Experiment of cavitation and ballistic characteristics of slender body underwater movement
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摘要: 为了研究细长体水下高速运动时空泡的产生、闭合及脱落特性，及影响细长体空泡形态及弹道特性的复杂因素等，初步开展了细长体模型水下高速运动的实验研究，分析了不同初始空化数下细长体模型在水中高速运动的一系列流动现象，重点研究了空泡的发展、闭合、尾部回射流和尾部脱落特性，以及轴对称细长体模型弹道特性与空泡形态变化之间的关系和转动特性随时间的变化历程等。结果表明：细长体水下高速运动时形成超空泡，空泡头部光滑透明，尾部凝结有汽水混合物且有交替脱落的含气漩涡；初始空化数对细长体的速度衰减有所影响；受初始扰动影响，细长体水下运动伴随有绕头部的转动且初始扰动影响细长体俯仰角随时间的变化历程。Abstract: Experimental studies of the slender body's underwater movement were conducted using high-speed camera. Based on the results from the experiment, we examined the characteristics of the cavitation and ballistic of the slender body moving underwater. The experimental results show that the slender body's underwater movement is accompanied with a supercavity, and the slender body's movement and rotation occur in the supercavity except for the contact between the slender body's head and the supercavity wall and the supercavity wall is transparent and smooth except for its tail. The impact between the tail of the slender body and the supercavity wall results from the slender body's rotation in the supercavity, called the tail slap, which serves to stabilize the slender body's movement in the supercavity as a result form the initial perturbation of the flow field. The cavity evolution, closure and shedding were discussed in detail. Series of different flow mechanisms and the relationship between ballistic characteristics and cavity morphology were also analyzed with different initial velocities. The slender body has different accelerations with different initial velocities and the effect of the drag reduction using super cavitation is influenced by factors such as cavity length, diameter and aspect ratio, etc. The initial perturbation angle affects the variation of the angle between the slender body and the cavity axis.
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Key words:
- multiphase flow /
- vaporization /
- turbulent flow /
- slender body /
- cavity
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图 1 细长体水下运动实验系统示意图
Figure 1. Schematic of experimental facility of slender body underwater movement
图 5 细长体水下运动空泡形态图
Figure 5. Morphology ot cavity caused by slender body moving under water
图 7 不同时刻空泡尾部的闭合及脱落
Figure 7. Closure and shedding characteristics of cavity tail at different times
图 8 不同初始速度下细长体模型的速度变化
Figure 8. Slender body velocities vs. time with different initial velocities
图 9 三组工况下当t=4ms的模型运动对比图
Figure 9. Comparison of underwater slender body movement in three different conditions (t=4ms)
图 10 不同初始速度下细长体模型的水平位移变化
Figure 10. Slender body trajectories in x direction vs. time with different initial velocities
图 11 不同初始速度下细长体模型的垂直位移变化
Figure 11. Slender body trajectories in y direction vs. time with different initial velocities
图 13 不同初始速度下细长体空泡轴线与x轴夹角变化
Figure 13. Angle α vs. time with different initial velocities
图 14 不同初始速度下细长体模型轴线与x轴线夹角变化
Figure 14. Angle β vs. time with different initial velocities
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