粒子分离器气动特性数值研究

本文利用张量分析建立了三维贴体坐标系上的通用输运方程;采用贴体网格计算了粒子分离器二相流的三维流场;建立了三维的粒子运动轨迹微分方程,理论上分析了粒子分离器结构设计对其性能的影响,与试验结果吻合较好。     

NND格式在航天飞机头部段N—S方程求解中的应用

本文采用实质上为二阶精度的无波动、无自由参数的耗散差分格式(NND格式)求解了非定常的二维和三维完全N-S方程,对类似于航天飞机头部外形的超声速粘性气体绕流流场进行了模拟。在计算中,使用了代数网格生成技术,对脱体激波采用了装配法。作为验证算例的二维圆柱绕流计算结果同文献[4]的数据进行了比较。二维凹陷外形绕流的计算结果同无粘流结果进行了对比,由于粘性流动出现了分离,二者的壁面压力是有差异的。最后,对三维外形的绕流也进行了模拟,计算结果提供了流场的细节。     

微型飞行器桨翼气动干扰的数值模拟

对某一固定翼微型飞行器进行了桨翼气动干扰数值模拟研究,采用作用盘理论模拟真实桨盘的工作状态,通过时间平均稳态处理将非定常流场简化为准定常流场计算。利用FLUENT的用户自定义函数UDF实现作用盘前后压力、速度的变化。通过与无滑流影响下单独机身数值计算结果的比较,结果显示螺旋桨滑流延缓了机体上表面的气流分离,增强气流再附着能力,飞机的失速迎角增加2°,升力、阻力、俯仰力矩系数增加2%～5%,升阻比减小2%～3%。     

CygX-1/A candidate of the black hole

Among discrete galactic X-ray sources, Cyg X-1 has been noted for its peculiar features in several respects. It is one of the few sources with a hard power law spectrum extending beyond several hundred keV. Cyg X-1 also distinguishes itself by its profound time variability over a wide range of time scales. The most remarkable incident was that its optical identification with a spectroscopic binary HDE226868 has led to a presumption that it is a black hole. This possibility has induced continuous interests in the physical character of this source in conjunction with the nature of the black hole. The purpose of this paper is to summarize presently available pieces of knowledge on this source to help the design of future experimental and theoretical works, while the complexity of the source characteristics still has prevented us to construct a clear, coherent picture of this source in spite of the fact that numerous observational facts have been accumulated.     

Tests of the JAPHAR dual mode ramjet engine

In 1997, ONERA and DLR decided to join their efforts on hypersonic air-breathing vehicles in the frame of the JAPHAR program. For this purpose, a vehicle demonstrator has been chosen as a guideline for the studies and a dual mode ramjet engine has then been designed for this vehicle. An experimental scramjet has been derived from it. A first tests campaign has been performed for simulated flight Mach number of 4.9, 5.8 and 7.5 [P. Novelli, W. Koschel, ISABE paper 99-7091, in: 14th Symp. ISABE, Florence, Italy, 1999; O. Dessornes, D. Scherrer, P. Novelli, ISABE paper 2001-1135, Bengalore, India] followed by complementary tests that consisted of weighing the test chamber. Finally, an additional test campaign was carried out in 2003 with a modified injection set-up and also with a calorimetry device that allowed to determine the combustion efficiency experimentally, which wasn't done before. In order to work as a dual mode ramjet, the combustion chamber has two injection stages. The first is mainly dedicated to supersonic combustion whereas the second allows to have a subsonic combustion with a thermal throat located near the chamber end. The main experimental results are discussed and comparisons with 3D Naviers–Stokes computation are also presented.     

旋转方截面U型通道分离流二阶相关分量测量

为了深入了解旋转涡轮叶片内冷通道中的紊流特性，并为CFD研究提供实验数据，用激光多普勒测速仪（LDA）测量了旋转U型通道中分离流的雷诺应力分量。通道的转轴与弯道的曲率轴平行，测量是在与转轴垂直的对称平面中进行的，流动状态为Re=100,000,Ro=0,0.2和－0．2。直接测量的分量为ux^2^-,Ux^2^-和uxux^-，结果表明旋转对紊流分布的形式有很强的影响。在测量的三种旋转状态中Ro=0.2的正转和Ro=0.2的负转分别具有最低和最高的紊流强度。根据测量到的信息估算了雷诺应力uiuj^-的产生率，结果显示负转的产生率比正转时高。     

