Collisional evolution of dust aggregates. From compaction to catastrophic destruction
Collisional evolution of dust aggregates. From compaction to catastrophic destruction
复制标题
尘埃聚集体的碰撞演化。
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
C. Dominik
中科院分区：
文献类型：
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作者：
D. Paszun;C. Dominik
尘埃聚集体的凝聚发生在各种天体物理环境中。每一种都以影响生长的不同条件为特征，例如，最小成分（单体）的相对速度、组成和尺寸。在这里，我们研究的微观物理碰撞的尘埃聚集在一个四维参数空间。参数包括碰撞能量、团聚体的初始致密性、碰撞伙伴的质量比和冲击参数。为此，我们采用了最先进的分子动力学类型的模型，已被广泛和成功地测试对实验室实验的状态。它模拟了通过货车范德华表面力动态相互作用的单个单体的运动。聚集体的结构通过提供关于内部结构、单体的堆积密度和聚集体的投影表面积的信息的填充因子来量化。我们的研究结果表明，由于拉伸力作用在偏移碰撞的影响参数，导致细长颗粒的形成的重要性。在正面碰撞中，聚集体在较低的能量下被压实。足够高的能量导致重组以达到最大压实。如果提供更多的能量，就会形成煎饼状的结构。我们发现，碰撞的结果可以用一种简单的方式表示。一个非常明显的大碎片组件共存的幂律分布的小碎片。这些小碎片的结构参数很好地描述了一个简单的关系，在很大程度上独立于初始的紧凑性，冲击能量或冲击参数。模拟结果表明，高质量比碰撞的侵蚀可能是显着的。喷射质量可以比冲击器质量高几个数量级。这与等质量聚集体的碰撞形成对比，其中相同的冲击能量可以导致完美的粘附。这些发现被总结为一个简单的碰撞配方的形式。配方指定碰撞的结果，在影响参数上取平均值。它以表格形式提供了一系列物理参数，如碰撞能量和碰撞前填充系数。通过提供配方的局部和全局分支来考虑对撞击器和目标的质量比的依赖性。
The coagulation of dust aggregates occurs in various astrophysical environments. Each one is characterized by different conditions that influence the growth, e.g., relative velocities, composition, and size of the smallest constituents (monomers). Here we study the microphysics of collisions of dust aggregates in a four-dimensional parameter space. The parameters are the collision energy, the initial compactness of agglomerates, the mass ratio of collision partners, and the impact parameter. For this purpose we employ a state of the art molecular dynamics type of model that has been extensively and successfully tested against laboratory experiments. It simulates the motion of individual monomers interacting dynamically via van der Waals surface forces. The structure of aggregates is quantified by the filling factor that provides information about the internal structure, the packing density of monomers, and the projected surface area of aggregates. Our results show the importance of the impact parameter that causes formation of elongated particles, due to tensile forces acting in offset collisions. In head-on impacts, aggregates are compacted at lower energies. A sufficiently high energy causes restructuring to reach maximum compaction. If more energy is provided, pancake-like structures are formed. We find that the outcome of collisions can be represented in a simple way. A highly pronounced large fragment component coexists with a power-law distribution of small fragments. The structural parameter of these small fragments is described very well by a simple relation, largely independent of the initial compactness, impact energy or impact parameter. The simulations show that erosion by collisions with high mass-ratio can be significant. The ejected mass can be several orders of magnitude higher than the impactor mass. This contrasts with collisions of equal mass aggregates, where the same impact energy can lead to perfect sticking. These findings are summarized in the form of a simple collision recipe. The recipe specifies the outcome of a collision, averaged over the impact parameter. It is provided in tabular form for a range of physical parameters such as impact energy and pre-collision filling factor. The dependence on the mass ratio of impactor and target is taken into account by providing both a local and a global branch of the recipe.