Re: mesa-users] Massive stars not reaching TPAGB

[Max K. <ka...@rp...>]

I ran a 7 Msun model starting yesterday, with mesh_delta_coeff set to
something like 0.2, and a wind scheme roughly the same as Bill's, and it got
through about 53000 timesteps and to a mass of about 1.3 Msun by itself,
before it ran into convergence issues.

Max Katz
Rensselaer Polytechnic Institute
Physics, Class of 2011


On Tue, Jul 20, 2010 at 1:21 PM, Bill Paxton <pa...@ki...> wrote:

> I'm CC'ing this to the mesa-users list because it is an interesting case,
> and
> it has a message for everyone -- sometimes when the code doesn't
> do what you want it to do, there might be an interesting physical reason.
> it isn't always a bug in the code (usually it is, but not always!)
>
>
> Hi Eric,
>
>
> Turning on velocities and supersonic winds has given some interesting
> results!
>
> I restarted the run at step 12000 which was a bit before the surface
> velocities went crazy before.
>
> Here's a plot of v_surf/csound_surf covering the period where the previous
> run died.
>
>
> when the outward velocity is supersonic, the supersonic wind routine kicks
> in.
> the effect is dramatic!  look at the mass loss -- about 0.5 Msun ejected in
> a supersonic wind!
>
>
> however the timesteps have gotten small, so now the progress is slow.
>
>
>
> I'll see if I can find a way around that.   however this profile shows
> that we are getting into difficult territory -- we have supersonic infall
> happening in the lower envelope at the same time we have nearly
> supersonic outward velocities near the surface.   a lot of the envelope
> that we tried to eject is now falling back and running into the lower
> part of the envelope.  a train wreck in progress.   if left to itself
> the code will try to follow the gory details and that will take lots
> and lots of tiny timesteps.   if we don't care about the details,
> we need to find a way to make the code ignore them.
> but that needs to be done in a way that doesn't mess up
> the results for the stuff we are actually interested in.
> tricky business this stellar evolution!  ; - )
>
>
>
>
> -Bill
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