Shock Wave Simulation of Underwater Explosion
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摘要: 由于在水下爆炸冲击波的数值仿真研究中,水的状态方程、人工黏性系数和网格尺寸对数值计算结果影响很大,采用常规TNT炸药的水下爆炸为例,以冲击波的峰值压力和比冲量为衡量指标,研究了这3个主要影响因素对数值仿真结果的影响。首先,通过采用常用的5种水的状态方程进行系列仿真,给出了各种状态方程的适用范围;其次,讨论了人工黏性系数对计算结果的影响,并给出了一次与二次人工黏性系数的建议取值范围;最后,通过对不同炸药当量及不同网格尺寸开展系列运算,从而得到不同炸药当量在满足工程计算精度要求下所对应的建议网格尺寸,并得到了不同炸药当量所对应的建议网格尺寸的表达式。Abstract: The state equation of water, artificial viscosity coefficient and mesh size have a great influence on the numerical results of underwater explosion shock wave. In order to improve the simulation accuracy of underwater explosion shock wave, the peak pressure and specific impulse of the conventional TNT explosive underwater explosion are taken as the measurement indicators, and the influence of these factors on the numerical simulation results is studied. For the five kinds commonly state equations of water, the specific values of the artificial viscosity coefficients under different working conditions and appropriate grid size for different explosive equivalents are given. These parameters can provide reference for improving simulation accuracy of underwater explosion shock wave under different working conditions. First, through a series of simulations of the commonly used five kinds of state equations of water, the calculation results of peak pressure and specific impulse are compared with the empirical formula, and the error analysis is carried out to give the applicable scope of each state equation. Secondly, the influence of the artificial viscosity coefficient on the calculation results is discussed, and a series of calculations are carried out for the primary and secondary artificial viscosity coefficients under different working conditions. The recommended range of values for the primary and secondary artificial viscosity coefficients under different working conditions is given. Finally, through a series of calculations on 0.1, 0.5, 1, 10, 50, 100, 500 and 1 000 kg equivalent explosives and different grid sizes, the recommended mesh sizes corresponding to different explosive equivalents under the requirement of engineering calculation accuracy are obtained by limiting the relative error of peak pressure less than 10%. The expressions of the recommended mesh sizes corresponding to different explosive equivalents are also given.
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Key words:
- underwater explosion /
- numerical simulation /
- equation of state /
- artificial viscosity /
- element density
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A/GPa B/GPa R1 R2 ω ρ0/(kg∙m–3) e/(J∙kg–1) 371.2 3.231 4.15 0.95 0.3 1630 4.19 ×106 表 2 常用Mie-Grüneisen状态方程不同形式的参数
Table 2. Commonly used parameters of the Mie-Grüneisen equation of state
表 3 Autodyn程序提供的水多项式状态方程参数[12, 23]
Table 3. Polynomial state equation parameters of water provided by the Autodyn program[12, 23]
A1/GPa A2 /GPa A3 /GPa T1 /GPa T2/GPa B0 B1 2.2 9.54 14.57 2.2 0 0.28 0.28 表 4 Dytran中水的多项式状态方程的参数[24–25]
Table 4. Polynomial state equations parameters of water in Dytran[24–25]
a1/GPa a2/GPa a3/GPa b0 b1 b2 b3 2.002 9.224 8.767 0.493 4 1.393 7 0 0 表 5 1 kg炸药无限水域爆炸冲击波峰值压力
Table 5. Shock wave peak pressure of 1 kg explosive infinite water fields explosion
MPa State equation of water R/R0 7 10 15 20 25 30 35 Autodyn polynomial 165.7 95.6 56.7 40.6 31.3 24.6 20.3 Dytran polynomial 170.7 97.6 57.4 41.2 31.5 25.1 20.8 Steiberg 169.8 97.7 57.7 41.6 31.1 25.3 21.1 SNL 218.7 123.1 71.2 46.2 36.8 30.8 25.7 HULL 182.5 106.7 62.8 45.2 34.9 28.4 23.7 Empirical formula 196.7 115.2 68.3 49.4 38.4 31.2 26.2 表 6 1 kg炸药无限水域爆炸冲击波比冲量
