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Kinematics,Deformation,and Aerodynamics of a Flexible Flapping Rotary Wing in Hovering Flight

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Journal of Bionic Engineering 2021年第1期18卷 197-209页

作者： chao zhou Jianghao Wu School of Aeronautic Science and Engineering Beihang UniversityBeijing 100191China School of Transportation Science and Engineering Beihang UniversityBeijing 100191China

The Flapping Rotary Wing(FRW)is a micro air vehicle wing layout coupling flapping,pitching,and rotating *** can gain bencfits in high lift from a fast passive rotating motion,which is tightly related to the passive pitching motion directly caused by wing flexible ***,flexible deformation is crucial for the wing kinematics and aerodynamic performance of an *** this paper,we explored the effct of flexibility on wing kinematics and acrodynamics on the basis of a mechanical FRW model.A photogrammetric method was adopted to capture motion images according to which wing orientations and deformations were *** acrodynamic force was computed using computational fluid dynamic method,and wing kinematics and deformations were used as simulation *** experimental measurements presented the real orientation and deformation pattem of a real *** wing passive deformation of a high-intensity FRW was found to be mainly caused by inertial force,and a linear positive spanwise twist was observed in the *** effects of wing deformation on aerodynamic force production and the underlying mechanism were *** showed that lift augment,rotating moment enhancement,and power efficiency improvement can be achieved when a wing becomes *** spanwise twist mainly accounts for these changes in aerodynamics,and increment in spanwise twist could further contributes to aerodynamic improvement.

关键词： bionic robot micro air vehicle flapping wing flexibility unsteady aerodynamic twist deformation

Thermal Conduction and Insulation Modification in Asphalt-Based Composites

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Journal of Materials Science & Technology 2012年第3期28卷 285-288页

作者： Xiaofeng zhou Shengyue Wang chao zhou School of Transportation Southeast UniversityNanjing 210096China School of Energy and Environment Southeast UniversityNanjing 210096China Department of Fundamental Sciences Yancheng Institute of TechnologyYancheng 224003China

The relationship between thermal conductivity and properties of mixing particles is required for quantitative study of heat transfer processes in asphalt-based materials. In this paper, we measured the e？ective ther- mal conductivity of asphalt-based materials with thermal conduction （graphite） and insulation （cenosphere） powders modification. By taking account of the particle shape, volume fraction, the thermal conductivity of filling particles and base asphalt, we present a new differential effective medium formula to predict the thermal conductivity modification in asphalt-based composite. Our theoretical predications are in good agreement with the experiment data. The new model can be applied for predicting the thermal properties of asphalt-based mixture, which is available for most of thermal modification in two-phase composites.

关键词： Thermal conductivity Asphalt-based composites Graphite Cenosphere Differential effective medium formula

Optimized operation plan for sewer sediment control

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2010年第5期11卷 335-341页

作者： Yong-chao zhou Tian LI Institute of Municipal Engineering Zhejiang University Hangzhou 310058 China College of Environmental Science and Engineering Tongji University Shanghai 200096 China

Severe operational problems of sediment deposition have frequently occurred in stormwater sewer systems in Shanghai city due to the flat topography of the area and serious illicit connections. To control sewer sediment and its subsequential problems,optimized operation plans were proposed and an innovative performance assessment method was developed. Simula-tion results demonstrated that,through changing the way of pump operation and installing necessary actuators in the system,the optimized operations,especially batch intermittent intercept plan,effectively improved the flow velocity in the entire system in dry-weather condition. In conclusion,the optimized operation is an innovative idea for improving the performance and solving the problem of sediment deposition in the sewer system in Shanghai,China.

关键词： Sewer system Sediment control Performance assessment Simulation

Effect of flexibility on unsteady aerodynamics forces of a purely plunging airfoil

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Chinese Journal of Aeronautics 2020年第1期33卷 88-101页

作者： chao zhou Yanlai ZHANG Jianghao WU School of Transportation Science and Engineering Beihang UniversityBeijing 100083China

Introducing flexibility into the design of a vertically flapping wing is an effective way to enhance its aerodynamic *** less previous studies on the aerodynamics of vertically flapping flexible wings focused on the lift generated in a wide range of angle of attack·a 2D numerical simulation of a purely plunging flexible airfoil is employed using a loose fluid–structure interaction *** aerodynamics of a fully flexible airfoil are firstly studied with the flexibility and angle of *** verify whether an airfoil could get aerodynamic benefit from the change in structure,partially flexible airfoil with rigid leading edge and flexible trailing edge were further *** show that flexibility could always reduce airfoil drag while lift and lift efficiency both peak at moderate *** freestream velocity is constant,lift is maximized at a high angle of attack about 40°while this optimal angle of attack reduces to 15°in drag-balanced *** airfoil drag reduction,lift augmentation as well as efficiency enhancement mainly attribute to the passive pitching other than the camber *** deformed airfoil with the longest length of moderate flexible trailing edge can achieve the highest *** study may provide some guidance in the wing design of Micro Air Vehicle(MAV).

