Recent experience with different methods of drag prediction

During the recent past the process of engineering design has changed entirely because of rapid developments in computational simulations. In aerodynamic design, computational fluid dynamics (CFD) methods are slowly superseding empirical methods and design engineers are spending more and more time applying CFD tools to analyze and predict the aerodynamic characteristics of vehicles. The purpose of this paper is to review recent experiences in CFD-based drag prediction with an emphasis on flow solutions governed by the Euler and Reynolds-averaged Navier–Stokes equations. For these types of flow solutions, various drag analysis methodologies are outlined and applied to determine the drag of components of as well as whole-body airplanes, helicopters, and ground-based vehicles at subsonic and transonic flow conditions. The review demonstrates that although significant progress has been made, CFD-based drag prediction still faces a number of hurdles that must be dealt with before it will become more widely accepted.     

Computational prediction of airfoil dynamic stall

The term dynamic stall refers to unsteady flow separation occurring on aerodynamic bodies, such as airfoils and wings, which execute an unsteady motion. The prediction of dynamic stall is important for flight vehicle, turbomachinery, and wind turbine applications. Due to the complicated flow physics of the dynamic stall phenomenon the industry has been forced to use empirical methods for its prediction. However, recent progress in computational methods and the tremendous increase in computing power has made possible the use of the full fluid dynamic governing equations for dynamic stall investigation and prediction in the design process. It is the objective of this review to present the major approaches and results obtained in recent years and to point out existing deficiencies and possibilities for improvements. To this end, potential flow, boundary layer, viscous–inviscid interaction, and Navier–Stokes methods are described. The most commonly used numerical schemes for their solution are briefly described. Turbulence models used for the computation of high Reynolds number turbulent flows, which are of primary interest to industry, are presented. The impact of transition from laminar to turbulent flow on the dynamic stall phenomenon is discussed and currently available methods for its prediction are summarized. The main computational results obtained for airfoil and wing dynamic stall and comparisons with available experimental measurements are presented. The review concludes with a discussion of existing deficiencies and possibilities for future improvements.     

Radiation from accreting magnetized neutron stars

We review some recent developments in our understanding of accreting magnetized neutron stars. A brief summary of the observations is given, on which current phenomenological models are based. The main part of this paper is a discussion of recent work by several groups on the radiative transfer problem in a strong magnetic field and its application to models of the structure and properties of self-consistent neutron star polar cap emission regions. The assumptions and uncertainties involved are discussed, recent progress is evaluated, and current and future problems are indicated.Smithsonian Visiting Scientist, partially supported through NASA Grant NAGW-246, on leave from Max-Planck-Institut für Physik und Astrophysik MPA, Garching.     

Concepts of turbulence and C.F.D. applications

The article's main theme is the ‘turbulence modelling’ used in present days' computational schemes. This modelling is an effort to account for the influence of turbulent motion on diffusion processes, and reflects our efforts to bridge what is generally recognized as the ‘closure gap’, i.e. to replace a needed phenomenological relation(s) with hypotheses of some kind. In this way one tries to remedy our lack of knowledge of turbulent motion. For that purpose a number of ideas and concepts over the past 60 years is mentioned and their incorporation in numerical analysis is discussed. The main emphasis is placed on the physical concepts and their consequences.     

跨音速离心压气机的现状和发展

叙述了国内外跨音离心压气机的发展概况以及内部流场的计算方法和气动设计方法的现状和发展, 提出了作者自己的看法。      

Multi Objective Robust Active Vibration Control for Flexure Jointed Struts of Stewart Platforms via H∞ and μ Synthesis

Active vibration control is needed for future space telescopes, space laser communication and other precision sensitive payloads which require ultra-quiet environments. A Stewart platform based hybrid isolator with 6 hybrid struts is the effective system for active/passive vibration isolation over 5-250 Hz band. Using an identification transfer matrix of the Stewart platform, the coupling analysis of six channels is provided. A dynamics model is derived, and the rigid mode is removed to keep the signal of pointing control. Multi objective robust H∞ and μ synthesis strategies, based on singular values and structured singular values respectively, are presented, which simultaneously satisfy the low frequency pointing and high frequency disturbance rejection requirements and take account of the model uncertainty, parametric uncertainty and sensor noise. Then, by performing robust stability test, it is shown that the two controllers are robust to the uncertainties, the robust stability margin of H, controller is less than that of μ controller, but the order of μ controller is higher than that of H, controller, so the balanced controller reduction is provided. Additionally, the μ controller is compared with a PI controller. The time domain simulation of the μ controller indicates that the two robust control strategies are effective for keeping the pointing command and isolating the harmonic and stochastic disturbances.     

Material optimization: bridging the gap between conceptual and preliminary design

This paper presents a collection of tools for conceptual structure design. The underlying model is the ‘free material optimization’ problem. This problem gives the best physically attainable material and is considered as a generalization of the sizing/shape optimization problem. The method is supported by powerful optimization and numerical techniques, which allow us to work with bodies of complex initial design and with very fine finite-element meshes. The computed results are realized by composite materials. We consider a particular class of fibre-reinforced composite materials, manufactured by the so-called tape-laying technology. In the post-processing phase, stress/strain-trajectories are plotted which indicate how to place these tapes; they also show the proposed thickness of the tapes. Several examples demonstrate the efficiency of this approach to conceptual design of engineering structures.     

