Numerical simulations of highly porous dust aggregates in the low-velocity collision regime Implementation and calibration of a smooth particle hydrodynamics code
Numerical simulations of highly porous dust aggregates in the low-velocity collision regime Implementation and calibration of a smooth particle hydrodynamics code
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低速碰撞状态下高孔隙尘埃聚集体的数值模拟 平滑粒子流体动力学代码的实现和校准
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发表时间：
2009
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通讯作者：
J. Blum
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作者：
R. J. Geretshauser;R. Speith;C. Güttler;M. Krause;J. Blum
上下文一个非常有利的星子形成机制是碰撞生长。单个尘埃颗粒以原行星盘中气流产生的相对速度相互撞击。它们通过货车德瓦尔斯力粘在一起，形成一厘米大小的蓬松聚集体。负责任何额外增长的机制尚不清楚，因为在相关的速度和大小制度的聚集碰撞的结果不能在实验室中的原行星盘条件下进行研究。为了更深入地了解行星的增长，需要对分米以上的尘埃聚集体碰撞进行实际统计。目标。通过结合实验和数值计算的努力，我们希望校准和验证的计算机程序能够准确地模拟高度多孔尘埃聚集体的宏观行为。在彻底测试了它的数值限制后，我们检查了该程序，特别是对压实，弹跳和碎片行为的真实再现。这证明了我们的代码，这将被用来模拟尘埃聚集体碰撞，并在未来的工作中准确地确定碎片统计的有效性。方法.我们采用光滑粒子流体动力学（SPH）数值方案与扩展的模拟固体和修改版本的Sirono孔隙度模型。实验测得的宏观材料性质的二氧化硅粉尘实施。通过模拟三种不同的设置，我们校准和测试的抗压强度关系（压实实验）和体积模量（反弹和破碎实验）。将直接比较实验和模拟的数据。结果SPH已被证明是模拟高速碰撞的合适工具。在这项工作中，我们证明了它的应用领域可能超出低速实验和碰撞。它也可以用来模拟高孔隙率物体在这种速度状态下的行为，达到非常高的精度。压实实验中密度结构的正确再现，回弹实验中的恢复系数，以及破碎实验中的碎片质量分布，说明了我们的代码模拟模拟粉尘聚集体的弹性和塑性性质的有效性和一致性。这个校准过程的结果是一个SPH代码，可以用来调查多孔尘埃在低速制度的碰撞结果。
Context. A highly favoured mechanism of planetesimal formation is collisional growth. Single dust grains hit each other with relative velocities produced by gas flows in the protoplanetary disc. They stick together with van der Waals forces and form fluffy aggregates up to a centimetre size. The mechanism responsible for any additional growth is unclear since the outcome of aggregate collisions in the relevant velocity and size regime cannot be investigated in the laboratory under protoplanetary disc conditions. Realistic statistics for dust aggregate collisions beyond decimetre size are required to obtain a deeper understanding of planetary growth. Aims. By combining experimental and numerical efforts, we wish to calibrate and validate a computer program capable of accurately simulating the macroscopic behaviour of highly porous dust aggregates. After testing its numerical limitations thoroughly, we check the program especially for a realistic reproduction of the compaction, bouncing, and fragmentation behaviour. This demonstrates the validity of our code, which will be utilised to simulate dust aggregate collisions and accurately determine the fragmentation statistics in future work. Methods. We adopt the smooth particle hydrodynamics (SPH) numerical scheme with extensions to the simulation of solid bodies and a modified version of the Sirono porosity model. Experimentally measured macroscopic material properties of SiO2 dust are implemented. By simulating three different setups, we calibrate and test for the compressive strength relation (compaction experiment) and the bulk modulus (bouncing and fragmentation experiments). Data from experiments and simulations will be compared directly. Results. SPH has already proven to be a suitable tool for simulating collisions at rather high velocities. In this work, we demonstrate that its area of application may be beyond low-velocity experiments and collisions. It can also be used to simulate the behaviour of highly porous objects in this velocity regime to very high accuracy. A correct reproduction of density structures in the compaction experiment, of the coefficient of restitution in the bouncing experiment, and of the fragment mass distribution in the fragmentation experiment illustrate the validity and consistency of our code for the simulation of the elastic and plastic properties of the simulated dust aggregates. The result of this calibration process is an SPH code that can be utilised to investigate the collisional outcome of porous dust in the low-velocity regime.