关键词： Aerodynamic forces Flexibility Fluid structure interaction Low Reynolds number Plunging airfoil Self-propulsion

Aerodynamic periodicity of transient aerodynamic forces of flexible plunging airfoils

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Chinese Journal of Aeronautics 2021年第1期34卷 10-21页

作者： zhou chao ZHANG Yanlai WU Jianghao School of Aeronautics Science and Engineering Beihang UniversityBeijing 100083China School of Transportation Science and Engineering Beihang UniversityBeijing 100083China

For flapping micro-air vehicles,periodical aerodynamics in every plunging period is always desired in the design of aircraft controlling *** the periodic plunges of rigid airfoil,either periodical or non-periodical aerodynamic forces can be *** airfoils are usually flexible so that the effect of flexibility on unsteady characteristics of aerodynamic periodicity should be *** this study,a fluid structure interaction analysis is employed to systematically investigate the aerodynamic periodicity of a periodically plunging flexible *** influences of several dimensionless kinematic and structural parameters on aerodynamic periodicity are *** results show that the aerodynamic periodicity of plunging flexible airfoil qualitatively resembles that of rigid airfoil as the mechanisms contributing to aerodynamic periodicity are kept for airfoil with various ***,aerodynamic periodicity at small plunging amplitude and high Reynolds number can be improved as airfoil becomes medium flexible but worsened as airfoil is very *** reason is that the deformation of the airfoil changes the strength and structure of the nearby vortices,thereby leading to weak vortex–vortex and vortex–airfoil *** extent of improvement in aerodynamic periodicity is also found significantly influenced by incoming velocity.

关键词： Aerodynamic periodicity Flapping wing Flexibility Micro-air vehicle Vortex structure

Effects of Elevated CO_2 Concentration on the Biomasses and Nitrogen Concentrations in the Organs of Sainfoin(Onobrychis viciaefolia Scop.)

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Agricultural Sciences in China 2009年第4期8卷 424-430页

作者： zhou Zheng-chao SHANGGUAN zhou-ping College of Tourism and Environmental Sciences Shaanxi Normal University Xi＇an 710062 P.R. China State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau Institute of Soil and Water Conservation Chinese Academy of Sciences Yangling 712100 P.R. China

In forage grasses, the nitrogen concentration is directly related to the nutritional value. The studies examined the hypothesis that global elevation of CO2 concentration probably affects the biomass, nitrogen （N） concentration, and allocation and distribution patterns in the organs of forage grasses. While sainfoin （Onobrychis viciaefolia Scop.） seedlings grew on a low nutrient soil in closed chambers for 90 days, they were exposed to two CO2 concentrations （ambient or ambient＋350 μmol mol^-1 CO2） without adding nutrients to them. After 90 days exposure to CO2, the biomasses of leaves, stems, and roots, and N concentrations and contents of different parts were measured. Compared with the ambient CO2 concentration, the elevated CO2 concentration increased the total dry matter by 25.07%, mainly due to the root and leaf having positive response to the elevated CO2 concentration. However, the elevated CO2 concentration did not change the proportions of the dry matters in different parts and the total plants compared with the ambient CO2 concentration. The elevated CO2 concentration lowered the N concentrations of the plant parts. Because the dry matter was higher, the elevated CO2 concentration had no effect on the N content in the plants compared to the ambient CO2 concentration. The elevated CO2 concentration promoted N allocations of the different parts significantly and increased N allocation of the underground part. The results have confirmed the previous suggestions that the elevated CO2 concentration stimulates plant biomass production and decreases the N concentrations of the plant parts.

关键词： biomass CO2 N allocation N content C/N ratio sainfoin

Comparison of aerodynamic characteristics between a novel highly loaded injected blade with curvature induced pressure-recovery concept and one with conventional design

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Chinese Journal of Aeronautics 2017年第3期30卷 939-950页

作者： Zhiyuan CAO chao zhou Zhili SUN Stute Key Laboratory fot Turbulenee and Complex Systems College of Engineering Peking University Beijing 100871 China BIC-ESA T Peking University Beijing 100871 China Collabarative Innovation Center of Advaneed Aero-Engine Beijing 100083 China

