双模量隔冲减振器在半正弦波冲击环境下响应的数值分析

将环境对双模量隔冲减振器的冲击分为两个阶段,在半正弦波冲击作用阶段采用双自由度模型进行响应计算,并以终了时刻的位移和速度作为自由振动阶段的初始条件,对自由振动阶段的单自由度模型进行响应计算。分析了某双模量隔冲减振系统在受半正弦波环境冲击下的响应特性,并与线性系统在受该冲击下的性质进行了比较。分析结果表明较易实现的双模量隔冲减振器具有较好的效果。     

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为了提高舰船及其设备的抗冲击能力,满足最新抗冲击标准的要求,同时提高传统冲击试验 机的最大测试能力,提出了一套全液压驱动的新型重载舰船设备抗冲击试验系统模型, 以解决系统高能量存储及瞬间释放和避免二次撞击的关键问题. 构建了系统非线性 动力学模型,并利用数值计算方法考察了在不同冲击速度测试条件下冲击机系统所能达到的 预期性能. 结果表明: 该系统可以产生与最新抗冲击标准BV043/85和MIL-S-901D相吻合的 冲击加速度波形,同时可根据不断提高的抗冲击标准以及测试能力要求进行相应的扩展.     

Normal shock wave oscillations in supersonic diffusers

The present paper describes experimental investigations for shock oscillations caused by normal shock wave/turbulent boundary layer interaction in a supersonic diffuser. An array of wall-mounted transducers and especially a line image sensor for the nonintrusive detection of shock displacements were employed to investigate the interactions at low supersonic speeds. The line image sensor was collimated with a conventional schlieren optical system and was a good indicative of capturing the shock oscillating motions in the present configuration. This study shows that the amplitude of the shock motions increases with approaching flow Mach number, and the cause of oscillation of the shock wave can, however, be independent of the Mach number. In addition, the present system employed to determine the shock wave positions and displacements can be effectively applied to a variety of practical problems.This article was processed using Springer-Verlag T_EX Shock Waves macro package 1.0 and the AMS fonts, developed by the American Mathematical Society.     

一种弹体入水冲击波阴影成像可视化系统及其试验研究

扩大成像视野对于开展充水容器中弹体入水冲击波传播及弥散方面的可视化研究具有重要的实际意义。阴影成像技术适用于大视野实验,且对流场冲击波和扰动的可视化研究具有简单性和通用性,其中直接阴影成像最为简单,但可靠点光源的缺乏是阻碍其发展应用的瓶颈。因此基于国产短弧氙灯管,自制了短弧氙灯点光源,根据阴影成像原理,设计出一种弹体入水冲击波阴影成像可视化系统,详细介绍了其组成和运行原理。利用该系统对高速弹体入水进行了试验研究,获得了弹体入水冲击波的阴影成像和冲击波信号的压力时程曲线,通过阴影成像和冲击波信号相结合分析了弹体入水冲击波的传播特性,并进行了理论验证。结果表明:该弹体入水冲击波阴影成像可视化系统具有可靠性和设计的合理性。弹体高速入水后,初始冲击波的强度最大,随着冲击波的传播,冲击波强度逐渐降低,水中冲击波的传播速度不断降低,球形冲击波的半径逐渐增大。     

Transonic Shocks in Compressible Flow Passing a Duct for Three-Dimensional Euler Systems