民用飞机气动外形数值优化设计面临的挑战与展望

系统回顾了气动外形优化的主要环节，对优化体系中学科分析、参数化建模、网格重构技术、敏度分析、优化算法、代理模型、目标函数/约束处理等各个环节的进展，及气动综合优化面临的挑战、基础科学问题进行了总结。结合课题组在优化体系建设上开展的研究工作，针对民用飞机气动外形综合设计的需求，提炼了工程型号对优化体系构建的具体要求。并对今后的研究工作以及未来发展方向进行了展望与建议。通过文章系统整理论述，希望能够为气动数值优化设计研究人员提供一些有意义的建议和参考，促进设计空气动力学、以及多学科优化技术的发展。     

Turbulence modeling with application to turbomachinery

The prediction of turbulent flows is a nontrivial problem in internal and external aerodynamics and in many other branches of engineering. The problem appears in perhaps its greatest generality in gas turbines, where predictions of turbine blade temperature are crucial to engine efficiency or life, and predictions of the composition of combustion products is essential in meeting environmental regulations. Therefore it is logical, and hopefully useful, to make turbomachinery problems the theme of a discussion of the current state of turbulence modeling. The present article contains enough background on the physics of turbulence to illuminate the problems of modeling, but it is not a review of turbulence research in general. Topics of current concern which are dealt with in detail include the validity of the ‘law of the wall’, the universal near-wall scaling which is the foundation of prediction methods for attached flows and the effect of compressibility on turbulence.     

9th Annual Battery Conference on Advances and Applications

The developments in batteries reported at the 8th Annual Battery Conference on Advances and Applications, are discussed. It was sponsored by the electrical engineering department of California state university, long beach, CA, with IEEE-AESS cooperation. Previous well-funded battery research had been directed toward getting low weight in spacecraft batteries, which had to be boosted into orbit with expensive rockets. Ni-H₂ batteries, even though costly, won the race. Their demonstrated life, like 30,000 charge-discharge cycles, gives an earth-orbiting satellite decades of usable life. Other types of batteries discussed are: aircraft batteries; electric vehicle batteries; Ni-Cd cells; Zn-Br batteries; industrial Pb-acid batteries; rechargeability; computer controlled charging; and small rechargeable and primary batteries     

Assistant systems for aircraft guidance: cognitive man-machine cooperation

This paper presents the concept of cognitive assistant systems which represents an approach to ensure the highest degree possible of situation awareness of the flight crew as well as a satisfactory workload level. This concept offers the solution to counteract susceptibility to pilot errors typical of lack of attention or other cognitive limitations. It is founded on cognitive system engineering. This technology enables a cockpit design in order to systematically comply with the requirements of ‘Human-Centred Automation (HCA)’. The underlying approach behind the concept has become real with the development of the cockpit assistant system prototype family CASSY/CAMA as described in this paper. CASSY/CAMA has been extensively tested in a flight simulator and successfully field tested with the ATTAS (Advanced Technologies Testing Aircraft System) of the DLR. Some of the test results with CAMA will be presented in this paper.     

大型液体火箭发动机的最新发展

根据美国对ＳＳＭＥ和ＳＴＭＥ的改进设计以及前苏联、欧洲和日本分别对ＲＤ－０１２０、Ｖｕｌｃａｉｎ和ＬＥ－７发动机的开发研究，探讨在研制未来大推力液体火箭发动机（ＬＲＭ）中各国的指导思想和设计原则，分析世界在这一领域的发展动向。     

飞机设计中的新指标—战斗恢复力

本文介绍了飞机战斗恢复力的主要特征,着重探讨了设计中提高飞机战斗恢复力的措施,旨在为以后飞机设计方案论证提供一个参考依据。     

基于代理模型的高效全局气动优化设计方法研究进展

基于高可信度计算流体力学的数值优化设计方法，在提高飞行器气动与综合性能方面正发挥着越来越重要的作用。基于代理模型的优化算法（SBO），由于能够实现高效全局优化，逐渐成为了气动优化设计领域的研究热点之一。近20年来，代理优化算法研究已取得了长足进步，多种先进的新型代理模型被提出，优化理论和算法也不断完善和发展。以飞行器精细化气动优化设计为背景，综述了基于代理模型的高效全局气动优化设计方法研究进展。首先，介绍了基于变可信度代理模型的气动优化设计方法、结合代理模型和伴随方法的气动优化设计方法以及基于非生物进化的并行气动优化设计方法的研究现状和最新进展。然后，针对飞行器气动优化设计学科领域的前沿问题，介绍了基于代理模型的多目标气动优化设计方法、混合反设计/优化设计方法、稳健气动优化设计方法的研究进展，以及基于代理模型的多学科优化设计方法的研究进展。文献综述表明，代理优化算法在设计效率、全局性以及鲁棒性等方面性能优良，已经发展到可以解决100维（100个设计变量）以内的气动优化设计问题，具有良好的工程应用前景。最后，探讨了基于代理模型的高效全局气动优化设计在理论、方法及飞行器设计应用方面所面临的问题和挑战，给出了未来研究方向的建议。     

