Streaming instability with multiple dust species – II. Turbulence and dust–gas dynamics at non-linear saturation
Streaming instability with multiple dust species – II. Turbulence and dust–gas dynamics at non-linear saturation
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多种粉尘的流动不稳定性 - II. 非线性饱和下的湍流和粉尘 - 气体动力学
DOI：
10.1093/mnras/stab2959
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发表时间：
2021
影响因子：
4.8
通讯作者：
Zhu, Zhaohuan
中科院分区：
文献类型：
--
作者：
Yang, Chao-Chin;Zhu, Zhaohuan
流动不稳定性是驱动尘埃气体动力学和最终在原行星盘中形成星子的基本过程。作为一种线性不稳定性，它已被证明，它的增长与尘埃尺寸的分布可以分为两个不同的制度，快速和缓慢的增长，这取决于尘埃尺寸分布和总的尘埃与气体的密度比。使用数值模拟的非分层光盘，我们带来了三种情况下，在不同的制度进入非线性饱和。我们发现，这两个快速增长的情况下的饱和状态是类似的单物种对应。最大无因次停留时间τs，max= 0.1和τ s = 2的一个粒子驱动湍流的垂直尘气涡，而τs，max= 2和τ s = 0.2的另一个粒子导致径向交通堵塞和尘埃粒子的非定常结构。前者的粉尘密度分布在低密度区比较平坦，而后者的粉尘密度分布有一个低端截止点。相比之下，一个缓慢增长的情况下，结果在一个几乎静止的状态。此外，我们发现，在快速增长的制度，发生显着的灰尘隔离的大小，大颗粒向密集区移动，而小颗粒留在扩散区，和每个尘埃物种的平均径向漂移是明显改变（初始）阻力平衡。前一种效应可能会使多波长观测得到的光谱指数发生偏斜，并改变卵石云形成微行星的初始尺寸分布。后者沿着湍流扩散可能影响年轻原行星盘中固体物质的径向输运和混合。
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 ϵ. Using numerical simulations of an unstratified disc, we bring three cases in different regimes into non-linear 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 τs,max= 0.1 and ϵ = 2 drives turbulent vertical dust–gas vortices, while the other with τs,max= 2 and ϵ = 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 cut-off. 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 multiwavelength 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.