In this paper we study the transonic shock in steady compressible flow passing a duct. The flow is a given supersonic one at the entrance of the duct and becomes subsonic across a shock front, which passes through a given point on the wall of the duct. The flow is governed by the three-dimensional steady full Euler system, which is purely hyperbolic ahead of the shock and is of elliptic–hyperbolic composed type behind the shock. The upstream flow is a uniform supersonic one with the addition of a three-dimensional perturbation, while the pressure of the downstream flow at the exit of the duct is assigned apart from a constant difference. The problem of determining the transonic shock and the flow behind the shock is reduced to a free-boundary value problem. In order to solve the free-boundary problem of the elliptic–hyperbolic system one crucial point is to decompose the whole system to a canonical form, in which the elliptic part and the hyperbolic part are separated at the level of the principal part. Due to the complexity of the characteristic varieties for the three-dimensional Euler system the calculus of symbols is employed to complete the decomposition. The new ingredient of our analysis also contains the process of determining the shock front governed by a pair of partial differential equations, which are coupled with the three-dimensional Euler system. The paper is partially supported by National Natural Science Foundation of China 10531020, the National Basic Research Program of China 2006CB805902, and the Doctorial Foundation of National Educational Ministry 20050246001.     

声振耦合分析在冲击波测量中的应用

为了高精度地测量空气冲击波形,采用声振耦合分析对该测量系统的频响特性进行了理论计算,并在激波管中进行了动态响应实验。通过上述研究,得出了探头在3个不同量程时的适宜阻尼孔径。结果表明,探头的阻尼孔直径和波形上升时间的计算值与实验值都是基本符合的,并且该测量系统在强爆炸中测得的冲击波压力波形也具有良好的频响特性。     

Three-dimensional propagation of the transmitted shock wave in a square cross-sectional chamber

An investigation into the three-dimensional propagation of the transmitted shock wave in a square cross-section chamber was described in this paper, and the work was carried out numerically by solving the Euler equations with a dispersion-controlled scheme. Computational images were constructed from the density distribution of the transmitted shock wave discharging from the open end of the square shock tube and compared directly with holographic interferograms available for CFD validation. Two cases of the transmitted shock wave propagating at different Mach numbers in the same geometry were simulated. A special shock reflection system near the corner of the square cross-section chamber was observed, consisting of four shock waves: the transmitted shock wave, two reflection shock waves and a Mach stem. A contact surface may appear in the four-shock system when the transmitted shock wave becomes stronger. Both the secondary shock wave and the primary vortex loop are three-dimensional in the present case due to the non-uniform flow expansion behind the transmitted shock.PACS: 43.40.Nm     

爆轰波与激波对撞的实验研究

对乙炔氧气混合气体中爆轰波与激波的正面对撞现象的实验研究是以高速摄影获取两波对撞的x-t纹影图,以烟迹板记录对撞中的爆轰胞格图案,并基于激波理论和经典CJ爆轰理论求解了两波对撞的稳态解并探寻其规律. 研究发现透射波系包括一道激波和爆轰波,以及紧随爆轰波后的稀疏波区,这一结果对应于一维理论分析中的CJ解. 透射波系基本不受初始压强影响;初始温度也只成比例地改变流场整体速度,温度越高,速度越快;对波系起实质影响作用的是入射激波强度,激波越强,则整个透射流场呈现偏向激波的趋势;理论分析还指出,稀疏波区的出现不可避免,当激波强度趋于声波稀疏波区趋于消失,激波越强则疏波区趋于扩大. 两波对撞存在一个有限的转变阶段,透射爆轰首先减缓,接着迅速迸发为过驱爆轰,然后再逐渐平衡为CJ爆轰. 对于强不稳定的燃气,对撞后爆轰波在空间上的发展极不均衡,一些区域发生火焰面与诱导激波的严重脱离,随后的火焰面失稳发展为诱导激波区内的爆轰波,实验观察到了这种爆轰在烟迹板上留下的极为精细的迹线.      

