Asymmetry of ejecta flow during oblique impacts using three-dimensional particle image velocimetry
Asymmetry of ejecta flow during oblique impacts using three-dimensional particle image velocimetry
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DOI：
10.1029/2003je002075
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发表时间：
2003-08-23
影响因子：
4.8
通讯作者：
Heineck, JT
中科院分区：
文献类型：
--
作者：
Anderson, JLB;Schultz, PH;Heineck, JT
三维粒子图像测速 (3D PIV) 应用于撞击坑实验，可以直接测量坑生长时喷射幕内喷射粒子的位置和速度。实验室实验在 NASA 艾姆斯垂直炮靶场进行，以接近 1 km/s（直径 6.35 毫米的铝球）的速度在真空中以与水平面成 90 度和 30 度的角度冲击中粒（0.5 毫米）颗粒沙目标。这项研究检查了陨石坑增长的前 50%，在此期间陨石坑已增长至最终半径的一半。根据 3D PIV 数据，将喷射物颗粒的弹道轨迹推断回目标表面，以确定喷射速度、角度和位置。对于垂直撞击，这些喷射参数在陨石坑中心周围的所有方向（方位角）上保持恒定。 30 度的影响表现出方位角的不对称性，这种不对称性一直持续到挖掘阶段的水流中。这些不对称性表明单个固定点源不足以描述倾斜撞击期间的地下流场。
Three-dimensional particle image velocimetry (3D PIV) applied to impact cratering experiments allows the direct measurement of ejecta particle positions and velocities within the ejecta curtain as the crater grows. Laboratory experiments were performed at the NASA Ames Vertical Gun Range with impact velocities near 1 km/s (6.35-mm diameter aluminum spheres) into a medium-grained (0.5 mm) particulate sand target in a vacuum at 90degrees and 30degrees from the horizontal. This study examines the first 50% of crater growth, during which the crater has grown to one half its final radius. From the 3D PIV data, the ballistic trajectories of the ejecta particles are extrapolated back to the target surface to determine ejection velocities, angles, and positions. For vertical impacts these ejection parameters remain constant in all directions (azimuths) around the crater center. The 30degrees impacts exhibit asymmetries with respect to azimuth that persist well into the excavation-stage flow. These asymmetries indicate that a single stationary point source is not adequate to describe the subsurface flow field during an oblique impact.