Streaming Instability with Multiple Dust Species: II. Turbulence and Dust-Gas Dynamics at Nonlinear Saturation. (arXiv:2110.06248v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Yang_C/0/1/0/all/0/1">Chao-Chin Yang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhu_Z/0/1/0/all/0/1">Zhaohuan Zhu</a>
The streaming instability is a fundamental process that can drive dust-gas
dynamics and ultimately planetesimal formation in protoplanetary discs. As a
linear instability, it has been shown that its growth with a distribution of
dust sizes can be classified into two distinct regimes, fast- and slow-growth,
depending on the dust-size distribution and the total dust-to-gas density ratio
$epsilon$. Using numerical simulations of an unstratified disc, we bring three
cases in different regimes into nonlinear saturation. We find that the
saturation states of the two fast-growth cases are similar to its
single-species counterparts. The one with maximum dimensionless stopping time
$tau_mathrm{s,max}=0.1$ and $epsilon=2$ drives turbulent vertical dust-gas
vortices, while the other with $tau_mathrm{s,max}=2$ and $epsilon=0.2$ leads
to radial traffic jams and filamentary structures of dust particles. The dust
density distribution for the former is flat in low densities, while the one for
the latter has a low-end cutoff. By contrast, the one slow-growth case results
in a virtually quiescent state. Moreover, we find that in the fast-growth
regime, significant dust segregation by size occurs, with large particles
moving towards dense regions while small particles remain in the diffuse
regions, and the mean radial drift of each dust species is appreciably altered
from the (initial) drag-force equilibrium. The former effect may skew the
spectral index derived from multi-wavelength observations and change the
initial size distribution of a pebble cloud for planetesimal formation. The
latter along with turbulent diffusion may influence the radial transport and
mixing of solid materials in young protoplanetary discs.
The streaming instability is a fundamental process that can drive dust-gas
dynamics and ultimately planetesimal formation in protoplanetary discs. As a
linear instability, it has been shown that its growth with a distribution of
dust sizes can be classified into two distinct regimes, fast- and slow-growth,
depending on the dust-size distribution and the total dust-to-gas density ratio
$epsilon$. Using numerical simulations of an unstratified disc, we bring three
cases in different regimes into nonlinear saturation. We find that the
saturation states of the two fast-growth cases are similar to its
single-species counterparts. The one with maximum dimensionless stopping time
$tau_mathrm{s,max}=0.1$ and $epsilon=2$ drives turbulent vertical dust-gas
vortices, while the other with $tau_mathrm{s,max}=2$ and $epsilon=0.2$ leads
to radial traffic jams and filamentary structures of dust particles. The dust
density distribution for the former is flat in low densities, while the one for
the latter has a low-end cutoff. By contrast, the one slow-growth case results
in a virtually quiescent state. Moreover, we find that in the fast-growth
regime, significant dust segregation by size occurs, with large particles
moving towards dense regions while small particles remain in the diffuse
regions, and the mean radial drift of each dust species is appreciably altered
from the (initial) drag-force equilibrium. The former effect may skew the
spectral index derived from multi-wavelength observations and change the
initial size distribution of a pebble cloud for planetesimal formation. The
latter along with turbulent diffusion may influence the radial transport and
mixing of solid materials in young protoplanetary discs.
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