The four-population model: a new classification scheme for pre-planetesimal collisions
The four-population model: a new classification scheme for pre-planetesimal collisions
复制标题
四群体模型：星子碰撞前的新分类方案
DOI：
10.1051/0004-6361/201116901
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发表时间：
2011
影响因子：
6.5
通讯作者：
W. Kley
中科院分区：
文献类型：
--
作者：
R. J. Geretshauser;F. Meru;R. Speith;W. Kley
上下文在碰撞增长的星子形成的情况下，从厘米级大小的前星子的增长步骤，以千分之一级大小的星子仍然不清楚。从高度多孔的前星子中形成更大的物体可能会被破坏性碰撞中的碎片化和相互反弹与压实的结合所阻止。然而，适量的碎片是必要的，以解释所观察到的尘埃功能晚金牛座T光盘。因此，需要关于小行星碰撞前的结果的详细数据，而且必须以适当和精确的格式提出。目标。我们希望开发一种新的分类方案，它足够广泛，可以涵盖所有具有粘附、弹跳和碎片贡献的事件，足够准确，可以捕捉到重要的碰撞结果细微差别，同时又足够简单，可以在全球尘埃凝结模拟中实施。此外，我们希望证明我们的数值光滑粒子流体动力学（SPH）模型的可靠性和我们的新的碰撞结果分类以前的结果，以及我们的模拟结果的适用性。方法.我们提出并应用一个计划的基础上的定量方面的四个片段人口：最大和第二大的片段，幂律人口，和一个子分辨率人口。对于前星子碰撞的模拟，我们采用了扩展的SPH数值格式，用于多孔固体的模拟。在实验室基准实验的基础上，该模型先前进行了校准和测试，以正确模拟宏观高度多孔SiO2粉尘聚集体的压实，弹跳和破碎行为。结果我们表明，以前的尝试映射碰撞数据过于面向定性分类到坚持，反弹，和碎片事件。在我们的模拟中发现，中间类别很难映射到现有的定性分类。我们表明，四人口模型包括所有以前的分类，并允许过渡。这是因为它基于每个群体的定量特征属性，例如质量，动能和填充因子。此外，数值孔隙度模型成功地通过了另一个基准测试：正确模拟实验室实验产生的碰撞结果类型的整个列表。作为一个示范的适用性和权力的四人口模型，我们利用它提出的碰撞速度的影响，在迎面碰撞的中间孔隙度聚集体的研究结果。
Context. Within the collision growth scenario for planetesimal formation, the growth step from centimetre-sized pre-planetesimals to kilometre-sized planetesimals remains unclear. The formation of larger objects from the highly porous pre-planetesimals may be halted by a combination of fragmentation in disruptive collisions and mutual rebound with compaction. However, the right amount of fragmentation is necessary to explain the observed dust features in late T Tauri discs. Therefore, detailed data on the outcome of pre-planetesimal collisions is required and has to be presented in a suitable and precise format. Aims. We wish to develop a new classification scheme broad enough to encompass all events with sticking, bouncing, and fragmentation contributions, accurate enough to capture the important collision outcome nuances, and at the same time simple enough to be implementable in global dust coagulation simulations. We furthermore wish to demonstrate the reliability of our numerical smoothed particle hydrodynamics (SPH) model and the applicability of our new collision outcome classification to previous results as well as our simulation results. Methods. We propose and apply a scheme based on the quantitative aspects of four fragment populations: the largest and second largest fragment, a power-law population, and a sub-resolution population. For the simulations of pre-planetesimal collisions, we adopt the SPH numerical scheme with extensions for the simulation of porous solid bodies. On the basis of laboratory benchmark experiments, this model was previously calibrated and tested for the correct simulation of the compaction, bouncing, and fragmentation behaviour of macroscopic highly porous SiO2 dust aggregates. Results. We demonstrate that previous attempts to map collision data were much too oriented on qualitatively categorising into sticking, bouncing, and fragmentation events. Intermediate categories are found in our simulations that are difficult to map to existing qualitative categorisations. We show that the four-population model encompasses all previous categorisations and in addition allows for transitions. This is because it is based on quantitative characteristic attributes of each population such as the mass, kinetic energy, and filling factor. In addition, the numerical porosity model successfully passes another benchmark test: the correct simulation of the entire list of collision outcome types yielded by laboratory experiments. As a demonstration of the applicability and the power of the four-population model, we utilise it to present the results of a study on the influence of collision velocity in head-on collisions of intermediate porosity aggregates.