Bubble and jet induced by underwater wire explosion in a narrow tube
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摘要: 以高速摄影为主要手段，揭示直管中爆炸诱导气泡和射流的典型演变过程，并测试爆炸深度和爆炸能量对该现象的影响。研究发现直管中爆炸诱导的表面射流分为光滑和粗糙的两段，这区别于自由表面射流的形态；爆炸气泡的发展经历一个先膨胀再坍缩的过程，其中封闭坍缩以气泡顶部形成内向射流为特征。表面射流速度主要来自爆炸早期短时间内气泡膨胀赋予水体的冲量，且整体上与起爆能量成正相关，而与爆炸深度成反相关；用准一维的简化模型能够很好地描述它们之间的依赖关系，计算结果不仅在趋势上与实验结果一致，数值上也能很好吻合。Abstract: A high-speed video camera was employed to record the flow field directly. Different explosion energy (discharging voltage) and explosion depth were examined. It is found that the surface jet formed in the narrow tube consists of a smooth upper body and a rough root, which differs from the general recognition of free surface jets. The bubble induced by the wire explosion underwent an expansion-collapse process, and the close-in collapse was characterized by a downward inner jet popping out from the bubble roof. The study also reveals that the strength of the surface jet increases with the explosion energy while decreases with explosion depth. A quasi-one-dimensional theoretical model was proposed to analyze the parametric dependences. It turns out not only the variation trend but also the exact value of both maximum bubble scale and jet velocity can be well predicted by this model.
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Key words:
- mechanics of explosion /
- jet /
- underwater wire explosion /
- straight tube /
- bubble
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图 2 Uc=300 V，h=15 mm，直管中气泡及界面射流发展高速摄影图像
Figure 2. Sequential images of the interfacial flow in a straight tube with Uc=300 V and h=15 mm
4(a) Uc=300 V，h=5 mm, 直管中气泡及界面射流发展高速摄影图像
4(a). Sequential images of the interfacial flow in a straight tube with Uc=300 V and h=5 mm
4(b) Uc=300 V, h=25 mm时, 直管中气泡及界面射流发展高速摄影图像
4(b). Sequential images of the interfacial flow in a straight tube with Uc=300 V and h=25 mm
图 5 气泡最大长度和表面射流速度随爆炸深度的变化
Figure 5. Maximum bubble length and surface jet velocity varied with explosion depth
图 6 直管中不同深度爆炸波与自由界面作用示意图
Figure 6. Schematic of interaction patterns of a free surface and an explosion at varied depths in a straight tube
图 7 h=20 mm, Uc=150, 350 V时，直管中气泡及界面射流发展高速摄影图像
Figure 7. Sequential images of the interfacial flow in a straight tube with h=20 mm and Uc=150, 350 V
图 8 气泡最大长度和表面射流速度随充电电压(能量)的变化
Figure 8. Maximum bubble length and surface jet velocity varied with charging voltage (energy)
图 10 理论计算得到的气泡长度随时间的变化
Figure 10. Evolution history of bubble length by theoretical calculation
表 1 气柱初始条件设置
Table 1. Initial conditions for gas column
初始条件 L0/mm pb0/MPa 1 0.001 367.00 2 0.010 38.20 3 0.100 4.23 
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