A nondimensional analysis of dusty shock waves in steady flows

The governing equations describing the flow field which results when a dust-gas suspension passes through a normal shock wave were nondimensionalized. The nondimensionalization resulted in a set of nondimensional groups of parameters which, if kept constant, lead to a self-similar solution. An investigation of these nondimensional groups of parameters revealed, for example, that the relaxation length depends linearily on the material density of the solid particles. Dependence of the relaxation length on the other parameters of thd dust is discussed.     

Unsteady shock waves in supersonic nozzles

The present paper describes the numerical and experimental results on unsteady nozzle flows induced by nonstationary shock waves. The two-dimensional Navier-Stokes equations are numerically solved using the upwind TVD finite-difference scheme of the Harten-Yee type. For the purpose of computational visualization of shock waves in transient nozzle starting process, computer shadow graphs are developed based on the principle of the optical shadowgraph. Visualization experiments employing a conventional shock tube are also performed. Comparison of numerical and experimental results shows satisfactory agreement. Furthermore, the steady flow establishment process around an airfoil model installed inside the nozzle is numerically investigated. The simulated results successfully reveal the unsteady viscous flow structure around the model.     

Interaction of travelling shock waves with orifices inside ducts

When a shock wave moves down in a duct and reaches an orifice plate located inside it, reflected and transmitted shocks appear. A theoretical model to estimate such effects has been outlined, and experiments have been carried out measuring pressures upstream and downstream of the orifice. The experimental results obtained agree fairly well with the theoretical ones. Some anomalous phenomena have been observed, probably due to unsteady boundary layer growth or time lag in the establishment of steady-flow conditions through the orifice.     

Morphological transformation of shock waves behind a flat plate

The interaction of a travelling shock with the shear layer of a flat plate is studied computationally. The Euler and Navier-Stokes equations are solved numerically on quadrilateral unstructured adaptive grids. The flat plate is installed horizontally on the central axis of a shock tube. The shear layer is first created by two shock waves at different speeds splitted by a flat plate. A series of small vortices is developed as a consequence in the shear layer. The shock wave reflected at the end wall impinges the shear layer. The complicated shock dynamics in the evolution to the pseudo-steady state is represented with the morphological transformation of a planar shock into an oblique shock.     

Vibrational protection provided by automobile suspensions with both hydraulic and inertial-frictional shock absorbers

A mathematical model is used to investigate automobile suspensions with both hydraulic and inertial-frictional shock absorbers. The optimal parameters of this combined damping system are determined for the suspension of the GAZ-66 vehicle. A prototype inertial-frictional shock absorber is described, and the results of road tests on the Gazel ambulance are presented.     

飞秒激光诱导的空气等离子体冲击波探究

一定强度的飞秒激光聚焦于空气能生成空气等离子体并诱导生成冲击波。为了观察该冲击波传播特性,引入了超快时间分辨涡旋滤波成像技术,并对观测到的冲击波动力学过程进行了分析。实验探测到泵浦能量为1.5 mJ的飞秒激光经过透镜聚焦到空气中产生等离子体空气冲击波,分析了在3~15 μs时间段冲击波的动态演化过程。结果表明,飞秒激光等离子体空气冲击波在传输时以不对称的球形形状向外扩散,且沿着激光传播方向的传播速度与背着激光传播方向的传播速度不同,分别为372 m/s和341 m/s。这一观察结果与传统的点爆炸模型的对称情形不同,尝试对该不对称动力学过程进行了合理解释。     

用于激光驱动冲击波诊断的成像型VISAR设计

利用激光驱动冲击波是高压状态方程研究的主要手段之一,一般利用扫描光学高温计(SOP)对冲击波进行诊断,但SOP存在的靶场干扰、无法实现弱冲击波测量和状态方程绝对测量等缺陷。为解决这些问题,提出了一种用于激光驱动冲击波诊断的双灵敏度成像型任意反射面速度干涉仪(VISAR)设计,并给出了VISAR各组成部分的技术要求。     

