高超声速边界层转捩及基于层流脉动能的转捩预测

高超声速边界层转捩现象长期以来一直是高超声速飞行器空气动力学的关键课题之一,其中转捩位置预测是转捩研究的一个重要内容。总结了高超声速边界层转捩的特征,在此基础上,分析了传统高超声速边界层转捩工程预测方法的局限,并重点介绍了基于层流脉动能的新的转捩起始位置预测方法的基本原理,及其理论建模和数值模拟研究的进展。     

圆锥前体大攻角绕流的数值计算与分析

采用层流模型、Gamma theta转捩模型和SST湍流模型对半顶角10°的圆锥前体进行大攻角绕流的数值模拟,以探究其流动特性。给出了30m/s,不同攻角下流场的总压系数、速度矢量和涡量云图。研究发现,采用Gamma theta转捩模型可较好的模拟转捩流动;攻角大于10°时出现主涡,每个主涡都有一个总压系数最小值和无量纲的轴向涡量绝对最大值,它们均位于涡核处,量值随风速和攻角而变化。     

全球快讯

<正>德克萨斯AM大学对高超声速层流-湍流附面层转捩研究进行首次评估2010年6月9日,德克萨斯AM大学的航空航天系主持了对其国家高超声速中心的高超声速层流-湍流附面层转捩研究工作的第一次评估。     

欧拉方程计算气动力时的粘性修正研究

在采用欧拉方程进行气动力计算过程中，由表面压力积分来估计的阻力只考虑了压差阻力，计算得到的无粘阻力分解成诱阻和波阻。为考虑粘性，需进行边界层修正。在层流边界层计算时采用Cohen—Reshotko方法，边界层转捩计算采用Granville方法，湍流边界层计算采用Green方法。计算结果表明，通过粘性修正计算得到的升力、阻力系数(加上了摩擦阻力)更加接近风洞试验结果。     

边界层转捩飞行测量方法及实现

针对高超声速边界层转捩飞行试验研究的需要,通过一体化的变厚度薄壁测温和热流辨识方法,利用测量薄壁内壁温度辨识表面热流可实现飞行器表面转捩位置的测量。考虑到飞行器高速飞行过程中表面气动加热和振动环境要求,对测量结构和机体结构开展了一体化模块设计,提高了测量结构的整体承载抗热振能力;利用热振联合地面试验系统,在飞行状态地面模拟条件下,对测热部件进行了热振联合试验考核,验证了测量结构的安全性和可靠性。地面热振联合试验和飞行试验结果表明,该型转捩测量结构可承受飞行条件气动加热和振动环境,能迅速地响应和准确地反映气动加热环境热流的变化,可准确捕捉飞行条件下高超声速边界层转捩现象。获取的热流转捩测量数据,可为高超声速转捩预测计算模型提供校准数据。     

高超声速飞行器转捩特性及表面特征研究

高超声速飞行器飞行时,会出现转捩问题,其对飞行器力/热特性和飞行器的设计均有显著影响。本文采用数值和工程方法相结合,对高超声速飞行器迎风面的转捩情况进行预测,同时对飞行器表面粗糙度和表面缺陷对转捩特性的影响进行研究。本文得到了飞行器飞行的转捩高度,同时,获得了转捩特性与表面粗糙度、表面缺陷的相关关系,对该类飞行器的设计有一定借鉴意义。     

美国HTV-2及相关基础项目对转捩问题的研究

边界层转捩是高超声速飞行器在研制过程中必须考虑的重要空气动力学问题,对飞行器的控制和防热设计具有重要影响。介绍了美国HTV-2项目和相关的HIFiRE-5项目在地面试验阶段针对边界层转捩问题所做的数值仿真和地面风洞试验,总结了美国在高超声速边界层转捩研究方面的主要特点。     

美国建立国家高超声速中心

介绍了美国新成立的3个国家高超声速中心--组合循环推进中心、材料与结构科学研究中心、层流-湍流转捩研究中心的成员组成和主要研究方向.     