The geologic development of Mars: A review

The planet Mars has been the subject of a continuing program of exploration with the flyby missions of 1964 and 1969, the orbiter of 1971, and the present Viking Project with both orbiters and landers. The overall view of Mars has changed from Earthlike in the prespacecraft era to Moonlike following the flyby missions and finally to a planet with intermediate characteristics. There are many impact craters as on the Moon, but tectonic and volcanic features resembling structures on Earth are also present. However, there is a lack of evidence for the compressional deformation associated with terrestrial plate tectonics and continental drift.The current analyses indicate that Mars has a differentiated interior with a crust and mantle and perhaps a core. Whatever the nature of interior processes, whether overall mantle expansion, plumes, or full scale convection, the effects at the surface have been predominantly vertical with formation of broad regions of uplift and depression. One of the results is hemispheric asymmetry with cratered terrain in the south and younger uncratered plains in the north.     

A user-friendly yield criterion for metals exhibiting tension-compression asymmetry

The aim of this paper is to model the yielding asymmetry of pressure-insensitive metals, including but not limited to Ni₃Al alloys. The main focuses are put on the flexibility and manipulative convenience. The parameters of theory are kept to a minimum and can be determined by as few tests as possible. These requirements are fulfilled by constructing a yield function using the second and third-invariants of a linearly transformed stress tensor. The proposed yield criterion has a simple mathematical form and has only seven parameters when used in three-dimensional stresses. Compared with existing theories, the new yield criterion has much fewer parameters, which makes it very convenient for practical applications. The coefficients of the criterion are identified by an error minimization procedure. Applications to a Ni₃Al based intermetallic alloy as well as a Cu-Al-Be shape memory alloy and comparison to other criteria show that the proposed criterion has nearly the same predictive ability and flexibility with other criteria. The proposed yield criterion can estimate the coefficients by using less data, which is a big advantage compared with other similar theories, especially when there is a limited number of experimental data.     

Influence of periodic wakes on the development of a boundary layer

The flow in turbomachinery is strongly influenced by the rotor-stator interactions. It is known that the unsteadiness of the flow has for effect to advance the laminar-turbulent transition and to alter the heat transfer. The problem of the wake-boundary layer interaction has been studied experimentally by using a simplified geometrical configuration. The stator blade is simulated by a flat plate on which the development of the boundary layer disturbed by periodic wakes is observed. The wakes are generated by moving bars having a circular section, put upstream of the flat plate and running with a constant velocity in the wind of a low-speed tunnel. Numerical studies relating to the phenomenon of interaction are limited. Part of the experimental study has been carried out in a fully turbulent flow in order to avoid the problem of transition. These results are compared with those from a code solving the fully turbulent unsteady boundary layer equations.     

《新时代交互英语》评介

通过介绍《新时代交互英语》（NEW ERA INTERACTIVE ENGLISH）内容和特点，选择合适的教材对大学英语教学至关重要，笔者针对试点班学生所选的《新时代交互英语》一书，对其视、听、说教程的内容和优缺点做了分析和评价，并以问卷调查形式更加清晰的了解到学生对于该套教材以及新的听说教学模式的反馈和意见，为新形势下教师的教学提供了帮助。     

ATS-6 Description and Performance

The Applications Technology Satellite-6 (ATS-6) uses a 9l1-r parabolic antenna with high gain to enable communications with simple, low-cost ground stations with 3-m-diameter antennas. The structural system met all of its requirements, deployed properly, and preserved sensor alignment within 0.1 degree. The thermal control system has kept all temperatures within specified limits. The communications subsystem in-orbit performance has also exceeded specifications with high receiver gain-to-temperature ratios and high transmitter El RP. The spacecraft propulsion system performance has been within specifications. The near-perfect geosynchronous orbit achieved by the Titan IIIC resulted in a 8-kg fuel saving which should extend mission life. The attitude and control subsystem is providing the necessary stabilization and accurate slewing control. The electrical power subsystem provided 40 W more than the specified value at the last summer solstice. The telemetry and command subsystem performance has also been nominal.     

Relativistic Energy-Momentum of a Body with a Finite Volume

The problem of energy-momentum in a body with a finite volume has been causing confusion in the theory of relativity, especially in relativistic thermodynamics. Its correct understanding has been given since the early years of relativity, however, erroneous misunderstandings are still found in papers and textbooks to this date. The present paper introduces a simple paradox to demonstrate the problem, and gives a brief review on a way to handle the energy-momentum correctly.     

