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Nonlinear Aeroelastic Response of High-aspect-ratio Flexible Wings

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Chinese Journal of aeronautics 2009年第4期22卷 355-363页

作者： Zhang Jian,Xiang Jinwu school of Aeronautic science and Engineering,beijing {3. of aeronautics and astronautics,beijing 100191,China school of Aeronautic science and Engineering Beijing University of Aeronautics and Astronautics Beijing 100191 China

The aeroelastic analysis of high-altitude, long-endurance （HALE） aircraft that features high-aspect-ratio flexible wings needs take into account structural geometrical nonlinearities and dynamic stall. For a generic nonlinear aeroelastic system, besides the stability boundary, the characteristics of the limit-cycle oscillation （LCO） should also be accurately predicted. In order to conduct nonlinear aeroelastic analysis of high-aspect-ratio flexible wings, a first-order, state-space model is developed by combining a geometrically exact, nonlinear anisotropic beam model with nonlinear ONERA （Edlin） dynamic stall model. The present investigations focus on the initiation and sustaining mechanism of the LCO and the effects of flight speed and drag on aeroelastic behaviors. Numerical results indicate that structural geometrical nonlinearities could lead to the LCO without stall occurring. As flight speed increases, dynamic stall becomes dominant and the LCO increasingly complicated. Drag could be negligible for LCO type, but should be considered to exactly predict the onset speed of flutter or LCO of high-aspect-ratio flexible wings.

关键词： nonlinear aeroelasticity limit-cycle oscillation Galerkin methods geometrical nonlinearities dynamic stall HALEaircraft

Key Parameters and Conceptual Configuration of Unmanned Combat Aerial Vehicle Concept

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Chinese Journal of aeronautics 2009年第4期22卷 393-400页

作者： Wang Ganglin Faculty 513.school of Aeronautic science and Engineering,beijing {3. of aeronautics and astronautics,beijing 100191,China Faculty 513 School of Aeronautic Science and Engineering Beijing University of Aeronautics and Astronautics Beijing 100191 China

The nature and characteristics of attack unmanned combat aerial vehicle （UCAV） are analyzed. The principles of selecting takeoff thrust-weight ratio and takeoff weight of attack UCAV are presented by analyzing the statistical data of weights for various main combat aircraft. The UCAV airborne weapons are analyzed, followed by the preliminary estimation of the payload weight. Various typical engines are analyzed and one of them is selected. Then the takeoff weight of the UCAV is determined. Based on some basic parameters and assumptions, the qualitative decomposition calculation for takeoff weight is completed. The key factors for obtaining longer endurance of aircraft with small aspect ratio configuration are found to be high lift-drag ratio and internal space. On the basis of the conclusions mentioned above, a highly blended flying-wing plus lifting body concept is proposed. According to this concept, the UCAV configuration is designed and optimized. Finally, the UCAV configuration with small aspect ratio, high lift-drag ratio, and high stealth characteristic is obtained.

关键词： aircraft design unmanned aerial vehicles unmanned combat aerial vehicles conceptual design aerodynamicsstealth

Nonlinear flutter analysis of stiffened composite panels in super-sonic flow

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science China(Physics,Mechanics & Astronomy) 2010年第2期53卷 336-344页

作者： YUAN KaiHua & QIU ZhiPing school of Aeronautic science and Engineering,beijing {3. of aeronautics and astronautics,beijing 100191,China school of Aeronautic science and Engineering Beijing University of Aeronautics and Astronautics Beijing China

The flutter instability of stiffened composite panels subjected to aerodynamic forces in the supersonic flow is investigated. Based on Hamilton's principle,the aeroelastic model of the composite panel is established by using the von Karman large deflection plate theory,piston theory aerodynamics and the quasi-steady thermal stress theory. Then,using the finite element method along with Bogner-Fox-Schmit elements and three-dimensional beam elements,the nonlinear equations of motion are derived. The effect of stiffening scheme on the flutter critical dynamic pressure is demonstrated through the numerical example,and the nonlinear flutter characteristics of stiffened composite panels are also analyzed in the time domain. This will lay the foundation for design of panel structures employed in aerospace vehicles.

