[mesa-users] rotational asymmetry

Amber Lauer alauer1 at tigers.lsu.edu
Mon Apr 20 01:26:39 EDT 2015


The largest simulation I'm aware of is Horizon run 23 on Tachyon ii,
htttp://astro.kias.re.kr at 3.74 x10^11 particles.

Following his calculation i get 51.89 years.

On Sun, Apr 19, 2015 at 10:33 PM, Francis Timmes <fxt44 at mac.com> wrote:

> for extra fun, generate an order-of-magnitude estimate
> of the cost, in dollars, of doing such a calculation.
>
> fxt
>
>
>
>
> > On Apr 19, 2015, at 7:24 PM, Matteo Cantiello <matteo at kitp.ucsb.edu>
> wrote:
> >
> > Hi Amber,
> > Casey Meakin gave a talk at the IAU symposium 252 "The art of stellar
> evolution in the 21st century" (Sanya 2009)
> > where he predicted that, assuming Moore's law,  a fully resolved stellar
> turbulence calculation will be feasible in ~60 years.
> > I suggest you have a look at his argument and maybe update it given
> current computational resources.
> > It could be a fun exercise (and please share this with the mailing list
> if you find something interesting).
> >
> > http://arxiv.org/pdf/0806.4542.pdf
> >
> > Cheers,
> >
> > -M
> >
> >
> > Matteo Cantiello  |  http://matteocantiello.com/
> > Associate Specialist in Astrophysics  | Kavli Institute for Theoretical
> Physics
> > Chief Scientist and Board Member, Authorea  |  https://www.authorea.com/
> >
> > On Apr 19, 2015, at 6:45 PM, Amber Lauer <alauer1 at tigers.lsu.edu> wrote:
> >
> >> I thank everyone for their answers, this will help me should this
> question arise. My understanding is that the reason for our dependence on
> 1D and sometimes 2D approximations to 3D situations is necessity, not
> denial. While we would ideally all love to use 3D, particle-for-particle
> identical models, the computational power and algorithms just aren't there
> yet. In my paper I project that such capabilities could still be 20 years
> away.
> >>
> >> On Sun, Apr 19, 2015 at 10:07 AM, Stan Woosley <woosley at ucolick.org>
> wrote:
> >> Fully agreed and a bit more.
> >>
> >> Unless rapidly rotating, stars are spheres and to first order, well
> >> described in 1D codes. 1D models of the solar interior are quite
> >> good, but even there, there are exceptions. Convection, wherever it
> >> occurs, is inherently multi-dimensional. It is approximated by
> >> parameters (mixing length theory) in a 1D code, that usually work well
> >> but not always, especially at the boundaries of those regions. The outer
> >> quarter of the sun's radius (2% of its mass) is convective. The
> >> solar surface is a seething morass of convective blobs, tangled magnetic
> >> fields, reconnection, spots,  flares,  and propagating
> >> waves. Entire fields study each of these - e..g. helioseismology.
> >>
> >> When massive stars die, rotation and symmetry breaking plays a big
> >> role. The most extreme case that we know comes from stars are
> >> gamma-ray bursts. Narrow jets of relativistic matter moving out
> >> along the poles and not at other angles. Even without rotation,
> >> neutrino  transport calculations of the explosion require 3D to get
> >> the neutrino deposited power at all right.
> >>
> >> Observations of supernovae and supernova remnants in general
> >> show that they are not spheres. Polarization measurements show
> >> deformation, and look at any modern picture of the Crab or Cas  A
> >> remnants to see how much they differ from spheres.
> >>
> >> Then there are the more docile effects of differential rotation that
> >> affect the sizes of stellar cores, surface abundances, and angular
> momentum
> >> of the compact remnants - Eddington Sweet circulation, dynamical and
> secular
> >> shear, and various other instabilities that make helium cores bigger
> >> and enrich the stellar surface with elements made deep within.
> >>
> >> 1D is often a good approximation and it is cheap and easy, but real
> stars
> >> are 3D.
> >>
> >> Stan
> >>
> >>
> >>
> >> On Apr 19, 2015, at 2:00 AM, Santiago Andres Triana <repepo at gmail.com>
> wrote:
> >>
> >> > Hi Amber,
> >> >
> >> > In the case of rapidly rotating stars the spherical symmetry is lost
> >> > (by centrifugal deformation) and therefore the spherical harmonics
> >> > that we all know and love are not appropriate to describe pulsations.
> >> > A 2D code would be necessary here to describe the equilibrium
> >> > structure as well (e.g. the ESTER code). 1D models assume "shellular"
> >> > differential rotation (dependent only on radius) while in 2D the
> >> > models are allowed to have latitude-dependent differential rotation.
> >> > Mixing properties are therefore different. In 1D we treat mixing
> >> > mechanisms as diffusion processes, but in reality some of those
> >> > processes cannot be described properly as such, e.g. when shear from
> >> > differential rotation is latitude dependent.
> >> >
> >> > This topic is really complex! I would recommend the excellent
> >> > monography by A. Maeder (Physics, Formation and Evolution of Rotating
> >> > Stars) to have an overview. Hope it helps!
> >> >
> >> > Cheers,
> >> >
> >> > Santiago
> >> >
> >> > On Sun, Apr 19, 2015 at 4:04 AM, Amber Lauer <alauer1 at tigers.lsu.edu>
> wrote:
> >> >> I've been asked a few times to describe what is lost in a 1d model
> vs 2d or
> >> >> even 3d, and the astrophysical answer I got when consulting
> professors was
> >> >> "not much". However, I'm preparing for my general exam and would
> like to
> >> >> have a more thorough answer. Does anyone have any input?
> >> >>
> >> >> --
> >> >> Amber Lauer. M.S. Physics
> >> >> PhD Student,
> >> >> Dept. of Physics & Astronomy,
> >> >> Louisiana State University
> >> >>
> >> >>
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> >> >
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> >>
> >>
> >>
> >> --
> >> Amber Lauer. M.S. Physics
> >> PhD Student,
> >> Dept. of Physics & Astronomy,
> >> Louisiana State University
> >>
> ------------------------------------------------------------------------------
> >> BPM Camp - Free Virtual Workshop May 6th at 10am PDT/1PM EDT
> >> Develop your own process in accordance with the BPMN 2 standard
> >> Learn Process modeling best practices with Bonita BPM through live
> exercises
> >> http://www.bonitasoft.com/be-part-of-it/events/bpm-camp-virtual-
> event?utm_
> >>
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> >
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> > Develop your own process in accordance with the BPMN 2 standard
> > Learn Process modeling best practices with Bonita BPM through live
> exercises
> > http://www.bonitasoft.com/be-part-of-it/events/bpm-camp-virtual-
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>


-- 
Amber Lauer. M.S. Physics
PhD Student,
Dept. of Physics & Astronomy,
Louisiana State University
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