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A new bionic MAV's flapping motion based on fruit fly hovering at low Reynolds number

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Acta Mechanica Sinica 2007年第5期23卷 485-493页

作者： Peng Bai Erjie Cui Feng Li Weijiang Zhou Bingyan Chen China Academy of Aerospace Aerodynamics Beijing 100074 China

On the basis of the studies on the high unsteady aerodynamic mechanisms of the fruit fly hovering the aerodynamic advantages and disadvantages of the fruit fly flapping motion were analyzed. A new bionic flapping motion was proposed to weaken the disadvantages and maintain the advantages, it may be used in the designing and manufacturing of the micro air vehicles （MAV＇s）. The translation of the new bionic flapping motion is the same as that of fruit fly flapping motion. However, the rotation of the new bionic flapping motion is different. It is not a pitching-up rotation as the fruit fly flapping motion, but a pitching-down rota- tion at the beginning and the end of a stroke. The numerical method of 3rd-order Roe scheme developed by Rogers was used to study these questions. The correctness of the numerical method and the computational program was justified by comparing the present CFD results of the fruit fly flapping motion in three modes, i.e., the advanced mode, the symmetrical mode and the delayed mode, with Dickinson＇s experimental results. They agreed with each other very well. Subsequently, the aerodynamic characteristics of the new bionic flapping motion in three modes were also numerically simulated, and were compared with those of the fruit fly flap- ping. The conclusions could be drawn that the high unsteady lift mechanism of the fruit fly hovering is also effectively utilized by this new bionic flapping. Compared with the fruit fly flapping, the unsteady drag of the new flapping decreases very much and the ratio of lift to drag increases greatly. And the great discrepancies among the mean lifts of three flapping modes of the fruit fly hovering are effectively smoothed in the new flapping. On the other hand, this new bionic flapping motion should be realized more easily. Finally, it must be pointed out that the above conclusions were just drawn for the hovering flapping motion. And the aerodynamic characteristics of the new bionic flapping motion in forwa

关键词： Flapping wing Low Reynolds number.MAV's Unsteady Numerical simulation

Influence of shock attenuation on tailored operation in free piston shock tunnels

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Chinese Journal of Aeronautics 2021年第2期34卷 279-287页

作者： Hao ZHU Hainan JIANG China Academy of Aerospace Aerodynamics Beijing 100074China

The free piston shock tunnel is a type of shock tunnel with high performance. For this type of tunnel, the influence mechanism of shock wave attenuation on tailored operation is explored by numerical simulation and theoretical analysis. By introducing the normalized velocity, the simple constraint equation for shock wave under the tailored operation is deduced. Moreover, the real gas effect is also taken into account in this equation. Based on the equation, the tailored operation of shock tunnels can be predicted with very few calculations. The present study shows that the change rate of the thermodynamic state of the gas behind the shock wave is inconsistent with the attenuation rate of the shock wave, which is the fundamental reason why the wind tunnel achieves tailored operation at a lower Mach number of shock waves. This lower Mach number of shock waves differs from the corresponding ideal value by a factor, which is about the square root of shock attenuation rate.

关键词： Attenuation Constraint equation Free piston shock tunnel Real gas effect Shock wave Tailored operation

Trajectory and attitude deviations for internal store separation due to unsteady and quasi-steady test method

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Chinese Journal of Aeronautics 2022年第2期35卷 74-81页

作者： Wei SONG Jingang DONG Wei LU Zenghui JIANG Aerodynamic Science Center China Academy of Aerospace AerodynamicsBeijing 100074China

The deviations of trajectory and attitude angle for internal store separation are evaluated by two wind tunnel test *** is the Freedrop Test(FDT),which is known as unsteady and time-dependent method of scaled *** other is the Captive Trajectory System(CTS)test,which is usually regarded as a quasi-steady and time-averaged test *** result shows that there is a streamwise adverse pressure gradient on the cavity resulting in a nose-up pitching moment coefficient(>0)acting on the store *** the initial pitch angular velocity is 0,the store exits the shear-layer with a nose-up pitch attitude causing the store to climb back towards and collide with the ***,the store passes through the shear-layer into the freestream with a nose-down pitch,which causes a successful separation event when the initial pitch angular velocity<*** pitch angle obtained by unsteady test method is different from that by quasisteady test *** time-dependent test includes the aerodynamic force induced by pitch angular velocity whereas the time-averaged method(CTS)cannot reflect the effect of unsteady aerodynamic *** deviation of vertical displacement is not obvious for FDT and CTS test since the store has an initial vertical velocity,which is dominant for the vertical *** means that the highly unsteady flow can create unpredictability in aerodynamic pitching moment of the store,which can lead to the deviation of pitch angle for internal store separation.