Effect of recess geometry on shock wave formation in circular gas bearings

An analytical method, based on the concept of shock wave formation in the bearing clearance, is used to develop a mathematical model by which the pressure distribution along the fluid film can be predicted. Based on this model, the limiting conditions for shock free operation are determined. The effects of recess geometry and inlet gas conditions are analysed. Experimental pressure distributions along the fluid film at different values of film thickness, supply pressure and rotating speed compare well with the theory. The analysis reveals that a bearing with a tapered recess has a higher resistance to shock wave formation than a conventional bearing having the same recess volume. Moreover, the tapered recess bearing has superior stability to the conventional bearing for the same recess depth.     

气相色谱仪抗冲击结构设计的改进

在气相色谱仪的运输和使用过程中,由于受到冲击或跌落,仪器破损现象时有发生。为了适应仪器全球化储运的需求,降低仪器的破损率,对产品的结构质量提出了更高的要求,本公司将仪器的抗冲击级别提高到裸机50G（非操作冲击）。本文介绍了如何优化产品的机械结构设计,提高仪器的抗冲击能力,同时进一步降低制造成本,提高客户的满意度。     

Characteristics and measurement of supersonic projectile shock waves by a 32-microphone ring array

This paper discusses about the characteristics of supersonic projectile shock wave in muzzle region during firing of high explosive anti-tank (HEAT) and high explosive (HE) projectiles. HEAT projectiles are fired horizontally at a muzzle velocity of Mach 3.5 from a medium caliber tank gun equipped with a newly designed multi-perforated muzzle brake, whereas HE projectiles are fired at elevation angles at a muzzle velocity of Mach 2 from a large caliber howitzer equipped with a newly designed double-baffle muzzle brake. In the near field, pressure signatures of the N-wave generated from projectiles are measured by 32-microphone ring array wrapped by cotton sheath. Records measured by the microphone array are used to demonstrate several key characteristics of the shock wave of supersonic projectile. All measurements made in this study can be a significant reference for developing guns, tanks, or the chassis of fighting vehicles.     

冲击波结合关节松动术治疗肩周炎疗效

目的 :分析冲击波结合关节松动术治疗肩周炎的临床效果。方法 :选取我院2013年5月—2015年5月收治的120例肩周炎患者,按照随机原则分为观察组及对照组,各60例,均予关节松动术治疗,观察组在此基础上加用冲击波治疗。比较两组患者视觉模拟评分(VAS)、肩关节疼痛与功能障碍指数(SPADI)变化,并依据肩关节活动度(ROM)变化评价其临床疗效。结果 :两组患者治疗后VAS评分均显著降低,观察组降低更为明显,差异有统计学意义(P<0.05)。两组患者治疗2疗程后SPADI均显著下降,观察组下降更为明显,差异有统计学意义(P<0.05)。观察组临床有效率为95.0%,显著高于对照组的76.7%,差异有统计学意义(P<0.05)。结论 :冲击波结合关节松动术能够进一步缓解肩周炎患者疼痛、促进肩关节功能的早期恢复。     

基于激波原理的气体动态温度校准装置研究

基于气体介质动态温度校准需求,研制了一套基于激波原理的气体动态温度校准装置。针对传统激波管产生激波持续时间短无法激励温度传感器的问题,通过改造传统激波管结构,实现了激波过程后稳态温度气体持续流动,克服了传感器有效激励问题。为了实现快速响应温度传感器的高质量动态校准,通过激波过程温度幅值补偿研究,减小了温度幅值不稳定对于动态校准结果的影响。此外,通过激波非定常边界层对于温度的影响分析,得到了忽略温度随壁面参数变化的条件,提高了激励信号发生的可靠性。最后,基于试验手段对于校准装置的可溯源性进行了分析和验证,试验结果表明所研制的气体动态温度校准装置可以产生阶跃上升时间为1.6 ms,稳态幅值为320℃,持续时间为40 s的动态温度激励信号,基本满足温度传感器动态校准需求。     

