用DEM研究低重力环境中的颗粒物理学
Granular physics in low-gravity environments using DEM
摘要：
不同大小的颗粒物质存在于几个没有大气层的太阳系天体的表面。与颗粒材料相关的现象已经在称为颗粒物理学的学科框架内进行了研究;在实验室中进行了实验研究，并且在过去的几十年中，通过进行数值模拟。离散单元法模拟由一组通过其接触点相互作用的颗粒形成的介质的力学行为。在再现真空和低重力环境的困难，使数值模拟在这些条件下的粒状介质的研究最有前途的技术。本文用离散元方法研究了太阳系小天体的相关过程。介绍了小行星爱神星和丝川号在低重力环境中尺寸分离的模拟结果。分析了不同密度粒子的分离情况，特别是P/Hartley 2号彗星的情况。在这些不同的重力环境中，表面的震动可能会导致粒子以非常低的相对速度从表面喷出。引起上述过程的震动是由于：冲击，爆炸，如通过释放内部应力或重新容纳材料释放能量。还模拟了冲击引起的地震波通过粒状介质的过程。本文介绍了离散元法在低重力环境下岩石团聚体物理演化研究中的几个应用。
英文摘要：
Granular materials of different sizes are present on the surface of several atmosphere-less Solar System bodies. The phenomena related to granular materials have been studied in the framework of the discipline called Granular Physics; that has been studied experimentally in the laboratory and, in the last decades, by performing numerical simulations. The Discrete Element Method simulates the mechanical behavior of a media formed by a set of particles which interact through their contact points. The difficulty in reproducing vacuum and low-gravity environments makes numerical simulations the most promising technique in the study of granular media under these conditions. In this work, relevant processes in minor bodies of the Solar System are studied using the Discrete Element Method. Results of simulations of size segregation in low-gravity environments in the cases of the asteroids Eros and Itokawa are presented. The segregation of particles with different densities was analysed, in particular, the case of comet P/Hartley 2. The surface shaking in these different gravity environments could produce the ejection of particles from the surface at very low relative velocities. The shaking causing the above processes is due to: impacts, explosions like the release of energy by the liberation of internal stresses or the re accommodation of material. Simulations of the passage of impact-induced seismic waves through a granular medium were also performed. We present several applications of the Discrete Element Methods for the study of the physical evolution of agglomerates of rocks under low-gravity environments.
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