饼形破片入水侵彻速度衰减公式的修正

Correction of water-penetrating velocity attenuation formula for "Pie" fragment

[目的]破片是舰船液舱防护的重点对象,开展高速饼形破片入水速度衰减特性研究可为液舱的防护分析和优化提供理论参考。[方法]首先,考虑破片入水过程中阻力系数的变化,引入经验系数a和b,改进经典理论公式;然后,采用数值仿真方法模拟破片入水过程,将仿真结果与经典理论公式和改进公式的计算结果进行对比;最后,通过经验系数a和b,研究初始速度和长径比对破片侵彻速度衰减规律的影响。[结果]结果显示,与经典公式相比,改进公式更适用于研究饼形破片入水侵彻速度的衰减特性。阻力系数与长径比有关:当长径比小于0.5时,阻力系数受侵彻位移变化的影响较大;当长径比大于0.5时,阻力系数受侵彻位移变化的影响较小,可以把阻力系数看作常数。[结论]利用改进的理论公式可以简单计算液舱对饼形破片的防护效果。

[Objectives]Fragment is the key object of vessel liquid tank protection, and the study on the water-penetrating velocity attenuation characteristic of the high-speed "pie" fragment can provide theoretical reference for the protection analysis and optimization of the vessel liquid tank.[Methods]First to consider the change in resistance coefficient during water-penetrating process of fragment,the classical theoretical formula is modified by introducing the empirical coefficient a and b. Then, numerical simulation method is used to simulate the water-penetrating process of fragment,and the simulation results are compared with the calculation results from classical theoretical formula and improved formula. Finally,the influences of the initial velocity and slenderness ratio on the fragment penetration velocity attenuation are studied by the empirical coefficient a and b.[Results] The improved formula is more suitable than the classical formula to study the attenuation characteristics of the water-penetrating velocity of the "pie" fragment. The resistance coefficient is related to the slenderness ratio:when the slenderness ratio is less than 0.5,the resistance coefficient is greatly affected by the change of the penetration distance;when the slenderness ratio is greater than 0.5,the resistance coefficient is less affected by the change of the penetration distance, and the resistance coefficient can be treated as a constant.[Conclusions]The protective effect of vessel liquid tank on "pie" fragment can be calculated simply by using the improved theoretical formula in this paper.