Table 6. Shock wave impulse of 1 kg explosives infinite water fields explosion
N·s·m–2 State equation of water R/R0 7 10 15 20 25 30 35 Autodyn polynomial 12 522.9 9 116.8 6 355.1 4 919.6 4 033.4 3 429.3 2 989.7 Dytran polynomial 12 284.8 8 943.4 6 234.2 4 826.0 3 956.7 3 364.1 2 932.8 Steiberg 12 130.7 8 831.3 6 156.0 4 765.5 3 907.1 3 321.9 2 896.0 SNL 13 237.3 9 636.9 6 717.6 5 200.2 4 263.5 3 624.9 3 160.2 HULL 11 976.6 8 719.1 6 077.9 4 704.9 3 857.5 3 279.7 2 859.2 Empirical formula 14 007.7 10 197.8 7 108.6 5 502.9 4 511.7 3 835.9 3 344.1 表 7 5种常用水的状态方程的适用范围与特点
Table 7. Applicable scope and characteristics of common five kinds of state equations for water
State equation of water Scope of application Autodyn polynomial The overall error of the peak pressure is too large, and the far field error is larger than the near field. The near field error of the specific impulse calculation is smaller than the far field. Dytran polynomial The near-field peak pressure error is small, the specific impulse error is large, the far-field peak pressure error is large, and the specific impulse error is small. Steiberg The near-field peak pressure error is small, the specific impulse error is large, the far-field peak pressure error is large, and the specific impulse error is small. SNL The mid-field attenuation of the pressure peak is fast, and the far-field error is small. The difference between the near-field and the far-field error is not large, which is suitable for far-field calculation. Empirical formula The pressure peak error is small overall, and the specific impulse error is gradually increased from near to far, suitable for near-field calculation. 表 8 人工黏性对计算结果的影响
Table 8. Artificial viscosity effects on calculation results
Artificial viscosity coefficient Recommended range
of valuesImpact on calculation results Primary viscosity coefficient 0.005–0.040 The peak pressure of the underwater shock wave has a great influence, the contrast impulse has little effect, the primary viscosity coefficient increases, and the peak pressure decreases. Secondary viscosity coefficient 0.8–1.0 Less influence on peak pressure and specific impulse. 表 9 1 kg炸药采用不同网格尺寸得到的峰值压力
Table 9. Peak pressure of 1 kg explosive with different grid sizes
MPa Grid size/mm R/R0 7 10 15 20 25 30 35 2 188.8 110.6 65.6 47.4 36.8 30.0 25.2 5 179.0 104.8 62.1 44.9 34.9 28.4 23.9 8 161.3 94.5 56.0 40.5 31.4 25.6 21.5 12 135.7 81.5 46.1 35.7 26.5 21.5 18.1 15 112.1 65.7 38.9 27.1 21.9 17.8 14.9 20 85.6 52.4 28.7 20.7 16.1 13.1 11.0 Empirical formula 196.7 115.2 68.3 49.4 38.4 31.2 26.2 表 10 1 kg炸药采用不同网格尺寸得到的比冲量
Table 10. Specific impulse of 1 kg explosive with different grid sizes
N·s·m–2 Grid size/mm R/R0 7 10 15 20 25 30 35 2 12 228.8 10 197.7 6 205.8 4 803.9 3 938.6 3 348.7 2 919.4 5 12 004.6 8 902.6 6 092.0 4 715.9 3 866.5 3 287.3 2 865.9 8 12 172.7 8 739.4 6 177.3 4 781.9 3 920.6 3 333.3 2 906.0 12 11 752.4 8 861.8 5 964.1 4 616.8 3 785.3 3 218.3 2 805.7 15 11 472.3 8 555.9 5 821.9 4 506.8 3 695.0 3 141.6 2 738.8 20 11 822.5 8 351.9 5 999.6 4 644.4 3 807.8 3 237.4 2 822.4 Empirical formula 14 007.7 10 197.8 7 108.6 5 502.9 4 511.7 3 835.9 3 344.1 表 11 不同炸药当量下适宜网格尺寸
Table 11. Appropriate grid size for different explosive equivalents
Explosive equivalent/kg Suitable grid size/mm 0.1 1.5 0.5 3 1 5 10 10 50 16 100 20 500 35 1 000 50 -
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