Study of simple plane wave generator with an air-metal barrier

Plane wave generators (PWGs) are used to accelerate flyer plates to high velocities with their generated plane waves, which are widely used in the test of dynamic properties of materials. The traditional PWG is composed of two explosives with different detonation velocities. It is difficult to implement the related fabrication processes and control the generated waves due to its complicated structures. A simple plane wave generator is presented in this paper, which is composed of two identical cylindrical high explosive (HE) charges and an air-metal barrier. A theoretical model was established based on two different paths of the propagation of detonation waves, based on which the size of air-metal barrier was calculated for a given charge. The corresponding numerical simulations were also carried out by AUTODYN-2D^® based on the calculated results, which were used to compare with the theoretical calculations. A detonation wave with a flatness of 0.039 μs within the range of 70-percent diameter of the main charge was obtained through the simulations.     

高超声速飞行器中若干气动难题的实验研究

回顾了近几年本研究团队在高超声速飞行器若干气动难题方面的实验研究进展。在边界层转捩方面,测量了边界层转捩现象,研究了攻角效应对圆锥边界层转捩的影响,获得了边界层转捩的脉动特性以其对飞行器表面热流和摩阻的影响。在激波-边界层干扰方面,分析了突起物形状变化对流动特性的影响,研究了复杂外形的流动特性。     

双浮体波浪能转换装置中重心布置对波浪能吸收影响分析

提出一种基于横摇运动的双浮体波浪能转换装置,利用水面浮体与水下浮体之间的相对横摇运动实现对波浪能的吸收。在保持水下浮体稳定的前提下,水面浮体的横摇运动决定了整个装置对波浪能吸收情况。水面浮体的横摇运动受其横摇固有频率的影响,主要是重心布置。为了合理选择水面浮体的重心位置,采用数值分析的方法对箱型浮体在长峰不规则波下的工作情况进行分析,讨论重心布置对波浪能吸收的影响以及对PTO参数选择的影响。结果表明,重心的布置可改变波浪能吸收的频段,重心布置越低,可吸收的波浪能频段越广,越有利于波浪能的吸收。     

波浪扰动下的小型潜射导弹出水动力学建模与仿真

运用Morison公式,提出波浪扰动作用下,考虑弹体运动与波浪耦合的导弹出水过程动力学模型,并对小型潜射导弹的出水过程进行仿真和分析。以弹体姿态变化为例,研究弹体运动与波浪间的耦合关系对波浪扰动作用的影响,分析海情等级、波浪相位、出水速度、出水姿态角等因素对导弹出水过程的影响。结果表明,考虑弹体运动与波浪间耦合关系的出水动力学模型更加准确;潜射导弹的小型性和快速出水特性有利于降低波浪对导弹出水姿态的影响;对快速出水的潜射导弹,波浪扰动分析时须考虑海情等级、出水时间和波浪相位的影响。     

多点偏心起爆对破片速度增益的影响

多点偏心起爆后,爆轰波相互作用在定向区域内产生了马赫波超压,使得该区域破片速度产生增益.利用爆轰波反射理论,建立多点偏心起爆后爆轰波相互作用特性的理论模型,并确定定向区内破片速度的增益特性.3种不同起爆方式的仿真计算和静爆试验结果对比表明,定向区内不同起爆方式得到的破片增益程度较为吻合.     

调频连续波ISAR目标微多普勒特征分析

分析了调频连续波逆合成孔径雷达(FMCW-ISAR)的回波信号特性,讨论了脉冲持续时间内目标连续运动引起的多普勒频移对成像的影响,推导出导致一维距离像主瓣展宽和走动的相位因子,并进一步研究了该相位因子对基于调频连续波逆合成孔径雷达的目标微多普勒特征的影响,在此基础上讨论了调频连续波逆合成孔径雷达目标微多普勒特征与脉冲式逆合成孔径雷达目标微多普勒特征的主要区别.最后的仿真试验验证了理论分析的正确性.     

Experimental and numerical study of the blast wave decrease using sandwich panel by granular materials core

Among the intrinsic properties of some materials, e.g., foams, porous materials, and granular materials, are their ability to mitigate shock waves. This paper investigated shock wave mitigation by a sandwich panel with a granular core. Numerical simulations and experimental tests were performed using Autodyn hydro-code software and a shock tube, respectively. The smoothed particle hydrodynamics (SPH) method was used to model granular materials. Sawdust and pumice, whose properties were determined by several compression tests, were used as granular materials in the sandwich panel core. These granular materials possess many mechanisms, including compacting (e.g., sawdust) and crushing (e.g., pumice) that mitigate shock/blast wave. The results indicated the ineffectiveness of using a core with low thickness, yet it was demonstrated to be effective with high thickness. Low-thickness pumice yielded better results for wave mitigation. The use of these materials with a core with appropriate core reduces up to 88% of the shock wave. The results of the experiments and numerical simulations were compared, suggesting a good agreement between the two. This indicates the accuracy of simulation and the ability of the SPH method to modeling granular material under shock loading. The effects of grain size and the coefficient of friction between grains have also been investigated using simulation, implying that increasing the grain size and coefficient of friction between grains both reduce overpressure.     

Trajectory predictions of new lift separation sabots

This paper presents a modified analytical model to evaluate the trajectories of various lift separation sabot configurations. The aerodynamic forces acting on the sabot surfaces during a supersonic flight are modeled in the present analytical model by incorporating the pressures on the windward side of the sabot due to the detached/attached shock and its reflections and then integrated using the 3-DoF dynamical equations. The trajectory and the aerodynamic coefficients were obtained for these config-urations at a projectile Mach number of 3. The sabot configurations, which include two new designs, are compared with each other and with the conventional free flight trajectory data of the conventional sabots. The mechanical interaction between the sabot and projectile is also addressed in the present work. The comparison shows that the new designs with the aerodynamic surfaces close to the center of gravity, lift-off from the projectile with minimal mechanical interaction compared to a conventional sabot.     

大地靶场地面散射特性的测试方法

通过对大地靶场地面电磁环境特性的分析,依照大地靶场对武器系统工作状态的影响,提出了大地靶场地面散射特性的测试原理。同时对测量方法、测量系统等,也作了具体的分析论证,这对武器系统的研制、生产、试验等环节及地杂波特性的研究具有重要的意义。     

发动机缸内压缩压力非接触式检测方法研究

发动机汽缸压缩压力是检测发动机机密封性的重要参数.发动机密封性降低,会造成发动机经济性、动力性下降及废气排放指标恶化,因此对各缸压缩压力的检测具有重要意义.现提出一种利用曲轴瞬时转速,进行不解体检测坦克发动机汽缸压缩压力的方法.通过实车测量获得缸压及转速的特征参数,利用灰色理论模型的方法建立了发动机转速脉动与汽缸压缩压力的数学关系.试验结果表明,利用这种方法进行缸内压缩压力测量是可行的.