Binary simulation

  1. In fact binary star, but the secondary is 400AU away from the primary and its mass is only 1e-9 solar mass (Pluto), so its impact is negligible.

Primary star use Krumholz accretion criterion. I think rectangular geometry induce the asymmetry and the accreted gas has similar behaviour to the no accretion case.

Why the Krumholz accretion will give more symmetric simulation?

In Lagrangian picture (lab frame):

is Boltzmann constant, is isothermal temperature.

therefore:

Since gas is not in Keplerian motion - pressure balance a fraction of gravity.

The effective gravity is smaller than the case without isothermal assumption. Gas can stay in higher orbit if there is pressure gradient. In isothermal simulation without accretion, it is really the case.

Krumholz accretion remove gas, therefore remove pressure. Gas will suffer much more "gravity" and fall back - finally ate by the sink particle.

So even if there is some asymmetry, i.e. angular momentum in this simulation, we can not see because gas is eaten. But in no accretion case, the unwanted "angular momentum" is amplified by pressure.

In all, simulation become more insensitive to angular momentum if there is accretion. That is why Krumholz accretion seems to make the fall back symmetric. Actually it is not convincing.

z0.gif​

y0.gif​

  1. Plot of isosurface of density around sink particle(half of the MAX density). The data of this movie is from the same simulation of the above one.

iso.gif​

  1. Wind density decays exponentially at first. After 1 e folding time, I shut off the wind(at cycle 150, time=50). There is still a simulation that does not shut off the wind running on bluehive. Wind is ejected from the primary at escape velocity from 10 AU.

z0binary.gif​

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