关键词： Captive trajectory system Freedrop test Internal weapons Store separation Unsteady test method

Preparation and Properties of Organically Modified Sepiolite/High-performance Epoxy Nanocomposites

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Chinese Journal of Aeronautics 2006年第B12期19卷 41-46页

作者： LU Hai-jun Aerospace Institute of Special Materials and Technology Beifing 100074 China

Fibrous organic sepiolites （OSEP） and novel epoxy/OSEP nanocomposites were prepared, and different methods were investigated to produce an intercalated/exfoliated structure of OSEP. Experimental results show that the modifier molecules can be easily adsorbed by the sepiolite, but the layer space （d001 of the sepiolite, linked by means of covalent bond, remains unchanged. A proper method to solve this problem appears to exert large shearing force on the original sepiolite followed by its organic modification （OSEP2）. The morphology observation shows that there are formed an even dispersion of nano-sized OSEP2 fibers in epoxy resin and a structure intercalated by epoxy molecules, which lead to significantly improved mechanical properties. Impact strength of the epoxy/OSEP2 nanocomposite increases from 32.1 kJ/m^2 to 44.4 kJ/m^2, 38.3% higher than that of pristine matrix with 3 wt% OSEP2 content. It is also noted that the flexural strength of the OSEP/epoxy composites has risen by about 3% higher than that of the pure epoxy resin.

关键词： sepiolite intercalation/exfoliation epoxy nanocomposites

Time-varying fault-tolerant formation tracking based cooperative control and guidance for multiple cruise missile systems under actuator failures and directed topologies

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Journal of Systems Engineering and Electronics 2019年第3期30卷 587-600页

作者： XU Xingguang WEI Zhenyan REN Zhang LI Shusheng School of Automation Science and Electrical Engineering Beihang University Beijing 100191 China Beijing Institute of Mechanical and Electrical Engineering Beijing 100074 China Beijing Aerospace Technology Institute Beijing 100074 China

This paper studies time-varying fault-tolerant formation tracking problems for the multiple cruise missile system under directed topologies subjected to actuator failures. Firstly, the timevarying fault-tolerant formation tracking process for the multiple cruise missile system is divided into the guidance loop and the control loop. Then protocols are constructed to accomplish distributed fault-tolerant formation tracking in the guidance loop with the adaptive updating mechanism, in the condition where neither the knowledge about actuator malfunctions nor any global information of the communication topology remains available. Moreover, sufficient conditions to accomplish formation tracking are presented, and it is shown that the multiple cruise missile system can carry on the predefined time-varying fault-tolerant control (FTC) formation tracking through the active disturbances rejection controller (ADRC) and the proportion integration (PI) controller by the way of the fault-tolerant protocol utilizing the designed strategies, in the event of actuator failures. At last, numerical analysis and simulation are designed to verify the theoretical results.

关键词： fault-tolerant formation tracking consensus-based cruise missile active disturbances rejection controller (ADRC)

Central Discontinuous Galerkin Method for the Navier-Stokes Equations

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Journal of Beijing Institute of Technology 2017年第2期26卷 158-164页

作者： Tan Ren Chao Wang Haining Dong Danjie Zhou Beijing Electro-Mechanical Engineering Institute Beijing 100074 China

Central discontinuous Galerkin（CDG）method is used to solve the Navier-Stokes equations for viscous flow in this *** CDG method involves two pieces of approximate solutions defined on overlapping *** advantages of the redundant representation of the solution on the overlapping meshes,the cell interface of one computational mesh is right inside the staggered mesh,hence approximate Riemann solvers are not needed at cell *** order total variation diminishing（TVD）Runge-Kutta（RK）methods are applied in time *** examples for 1D and2 D viscous flow simulations are presented to validate the accuracy and robustness of the CDG method.

关键词： central discontinuous Galerkin (CDG) method Navier-Stokes equations total variationdiminishing ( TVD ) Runge-Kutta (RK) methods

Optimization and verification of free flight separation similarity law in high-speed wind tunnel

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Chinese Journal of Aeronautics 2020年第2期33卷 501-507页

作者： Fei XUE Xin JIN Peihua FENG Han QIN Zenghui JIANG Yuchao WANG Peng BAI China Academy of Aerospace Aerodynamics Beijing 100074China AVIC Chengdu Aircraft Design&Research Institute Chengdu 610091China Beijing Machinery and Electronics Engineering Institute Beijing 100074China