飞行器表面气动加热抑制方法——层流控制技术

采用边界层流动控制方法可以有效抑制气动热的生成,减少热流向壁面的传递,从而降低飞行器表面温度和热流。由层流控制的机理入手,分析了流动稳定性理论在层流控制中的作用,并列举了目前常用的转捩预测方法。在多种层流控制方法中,重点介绍了混合层流控制和微尺度粗糙元层流控制。     

高超声速飞行器尾迹转捩及其对雷达散射截面的影响

当飞行器在大气层中以高超声速飞行时,在下游形成的等离子体尾迹有可能引起雷达散射截面（RCS）突增现象,影响飞行器的探测、跟踪和识别。在自由飞弹道靶上开展高超声速模型流场特性试验研究,测量不同马赫数和靶室压力下模型尾迹的流场结构和转捩位置,利用转捩准则对试验结果进行分析,讨论了转捩位置变化对高超声速飞行器RCS特性产生的影响。结果表明：模型特征尺寸、飞行马赫数和压力等是影响转捩位置的主要参数;尾迹对高超声速飞行器RCS的影响非常复杂,将改变RCS大小,使雷达成像变模糊甚至产生假目标。     

Nitrosation and Nitration of Tetraacetyldibenzylhexaazaisowurtzitane

Tetraacetyldibenzylhitane (TADBIW) was subjected to debenzylation by nitrosating with inorganic materials available commercially to synthesize tetraacetyldinitrosohexaazaisowurtzitane (TADNSIW). TADNSIW was purified, and its structure was determined by FTIR, 1H NMR, MS and element analysis. The debenzylation reaction of TADBIW gave quantitative benzaldehyde as a by-product. This indicates that the reaction produces an imine cation as an intermediate. Hexanitrohexaazaisowurtzitane (HNIW) was prepared from unpurified TADNSIW with the yield over 96.0 % and the purity more than 98.0 %. And the mechanism of the reaction from TADNSIW to HNIW is proposed to be oxidation of nitroso and nitration of acetyl on the molecule of TADNSIW, This reaction system involved is simple, and the reaction can complete within a short time and under mild conditions. The product can be easily to separate and the waste disposed readily.     

A Robust Algorithm for Watermarking 2D Vector Maps with Low Shape-Distortions

The technique of watermarking has been introduced into 2D vector maps for many potential applications such as protecting the copyright of important GIS （geographical information system） data and tracing the data source of military maps. In most previous works, although the validity of the map data could be preserved during the embedding procedure, the shape-distortions of the map elements are usually neglected which would tend to degrade the invisibility of the watermarking schemes. A shape-preserving algorithm for watermarking 2D vector maps is presented in this paper. A 1D distance sequence extracted from the original map is adopted as the cover data instead of 2D coordinates. A watermark bit is represented by changing the distributions of the cover data. The embedding procedure induces lower shape-distortions than in former works. Experimental results indicate better invisibility of the proposed scheme, as well as its robustness to certain attacks such as map simplification, interpolation, additive noise and most geometric transforms.     

Open Rule-setting System Applied to Conceptual Design of Engines

Open rule-setting method advanced in this paper concentrates on providing designers of engines with a convenient way to express their design innovations and develop the expected prototypes in the early CAD stage, and constitute effective models for the following analysis process of CAE and CAPP. The problems arisen in the process of conceptual design with the traditional experience-based development method are analyzed. Based on those analyses, open rule-setting method is presented and some associated technical problems are discussed. The functional framework of open rule-setting system was built as software engineering methods. The speciality of the engine product as a kind of complex product and the requirement of the engine product based on its structural particularity to rule-setting system are considered carefully. A demonstration is supplied to illustrate how the open rule-setting method enhances the efficiency and quality of the engine conceptual design.     