炸药水中爆炸冲击波超高速同时分幅/扫描摄影技术

研究了超高速同时分幅/扫描摄影技术在炸药水中爆炸冲击波传播中的应用效果,并采用自研的同时分幅/扫描超高速光电摄影系统对炸药水中爆炸过程进行拍摄。结果表明,该系统能够拍摄同一时基、同一空基且具有超高时空分辨的一维和二维图像,进而成功观察到?60 mm×66 mm TNT炸药在水中爆炸冲击波传播过程,获得该过程冲击波阵面平均传播速度及压力。这可为水中兵器战斗部的设计及毁伤效能评估提供参考。     

冲击波超压测试系统二次仪表频域特性

从二次仪表对冲击波的峰值、持续时间和比冲量3个主要参数的影响出发,首先构建了冲击波信号用以分析冲击波信号特性;搭建了适配器等效电路,对适配器的低频特性进行了实验研究;在MATLAB平台上构建了5种常用滤波器模型,模拟了不同类型滤波器和不同截止频率下测试系统的输出。模拟和实验结果表明:适配器的低频特性影响冲击波信号的持续时间和比冲量;在5种滤波器中贝塞尔滤波器最适合冲击波测试系统;滤波器截止频率对冲击波超压峰值影响明显;小型试验对测试系统的带宽要求高。     

Experimental study of toroidal shock wave focusing in a compact vertical annular diaphragmless shock tube

The paper reports results of experiments regarding toroidal shock wave focusing in a vertical shock tube as a part of a series of converging shock wave studies. This compact vertical shock tube was designed to achieve a high degree of reproducibility with minimum shock formation distance by adopting a diaphragmless operating system. The shock tube was manufactured in the Institute of Fluid Science, Tohoku University. An aspheric lens shaped cylindrical test section was connected at the open end of the shock tube to visualize the diffraction and focusing of the toroidal shock wave released from the ring shaped shock tube opening. Pressure transducers were flush mounted on the shock tube’s test section to measure pressure histories at the converging test section. Double exposure holographic interferometry was employed to quantitatively visualize the shock waves. The whole sequence of toroidal shock wave diffraction, focusing, and its reflection from the symmetrical axis were successfully studied. The transition of reflected shock waves was observed.     

干摩擦系统在基础位移冲击激励下的特性

本文给出了具有软化弹簧特性的干摩擦隔振系统隔离基础位移冲击激励的理论分析和结果,分析结果表明干摩擦隔冲系统远优于线性阻尼系统,隔冲效果很明显.     

Experimental and numerical analysis of the structure of pseudo-shock systems in laval nozzles with parallel side walls

Detailed numerical and experimental investigations of pseudo-shock systems in a Laval nozzle with parallel side walls are carried out. The location of the pseudo-shock system is defined in this system of two choked Laval nozzles by the ratio of the critical cross sections A₂^*/A₁^*{{A}_{2}^*/{A}_{1}^*} , the stagnation pressure loss across the shock system and viscous losses. The wall pressure distributions and high-speed schlieren videos recorded in the experiments are compared to the results of a steady and an unsteady numerical simulation. For the steady case, good agreement is found between the calculated and measured shock structure and pressure distribution along the primary nozzle wall, except for a remaining slight deviation in the shock position. For the unsteady case, in which asymmetric shock configurations are observed, deviations of the results with respect to the stochastic wall attachment of the shock system are given which indicate the necessity of further investigations on that topic.     

Effect of shock interactions on the attitude stability of a toroidal ballute for reentry vehicles

The effect of shock interactions on the attitude stability of a reentry vehicle system with a toroidal ballute was investigated. The hypersonic wind tunnel experimental results showed that when the shock interaction occurred near or outside the ballute, an unstable oscillation of the ballute was observed. This was caused by the local high-pressure region on the ballute surface created by the shock interaction between the shock from the reentry capsule and the shock from the ballute. To avoid this unstable oscillation, the radius of the ballute should be designed to be large enough so that the shock from the capsule will be located inside the ballute, which can avoid the local high-pressure region on the ballute surface.     