Based on the similarity of separation time,a similarity law optimization method for high-speed weapon delivery test is *** typical separation state under wind load is simulated by the numerical *** real separation data of aircraft,separation data of previous test methods,separation data of ideal wind tunnel test of previous methods,and simulation data of the proposed optimization method are obtained.A comparison of the data shows that the method proposed can improve the performance of *** law optimization starts with the development of motion equations and dynamic equations in the windless state to address the problems of mismatching between vertical and horizontal displacement,and to address the problems of separation trajectory distortion caused by insufficient gravity acceleration of the scaling model of existing light *** ejection velocity of the model is taken as a factor/vector,and is adjusted reasonably to compensate the linear displacement insufficiency caused by the insufficient vertical acceleration of the light model method,so as to ensure the matching of the vertical and horizontal displacement of the projectile,and to improve the consistency between the test results of high-speed projection and the actual separation *** optimized similarity law is applicable to many existing free-throwing modes of high-speed wind *** optimized similarity law is not affected by the ejection velocity and hanging mode of the *** optimized similarity law is suitable not only for the launching of the buried ammunition compartment and external stores,but also for the test design of projectile launching and gravity separation.

关键词： Carrier and missile interference Ejection separation Gravity separation High-speed weapon delivery Multi-body separation Similarity law optimization

TYPES OF FLOW OVER LEESIDE OF A SLENDER TAPERED WING AT SUPERSONIC SPEED　

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Chinese Journal of Aeronautics 1996年第3期9卷 225-233页

作者： Hong Jinsen(Beijing Institule of Aeronaulics, Beijing, China, 100074) Beijing Institute of Aeronautics Beijing 100074 China

A flow visualization experiment is reported over the leeside of a slender tapered wing with a leading edge sweep back angle of 65°and a bicovex section. By using laser vapor-screen. schlieren and oil-flow techniques. the test was carried out at Mach numbers of 1.10, 1.53, 2.53, 3.01, and 4.01 for angles of attack from 5°through 25°.Photos of flow off-body and on the surface have been taken. The vapor-screen photos show seven distinct types of flow developed over the delta region on the wing. These types of flow are displayed in a plane of Mach number and angle of attack normal to the leading-edge. In the region of side-edge, there are side vortices formed, and in the downstream of trailing-edge. vortex wakes shed. The variety of bow shock positions at different Mach numbers and the positions of separating lines induced by shock wave with Mach numbers and angles of attack have been obtained. based upon the schlieren plus the vapor-screen photos in the sections. The oil-flow visualization clearly shows primary reattachment. secondary separation. secondary reattachment lines. and side edge vortices on the lee-surface. The results of this test shows in good agreement with other relevant experiments and numerical simulation results.

关键词： flow visualization vortices shock waves boundary layer separation

Decomposition processing and precipitation hardening of rapidly solidified Al-Cr-Y-Zr alloy

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中国有色金属学会会刊：英文版 2002年第1期12卷 16-20页

作者：李伟李松瑞马正青肖于德黎文献 DepartmentofMaterialsScienceandEngineering CentralSouthUniversityChangsha410083China BeijingElectro-mechanicalTechnologyInstitute Beijing100074China

Foil powders of Al 5.0 Cr 4.0 Y 1.5 Zr (%) were prepared by using a multi stage atomization rapid solidification powder making device. The obtained powders were exposed thermally at various temperatures. Variation of microstructures and properties of the alloy powders was investigated by micro hardness measurement, X ray diffraction, differential thermal analysis, and transmission electron microscopy with energy disperse X ray analyses. The results show that cubic Al 20 Cr 2Y ( a = 1.437?nm) and metastable Ll 2 Al 3Zr (FCC, a = 0.405?1?nm) or equilibrium DO 23 Al 3Zr (tetragonal structure, a = 0.409?1?nm, b = 1.73?0?nm) are main second phases precipitated from supersaturated solid solution of the rapidly solidified foil powders during thermal exposure. The cubic dispersion precipitates prior to the two other Al 3Zr type intermetallic phases in the course of the decomposition. Precipitation of incoherent Al 20 Cr 2Y results in softening of foil powder, and coherent Ll 2 Al 3Zr has intensive precipitation strengthening effect. The Al 20 Cr 2Y phase is structurally stable, but it is prone to coarsen and polygonize above 450?℃. Both Al 3Zr type intermetallic phases have much smaller coarsening rate than Al 20 Cr 2Y at temperature higher than 450?℃. These two phases are able to keep their fine spherical morphologies up to 550?℃, but Al 3Zr transforms into DO 23 structure from Ll 2 structure during thermal exposure above 550?℃.

关键词：快速凝固耐热铝合金分解淀积硬化铝铬钇锆合金