[mesa-users] crazy C shell burning

[Tuguldur Sukhbold]

thanks Bill! I'll update my version now.

Tuguldur







On Apr 18, 2013, at 3:49 PM, Bill Paxton <paxton at kitp.ucsb.edu> wrote:

> Hi Tug,
> 
> I've finally cleared other tasks enough to run your problem case using my current version (4917),
> and it seems that enough has changed in the code that I can't reproduce the crazy behavior for alpha=1.
> 
> here's my alpha = 2 plot
> 
> 
> !DSPAM:10228,517078ca22465172242618!
> <T_Rho_alpha_2.pdf>
> 
> and here's plot I get for alpha = 1
> 
> 
> !DSPAM:10228,517078ca22465172242618!
> <T_Rho_alpha_1.pdf>
> identical inlists except for mixing_length_alpha.
> 
> Could you try this with a more recent version of mesa --- 4906 is the current release.
> I hope you understand my reluctance to go chasing bugs in old versions!
> 
> Thanks,
> Bill
> 
> here's the inlist I used.
> 
> 
> !DSPAM:10228,517078ca22465172242618!
> <inlist_tug>
> 
> 
> 
> 
> 
> 
> On Apr 16, 2013, at 10:24 PM, Tuguldur Sukhbold wrote:
> 
>> Dear MESA users,
>> 
>> many of us are now well aware that due to lack of NSE treatment you're likely to get into trouble during Si burning. But in my 2+ year experience with MESA I have seen many times this weird behavior well before Si ignition, during the C burning. The attached plot shows the central T and rho evolution during C burning for two identical 15Msun models with different alpha_mlt. You see the alpha_mlt=2 case goes smoothly, but the alpha_mlt=1 case is doing some crazy stuff. I could wait for thousands of time steps and it would be just doing its weird loops back and forth, and never manage to ignite Ne.
>> 
>> With older MESA versions I noticed sometimes even very slight changes in the composition could result into this problem during C burning. If I remember correctly, during the last summer school Josh Shiode also reported similar results when he played with the time step and zoning (?) parameters.
>> 
>> I was wondering if anybody had looked into details of why this happens? how to avoid? previously I used to almost 'randomly' play with certain parameters until I find that sweet spot to make it through C burning. But now I am trying to make a detailed comparison with another code, so i need to be a bit careful.
>> 
>> thanks,
>> Tuguldur
>> 
>> ***just to clarify, in this plot the alpha_mlt=1 case only shows data since the ignition of C in the core. While the other case shows data from previous evolution.
>> 
>> <Screen Shot 2013-04-16 at 9.51.50 PM.png>
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