In marine warfare, the water jets formed by near-field underwater explosions can cause serious local damage to ship structures. With more knowledge on near-field underwater explosions, the phenomenon of water jet has become a hot research topic in recent years. To study the formation mechanism of water jet during near-field explosion under the bottom of a ship, an underwater explosion experiment was carried out, in which 2.5 g of TNT was detonated under the bottom of a clamped square plate at different explosion distances. A high-speed camera was used to record the evolution of the bubble jet. At the same time, a free-field underwater pressure sensor was used to measure the pressure field in the water tank. The experimental results show that with the increase of the burst distance, the process of bubbles evolving to form jets at the bottom of the square plate can be divided into two types; that is, the adsorption type and non-adsorption type. Then, by employing ABAQUS software andusing the CEL method, a series of numerical simulations were carried out for the experiment. The numerical simulation results show that the critical point for the conversion from the adsorption jet to the non-adsorption jet is between 0.821 times the maximum bubble radius and 0.867 times the maximum bubble radius. Because the upper part of the bubble is difficult to expand freely under the barrier of the steel plate, the corresponding burst distance when the bubble is adsorbed is smaller than the maximum bubble radius. By analyzing the velocity cloud diagram at the jet being formed, it is found that with the increase of the burst distance, because the clamped square plate accelerates the process of bubble collapse, the time of jet formation is advanced. The maximum velocity during the formation process of water jet and the velocity when water jet hits the steel plate both increase first and then decrease with the increase of the burst distance, reaching the maximum near the critical point. The maximum jet velocity can reach 621 m/s, the maximum jet velocity when jet hits the steel plate can reach 269 m/s. Because the larger the burst distance, the later the bubble collapses, and the more concentrated the energy in the bubble, which makes the jet velocity larger, but when the burst distance is too large, the Bjerknes effect of the steel plate on the bubble will be weakened, which will reduce the jet velocity. Consequently, a critical point of the burst distance exists, at which the jet velocity renders a maximum.

采用分离式霍普金森压杆系统和高温设备对ZL101A铝合金进行了常温和高温下的动态压缩实验,得到了应变率范围为2900～6100 s?1、温度范围为20～600℃的动态压缩应力-应变曲线.实验结果表明:ZL101A铝合金具有应变率硬化效应,并且随着温度的升高,应变率硬化效应减弱;ZL101A铝合金在不同应变率下均存在明显的温度软化效应,且随着温度的升高,塑性变形引起的绝热温升使热软化作用增强.为了得到应变率和温度对材料流变应力的影响,将应变率效应和温度效应进行解耦,得到一种适用于ZL101A铝合金材料的动态本构模型.对比模型预测结果与实验数据发现,建立的本构模型可以很好地描述ZL101A铝合金的流变应力特征.

为研究室内环境中不同初始风场条件对刺激剂防暴弹威力效能的影响,在尺寸为10.9 m×9.1 m×3.28 m的平房内开展了三种不同送风速度下(1.0 m/s、1.2 m/s和1.5 m/s)OC刺激剂防暴弹的爆炸扩散试验.首先在室内空间中布置36个采样点,采用智能多路气体采样器采集刺激剂并计算采样点浓度.接着对不同风速、不同时间、不同空间位置的试验浓度数据进行分析,从而得到爆炸后刺激剂浓度在时空中的分布规律及其在不同送风条件下的影响规律.可得到如下结论:刺激剂在爆炸作用下形成的气溶胶会受到室内风场的影响呈现浓度差,浓度由上风口至下风口逐渐升高;刺激剂气溶胶颗粒受重力影响向低处聚集,室内低处刺激剂浓度较高;初始流场的风速大小对刺激剂气溶胶颗粒扩散效果影响较大,一定范围内,风速越大刺激剂扩散速度越快.在此基础上,以试验数据作为训练样本,采用BP神经网络方法建立了1.0～1.5 m/s速度范围内的浓度预测模型.通过对比试验数据得到该模型预测误差为5％,并应用该模型开展了相关预测,结果表明:在送风速度为1.0～1.5 m/s的范围内,测点的浓度值随风速的增加而基本呈线性降低,且高度1.5 m的测点浓度值高于高度为0.5 m的测点,2.5 m高度处的测点浓度最低.

