Experiments on sticking, restructuring, and fragmentation of preplanetary dust aggregates
Experiments on sticking, restructuring, and fragmentation of preplanetary dust aggregates
复制标题
DOI：
10.1006/icar.1999.6234
复制
发表时间：
2000-01-01
期刊：
影响因子：
3.2
通讯作者：
Wurm, G
中科院分区：
文献类型：
--
作者：
Blum, J;Wurm, G
我们进行了实验室以及微重力实验中，我们研究了由微米大小的尘埃颗粒组成的小分形聚集体在不同速度下对固体目标的影响。在实验室中缓慢轰击目标会导致形成蓬松的灰尘层，其中观察到重力诱导的压实。为了减少重力聚集体的重组，因此，调查蓬松的灰尘聚集体的碰撞行为，我们进行了额外的实验，在微重力环境下的落塔。我们观察到，只要冲击速度高于每秒几米，团聚体就会被破坏。对于稍低的碰撞速度，检测到粘附到目标和从目标去除。在甚至更低的速度下，撞击的灰尘团块被目标捕获，具有统一的粘附概率，并且形成紧凑的灰尘层。当冲击能量不再足够大，以允许团聚重组，内部结构的影响聚集被保存，我们观察到一个非常多孔的灰尘层的增长。我们的实验结果是定性的，但不是在定量与理论预测一致。当使用最近测量的滚动摩擦力F-roll = 1.2 × 10（-9）N和破碎能E-br = 1.3 × 10（-15）J（对直径为1.9 μ m的SiO2球有效）的值时，可以达到计算机模拟和实验之间的完全定量一致。我们的实验结果表明，在太阳星云聚集重组，因此，逐渐增加的分形维数的尘埃团聚体，成为一个重要的过程时，聚集体直径超过几厘米，尘埃聚集体低于该尺寸预计不会受到冲击压实。(C)北京大学出版社.
We performed laboratory as well as microgravity experiments in which we studied the impact of small fractal aggregates consisting of micrometer-sized dust particles onto solid targets at various velocities. Slow bombardment of the target in the laboratory results in the formation of a fluffy dust layer in which gravity-induced compaction is observed. In order to reduce the gravitational aggregate restructuring and, hence, to investigate the collisional behavior of fluffy dust aggregates, we performed additional experiments in the microgravity environment of a drop tower. We observe that the agglomerates are disrupted as long as the impact velocities are above a few meters per second. For slightly lower collision velocities, both sticking to and removal from the target are detected. At even lower velocities, the impinging dust agglomerates are captured by the target with a sticking probability of unity, and a compact dust layer forms. When the impact energies are no longer sufficiently large to allow for agglomerate restructuring, the internal structures of the impacting aggregates are preserved, and we observe the growth of a very porous dust layer. The results of our experiments are in qualitative, but not in quantitative agreement with theoretical predictions. Full quantitative accordance between computer simulations and experiments can be reached when the recently measured values for the rolling friction force F-roll = 1.2 x 10(-9) N and for the break-up energy E-br = 1.3 x 10(-15) J (valid for 1.9-mu m-diameter SiO2 spheres) are used. Our experimental results suggest that aggregate restructuring in the solar nebula, and hence, the gradual increase of the fractal dimensionality of the dust agglomerates, becomes an important process when the aggregate diameters exceed a few centimeters, Dust aggregates below that size are not expected to be subjected to impact compaction. (C) 2000 Academic Press.