关键词： panel flutter piston theory finite element method quasi-steady thermal stress critical dynamic pressure stiffened composite panel

Relaying Selection with Network-coded Cooperative Protocols in Aeronautical Communications

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Chinese Journal of aeronautics 2010年第1期23卷 75-83页

作者： Du Bing,Zhang Jun school of Electronics and Information Engineering,beijing university of {3. and astronautics,beijing 100191,China school of Electronics and Information Engineering Beijing University of Aeronautics and Astronautics Beijing 100191 China

In this article, we exploit the idea of network-coded cooperative protocol in aeronautical communications which combines different source nodes＇ information at the relay and joint decoding at the destination. Recently, the network coding in cooperative communications has been categorized into two mainstreams, bit-level and signal-level combinations, which are both discussed in the article. And to be exclusively,multiple access relay channel（MARC） is adopted. The mutual information expressions of both above-cited network-coded protocols are deduced, which prove that without proper selected relays to perform network coding, the spatial diversity of the proposed protocol cannot be obtained. This then leads to search for the selection and grouping algorithms. An adjacency matrix is defined to describe the connectivity of the nodes in one radio contact disk, so that, the selection and grouping of algorithm is equivalent to constructing this adjacency matrix to minimize the system outage probability evaluated in term of the mutual information. Besides, a network-coded cooperative protocol requires the acyclic network, of which the construction is to avoid loop-4 in the matrix. The article ends with simulations to demonstrate the viability of the proposed algorithms.

关键词： communication network coding outage probability mutual information bit-level signal-level

A New Scheme and Microstructural Model for 3. Full 5-directional Braided Composites

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Chinese Journal of aeronautics 2010年第1期23卷 61-67页

作者： Zhang Fan,Liu Zhenguo,Wu Zhe,Tao Guoquan school of Aeronautic science and Engineering,beijing {3. of aeronautics and astronautics,beijing 100191,China school of Aeronautic science and Engineering Beijing University of Aeronautics and Astronautics Beijing 100191 China

Three-dimensional（3.D）braided composites are a kind of advanced ones and are used in the aeronautical and astronautical fields more widely. The advantages, usages, shortages and disadvantages of 3. braided composites are analyzed, and the possible approach of improving the properties of the materials is presented, that is, a new type of 3. full 5-directional braided composites is developed. The methods of making this type of preform are proposed. It is pointed out that the four-step braiding which is the most possible to realize industrialized production almost has no effect on the composites＇ properties. By analyzing the simulation model,the advantages of the material compared with the 3. 4-directional and 5-directional materials are presented. Finally, a microstructural model is analyzed to lay the foundation for the future theoretical analysis of these composites.

关键词： 3. braided fabrics four-step braiding 3. full 5-directional braided composites preform microstructure

Application of Tandem Cascade to Design of Fan Stator with Supersonic Inflow

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Chinese Journal of aeronautics 2010年第1期23卷 9-14页

作者： Li Qiushi,Wu Hong,Zhou Sheng school of Jet Propulsion,beijing university of {3. and astronautics,beijing 100191,China school of Jet Propulsion Beijing University of Aeronautics and Astronautics Beijing 100191 China

This article proposes a tandem cascade constructed to tackle the thorny problem of designing the high-loaded stator with a supersonic inflow and a large turning angle. The front cascade adopts a supersonic profile to reduce the shock wave intensity turning the flow into subsonic,while the rear cascade adopts a subsonic profile with a large camber offering the flow a large turning angle. It is disclosed that the losses would be minimized if the leading edge of the rear cas- cade lies close to the pressure side of the front cascade at a distance of 20% pitch in pitch-wise direction without either axial spacing or overlapping in axial direction. The 2D numerical test results show that,with the inflow Mach number of 1.25 and the turning angle of 52° ,the total pressure loss coefficient of the tandem cascade reaches 0. 106 ,and the diffusion factor 0. 745. Finally,this article has designed and simulated a high-loaded fan stage with the proposed tandem stator,which has the pressure ratio of 3.15 and the efficiency of 86.3.% at the rotor tip speed of 495.3. m/s.