在2 m×2 m×2 m水箱中分别采用两种引爆方式对2.5 g、5 g和10 g圆柱形装药TNT进行了水下爆炸实验,得到了不同工况下冲击波和气泡脉动的压力时程曲线以及相应的气泡脉动过程.实验结果表明:使用电雷管对主装药进行引爆时,炸药并未完全起爆,冲击波峰值压力均小于经验公式计算得到的理论值,二者间平均误差为25.92％;而使用电雷管以及传爆药柱对主装药进行引爆后,炸药完全起爆,冲击波峰值压力与经验公式间的平均误差降低至4.37％,且整体较为稳定.在此基础上,对比两种引爆方式下的各项爆炸特性,发现炸药的不完全起爆会导致其爆炸后的气泡脉动周期和气泡膨胀最大半径有所减小,冲击波峰值压力、冲击波能以及气泡能明显降低,但对气泡脉动峰值压力的影响并不明显.

研究冲击波叠加效应对增强冲击波超压峰值的研究有着重要的作用.如果冲击波是在已有压力的水中推进,则波前和波后的压力差将会大于预估值,两个冲击波相遇会形成更强的冲击波.通过理论推导得到冲击波正相交与斜相交的方程,对曲线进行拟合、得到冲击波叠加的理论公式,并进行仿真计算和水箱爆炸试验.数值仿真计算和水箱爆炸试验结果表明,所得到的理论公式具有准确性和可靠性,证明了水下爆炸冲击波叠加后冲击波峰值增强效果明显,为后续水下爆炸冲击波叠加的毁伤效应研究奠定了基础.

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.

为了更准确地模拟小当量梯恩梯(TNT)水下爆炸的气泡脉动过程,对气泡脉动数值模拟结果的影响因素进行探究.应用Autodyn有限元软件对13 gTNT水下爆炸进行数值模拟发现,使用TNT的JWL状态方程和水的多项式状态方程及其参数,且网格尺寸为5 mm、边界条件为压力流出时,数值模拟结果与经验公式计算得到的理论值间误差较小.改变网格尺寸和边界条件,发现在满足工程精度前提下,网格尺寸为1 mm且边界条件为压力流出时数值模拟结果较准确,其中气泡脉动周期以及气泡膨胀最大半径的数值模拟结果与经验公式间的误差仅为3.61％和1％.对10 g TNT开展水下爆炸试验,并基于以上条件对试验进行数值模拟.发现各测点处试验结果与数值模拟结果间的误差较小,进一步验证了气泡脉动数值模拟的真实性和准确性.对10 gTNT炸药在不同爆炸深度下的气泡脉动进行数值模拟,得到了气泡脉动周期T和气泡膨胀最大半径Amax与爆炸深度H之间的关系:T = 23.2e-H/92.93+39.76e-H/12.74+2.08,Amax =0.12e-H/324.67+0.16e-H/14.85+0.07.

针对炸药水中爆炸能量损失特性,通过水下爆炸试验,测定了TNT,RS211,RBUL,GUHL,RS3-4等水下爆炸时的超压、冲击波能、气泡能等冲击波性能参数.对试验结果进行相似分析,得到了超压以及冲击波能的衰减规律,同时分析了装药的水下爆炸的能量输出结构及其能量损失特性.结果表明,RS211和RS3-4具有较高冲击波超压峰值,而RBUL、GUHL衰减较为缓慢,RBUL、GUHL水下爆炸能量可到达约1.8倍TNT当量.5kg炸药水下爆炸时,在0～3 m处,总能量损失△ed呈现抛物线形式的增长;在3m之后呈现线性增长;5 m之后为理想冲击波状态.

By applying theΠprinciple,three dynamic response scaling requirements were proposed between models and prototypes for stiffened plates subjected to underwater blast.Based on the above scaling requirements,a scaling method was put forward to predicate the dynamic responses of stiffened plates subjected to underwater blast,in which the prototypes was made of ship steel and the models was made of mild steel.And the fluid-solid coupling effect and the strain-rate effect were considered in the scaling method.Two samples were calculated to validate the scaling method.The scaling method can be used to guide the dynamic response prediction of real ship structures subjected to underwater blast by experimental models made of mild steel.

