Ejection-velocity distributions from impacts into coarse-grained sand
Ejection-velocity distributions from impacts into coarse-grained sand
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DOI：
10.1111/j.1945-5100.1999.tb01367.x
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发表时间：
1999-07-01
影响因子：
2.2
通讯作者：
Hörz, F
中科院分区：
文献类型：
--
作者：
Cintala, MJ;Berthoud, L;Hörz, F
通过基于激光的设备测量了从铝弹丸的七个影响到粗粒沙的七个影响的射出速度，该设备在弹道飞行中产生单个晶粒的频镜照片。然后可以非常精确地测量大多数喷射的速度和角度。冲击速度似乎对缩放，径向发射位置与弹出角度之间功能关系的影响似乎很小。正如维度分析所预测的那样，这七个实验涵盖了从0.8到1.9 km S（-1）的一系列冲击速度遵循幂律分布的测得的射出速度，但是如所预测的，在给定事件中，射血角度并不恒定。实际上，随着距冲击点的径向距离的增加，射血角度逐渐下降，但有迹象表明，随着最终火山口的位置接近，角度再次增加。根据鳞片尺寸和射血速分布确定的指数大不相同。尽管这可能意味着维度分析中使用的假设是无效的，但也有可能粗砂的成分晶粒在尺寸上与撞击器的直径相当，而是提出了一个更像是不均匀骨料的目标。大片段比均匀的连续培养基。
Velocities of ejecta from seven impacts of aluminum projectiles into coarse-grained sand have been measured with a laser-based apparatus that produces stroboscopic photographs of individual grains in ballistic flight. Speeds and angles of the majority of the ejecta can then be measured very precisely. There appears to be little effect of impact velocity on the functional relationship between the scaled, radial launch position and either the speed or angle of ejection; the seven experiments covered a range of impact velocities from 0.8 to 1.9 km s(-1) The measured ejection speeds follow power-law distributions, as predicted by dimensional analysis, but the angle of ejection is not constant throughout a given event as predicted. Indeed, the angle of ejection declines gradually with increasing radial distance from the impact point, but there are indications that the angle increases again as the position of the final crater's rim is approached. The exponents determined from scaled crater dimensions and ejection-speed distributions are substantially different. Although this might imply that assumptions used in the dimensional analysis are not valid, it is also possible that the coarse sand, whose component grains were comparable in dimension to the diameter of the impactors, instead presented a target that was more of an inhomogeneous aggregate of large fragments than a uniform, continuous medium.