堆积分数、微观摩擦与弹丸自旋在撞击成坑中的作用
Roles of packing fraction, microscopic friction and projectile spin in cratering by impact
AI总结：
本文通过DEM计算研究了弹丸撞击颗粒介质的成坑力学，发现弹丸下方致密区导致反弹，固体摩擦影响坑形态，初始自旋增加穿透长度，堆积分数差异引发标度定律多样性，并提出统一现有相关性的标度。
摘要：
从树上掉落的种子到小行星撞击行星和卫星，弹丸对颗粒靶的撞击在自然界中以不同尺度发生。本文研究了颗粒成坑力学中的未解问题，特别是作用在弹丸上的力，以及颗粒堆积、颗粒间摩擦和弹丸自旋的作用。为此，我们对固体弹丸撞击无黏性颗粒介质进行了DEM（离散元方法）计算，在不同的可用能量（在相对较小的数值范围内）下，我们改变了弹丸和颗粒属性（直径、密度、摩擦和堆积分数）。我们发现弹丸下方会形成一个更致密的区域，将其推回并导致其在运动结束时反弹，且固体摩擦对坑形态有显著影响。此外，我们表明穿透长度随弹丸的初始自旋增加而增加，且初始堆积分数的差异能够引发文献中发现的标度定律的多样性。最后，我们提出了一种ad hoc标度，它将我们的穿透长度数据坍缩，并可能统一现有的相关性。我们的结果为颗粒物质中陨石坑的形成提供了新见解。
英文摘要：
From small seeds falling from trees to asteroids colliding with planets and moons, the impact of projectiles onto granular targets occurs in nature at different scales. In this paper, we investigate open questions in the mechanics of granular cratering, in particular the forces acting on the projectile, and the roles of granular packing, grain-grain friction and projectile spin. For that, we carried out DEM (discrete element method) computations of the impact of solid projectiles on a cohesionless granular medium, where we varied the projectile and grain properties (diameter, density, friction and packing fraction) for different available energies (within relatively small values). We found that a denser region forms below the projectile, pushing it back and causing its rebound by the end of its motion, and that solid friction affects considerably the crater morphology. Besides, we show that the penetration length increases with the initial spin of the projectile, and that differences in initial packing fractions can engender the diversity of scaling laws found in the literature. Finally, we propose an ad hoc scaling that collapsed our data for the penetration length and can perhaps unify existing correlations. Our results provide new insights into the formation of craters in granular matter.
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