[mesa-users] exploring vibrations in mesa/star models

Francis Timmes fxt44 at mac.com
Mon Jan 2 18:09:11 EST 2012


hi jing,

it appears to me that you are interested in follow sound
waves bouncing around. if so, i think you should be using
a courant timestep limited explicit hydrodynamics code
to accurately follow this behavior. in my opinion,
mesa is not (yet, perhaps) the right tool for the job.

fxt



On Jan 2, 2012, at 9:56 AM, jingluan at caltech.edu wrote:

> Hi,
> 
> On Jan 1, 2012, at 8:49 PM, jingluan at caltech.edu wrote:
> 
>> we start with a perturbed initial model. Physically
>> the star should keep vibrating for a thermal (kh_timescale) time scale,
>> but mesa damped the vibration in about 1 vibration period
> 
> Does anyone have suggestions for Jing?
> All I can think of is to set max_years_for_timestep
> to make sure the timestep is limited
> to be much smaller than the period of vibration.
> But I don't have any direct experience with this
> sort of thing, so perhaps someone else has
> better ideas.
Thank you, Bill. We have tried to limit the maxtimestep to be e.g. 1/20 of
the vibration time scale. However, MESA keeps shrinking the real time step
model by model so that the first half of the vibration period never ends.
> 

> -Bill


> Hi Bill,
> 
> Is there any other method except artificial viscosity to help hydro-static
> convergence please? We start with a perturbed initial model. Physically
> the star should keep vibrating for a thermal (kh_timescale) time scale,
> but mesa damped the vibration in about 1 vibration period. I checked the
> hydro_eqn.f and turned off the artificial viscosity, but the vibration
> still got damped in the same manner. By reading the hydro_eqn.f file, I
> did not find any other trick except artificial viscosity. Did I miss
> something? Does mesa use some other technique to damp vibration please?
> 
> Thank you so much :-)
> 
> Sincerely,
> Jing
> 




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