论文标题
稀疏气体中的行星：滑动流动中的风侵蚀
Planetesimals in Rarefied Gas: Wind Erosion in Slip Flow
论文作者
论文摘要
一个行星通过其原动性圆盘的气体移动，在那里经历了头风。尽管环境压力很低，但如果流动足够强，这种风可能会侵蚀并最终破坏行星。我们第一次在原月光盘的压力下观察到地面和微重力实验的风侵蚀，即降至$ 10^{ - 1} \，\ rm mbar $。我们发现，侵蚀所需的剪切应力取决于与表面谷物有关的Knudsen数字。随着颗粒与气体分子的平均自由路径的比较，临界剪切应力会增加侵蚀。这使卵石桩的行星在较低压力下更稳定。但是，它并不能保存它们，因为实验还表明，对于亚毫米尺寸的晶粒而言，启动侵蚀的临界剪切应力非常低。
A planetesimal moves through the gas of its protoplanetary disc where it experiences a head wind. Though the ambient pressure is low, this wind can erode and ultimately destroy the planetesimal if the flow is strong enough. For the first time, we observe wind erosion in ground based and microgravity experiments at pressures relevant in protoplanetary discs, i.e. down to $10^{-1}\, \rm mbar$. We find that the required shear stress for erosion depends on the Knudsen number related to the grains at the surface. The critical shear stress to initiate erosion increases as particles become comparable to or larger than the mean free path of the gas molecules. This makes pebble pile planetesimals more stable at lower pressure. However, it does not save them as the experiments also show that the critical shear stress to initiate erosion is very low for sub-millimetre sized grains.
