[mesa-users] Convergence issues when simulating massive eruptions by modifying .mod file

Bill Paxton paxton at kitp.ucsb.edu
Thu Apr 18 12:32:43 EDT 2013


1) instantaneous mass loss

you can use very high mass loss rates (e.g. 10 to 100 Msun/year) with small timesteps (e.g., 1d-2 years) to remove a large amount of mass in a short time.
rather than playing with a wind recipe to remove the mass, you can directly set the "mass_change" parameter in the inlist.

         mass_change = 0d0 ! rate of accretion (Msun/year).  negative for mass loss.
            ! this only applies when the wind scheme = ''

you can set the max timestep too

         max_years_for_timestep = 0  ! max_years_for_timestep <= 0 means no upper limit.

the code might not be happy making the jump to very high mdot in a single step, 
so you may need to use these to turn the mass_change on.
      relax_mass_change = .false.
      relax_mass_change_min_steps = 10
      relax_mass_change_max_yrs_dt = 10 ! years
      relax_mass_change_init_mdot = 0 ! Msun/year
      relax_mass_change_final_mdot = 0 ! Msun/year

you may also need to use them again after mass removal to turn the mass_change off.

2) energy conservation with mass loss

interesting question!  
you can compute the energy loss rate for the mass_change rate yourself and remove that amount from 
the envelope using the "other_energy" hook.  once you have it working, let us know so we can add it as an option. ;-)


On Apr 18, 2013, at 8:43 AM, Alexey Zinger wrote:

> Hi Josiah,
> Thanks for pointing me to the relaxation routines direction! I haven't yet looked into those. Hopefully, they might get me through some of the simulations.
> Before fiddling with the .mod files I've tried to simulate the eruptions using the built-in wind schemes with high wind coefficients. There are two issues with this: first, I'm trying to observe how the star adjusts to a (nearly) instantaneous mass removal, and all of the wind routines remove mass gradually. Second, as far as I know, the wind schemes in the code do not account for the conservation of energy, and this might be important when so much mass is removed so quickly.
> Alexey
> On Thu, Apr 18, 2013 at 9:56 AM, Josiah Schwab <jwschwab at berkeley.edu> wrote:
> > I do this by artificially modifying the saved model file and restarting the evolution with loading that file.
> I tried manipulating model files once and in my experience (and as you seem to be finding) that way lies madness :)
> Is there something about MESA's built-in routines for changing the mass of model that are insufficient/inappropriate for what you want to explore?  What other (if any) approaches have you tried?
> My personal recommendation is to use an existing relaxation routine or to add something you write yourself to run_star_extras.f to do the relaxation.  I think it will save you a lot of grief.
> Perhaps others will share their experiences.
> Josiah
> ------------------------------------------------------------------------------
> Precog is a next-generation analytics platform capable of advanced
> analytics on semi-structured data. The platform includes APIs for building
> apps and a phenomenal toolset for data science. Developers can use
> our toolset for easy data analysis & visualization. Get a free account!
> http://www2.precog.com/precogplatform/slashdotnewsletter_______________________________________________
> mesa-users mailing list
> mesa-users at lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/mesa-users

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.mesastar.org/pipermail/mesa-users/attachments/20130418/8cf603b6/attachment.html>

More information about the Mesa-users mailing list