Man-machine-interface in modern transport systems from an aviation safety perspective

The early long-range-jets were operated by five cockpit crew members: Captain, Copilot, Flight Engineer, Navigator and Radio-Operator. Nowadays even the big jets are flown by only two pilots. This development could only be achieved by introducing new technologies to the airline industry and automating aircraft systems. Due to the scientific progress made in the last decades today's aircraft are most reliable – a fact which is clearly reflected by accident statistics. Technical failures became more and more unlikely and the lack of manpower on the flight deck was more than compensated. However, starting in the late 80s a number of accidents occurred to highly automated aircraft, which alarmed accident investigators worldwide. In most of the cases automation was a factor or at least one link in the accident chain of events. The Federal Aviation Administration (FAA) launched a study on “The Interfaces Between Flight Crews and Modern Flight Deck Systems” and came up with numerous findings. In the following article I like to discuss the topic ‘Man-Machine-Interface in modern Transport Systems’ from an Aviation Safety Perspective.     

湍流转捩工程预报方法研究进展综述

湍流转捩现象对边界层流动的阻力和热交换特性具有严重影响。准确地预测转捩对工程设计意义重大。近年来发展迅速的转捩模型是一种非常适合工程计算的转捩预报方法。本文将转捩模型分成了4个类型,并对每种转捩模型的发展过程加以阐述。在分析和讨论的基础上,总结了目前转捩模型的发展水平,同时也指出尚存的不足之处,为将来构建新的转捩模型以及相关的转捩研究提供建议。     

Industrial battery technologies and markets

Industrial battery market segments generally fall into two major categories--traction batteries, also called motive power batteries; and stationary batteries, also referred to as standby power batteries. The major industrial battery subcategories are discussed. Industrial trucks and rail and mine vehicles represent two major subcategories of motive power batteries. Industrial trucks include forklifts, automated guided vehicles (AGVs), various types of towing vehicles, floor cleaning equipment and so forth. Battery-powered rail and mine vehicles are used in mines where gas is present that could be ignited by spark ignition engines. Locomotive starting batteries and railcar emergency power batteries are also included in the second subcategory. The distinction is beginning to blur between valve-regulated industrial batteries and golf cart or marine batteries. Both industrial and SLI(starting/lighting/ignition)-derivative batteries are competing for markets in the future. The future trends in industrial battery production in Japan, USA and Europe are discussed     

工程结构的知识工程与专家系统

本文介绍计算机人工智能的一个重要应用分支——专家系统在工程结构设计与检验中的应用及其主要基础知识工程的情况。除了对这门新兴学科的基本概念作一简述以外,文中对知识工程的内容、组成和方法进行了讨论;并结合航空飞行器的设计与检验问题,具体讨论了对其建立专家系统的概念与模型。     

航空材料的冲击疲劳问题研究进展与展望

材料的冲击疲劳问题在航空工程中大量存在,舰载机的弹射起飞、拦阻着舰都是典型的冲击疲劳问 题。本文梳理了冲击疲劳概念的早期发展历程,综述了自2000年以来冲击疲劳领域的主要研究进展,包括材 料冲击疲劳性能的主要影响因素、材料冲击疲劳试验方法、冲击疲劳的损伤表征和寿命预计以及冲击疲劳问题 的数值计算方法等,指出材料的微观结构、边界条件、使用环境、冲击载荷类型等对冲击疲劳性能有显著影响。 总结了航空工程中冲击疲劳问题面临的主要挑战,并结合未来工程结构设计的需求,展望了航空领域冲击疲劳 技术的未来发展方向。     

Fourier methods for turbomachinery applications

Rapid increase in computing power has made a huge difference in scales and complexities of the problems in turbomachinery that we can tackle by use of computational fluid dynamics (CFD). It is recognised, however, that there is always a need for developing efficient methods for applications to blade designs. In a design cycle, a large number of flow solutions are sought to interact iteratively or concurrently with various options, opportunities and constraints from other disciplines. This basic requirement for fast prediction methods in a multi-disciplinary design environment remains unchanged, regardless of computer speed. And it must be recognised that the multi-disciplinary nature of blading design increasingly influences outcomes of advanced gas turbine and aeroengine developments. Recently there has been considerable progress in the Fourier harmonic modelling method development for turbomachinery applications. The main driver is to develop efficient and accurate computational methodologies and working methods for prediction and analysis of unsteady effects on aerothermal performance (loading and efficiency) and aeroelasticity (blade vibration due to flutter and forced response) in turbomachinery. In this article, the developments and applications of this type of methods in the past 20 years or so are reviewed. The basic modelling assumptions and various forms of implementations for the temporal Fourier modelling approach are presented and discussed. Computational examples for realistic turbomachinery configurations/flow conditions are given to illustrate the validity and effectiveness of the approach. Although the major development has been in the temporal Fourier harmonic modelling, some recent progress in use of the spatial Fourier modelling is also described with demonstration examples.