Impact Ejecta Near the Impact Point Observed Using Ultra‐high‐Speed Imaging and SPH Simulations and a Comparison of the Two Methods
Impact Ejecta Near the Impact Point Observed Using Ultra‐high‐Speed Imaging and SPH Simulations and a Comparison of the Two Methods
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DOI：
10.1029/2019je005943
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发表时间：
2020-03
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影响因子：
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通讯作者：
T. Okamoto;K. Kurosawa;H. Genda;T. Matsui
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文献类型：
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作者：
T. Okamoto;K. Kurosawa;H. Genda;T. Matsui
与撞击速度相当的高速撞击喷出物预计将有助于行星体之间的物质运输和远离撞击坑的喷出物沉积。我们使用实验和数值方法研究了45°和90°角下产生的高速喷射物的行为。千叶工业大学行星探索研究中心（日本）开发的实验系统使我们能够观察喷出物的初始生长。我们成功地以0.2 μs的间隔对4.8 mm直径的聚碳酸酯射弹以约4 km s−1的撞击速度撞击到聚碳酸酯板上的高速喷出物进行了成像。光滑粒子流体动力学（SPH）模拟的各种数值分辨率进行了相同的影响条件有关的实验。我们比较了实验和模拟的喷出物的形态和速度，我们证实了高分辨率模拟的密切匹配（≥106 SPH粒子代表抛射体）。根据我们的高分辨率模拟获得的喷出物速度分布，倾斜撞击的高速喷出物的喷出速度远大于垂直撞击的喷出速度。在倾斜撞击中，平行于目标表面的穿透射弹的平移运动可能会在喷出物的根部引起长期、持续的加速度。
High‐speed impact ejecta at velocities comparable to the impact velocity are expected to contribute to material transport between planetary bodies and deposition of ejecta far from the impact crater. We investigated the behavior of high‐speed ejecta produced at angles of 45° and 90°, using both experimental and numerical methods. The experimental system developed at the Planetary Exploration Research Center of Chiba Institute of Technology (Japan) allowed us to observe the initial growth of the ejecta. We succeeded in imaging high‐speed ejecta at 0.2 μs intervals for impacts of polycarbonate projectiles of 4.8 mm diameter onto a polycarbonate plate at an impact velocity of ~4 km s−1. Smoothed particle hydrodynamics (SPH) simulations of various numerical resolutions were conducted for the same impact conditions as pertaining to the experiments. We compared the morphology and velocities of the ejecta for the experiments and simulations, and we confirmed a close match for high‐resolution simulations (with ≥106 SPH particles representing the projectile). According to the ejecta velocity distributions obtained from our high‐resolution simulations, the ejection velocities of the high‐speed ejecta for oblique impacts are much greater than those for vertical impacts. The translational motion of penetrating projectiles parallel to the target surface in oblique impacts could cause long‐term, sustained acceleration at the root of the ejecta.