Free Collisions in a Microgravity Many-Particle Experiment. I.Dust Aggregate Sticking at Low Velocities
Free Collisions in a Microgravity Many-Particle Experiment. I.Dust Aggregate Sticking at Low Velocities
复制标题
微重力多粒子实验中的自由碰撞。
DOI：
10.1016/j.icarus.2011.10.002
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发表时间：
2012
期刊：
影响因子：
3.2
通讯作者：
J.
中科院分区：
文献类型：
--
作者：
Weidling;R.;Guttler;C.;Blum;J.
在过去的几年里，实验室里广泛地研究了与行星体生长有关的过程。在这些实验的基础上，建立了尘埃-集合体碰撞模型，并在此基础上进行了计算机模拟，以评估原行星尘埃集合体可以增长到多大，并分析哪些类型的碰撞与太阳星云相关，值得实验室进一步研究。毫米级尘埃集合体的粘滞阈值速度是这样一个临界值，到目前为止还只是从理论上推导出来的，因为相关的速度在实验室中无法达到。我们开发了一个微重力实验，使我们能够首次研究毫米级尘埃聚集体之间的自由碰撞，速度降至∼0.1厘米−1，以评估原行星尘埃演化模型的这一部分。在这里，我们给出了直径为0.5-2 mm的尘埃聚集体之间的125次自由碰撞的结果。速度在0.2cms和3cms−1之间的7次碰撞导致了粘滞，这表明从完美粘滞到完美反弹的转变具有一定的粘滞概率，而不是急剧的速度阈值。我们建立了一个模型来解释尘埃团聚体粘着的物理过程，从碰撞的结果推导出尘埃团聚体的动力学物质性质，并推导出尘埃团聚体始终粘在下面的速度。对于毫米大小的多孔尘埃聚集体，这个速度是8×10−5ms−1。
Over the past years the processes involved in the growth of planetesimals have extensively been studied in the laboratory. Based on these experiments, a dust-aggregate collision model was developed upon which computer simulations were based to evaluate how big protoplanetary dust aggregates can grow and to analyze which kinds of collisions are relevant in the solar nebula and are worth further studies in the laboratory. The sticking threshold velocity of millimeter-sized dust aggregates is one such critical value that have so far only theoretically been derived, as the relevant velocities could not be reached in the laboratory. We developed a microgravity experiment that allows us for the first time to study free collisions of mm-sized dust aggregates down to velocities of ∼0.1cms−1to assess this part of the protoplanetary dust evolution model. Here, we present the results of 125 free collisions between dust aggregates of 0.5–2mm diameter. Seven collisions with velocities between 0.2 and 3cms−1led to sticking, suggesting a transition from perfect sticking to perfect bouncing with a certain sticking probability instead of a sharp velocity threshold. We developed a model to explain the physical processes involved in dust-aggregate sticking, derived dynamical material properties of the dust aggregates from the results of the collisions, and deduced the velocity below which dust aggregates always stick. For millimeter-sized porous dust aggregates this velocity is 8×10−5ms−1.