Using numerical calculation software AUTODYN, the simulation for a cylinder shell subjected to underwater explosion shock wave generated by Pentolite explosive in shallow-water was carried out. In the calculation, a 2-D Euler model with fine meshes in explosive and its nearby water was established to catch the high frequency characteristic of the shock wave; the calculated results for 2-D model were mapped to a 3-D liquid-coupling-solid model for further calculation to solve the contradiction between calculation precision and time; the suitable materials model parameters and mesh type were chosen. The calculated results well coincide with the experiment results. The proposed method has a certain reference significance for simulating anti-shock structure numerically.

Blast power of JHL-2 aluminized explosive and a single-event fuel air explosion (FAE) was compared. Two types of explosives were kilogram-level charged and pressure-time curves of shock wave at 3 m,5 m and 7 m away from explosion center were obtained. Results show that when the charged volumes are the same,the peak pressures of JHL-2 are increased by 13.5%,39.0% and 18.5% higher than that of the single-event FAE at 3 m,5 m and 7 m away from explosion center respectively,and the positive phases of JHL-2 are increased by 21.5%,22.7% and 16.5% higher than that of the single-event FAE,while the positive phase durations of JHL-2 are shorter than that of the single-event FAE. Results show that blast power of aluminized explosive can achieve and even overtake that of single-event FAE.

This paper begins with a proposal for an experimental method for exact scaling of uniform impact load data for a clamped and stiffened plate without consideration of strain-rate effects.Next,the strain-rate effect was taken into account and a modified scaling method proposed.This results in a new experimental technique to eliminate differences between data for a scale model and the prototype by ensuring similar deformations for both the scale model and the prototype.This allows accurate prediction of the impact response of heavy-duty structures using a small-scale model.

The underwater testing method for explosion energy of explosives was introduced. The explosion properties of TNT and several aluminized explosives were studied through underwater explosion experiments. The underwater explosive performance of different explosives was compared. The results show that the performance parameters (shock wave peak pressures, impulse and energy flux) accord with explosion similar rules, and the explosion similar equation coefficient of these performance parameters for new formulation was obtained. The shock wave energy and bubble energy of these explosives were calculated and the method for calculating total energy was introduced. The detonation heat calculated by KHTR was compared with experimental total energy, showing that the experimental result is very consistent with the calculated one, the program KHTR to calculate detonation heat can be used.

Numerical simulation of TNT explosion in air was performed by AUTODYN software.Post-detonation burning effect in negative oxygen balance explosive was considered in the numerical calculation model.Calculated results including peak overpressure,specific impulse and positive time were compared with that calculated by similitude equations and experimental data from Baker.Results show that airblast peak overpressure near explosive calculated by Brode equation is much larger than that AUTODTN software and Henrych equation,because the peak pressure of airblast can not be distinguished from that of detonation products.

Numerical simulation results with AUTODYN software revealed Jing Ping Lu′s parameters of PBXW-115 ignition and growth model underestimate energy release of Al powders combustion.The effects of artificial viscosity coefficient and mesh density on simulation results were discussed.The larger artificial viscosity coefficients and coarser meshes can smear off peak pressure of shock wave severely,but affect impulse little.Based on Bocksterner′s underwater explosion experimental results,parameters of Miller energy release model were solved inversely.Weighted coefficient of impulse was twice as much as that of peak pressure in objective function.New model parameters obtained from underwater explosion test can express the size effect of aluminized explosive and can be applied to numerican simulation of near field and far field,while Lee-Trave model parameters can only be applied to the numerical simulation of near field and small yield underwater explosion.

Numerical simulation of energy output structure for an aluminized explosive and an idealized explosive in underwater explosion has been performed with AUTODYN software.Influence of artificial viscosity on simulation results has been discussed and comparisons of histories pressure profiles have been made.Aluminized explosive PBXN-105 can keep larger shock energy than PBX9010 in far-field because of combustion of aluminum powders.Numerical simulation of energy output structure for aluminized explosive can provide theoretical guide for designs of underwater explosives.

针对某型热动力鱼雷减速增程改装过程中出现的问题,对鱼雷的燃料各组分供应比例与航程之间的关系进行了分析计算,并提出了减速后获得较大航程的方法.