Characteristics of wall pressure generated by bubble jets in an underwater explosion
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摘要: 水下爆炸气泡射流载荷是中近场水下爆炸壁压载荷的重要组成部分, 将水下爆炸气泡射流简化为一段高速水柱来研究水下爆炸气泡射流载荷特性是研究水下爆炸气泡射流载荷的主要手段。本文基于腔内爆炸提出了一种新的高速水射流实验方法,并给出了实验装置设计、实验方法以及实验系统。基于实验系统,开展了不同工况下高速水射流的实验研究,研究了腔口位置、腔深对水射流形态的影响,并对水射流的形态形成因素进行了分析。使用压电型壁压传感器测得了水射流冲击壁压,给出了水射流冲击壁压的特性及其特点。实验结果表明:腔口位置与腔深是影响水射流端面形态的重要因素;生成的高速水射流冲击壁压峰值满足水锤理论。基于腔内爆炸的高速水射流实验方法能够应用于包括水下爆炸气泡射流在内的高速水射流形态、壁压特性的研究。Abstract: The loading of bubble jet is an important part of the whole loading induced by the middle-field and near-field underwater explosion. Due to the fact that the period of the bubble jet is extremely short and the jet occurs inside the complicated underwater explosion bubble, it is hard to investigate the bubble jet through the direct underwater explosion bubble. Therefore, simplifying underwater explosion bubble jet into a high-speed water column has been widely adopted by many researchers to investigate the bubble jet. Based on the in-cavity explosion, a new high-speed water jet experimental methodology was proposed, and the experimental device design, method and system were presented as well. The details about how to carry out the pertinent experiments were also illustrated. Based on the proposed experimental system, the experimental research on high-speed water jet under different conditions were carried out. It is found that the shapes of the generated high-speed water jet vary with the outlet position and the depth of the cavity. Three experiments with three different cavity depths but same outlet position, and other two experiments with same cavity depth but different outlet positions were carried out. According to the results, the shape of the water jet generated in the experiments with short cavity depth and surface-above outlet position cannot meet the requirements of the investigation. The influence of outlet position and depth of the cavity on the shape of the water jet was investigated and the mechanism of the water jet shape was analyzed. According to the requirements of the investigation of the bubble jet wall pressure, the adoptable outlet position and cavity depth were got. In the experiments, the piezoelectric wall pressure sensor was used to measure the wall pressure of the water jet. The whole water jet wall pressure can be divided into two phases: the initial impact pressure period and the later hydrodynamical pressure period. According to the results, the outlet position and the depth of the cavity are the two main factors affecting on the shape of the water jet. The initial impact pressure of the water jet meets the water hammer theory. The proposed water jet experimental methodology based on the in-cavity explosion can be used to investigate the shape of the high-speed water jet and wall pressure characteristics including the underwater explosion bubble jet.
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表 1 高速水射流形态
Table 1. Morphology of the high speed water column
腔口位置 腔深/mm 高速水射流形态 腔口高于水面 − 高速水射流端面中部形成尖突 腔口低于水面 75 水柱长度较短,且在后期受到爆炸气体产物喷出的影响,水柱出现破碎 腔口低于水面 150 水射流水柱存在间断,且水柱表面存在破碎,高速水射流端面呈现椭球形曲面 腔口低于水面 300 水柱较长、连续性较好、水柱表面较光滑,高速水射流端面呈现椭球形曲面 表 2 实验SZM1水柱端面位置
Table 2. Position of the head face of water column with test SZM1
采样时间/ms 水柱端面位置/mm −1.20 −12.85 −0.08 −8.55 −0.04 −4.30 0 0 表 3 工况SZM2、SZM3水柱端面位置
Table 3. Position of the head face of water column with tests SZM2 and SZM3
采样时间/ms 水柱端面位置/mm SZM2 SZM3 −1.20 −12.80 −12.75 −0.08 −8.53 −8.50 −0.04 −4.25 −4.30 0 0 0 表 4 实验SZM1、SZM2、SZM3初始水锤压力峰值对比
Table 4. Comparison of initial water hammer pressure peaks with tests SZM1, SZM2 and SZM3
实验 冲击速度/
(m·s−1)理论峰值/
MPa实测峰值/
MPa相对误差/
%SZM1 107.0 80.25 77.5 3.43 SZM2 106.5 79.88 74.3 7.00 SZM3 106.0 79.50 76.0 4.40 平均 106.5 79.88 75.9 4.98 -
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