水面舰船减阻节能球鼻艏理论及模型试验研究

基于线性兴波理论,对水面舰船加装减阻节能球鼻艏进行理论和试验研究,发现水面舰船加装减阻节能球鼻艏可获得较好的减阻效果。根据理论优化结果选取多个理论模型进行船模阻力及波形试验。试验结果表明,球鼻艏在特定的中高航速下可以使兴波阻力最多减少37%,总阻力最多减少15%。     

未来光电精确寻的制导技术发展前景预测

精确自寻的制导系统是精确制导武器中最重要的组成部分。精确寻的制导系统的性能直接影响武器的作战性能、应用范围和成本。分析了未来高技术战争对精确制导武器发展的要求,探索了21世纪光电精确寻的制导技术的发展趋势,分析了新的精确制导体制应具备的发展特点,并对未来的发展提出了建议和意见。     

Numerical simulation of the blast wave of a multilayer composite charge

The numerical simulation of a blast wave of a multilayer composite charge is investigated. A calculation model of the near-field explosion and far-field propagation of the shock wave of a composite charge is established using the AUTODYN finite element program. Results of the near-field and far-field calculations of the shock wave respectively converge at cell sizes of 0.25–0.5 cm and 1–3 cm. The Euler––flux-corrected transport solver is found to be suitable for the far-field calculation after mapping. A numerical simulation is conducted to study the formation, propagation, and interaction of the shock wave of the composite charge for different initiation modes. It is found that the initiation mode obviously affects the shock-wave waveform and pressure distribution of the composite charge. Additionally, it is found that the area of the overpressure distribution is greatest for internal and external simultaneous initiation, and the peak pressure of the shock wave exponentially decays, fitting the calculation formula of the peak overpressure attenuation under different initiation modes, which is obtained and verified by experiment. The difference between numerical and experimental results is less than 10%, and the peak overpressure of both internal and external initiation is 56.12% higher than that of central single-point initiation.     

Experimental research on the instability propagation characteristics of liquid kerosene rotating detonation wave

In order to study the instability propagation characteristics of the liquid kerosene rotating detonation wave (RDW), a series of experimental tests were carried out on the rotating detonation combustor (RDC) with air-heater. The fuel and oxidizer are room-temperature liquid kerosene and preheated oxygen-enriched air, respectively. The experimental tests keep the equivalence ratio of 0.81 and the oxygen mass fraction of 35% unchanged, and the total mass flow rate is maintained at about 1000 g/s, changing the total temperature of the oxygen-enriched air from 620 K to 860 K. Three different types of instability were observed in the experiments: temporal and spatial instability, mode transition and re-initiation. The interaction between RDW and supply plenum may be the main reason for the fluctuations of detonation wave velocity and pressure peaks with time. Moreover, the inconsistent mixing of fuel and oxidizer at different circumferential positions is related to RDW oscillate spatially. The phenomenon of single-double-single wave transition is analyzed. During the transition, the initial RDW weakens until disappears, and the compression wave strengthens until it becomes a new RDW and propagates steadily. The increased deflagration between the detonation products and the fresh gas layer caused by excessively high temperature is one of the reasons for the RDC quenching and re-initiation.     

Experimental study of transient pressure wave in the behind armor blunt trauma induced by different rifle bullets

Pressure wave plays an important role in the occurrence of behind armor blunt trauma (BABT), and ballistic gelatin is widely used as a surrogate of biological tissue in the research of BABT. Comparison of pressure wave in the gelatin behind armor for different rifle bullets is lacking. The aim of this study was to observe dynamic changes in pressure wave induced by ballistic blunt impact on the armored gelatin block and to compare the effects of bullet type on the parameters of the transient pressure wave. The gelatin blocks protected with National Institute of Justice (NIJ) class III bulletproof armor were shot by three types of rifle bullet with the same level of impact energy. The transient pressure signals at five locations were recorded with pressure sensors and three parameters (maximum pressure, maximum pressure impulse, and the duration of the first positive phase) were determined and discussed. The results indicated that the waveform and the twin peak of transient pressure wave were not related to the bullet type. However, the values of pressure wave’s parameters were significantly affected by bullet type. Additionally, the attenuation of pressure amplitude followed the similar law for the three ammunitions. These findings may be helpful to get some insight in the BABT and improve the structure design of bullet.     

面内阶跃载荷下薄板弹性动力屈曲差分解

根据薄板微元的动力平衡分析导出薄板动力屈曲控制方程,由屈曲瞬间能量转换率守恒条件得出一个压缩波前屈曲变形的附加约束方程,由此得到求解薄板动力屈曲问题的完备定解条件.以受载边夹支的薄板为倒,利用有限差分法得出了薄板前三阶动力屈曲模态和相应的两个特征参数值,并对比分析了薄板静、动力屈曲的差别.分析表明,薄板动力屈曲过程中产生屈曲动能,比静力屈曲要吸收更多的外部能量.     

柔性长鳍扭波推进数学模型分析

以"尼罗河魔鬼"鱼的柔性长背鳍扭波推进模式为研究对象,通过观察活鱼的游动模式,提取影响扭波推进的运动学要素,建立了描述柔性长背鳍扭波推进时动态曲面的数学模型。研究了鳍条仰角与摆动规律对鳍面的影响。最后,用细长体理论分析并计算出推力分布。研究表明,鳍条仰角在φ=85°的情况下所形成的鳍面与垂直鳍条所形成的鳍面相比,其最大偏离值与鳍长之比为1.7%,可以用垂直于基线的鳍条制作模型;鳍条按正弦规律摆动时所形成的扭波波形鳍面与实鱼鳍面相似。     

一种雷达波衰减型红外迷彩伪装遮障材料设计方案

伪装遮障以其伪装性能好、适应能力强、作业简单、携带方便而在现代战争中被广泛采用。在对遮障材料性能要求分析的基础上,提出了一种新型雷达波衰减型红外迷彩伪装遮障材料的设计方案。其在可见光、近红外、雷达波段均具有良好的反探测性能,可有效对抗现代高技术侦察手段和设施。     

基于空域相关滤波的雷达回波信号降噪方法

对雷达探测来说,如何有效地增强真实目标回波信号、提高信噪比水平是非常重要的。传统的降噪方法如平滑滤波、傅立叶降噪很难有效地降低与目标频谱相重叠的噪声。空域相关滤波算法是小波滤波算法中的一种,能够有效地解决这个问题。该算法是利用真实信号与噪声在尺度间的不同表现来实现的,能够在保留信号细节的同时,有效地降低噪声。仿真表明,该算法在雷达回波的降噪中取得了较好效果,有效地降低了噪声。     

某型飞机大气数据系统设计

大气数据系统是重要的机载电子设备,其性能、精度直接关系到飞机的飞行安全.在介绍某型号飞机大气数据系统的软硬件体系结构的基础上,从三个方面深入研究了提高大气数据系统精度的途径:大气数据计算模型;基于BP神经网络的压力测量温度误差补偿方法;一种计算型静压源误差补偿方法.其大气数据系统系统性能稳定,结构紧凑,速度快,精度高,软硬件升级简单.试验证明其大气数据系统能很好满足某型号飞机的使用要求.