This paper introduces a novel design method of highly loaded compressor blades with air *** methods were firstly validated with existing data and then used to develop and investigate the new method based on a compressor cascade.A compressor blade is designed with a curvature induced pressure-recovery concept.A rapid drop of the local curvature on the blade suction surface results in a sudden increase in the local pressure,which is referred to as a curvature induced ‘Shock＇.An injection slot downstream from the ‘Shock＇ is used to prevent ‘Shock＇ induced separation,thus reducing the *** a result,the compressor blade achieves high loading with acceptable ***,the design concept based on a 2D compressor blade profile is ***,a 3D cascade model is investigated with uniform air injection along the *** effects of the incidence are also investigated on emphasis in the current *** mid-span flow field of the 3D injected cascade shows excellent agreement with the 2D designed flow *** the highly loaded cascade without injection,the flow separates immediately downstream from the ‘Shock＇;the initial location of separation shows little change in a large incidence *** air injection with the same injection configuration effectively removes the flow separation downstream from the curvature induced ‘Shock＇ and reduces the size of the separation zone at different *** the endwall,the flow within the incoming passage vortex mixes with the injected *** a result,the size of the passage vortex reduces significantly downstream from the injection *** air injection,the loss coefficient along spanwise reduces significantly and the flow turning angle increases.

关键词： Axial compressor Air injection Curvature induced ‘Shock’ Flow control Separation

Fractal Surface Synthesis Based on Two Dimensional Discrete Fourier Transform

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Chinese Journal of Mechanical Engineering 2013年第6期26卷 1101-1108页

作者： zhou chao GAO Chenghui HUANG Jianmeng School of Mechanical Engineering and Automation Fuzhou University Fujian Provincial Research Center of Digital Design for Manufacturing

The discrete Fourier transform（DFT） is used for fractional Brownian motion（FBM） surface synthesis in tribology（i.e., contact, sliding, and sealing, etc）. However, the relationship between fractal parameters（fractal dimension and scale factor） and traditional parameters, the influence of fractal parameters on surface appearance, have not been deeply discussed yet. These lead to some kind of difficulty to ensure the synthesized surfaces with ideal fractal characteristic, required traditional parameters and geometric appearance. A quantitative relationship between fractal parameters and the root mean square deviation of surface （Sq） is derived based on the energy conservation property between the space and frequency domain of DFT. Under the stability assumption, the power spectrum of a FBM surface is composed of concentric circles strictly, a series of FBM surfaces with prescribed Sq could be synthesized with given fractal dimension, scale factor, and sampling numbers, but the ten-point height（Sz）, the skewness（Ssk） and the kurtosis（Sku） are still in random, where the probability distributions of Sz and Ssk are approximately normal distribution. Furthermore, by iterative searching, a surface with desired Abbott-Firestone curve could be obtained among those surfaces. An intuitive explanation for the influence of fractal dimension and scale factor on surface appearance is obtained by discussing the effects on the ratio of energy between high and low frequency components. Based on the relationship between Sq and surface energy, a filtering method of surface with controllable Sq is proposed. The proposed research ensures the synthesized surfaces possess ideal FBM properties with prescribed Sq, offers a method for selecting desired Abbott-Firestone curve of synthesized fractal surfaces, and makes it possible to control the Sq of surfaces after filtering.

关键词： fractional Brownian motion discrete Fourier transform fractal surface power spectrum

Unsteady Aerodynamic Forces and Power Consumption of a Micro Flapping Rotary Wing in Hovering Flight

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Journal of Bionic Engineering 2018年第2期15卷 298-312页

作者： chao zhou Yanlai Zhang Jianghao Wu School of Transportation Science and Engineering Beihang University Beijing 100191 China

The micro Flapping Rotary Wing （FRW） concept inspired by insects was proposed recently. Its aerodynamic performance is highly related to wing pitching and rotational motions. Therefore, the effect of wing pitching kinematics and rotational speed on unsteady aerodynamic forces and power consumption of a FRW in hovering flight is further studied in this paper using computational fluid dy- namics method. Considering a fixed pitching amplitude （i.e., 80°）, the vertical force of FRW increases with the downstroke angle of attack and is enhanced by high wing rotational speed. However, a high downstroke angle of attack is not beneficial for acquiring high rotational speed, in which peak vertical force at balance status （i.e., average rotational moment equals zero.） is only acquired at a comparatively small negative downstroke angle of attack. The releasing constraint of pitching amplitude, high rotational speed and enhanced balanced vertical force can be acquired by selecting small pitching amplitude despite high power consumption. To confirm which wing layout is more power efficient for a certain vertical force requirement, the power consumed by FRW is compared with the Rotary Wing （RW） and the Flapping Wing （FW） while considering two angle of attack strategies without the Reynolds number （Re） constraint. FRW and RW are the most power efficient layouts when the target vertical force is produced at an angle of attack that corresponds to the maximum vertical force coefficient and power efficiency, respectively. However, RW is the most power efficient layout overall despite its insufficient vertical force production capability under a certain Re.

关键词： micro air vehicle flapping rotary wing aerodynamic forces power consumption computational fluid dynamics