大小相等的冰粒团块之间的碰撞
Collisions between equal sized ice grain agglomerates
摘要：
根据最近对彗星物质结构的了解，原星子被认为具有低密度和高度多孔的聚集体。目前还不清楚星子是否可以通过碰撞生长从这些物体中形成。因此，重要的是数值研究的碰撞结果从低速冲击的相同尺寸的多孔团聚体，这是太大了，在实验室实验中检查。我们使用拉格朗日粒子方法光滑粒子流体动力学来求解描述弹性和塑性体动力学的方程。此外，考虑到孔隙率的影响，我们遵循先前开发的状态方程和材料强度与相对密度之间的某些关系。碰撞增长似乎可能相当低的碰撞速度和特定的材料强度。如果碰撞参量大于碰撞物体半径的50%，则碰撞残余物往往会旋转。对于小的碰撞参量，碰撞物体被有效地减慢，而没有多孔结构的显著压实，这可能增加生长的可能性。然而，原星子在大部分物质强度下并不粘在一起。旋转对碰撞生长的影响是后续研究中的一个重要问题。此外，对于原行星体的真实模拟，更详细地了解正确的材料参数至关重要。
英文摘要：
Following the recent insight in the material structure of comets, protoplanetesimals are assumed to have low densities and to be highly porous agglomerates. It is still unclear if planetesimals can be formed from these objects by collisional growth. Therefore, it is important to study numerically the collisional outcome from low velocity impacts of equal sized porous agglomerates which are too large to be examined in a laboratory experiment. We use the Lagrangian particle method Smooth Particle Hydrodynamics to solve the equations that describe the dynamics of elastic and plastic bodies. Additionally, to account for the influence of porosity, we follow a previous developed equation of state and certain relations between the material strength and the relative density. Collisional growth seems possible for rather low collision velocities and particular material strengths. The remnants of collisions with impact parameters that are larger than 50% of the radius of the colliding objects tend to rotate. For small impact parameters, the colliding objects are effectively slowed down without a prominent compaction of the porous structure, which probably increases the possibility for growth. The protoplanetesimals, however, do not stick together for the most part of the employed material strengths. An important issue in subsequent studies has to be the influence of rotation to collisional growth. Moreover, for realistic simulations of protoplanetesimals it is crucial to know the correct material parameters in more detail.
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