具有流体动力学turbulence的圆盘中行星上的粒子吸积
Particle accretion onto planets in discs with hydrodynamic turbulence
摘要：
原行星的生长过程可以通过吸积大量仍然存在于原行星盘中的固体，鹅卵石大小的物体来加速。这仍然是一个悬而未决的问题，如何有效地这一过程中的工作在现实的湍流盘。在这里，我们调查的卵石吸积湍流盘驱动的纯流体动力学垂直剪切不稳定性（VSI）。为了这个目的，我们进行全球性的三维模拟的局部等温，VSI湍流盘嵌入式原行星的核心从5到100 $M_\oplus$被放置在5.2 AU距离的恒星。此外，我们还跟踪了在这种湍流中，在气体和颗粒之间的拖曳力作用下，嵌入的不同尺寸的卵石群的演化。同时，我们进行了一组比较模拟层流粘性盘的颗粒经历随机踢。对于这两种情况下，我们测量的吸积率到核心的核心质量和斯托克斯数（$τ_s$）的粒子的函数，并比较它最近的MRI湍流模拟。总的来说，VSI湍流盘中的颗粒和具有随机反冲的层流情况下的颗粒的动态非常相似。对于小质量行星（即5和10 $M_\oplus$），与$τ_s = 1$良好耦合的粒子，在这个位置的尺寸约为1米，我们发现吸积效率（吸积粒子向内漂移的速率）约为1.6- 3%。对于更小和更大的颗粒，该效率更高。然而，$τ_s = 1$粒子的快速向内漂移使它们成为快速增长的最有效的粒子，导致质量倍增时间约为20，000年。对于质量在10到30 $M_\oplus$之间的核心达到卵石隔离质量，粒子被困在行星外部的最大压力下，切断了进一步的粒子吸积。
英文摘要：
The growth process of proto-planets can be sped-up by accreting a large number of solid, pebble-sized objects that are still present in the protoplanetary disc. It is still an open question on how efficient this process works in realistic turbulent discs. Here, we investigate the accretion of pebbles in turbulent discs that are driven by the purely hydrodynamical vertical shear instability (VSI). For this purpose, we perform global three-dimensional simulations of locally isothermal, VSI turbulent discs with embedded protoplanetary cores from 5 to 100 $M_\oplus$ that are placed at 5.2 au distance from the star. In addition, we follow the evolution of a swarm of embedded pebbles of different size under the action of drag forces between gas and particles in this turbulent flow. Simultaneously, we perform a set of comparison simulations for laminar viscous discs where the particles experience stochastic kicks. For both cases, we measure the accretion rate onto the cores as a function of core mass and Stokes number ($τ_s$) of the particles and compare it to recent MRI turbulence simulations. Overall the dynamic is very similar for the particles in the VSI turbulent disc and the laminar case with stochastic kicks. For the small mass planets (i.e. 5 and 10 $M_\oplus$), well-coupled particles with $τ_s = 1$, which have a size of about one meter at this location, we find an accretion efficiency (rate of particles accreted over drifting inward) of about 1.6-3%. For smaller and larger particles this efficiency is higher. However, the fast inward drift for $τ_s = 1$ particles makes them the most effective for rapid growth, leading to mass doubling times of about 20,000 yr. For masses between 10 and 30 $M_\oplus$ the core reaches the pebble isolation mass and the particles are trapped at the pressure maximum just outside of the planet, shutting off further particle accretion.
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