Research on Linux Network Device Driver

By analyzing the working principle of Linux network device driver, discussing the Linux network driver structure and its key technologies, the general network driver structure and its design methodologies in Linux system are summarized. Through modifying the network device driver of Linux device driver 3rd version snull, c and improving the COW technology, the Zero-Copy technology in Linux （kernel version 2.6.11 ） is implemented. In the end, the success test tells us that the thorough analysis of network device driver is the foundation of many applications, and it also provides a certain improvement to a lot of real applications, even to military application development.     

Method for Measuring Velocity of Warhead Fragments Based on Photoelectric Detection

For measuring velocity and impacting position of single fragment of warhead, a non-contact measuring method is proposed, in which a six-light-screen array, a position indicator, a multi-channel chronograph and a computer are used.The principle of measurement is described. The key device of the system is a light screen array sensor which consists of six light screens allocated with certain geometrical parameters. When the fragment flies through the light screen array, the time of passing through each of the screens is recorded by the multi-channel chronograph. According to the time data and the geometrical parameters of the array, the velocity vector and the location of the fragment can be calculated immediately. The presented method can be used to locate the fragment and to measure the real velocity on its flying direction. It can also be used to measure the velocity of a fragment swarm after the system is engineered further.     

数码电子雷管中影响点火头性能因素分析

阐述了数码电子雷管中,点火药剂细结晶三硝基间苯二酚铅（LTNR）的制备工艺;从点火药剂的种类、加入黏合剂的质量分数、桥丝直径、点火头的电阻值、防潮漆的蘸涂等方面对点火头性能的影响因素进行了探讨;通过震动试验、并联起爆试验、延期精度检测与考核,试验结果表明：一次性合成的细结晶LTNR是制造数码电子雷管点火头较为理想的点火药剂,按技术要求生产的点火头性能指标能够满足行业标准要求。     

Improvement and Experiment of the Reamer in Vibra Cutter Against Wave Edge of Titanium Sheet Alloy Parts

By analyzing the influencing factors of part quality making of sheet alloy of titanium by vibra cutter, the shape of upper reamer is set as cylinder and wedge-shaped form, and the lower reamer as plain and hemicycle form, and its main structural parameters are defined as well. Then it is validated further that such improved vibra cutter reamer can be used to process curve-edged parts of titanium alloy sheet. The experimental result shows that the titanium alloy sheet parts processed by above equipment have no sharpen angles for convex parts and evident crevasse of concave-edged part. In summary, such improvement can eliminate the free-waved edge and improve the manufacture quality of titanium alloy sheet parts greatly.     

Experimental Study on the Small Flyer Initiating Behavior of Fine-grained Explosives

The initiating behavior of fine-grained explosives by small flyer is studied. The diameter of small flyer in this device is 1 ram. The test results indicate that the granularity of explosives has great effect on its flyer initiating sensitivity.The flyer initiating sensitivity of the fine-grained explosives is higher and the critical initiating energy is lower than that of common explosives. For common explosive, the flyer initiating sensitivity increases as the density is reduced. But for the fine-grained explosive, the test results are exactly opposite.     

Algorithm for Multi-laser-target Tracking Based on Clustering Fusion

Multi-laser-target tracking is an important subject in the field of signal processing of laser warners. A clustering method is applied to the measurement of laser warner, and the space-time fusion for measurements in the same cluster is accomplished. Real-time tracking of multi-laser-target and real-time picking of multi-laser-signal are introduced using data fusion of the measurements. A prototype device of the algorithm is built up. The results of experiments show that the algorithm is very effective.     

Influence of Installing Error on the Surface Shape Precision of the Axial Symmetry Aspheric Workpiece in Lapping

A method to calculate the surface shape error, which is caused by the installing error between the workpiece and the lapping tool in the process of form lapping, is proposed. The mathematical model which the installing translation error influences on the workpiece surface shape error is established. The changing rule of the error is simulated through the calculating example of the paraboloid workpiece. The results indicate that the surface shape error of the workpiece is increasing with the increase of the installing translation error, it is also increasing gradually along the center point of the curve surface to the edge, and the influence is severer to the curve surface with great curvature than that of the small curvature when the translation error is the same.