LOW-VELOCITY COLLISIONS OF CENTIMETER-SIZED DUST AGGREGATES
LOW-VELOCITY COLLISIONS OF CENTIMETER-SIZED DUST AGGREGATES
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DOI：
10.1088/0004-637x/736/1/34
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发表时间：
2011-07-20
影响因子：
4.9
通讯作者：
Wurm, G.
中科院分区：
文献类型：
--
作者：
Beitz, E.;Guettler, C.;Wurm, G.
厘米和分米大小的尘埃体之间的碰撞对于理解导致星子形成的机制非常重要。我们进行了实验室实验，以研究该尺寸范围内的灰尘聚集体在低于或接近破碎阈值的速度下的碰撞行为。我们开发了两个独立的实验装置，其目标相同：研究自由粒子-粒子碰撞中弹跳、破碎和质量传递的影响。第一个装置是一个真空落体塔，自由落体高度为 1.5 m，为我们提供了 0.56 s 的微重力时间，以便我们观察到速度在 8 mm s(-1) 和 2 m s(-1) 之间的碰撞。第二种设置旨在更详细地研究部分破碎（当两种聚集体中只有一种被破坏时）和传质的影响。它可以测量吸积效率，因为样本在遭遇后可以安全回收。在非常低的速度下，我们发现弹跳符合预期，而 20 cm s(-1) 的碎片速度明显低于预期。我们提出了破坏性碰撞的临界能量 Q(star)，它比文献中之前的实验至少低两个数量级。在弹跳和破坏性碰撞之间的广泛范围内，只有一个样本在遭遇中破碎，而另一个样本则获得了质量。粒子质量的几个百分点的吸积效率取决于撞击速度和样品孔隙率。我们的结果将对原行星盘中的尘埃演化模型以及大型多孔星子体的强度产生影响。
Collisions between centimeter- and decimeter-sized dusty bodies are important in understanding the mechanisms leading to the formation of planetesimals. We performed laboratory experiments to study the collisional behavior of dust aggregates in this size range at velocities below and around the fragmentation threshold. We developed two independent experimental setups with the same goal: to study the effects of bouncing, fragmentation, and mass transfer in free particle-particle collisions. The first setup is an evacuated drop tower with a free-fall height of 1.5 m, providing us with 0.56 s of microgravity time, so that we observed collisions with velocities between 8 mm s(-1) and 2 m s(-1). The second setup is designed to study the effect of partial fragmentation (when only one of the two aggregates is destroyed) and mass transfer in more detail. It allows for the measurement of the accretion efficiency because the samples are safely recovered after the encounter. At very low velocities, we found that bouncing was as expected, while the fragmentation velocity of 20 cm s(-1) was significantly lower than expected. We present the critical energy for disruptive collisions Q(star), which were at least two orders of magnitude lower than previous experiments in the literature. In the wide range between bouncing and disruptive collisions, only one of the samples fragmented in the encounter, while the other gained mass. The accretion efficiency on the order of a few percentage points of the particle's mass depends on the impact velocity and the sample porosity. Our results will have consequences for dust evolution models in protoplanetary disks as well as for the strength of large, porous planetesimal bodies.