The spherical Brazil Nut Effect and its significance to asteroids
The spherical Brazil Nut Effect and its significance to asteroids
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DOI：
10.1016/j.icarus.2016.06.014
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发表时间：
2015-11
期刊：
影响因子：
3.2
通讯作者：
V. Perera;A. Jackson;E. Asphaug;R. Ballouz
中科院分区：
文献类型：
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作者：
V. Perera;A. Jackson;E. Asphaug;R. Ballouz
许多小行星很可能是碎石堆，是由重力和可能的内聚力聚集在一起的较小物体的集合。这些小行星因撞击而产生地震震动，从而激发其组成粒子。因此，有人认为它们的表面和次表面内部可能受到称为巴西坚果效应的尺寸分类机制的控制。我们研究了小行星模型的行为，该小行星是球形自引力聚集体，在地震振动的作用下具有二元尺寸分布的粒子。我们发现，在地震阈值之上，当存在摩擦时，较大的颗粒会上升到表面，这与之前专注于圆柱形和矩形盒配置的研究一致。与之前的工作不同，我们还发现即使摩擦力为零，尺寸分选也会发生，尽管摩擦力的存在确实有助于地震阈值以上的分选过程。此外，我们发现，虽然在表面附近可以进行强烈的尺寸分选，但即使在最剧烈的摇动下，最内部的区域仍然未分选。
Many asteroids are likely rubble-piles that are a collection of smaller objects held together by gravity and possibly cohesion. These asteroids are seismically shaken by impacts, which leads to excitation of their constituent particles. As a result it has been suggested that their surfaces and sub-surface interiors may be governed by a size sorting mechanism known as the Brazil Nut Effect. We study the behavior of a model asteroid that is a spherical, self-gravitating aggregate with a binary size-distribution of particles under the action of applied seismic shaking. We find that above a seismic threshold, larger particles rise to the surface when friction is present, in agreement with previous studies that focussed on cylindrical and rectangular box configurations. Unlike previous works we also find that size sorting takes place even with zero friction, though the presence of friction does aid the sorting process above the seismic threshold. Additionally we find that while strong size sorting can take place near the surface, the innermost regions remain unsorted under even the most vigorous shaking.