Noise-correlating radar based on retrodirective antennas

A new retrodirective antenna-based search radar system has been introduced. The suggested system uses a noise correlation technique to detect the presence and the direction of the target. Simulation and analytical results show an order of magnitude improvement in acquisition time of the radar when compared with a phased array antenna-based radar system with the same specifications, except transmit power. To the best knowledge of the authors, no radar of a comparable acquisition time has been designed to this date. Power versus acquisition time tradeoff has been compared with a phased array radar for evaluating performance of the system. The radar is self-tracking due to retrodirectivity of the antenna array, and is much easier to implement, as it does not require any phase shifters etc.     

旋涡运动与湍流模型

本文力图将熟知的湍流大涡运动现象与湍流模型理论联系起来以减少模型理论中的经验关系。 在剪切流中以球的流体动力系数,分析确定了涡球的运动,并以此确定剪切流中的湍流剪应力。由此得到了一个二方程模型,方程中仅包含球的流体动力系数。 平板湍流边界层的实例计算表明,计算的速度剖面在整个边界层中都能很好地与实验符合。     

烟火药水下燃烧的声辐射机理与实验研究（英文）

烟火药水下燃烧能够形成低频的水下声。法国烟火集团拉克鲁瓦防御公司研制出了一种＂烟火——声电＂声诱饵（1995）,但是至今还没有进行深入的研究与报道。本文就烟火药水下燃烧的声辐射机理进行了探讨。结果显示,其所辐射的噪声主要包括喷注噪声和气泡噪声,进一步的分析发现主要以气泡噪声为主,喷注湍流噪声为辅。为了证明此观点,实验研究了具有脉动燃烧效应的烟火药水下燃烧时的声辐射特性。     

基于MPI的大规模变量结构优化技术研究

针对大规模变量结构优化问题,研究了基于虚载荷法的位移敏度求解理论,提出了惩罚函数随优化迭代次数自适应变化的二次扩展内罚函数法,并结合牛顿法作为优化算法.采用MPI并行技术实现了敏度求解的局部并行计算,解决了大规模变量结构优化技术中的规模和效率问题.采用FORTRAN语言在HAJIF2013系统上对上述方法编程实现,实例表明,优化方法能够快速、稳定收敛到最优解,以及基于虚载荷法的位移敏度解析求解理论的高效性和准确性.     

超声速来流边界层厚度对浅腔声学特性的影响

通过分析不同来流边界层厚度与空腔深度比(δ/D)下腔内中心线上的脉动声压级的分布和不同测点的声压频谱特性,讨论了超声速来流边界层厚度对浅腔(长深比分别为12和15)声学特性的影响.试验来流马赫数为1.5,基于每米的雷诺数为2.26×107.结果表明,δ/D减小导致浅腔内的噪声更加强烈,腔前后部的声压级分布更不均匀;除了个别离散频率外,腔内不同测点其余离散频率对应的声压级都有不同程度的增大.δ/D减小引起空腔前部和后部区域几乎整个离散频率范围内的噪声声压级有明显升高;因超声速浅腔流动,腔中部产生的激波的干扰因素的影响,边界层流动特性对浅腔中部区域的声学特性影响较小.      

涡轮叶片高温低循环疲劳/蠕变寿命试验评定

利用试验方法确定了某型发动机 级涡轮叶片高温低循环疲劳寿命 ,试验计入了高温蠕变的影响。为了缩短试验时间 ,按照损伤等效原则 ,确定了等效加速试验载荷谱。试验是在采用感应加热、液压加载的菲利轮试验器上进行的。采用对数正态分布和威布尔分布对试验结果进行了统计分析 ,给出了置信度为 95 %、可靠度为 99.87%的叶片安全使用寿命。     

采用新型基准流场的高超内收缩进气道试验研究简

 由于新型变中心体基准流场具有压缩效率高、反射激波弱的优点,采用该基准流场设计了矩形转圆形内收缩进气道,在设计点马赫数Ma=6.0进行了风洞试验研究。试验中得到了进气道压缩面的沿程压力分布、隔离段出口皮托压分布等参数。通过和数值模拟对比分析,结果表明：进气道外压段的压力分布明显具有先增大后减小的特征,内压段的压力分布具有两级爬升的特点,且压升较小,流场结构较好。由于内压段流场激波强度弱,进气道总压恢复系数较高,达0.518,并产生了52倍的增压比,其抗反压能力在144倍以上。试验研究表明,采用新型变中心体基准流场能改善矩形转圆形内收缩进气道的内压段流场及隔离段流场,并能有效提高进气道的总压恢复系数。