[Mesa-users] How do you change timestep in MESA?

[Francis Timmes]

hi bea,

the essence of this case is low mass, m = 0.12 msun, at high metallicities, z=0.03.
i have been unable to get this to run in 12778. about halfway down the pre-ms
track the density corrections for cell 1 become large and alternating in sign.
this is what drives the timestep to small values. however, the model does run 
at smaller metallicities, z < 0.02. so for now, unless someone else offers a solution, 
you'll have to restrict the metallicity range of your study.
attached is my inlist.

on a more positive note, this case runs fine in recent developer versions.
maybe there will be a new public release one of these days ...

fxt


p.s. always cc mesa-users in your replies please.





> On Oct 4, 2020, at 6:53 PM, Bea Marie Cajandig <bmhcajandig at gmail.com> wrote:
> 
> Hello Mr. Timmes, 
> 
> Thank you for the response. I'll be attaching my inlists Sir. Pardon as my inlists are still a mess at this point, I am still learning how to use MESA. 
> 
> Again, thank you for helping me out Mr. Timmes. I have been following your tutorials on YouTube, and they are of very great help. 
> 
> 
> Regards,
> Bea
> 
> On Mon, Oct 5, 2020 at 2:52 AM Francis Timmes <fxt44 at mac.com> wrote:
> hi bea,
> 
> generally it means a model was unable to evolve despite trying tiny time steps.
> decreasing the minimum time step is unlikely to be a solution, but not enough 
> information is provided for anyone to potentially help.
> best practice is to at least share the inlist(s) one is using.
> 
> fxt
> 
> 
> 
> > On Oct 4, 2020, at 9:01 AM, Bea Marie Cajandig via Mesa-users <mesa-users at lists.mesastar.org> wrote:
> > 
> > Good day to all,
> > 
> > I am running a simulation on a red dwarf star, and it is always terminated with this message:
> > 
> > "stopping because of problems dt < min_timestep_limit
> > terminated evolution: cannot find acceptable model
> > termination code: min_timestep_limit"
> > 
> > I would like to ask a few questions in regards to this:
> > 1. What does this error mean?
> > 2. Where is the timestep adjusted? Where do you add the timestep value: &star_job or &controls?
> > 
> > Thank you in advance for helping me out. The help is very much appreciated. 
> > 
> > Cheers,
> > Bea




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