An electromagnetic generator of focused shock waves with a coaxial radiator excited by the axial current

The device hereafter described forms focused acoustic pressure pulses excited by a pulsed magnetic field affecting a cylindrical shell. A specific feature of the instrument is its coaxial radiator connected to a capacitive storage through a pulse transformer with a single-turn secondary winding that is used to excite the acoustic pulse. Design versions of the coaxial radiator are considered and estimates for setting design parameters are presented along with the test results obtained on a prototype model. The device can be used in shock-wave medical apparatuses for fragmentation of nephroliths and gall-stones.     

斜椭圆数控车加工规律性探究

分析研究了斜椭圆数控车加工的规律性问题。通过坐标旋转及平移确定斜椭圆的参数方程,找到圆心角与转角变量间的内在联系,总结出编制宏程序时的设计流程。最后通过实例进行了加工验证。     

斜孔加工技术在压缩机制造中的应用

斜孔加工的方法很多,主要以采用万向钻专用设备、普通摇臂钻利用万向旋转工作台组合、数控龙门铣辅助万能铣头以及数控镗床辅助万能头加工为主。本文从加工原理、加工步骤以及优缺点方面分别介绍了这几种斜孔加工方法,并指出随着产品的大型化发展趋势,很多设备如万向钻床、中小型数控镗铣床,因加工范围的局限性已不能满足未来压缩机发展的需要,大型数控万向钻床、超大型数控镗铣床的引进必将成为一种趋势。     

斜锲8节点空间等参单元分析

通常 ,测量被压弹性体的应变可以检测所受压力大小。在斜锲被检测平面上粘贴两对互相垂直应变片时 ,必须减小应变片横向应变负效应。为了同时分析两个互相垂直方向平面应变状态 ,本文分析被压斜锲应变 ,采用 8节点空间等参单元来划分斜锲连续体 ,被测平面节点呈互相垂直两个方向排列。数值计算由 ANSYS软件完成。比较结果 ,精度满足实际应用要求     

An extension of laser-interferometric CT measurement to unsteady shock waves and 3D flow around a columnar object

The 3D laser-interferometric CT measurement of the unsteady flow field induced by shock wave discharging from a circular nozzle next to a short columnar object in a shock tube experiment is presented as an extension of previous work of 3D measurement of open flow field. The 3D density distribution around the object is reconstructed with FBP (filtered back projection) and MLEM (maximum likelihood expectation maximization) algorithm from the incomplete projection data caused by the obstruction of the observation light for interferometry with an object in a test section. The 3D density-gradient distributions are also evaluated from the resultant 3D density distribution, we demonstrate that laser-interferometric CT measurement of interaction field of shock waves and an object come to sight.     

Three-view stereoscopy in dusty plasmas under microgravity: a calibration and reconstruction approach

A three-camera stereoscopy setup is presented that allows to reconstruct the trajectories of particles in dusty plasmas under microgravity. The calibration procedure for the three-camera setup takes the special circumstances into account that occur in close-range imaging of small particles. Additionally, a reconstruction algorithm is presented that is based on the epipolar geometry and delivers the essential particle correspondences. Further improvements are achieved by analyzing the dynamic particle behavior. Two applications of our calibration and reconstruction procedure are presented: A two-dimensional dust structure in the laboratory with a large percentage of hidden particles, and particles inside the void of a dust cloud under microgravity.     

基于宏程序的斜椭圆数控加工与研究

通过对斜椭圆加工过程的研究,分析了斜椭圆在数控车床上加工存在的问题,介绍了通过坐标旋转确立了斜椭圆的参数方程,总结了斜椭圆编制宏程序的流程,最后通过实例进行加工验证.