Hi!

I'm doing some tests with 15 M_S blue supergiant models and I found a few things that seriously bother me. I don't know if these are bugs or just problems of inexperienced user.

First of all, I started with plots of dimensionless Brunta-Vaisala frequency in function of logT for three models on different stages of evolution. As you can see in the attached figures, first model doesn't undergo central helium burning while the two following models do so and hence they have convective cores. There have been chosen to have similar T_eff. My first problem are the weird spikes that you can see. Some of them look like they have a bad sign, that means they should go to zero instead of infinity, but there are also peeks which don't seem to be related to presence of any convective zone. Has anyone else experienced similar problem? For me it looks like numerical problem, but of course I might be wrong.

Later on, I was trying to find a cause of this weird behavior of N and then I've found another problem. I plotted gradT, grada and gradr and there seems to be a problem with them. I guess that in core or in any shell that undergoes nuclear burning gradT is arbitrary set to equal grada (so that we have gradT = grada) and in the outer convective zones there is MLT in use. In these zones there are recipes how to set gradT using some combination of both grada and gradr. And here comes the problem: in the outer convective zone related to the Z-bump it seems to work properly (as you can see in the figure) but in the outermost zone related to He opacity bump it looks like the gradT = grada just like in the core. I've checked the default settings of mixing and I can't see any reason of these behavior.

I attached some figures and used inlist file. I would be grateful for any help because I have no idea how to fix these issues.

Cheers,
Jakub




 
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