[Mesa-users] numerical noise in Brunt-Vaisala -- eos issue

[Morgan Taylor]

Hi Alina and Josiah,

Thank you for the post!  I've been having the same problem and Frank and I
were also trying to understand the noise/spike.  Switching to PC removed
the peak for me as well, so I'm grateful for the post.

Thanks,
Morgan

On Wed, Jul 15, 2020 at 9:55 AM Alina Istrate via Mesa-users <
mesa-users at lists.mesastar.org> wrote:

> Hi Josiah,
>
> Thank you so much for the quick (and very kind) answer!
>
> By just using the PC eos, I am happy to report that it did remove the
> noisy peak and now I have a beautiful Brunt -Vaisala plot.  I am sure that
> the same fix would solve the problem for the more massive CO WD case.
>
>  Thanks again and looking forward to the new MESA release!
>
> Best regards,
> Alina
>
>
>
> On Wed, Jul 15, 2020 at 4:21 PM Josiah Schwab <jwschwab at ucsc.edu> wrote:
>
>> Hi Alina,
>>
>> First, thank you for the excellent message. This is a great example of
>> what a useful problem report looks like!
>>
>> Does anyone have a suggestion on how to get rid of this type of noise ?
>>>
>>
>> As you suspected, I think you're hitting an eos discontinuity,
>> specifically, the Z-switch between HELM and PC.  By default, that occurs at
>> PC_min_Z = 0.999d0, which matches the location of the jump in your
>> eos_sample.
>>
>> Evan was also displeased by these sudden switches between HELM and PC as
>> a function of composition in WD interiors and led a successful campaign to
>> eliminate PC_min_Z in future MESA versions.
>>
>> For now, I'd suggest putting that switch at Z = 0, so that MESA
>> always uses PC.
>>
>> Please try
>>
>>     set_eos_PC_parameters = .true.
>>     PC_min_Z = 0d0
>>     mass_fraction_limit_for_PC = 0d0 ! default of 1d-3 can also cause
>> small discontinuities
>>
>> in your star_job inlist and see if that helps.
>>
>> Let us know how it goes.
>>
>> Josiah
>>
>
>
> --
> *--------------------------------------------------------------------*
> Dr. Alina Istrate
> Institute for Mathematics, Astrophysics & Particle Physics
> Department of Astrophysics
> Radboud University
> P.O. Box 9010, MC 62
> NL-6500 GL Nijmegen, The Netherlands
> r: HG02.738
> a.istrate at astro.ru.nl
>
>
> _______________________________________________
> mesa-users at lists.mesastar.org
> https://lists.mesastar.org/mailman/listinfo/mesa-users
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.mesastar.org/pipermail/mesa-users/attachments/20200715/5740f630/attachment.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: baseSmoothBV.pdf
Type: application/pdf
Size: 21108 bytes
Desc: not available
URL: <https://lists.mesastar.org/pipermail/mesa-users/attachments/20200715/5740f630/attachment.pdf>