截锥形弹体在液体介质中运动速度衰减规律分析

On velocity attenuation of a truncated cone-shaped projectile vertically penetrating through liquid

水面舰船被动防护体系中液舱的主要功能之一是阻止高速弹体(爆炸破片)对内部重要结构、设备和人员的威胁,高速弹体打击液舱的过程包含着复杂的能量传递与耗散。为了分析弹体形状对其在液体介质中运动速度衰减的影响,开展了一系列不同头形因数的截锥形弹体在不同入水速度下弹体垂直侵彻液体介质过程的数值模拟,得到了垂直侵彻液体介质时弹体速度衰减特性,发现高速弹体在液体介质中运动的阻力因数与弹体形状和无量纲速度有关。基于对系列数值模拟计算结果的拟合分析,提出了计及头形因数的截锥形弹体垂直侵彻液体介质时的速度衰减经验公式,通过开展数值算例分析验证了公式计算结果的可靠性。本文中提出的经验公式可实现对高速弹体在液体介质中速度衰减的准确快速计算,为舰船防护液舱结构设计提供一定的参考。

One of the main functions of liquid tanks in the passive protective systems of surface warships is to prevent the damage by high-velocity projectiles(explosive fragments)to important internal structures,equipments and personnels.The process of high-velocity projectile penetrating through a liquid tank involves complex energy transfer and dissipation.To explore the influences of the head shape of a projectile and its water-entry velocity on the velocity attenuation of the projectile in fluid,a series of truncated cone-shaped projectiles with different head shape factors were developed to numerically simulate the processes of the truncated cone-shaped projectiles vertically penetrating through the fluid at different initial water-entry velocities.The velocity attenuation characteristics were obtained for the projectiles vertically penetrating through the fluid.The above results display that the resistance factor of a high-velocity projectile moving in the fluid is related with the projectile shape and the ratio of the instantaneous velocity of the projectile to its initial water-entry velocity.Based on the numerical simulations and the corresponding fitting results,an empirical formula was proposed by considering the projectile head factor to predict the velocity attenuation of the truncated cone-shaped projectiles vertically penetrating through the fluid.And a series of calculation examples were carried out to verify the formula.These calculation examples show that the formula is feasible and can be used to accurately calculate the velocity attenuation of high-velocity projectiles in fluid media and it is helpful for the structural design of the protective tanks of warships.