标题： 真空暴露颗粒集合体表面横向冲量引起的惯性膨胀模拟 显示英文标题

标题： Simulation of Lateral Impulse Induced Inertial Dilation at the Surface of a Vacuum-Exposed Granular Assembly

摘要： 我们首次证明，颗粒通道所经历的横向冲量可以在具有机械自由表面的颗粒介质中引发远距离的惯性体积膨胀。表面膨胀需要零覆盖压力（暴露在真空中），并且由略高于声速的波传播（>马赫数1.05）引发。我们使用开源软球离散元方法（SSDEM）软件模拟这一现象。我们制备了暴露在真空中的单分散、有粘性的球形颗粒通道，并将其建模为赫兹弹簧。我们通过再现声波、强冲击和剪切膨胀行为来验证我们的模型。然后我们在通道内产生冲击，以确定表面膨胀对波速、波型、初始填充分数和边界效应的敏感性。我们产生的冲击迅速衰减，并似乎以可以沿通道持续的孤立波形式传播。我们发现，惯性表面膨胀由压缩孤立波引起，对通道长度不敏感，随着床高增加而增加，并且随着初始填充分数显著增加。需要坚硬的地下地面来在整个通道内维持这种波。由横向传播的冲击载荷引起的自由表面膨胀可能与月球冷斑的形成有关，这些冷斑是年轻陨石坑周围低热惯性区域的远端区域。 显示英文摘要

摘要： We demonstrate for the first time that a lateral impulse experienced by a granular channel can induce an inertial bulk dilation over long distances across a granular medium with a mechanically free surface. The surface dilation requires zero overburden pressure (exposure to vacuum) and is precipitated by the passing of waves traveling barely above the sound speed (> Mach 1.05). We simulate this phenomenon using open source Soft Sphere Discrete Element Method (SSDEM) software. We prepare channels of monodisperse, cohesive spherical particles exposed to vacuum and modeled as Hertzian springs. We validate our model by recreating acoustic wave, strong shock, and shear dilation behavior. We then create shocks within the channel to determine the sensitivity of surface dilation to wave speed, wave type, initial packing fraction, and boundary effects. The shocks we create undergo a rapid decay in strength and appear to propagate as solitary waves that can be sustained across the channel. We find that an inertial surface dilation is induced by compressive solitary waves, is insensitive to channel length, increases with bed height, and increases substantially with initial packing fraction. A hard subsurface floor is required to maintain this wave over the entire channel. Free surface dilation induced by laterally propagating impulse loading could be implicated in the formation of Lunar Cold Spots, distal regions of low thermal inertia surrounding young craters on the Moon.