应用浮动冲击平台考核舰载设备响应分析

为研究安装甲板模拟器的浮动冲击平台系统考核舰载设备的机理,对整个系统建立有限元模型进行数值模拟并建立力学模型进行了理论分析。根据船体甲板结构产生的垂向低通滤波特性,提出甲板模拟器具有减缓高频冲击并满足设备安装频率要求的作用。将被试设备的浮动冲击平台考核系统简化为有阻尼的三自由度系统强迫振动模型,通过拉普拉斯变换方法求解了不同冲击环境下被试设备的响应。数值模拟与理论计算结果比较吻合,被试设备响应迅速达到峰值后逐渐衰减,振动频率由高频向低频过渡,在分析浮动冲击平台舰载设备考核系统长时间响应时需考虑阻尼的影响。     

Dust suspensions accelerated by shock waves

The motion of dust suspensions accelerated by shock waves has been experimentally investigated in a vertical shock tube, in which a completely developed plane shock wave of moderate strength propagates into a homogeneously distributed dust suspension with a planar interface. Trajectories of the accelerated interfaces as well as transmitted and reflected shock waves are recorded by using a shadowgraph system with a Cranz-Schardin camera. Two kinds of particle samples, i.e. porous lycopodium particles 30 μm in diameter and corn starch particles with a mean diameter of 10 μm, are employed. The effects of shock wave strength and particle loading ratio are also examined. Experimental data are compared with theoretical results, and the agreement is good. Received: 7 October 1998/Accepted: 1 June 1999     

舰载旋转机械基础冲击响应建模和数值计算

针对舰载旋转机械的水下非接触爆炸冲击动力学响应问题,提出了一种基础冲击转子-轴承系统建模理论.结合牛顿运动定理、动量矩定理和Timoshenko梁理论,推导出了系统动力学微分方程,方程综合考虑了转子的旋转惯性力、剪切力、陀螺效应、轴向力、轴向扭矩以及轴承的油膜力.通过在时间域和空间域分别采用直接积分法和Galerkin...     

浮动冲击平台冲击环境对设备响应的影响

对浮动冲击平台提供给设备的冲击环境及舰载设备在不同冲击环境下的响应进行了数值模拟和理论分析。以美国中型浮动冲击平台为计算模型,将设备基座的冲击环境与德国规范BV 043-85进行了比较,为分析两个体系在设备抗冲击要求中谱加速度的差异,对不同舰载设备进行数值模拟计算,并通过虚拟约束边界模态方法,提出不同冲击环境下基础激励的多自由度系统响应的计算方法。数值分析及理论计算结果表明:冲击谱中谱加速度对舰载设备响应影响较小,而谱位移和谱速度对设备响应有较大影响,理论计算得到的多自由度系统响应与数值模拟结果较一致,同时在进行浮动冲击平台设计时可不考虑谱加速度对设备响应的影响。     

STUDY ON THE FUEL AIR MIXING INDUCED BY A SHOCK WAVE PROPAGATING INTO A H_2-AIR INTERFACE

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Diaphragmless shock wave generators for industrial applications of shock waves

The prime focus of this study is to design a 50 mm internal diameter diaphragmless shock tube that can be used in an industrial facility for repeated loading of shock waves. The instantaneous rise in pressure and temperature of a medium can be used in a variety of industrial applications. We designed, fabricated and tested three different shock wave generators of which one system employs a highly elastic rubber membrane and the other systems use a fast acting pneumatic valve instead of conventional metal diaphragms. The valve opening speed is obtained with the help of a high speed camera. For shock generation systems with a pneumatic cylinder, it ranges from 0.325 to 1.15 m/s while it is around 8.3 m/s for the rubber membrane. Experiments are conducted using the three diaphragmless systems and the results obtained are analyzed carefully to obtain a relation between the opening speed of the valve and the amount of gas that is actually utilized in the generation of the shock wave for each system. The rubber membrane is not suitable for industrial applications because it needs to be replaced regularly and cannot withstand high driver pressures. The maximum shock Mach number obtained using the new diaphragmless system that uses the pneumatic valve is 2.125 ± 0.2%. This system shows much promise for automation in an industrial environment.