Eccentric gaseous discs are unstable to a parametric instability involving the resonant interaction between inertial-gravity waves and the eccentric mode in the disc. We present 3D global hydrodynamical simulations of inviscid circumbinary discs that form an inner cavity and become eccentric through interaction with the central binary. The parametric instability grows and generates turbulence that transports angular momentum with stress parameter $\alpha \sim 5 \times 10^{-3}$ at distances $\lesssim 7 \;a_{bin} $, where $a_{bin}$ is the binary semi-major axis. Vertical turbulent diffusion occurs at a rate corresponding to $\alpha_{diff}\sim 1-2\times 10^{-3}$. We examine the impact of turbulent diffusion on the vertical settling of pebbles, and on the rate of pebble accretion by embedded planets. In steady state, dust particles with Stokes numbers ${\it St} \lesssim 0.1$ form a layer of finite thickness $H_d \gtrsim 0.1 H$, where $H$ is the gas scale height. Pebble accretion efficiency is then reduced by a factor $r_{acc}/H_d$, where $r_{acc}$ is the accretion radius, compared to the rate in a laminar disc. For accreting core masses with $m_p \lesssim 0.1\; M_\oplus$, pebble accretion for particles with ${\it St} \gtrsim 0.5$ is also reduced because of velocity kicks induced by the turbulence. These effects combine to make the time needed by a Ceres-mass object to grow to the pebble isolation mass, when significant gas accretion can occur, longer than typical disc lifetimes. Hence, the origins of circumbinary planets orbiting close to their central binary systems, as discovered by the Kepler mission, are difficult to explain using an in situ model that invokes a combination of the streaming instability and pebble accretion.

中文翻译：

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偏心双星盘中的流体动力学湍流及其对双星原位形成的影响

偏心气态圆盘对于涉及惯性重力波和圆盘中偏心模式之间的共振相互作用的参数不稳定性是不稳定的。我们展示了无粘性环二元盘的 3D 全局流体动力学模拟，这些盘形成内腔并通过与中心二元相互作用而变得偏心。参数不稳定性增加并产生湍流，该湍流以应力参数 $\alpha \sim 5 \times 10^{-3}$ 在距离 $\lesssim 7 \;a_{bin} $ 处传输角动量，其中 $a_{bin}$是二元半长轴。垂直湍流扩散以对应于 $\alpha_{diff}\sim 1-2\times 10^{-3}$ 的速率发生。我们研究了湍流扩散对卵石垂直沉降的影响，以及对嵌入行星的卵石吸积率的影响。在稳定状态下，具有斯托克斯数 ${\it St} \lesssim 0.1$ 的尘埃粒子形成有限厚度的层 $H_d \gtrsim 0.1 H$，其中 $H$ 是气体标度高度。与层流盘中的速率相比，卵石吸积效率然后降低了一个因子 $r_{acc}/H_d$，其中 $r_{acc}$ 是吸积半径。用于增加核心质量 $m_p \lesssim 0.1\; M_\oplus$，${\it St} \gtrsim 0.5$ 粒子的卵石吸积也由于湍流引起的速度冲击而减少。这些效应相结合，使得谷神星质量的物体长到卵石隔离质量所需的时间比典型的圆盘寿命更长，此时可能会发生显着的气体吸积。因此，开普勒任务发现的环绕双星行星的起源，其轨道靠近其中央双星系统，