scaled-down underwater explosion model on a centrifuge apparatus
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摘要: 对离心机水下爆炸缩比实验方法进行探究，对离心机水下爆炸缩比实验的相似理论进行了推导，通过数值计算分析，探究了原模型、离心机缩比实验及常规缩比实验的冲击波载荷、气泡载荷以及气泡动力学行为。结果表明：常规缩比实验不能对气泡行为及垂直方向的近场载荷进行准确的预报，若要保证远场气泡脉冲峰值误差小于10%，则爆距需大于9.5倍气泡最大半径。而离心机缩比实验能够对原模型进行准确的预报，以小当量装药模拟大当量装药水下爆炸整个物理过程，且冲击波和气泡两个阶段完全相似。同时，水深也可以进行几何缩比，克服了常规缩比方法的缺陷。Abstract: In this paper, we investigated a novel method by carrying out a sclaed down underwater explosion experiment on a centrifuge apparatus and set up the similarity theory between the scaled down and actual underwater explosion experiment. Using numerical simulation, we also investigated the shock-wave load, the bubble load and bubble dynamic behaviors between original models, the novel scaled down experimental method and the conventional method. The results from our study indicate that the conventional scaled down model experiment is unable to accurately predict the bubble dynamics and the vertical near-field loading induced by the bubble collapse. When the deviation of the far-field bubble pulse is limited within 10%, the distance between the explosion source and the measuring point has to be larger than 9.5 times that of the maximum radius of the bubble. However, the novel experimental method can make a precise prediction for the original model. The experiment of a mini-charge underwater explosion almost reproduces the whole physical process of a mass-charge underwater explosion with the completely similar stages of the shock wave and the bubble. In addition, the depth of the water can also be scaled down, thereby overcoming the disadvantages of the conventional method. The present study aims at providing a novel way to perform underwater explosion model experiments.
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Key words:
- mechanics of explosion /
- scaled down experiment /
- centrifuge /
- underwater explosion /
- bubble
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图 1 常规缩比实验中测点处的冲击波压力
Figure 1. Pressure of measurement point in conventional scaled down experiment
图 2 离心机缩比实验中测点处的冲击波压力
Figure 2. Pressure of measurement point in centrifuge scaled down experiment
图 3 缩比实验结果与原模型的对比
Figure 3. Comparison of scaled down experiment with original experiment
图 4 常规缩比实验中的气泡运动行为
Figure 4. Bubble motion behavior in conventional scaled down experiment
图 5 原模型和离心机缩比实验的气泡运动行为
Figure 5. Bubble motion behavior in original and centrifuge scaled down experiment
图 7 距爆心垂直方向0.07 m处的气泡载荷
Figure 7. Bubble pressures with vertical distance 0.07 m from explosion center
图 8 距爆心水平方向0.07 m处的气泡载荷
Figure 8. Bubble pressures with horizontal distance 0.07 m from explosion center
图 9 距爆心垂直方向0.4 m处的气泡载荷
Figure 9. Bubble pressures with vertical distance 0.4 m from explosion center
图 10 距爆心水平方向0.4 m处的气泡载荷
Figure 10. Bubble pressures with horizontal distance 0.4 m from explosion center
图 11 原模型与常规缩比实验的气泡峰值压力比
Figure 11. Bubble peak pressure ratio of original to traditional scaling down experiment
表 1 量纲
Table 1. Dimensions
变量 物理量 符号 量纲 冲击波/气泡压力峰值 pmax L－1MT－2 因变量 周期/衰减常数 T T 气泡最大半径 Rb, max L 流体密度 ρw L－3M 爆点处流体静水压 pw L－1MT－2 炸药密度 ρc L－3M 自变量 药包半径 r L 单位质量爆热 Q L2T－2 水中声速 cw LT－1 重力加速度 g LT－2 
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表 2 模型与原型的相似关系
Table 2. Similar relation between original experiment and scaled down experiment
物理量 符号 原型模型比 爆距 R λ 爆热 Q 1 爆点处流体静压 pw 1 流体密度 ρw 1 声速 cw 1 装药密度 ρc 1 药包半径 r λ 重力加速度 g 1/λ 装药质量 W λ3 冲击波压力峰值 ps, max 1 二次脉动压力峰值 pb, max 1 冲击波时间衰减常数 Ts λ 脉动周期 Tb λ 气泡最大半径 Rb, max λ
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表 3 工况设置(λ=100)
Table 3. Conditions
模型 药量/kg 水深/m 惯性加速度/g 原模型 500 50 1 常规缩比实验 5×10-4 50 1 离心机缩比实验 5×10-4 0.5 100
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