Asymmetry of ejecta flow during oblique impacts using three-dimensional particle image velocimetry

被引:101
作者
Anderson, JLB
Schultz, PH
Heineck, JT
机构
[1] Brown Univ, Providence, RI 02912 USA
[2] NASA, Ames Res Ctr, Moffett Field, CA 94035 USA
关键词
oblique impacts; ejecta flow; particle image velocimetry; Ames Vertical Gun Range; experimental impacts;
D O I
10.1029/2003JE002075
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
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.
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页数:10
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