Characteristics of wall pressure and cavitation on the plate subjected to underwater explosion shockwaves at any angle of incidence
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摘要: 以平面波理论为基础，推导了无限平板在全入射角度下的冲击波壁压载荷计算公式，利用实验数据对壁压公式进行修正，提出了一种适用于计算有限尺度平板壁压的经验公式；分析了不同入射角度下壁压载荷的变化特性，初步研究了壁压载荷负压特性对平板局部空化的影响。结果表明：修正后的壁压曲线与实际壁压曲线吻合较好；入射角度的增大会加快壁压衰减过程，并使最低壁压的绝对值减小；随着药量或平板厚度的增加，壁压最低负压的绝对值增大，形成局部空化的能力增强；局部空化仅在一定条件范围内才会形成，空化范围受局部空化形成压力及冲击强度等因素的影响较大。Abstract: Wall pressure as a load parameter should be confirmed exactly, and then offered for investigating dynamic response of structure such as a plate subjected to underwater explosion.On the basis of plane shock wave hypothesis, a theoretical formula was deduced and proposed to calculate the wall pressure values of an infinite plate subjected to underwater explosion shockwaves at any angle of incidence.By using the wall pressure data derived from underwater explosion experiments, the theoretical formula of wall pressure was revised to be suitable for plates with finite dimensions.With the revised formula, the characteristics of the wall pressure on the plate were analyzed by considering various incidence angles, and the effects of the negative wall pressure values on local cavitation on the plate were discussed primarily.The results show that the wall pressure values derived from the revised formula agree well with those from the experiments.As the incidence angle increases, the wall pressure decays more rapidly, and the absolute value of the minimum wall pressure decreases.With the more explosive or the thicker plate, the absolute value of the minimum wall pressure is larger, and local cavitation takes place more likely.Local cavitation can only come into being in certain conditions, and the cavitation range will be affected by the factors such as cavitation pressure criterion, shock intensity, and so on.
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Key words:
- mechanics of explosion /
- plate wall-pressure /
- underwater explosion /
- shockwaves /
- local cavitation /
- oblique incidence
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图 1 任意角度入射冲击波作用下的无限平板
Figure 1. Infinite plate subjected to an inclined plane shockwave
图 2 函数f(α)计算值与实验值的比较
Figure 2. Comparison of theoretical and experimental results of f(α)
图 3 冲击波壁压理论值和实验值的比较
Figure 3. Comparison of theoretical and experimental results of wall pressure
图 6 不同药量条件下入射角度对最小壁压值的影响
Figure 6. Effect of incidence angle on minimum wall-pressure value
图 7 不同板厚条件下垂直爆距对局部空化区域半径的影响
Figure 7. Effect of minimum stand-off distance on radius of local cavitation zone
表 1 不同爆炸工况下冲击波壁压峰值实验值及理论值对比
Table 1. Comparison of theoretical and experimental results of wall pressure in test cases
No. me/kg R/m $\left(\sqrt{m_{\mathrm{e}}} / R\right) /\left(\mathrm{kg}^{0.5} \cdot \mathrm{m}^{-1}\right)$ mp/(kg·m-2) α /(°) pwt/MPa pwe/MPa Cp 1 0.005 0.10 0.707 7.8 3 191.680 124.960 0.652 2 0.005 0.15 0.471 7.8 5 121.220 80.010 0.660 3 0.050 1.00 0.224 7.8 6 33.820 22.560 0.667 4 6.000 19.55 0.125 93.6 6 7.420 5.580 0.752 5 6.000 10.21 0.240 93.6 20 15.520 12.240 0.789 6 6.000 15.23 0.100 23.4 67 0.154 0.068 0.442 7 6.000 15.23 0.100 23.4 4 0.170 0.127 0.747 8 1.000 12.59 0.079 23.4 83 5.910 0.990 0.168 9 1.000 12.99 0.077 23.4 64 5.770 2.250 0.390 10 1.000 8.83 0.113 23.4 69 8.920 4.890 0.548 11 1.000 5.33 0.188 23.4 65 15.780 9.050 0.574 12 1.000 4.69 0.213 23.4 27 18.240 14.140 0.775 13 6.000 16.56 0.148 23.4 77 8.600 2.240 0.260 14 6.000 16.50 0.148 23.4 69 8.640 3.600 0.417 15 6.000 15.07 0.163 23.4 50 9.580 4.200 0.438 注：工况1~3、5~8、13~15为函数f(α)拟合样本点工况；工况4、9~12为考查点工况。 
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表 2 不同爆炸工况下冲击波衰减常数实验值及理论值对比
Table 2. Comparison of theoretical and experimental results of θ in test cases
No. me/kg R/m $\left(\sqrt{m_{\mathrm{e}}} / R\right) /\left(\mathrm{kg}^{0.5} \cdot \mathrm{m}^{-1}\right)$ mp/(kg·m-2) α /(°) θpt/μs θpe/μs ε/% 1 0.005 0.10 0.707 7.8 3 3.5 3.2 8.6 2 0.005 0.15 0.471 7.8 5 3.6 3.6 0.0 3 0.050 1.00 0.224 7.8 6 4.5 4.5 0.0 4 6.000 10.21 0.240 93.6 20 13.6 13.3 2.2 5 2.000 15.21 0.093 23.4 81 2.5 2.3 8.0
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