关键词： fan/compressor tandem cascade stator supersonic inflow

Analysis and simulation of high strain compression of anisotropic open-cell elastic foams

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science China(Technological sciences) 2010年第3期53卷 863-869页

作者： LU ZiXing,HUANG JiXiang&CHEN Xin school of Aeronautic science and Engineering,beijing {3. of aeronautics and astronautics,beijing 100191,China school of Aeronautic science and Engineering Beijing University of Aeronautics and Astronautics Beijing China

By elongating the regular Kelvin model in one direction and keeping unchanged in the other two directions,the anisotropic model was ***,the simplified periodic structural cell was obtained according to the periodicity and symmetry of the model in the whole *** the half-strut element and elastic deflection theory to analyze the mechanical behavior as were adopted in the previous studies,this paper obtained the theoretical expressions for the compressive stress and strain as well as the corresponding curves in the rise and transverse *** addition,the theoretical results were examined by the finite element *** indicated that the theoretical analysis was very close to the finite element simulation when the strain was not too high,which confirmed the validity of theoretical *** the same time,the anisotropy was shown to have a significant effect on the mechanical properties of open-cell *** the anisotropy ratio increased,the compressive stress was improved in the rise direction but dropped in the transverse direction under the same strain.

关键词： open-cell foams elastic deformation Kelvin model anisotropy finite element

Effects of surface modification on thermal cycling lifetime of thermal barrier coatings with HVOF NiCrAlY bond coat

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Progress in Natural science:Materials International 2012年第3期22卷 237-243页

作者： Liyong Ni, Chungen Zhou Department of Materials science and Engineering, beijing university of aeronautics and astronautics, beijing 100191, China Department of Materials science and Engineering Beijing University of Aeronautics and Astronautics Beijing 100191 China

NiCrAlY bond coat was prepared by HVOF (high-velocity oxygen fuel) spray on nickel-based superalloy. Surface treatments like grit-blasting, shot-peening and vacuum treatment methods were carried out in order to study the effects of surface modification on thermal cycling lifetime of TBCs. The surface-modified TBCs exhibited better thermal shock resistance. Failure of TBCs with the as-sprayed bond coat occurred within the top coat and at the interface between spinels and the top coat, while that of after shot-peening, grit-blasting and vacuum treatment occurred mainly within the top coat. TGO (thermally grown oxide) formed on as-sprayed bond coat was composed of a Ni(Al,Cr)2O4 spinels outer layer and a Al2O3.inner layer. But, a continuous and uniform Al2O3.formed after surface modification. Formation of the mixed oxides (spinels) on the as-sprayed bond coat accelerated the failure of TBCs.

关键词： Thermal barrier coatings NiCrAlY HVOF Thermally grown oxide (TGO)

Bursting of Morris-Lecar neuronal model with current-feedback control

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science China(Technological sciences) 2009年第3期52卷 771-781页

作者： DUAN LiXia1, LU QiShao2 & CHENG DaiZhan3.1 College of science, North China university of Technology, beijing 100144, China {3., beijing university of aeronautics and astronautics, beijing 100191, China 3.Institute of Systems science, Chinese Academy of sciences, beijing 100190, China College of science North China University of Technology Beijing China school of science Beijing University of Aeronautics and Astronautics Beijing China Institute of Systems science Chinese Academy of Sciences Beijing China

The Morris-Lecar (ML) neuronal model with current-feedback control is considered as a typical fast-slow dynamical system to study the combined influences of the reversal potential VCa of Ca2+ and the feedback current I on the generation and transition of different bursting oscillations. Two-parameter bifurcation analysis of the fast subsystem is performed in the parameter (I, VCa)-plane at first. Three important codimension-2 bifurcation points and some codimension-1 bifurcation curves are obtained which enable one to determine the parameter regions for different types of bursting. Next, we further divide the control parameter (V0, VCa)-plane into five different bursting regions, namely, the "fold/fold" bursting region R1, the "fold/Hopf" bursting region R2, the "fold/homoclinic" bursting region R3. the "subHopf/homoclinic" bursting region R4 and the "subHopf/subHopf" bursting region R5, as well as a silence region R6. Codimension-1 and -2 bifurcations are responsible for explanation of transition mechanisms between different types of bursting. The results are instructive for further understanding the dynamical behavior and mechanisms of complex firing activities and information processing in biological nervous systems.

关键词： neuron bursting bifurcation fast-slow dynamics analysis codimension