检索结果-南通市图书馆

Resonance mechanism of flapping wing based on fluid structure interaction simulation

Chinese Journal of Aeronautics 2024年第5期37卷 243-262页

作者： Yueyang GUO Wenqing YANG Yuanbo DONG Dong XUE National Key Laboratory of Science and Technology on Aerodynamic Design and research School of AeronauticsNorthwestern Polytechnical UniversityXi'an 710072China research&Development institute of northwestern polytechnical university in Shenzhen Shenzhen 518063China yangtze river delta research institute of northwestern polytechnical university Taicang 215400China

Certain insect species have been observed to exploit the resonance mechanism of their wings.In order to achieve resonance and optimize aerodynamic performance,the conventional approach is to set the flapping frequency of flexible wings based on the Traditional Structural Modal(TSM)analysis.However,there exists controversy among researchers regarding the relationship between frequency and aerodynamic performance.Recognizing that the structural response of wings can be influenced by the surrounding air vibrations,an analysis known as Acoustic Structure Interaction Modal(ASIM)is introduced to calculate the resonant frequency.In this study,Fluid Structure Interaction(FSI)simulations are employed to investigate the aerodynamic performance of flapping wings at modal frequencies derived from both TSM and ASIM analyses.The performance is evaluated for various mass ratios and frequency ratios,and the findings indicate that the deformation and changes in vortex structure exhibit similarities at mass ratios that yield the highest aerodynamic performance.Notably,the flapping frequency associated with the maximum time-averaged vertical force coefficient at each mass ratio closely aligns with the ASIM frequency,as does the frequency corresponding to maximum efficiency.Thus,the ASIM analysis can provide an effective means for predicting the optimal flapping frequency for flexible wings.Furthermore,it enables the prediction that flexible wings with varying mass ratios will exhibit similar deformation and vortex structure changes.This paper offers a fresh perspective on the ongoing debate concerning the resonance mechanism of Flexible Flapping Wings(FFWs)and proposes an effective methodology for predicting their aerodynamic performance.

关键词： Flexible Flapping Wing(FFW) Acoustic Structure Interaction Modal(ASIM) Fluid Structure Interaction(FSI) Resonance mechanism Aerodynamic performance

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Synthesis and microwave absorption performance of heat-treated RF/SiO_(2)aerogels

引用

Defence Technology（防务技术） 2024年第4期34卷 177-186页

作者： Xinli Ye Hao Yu Kai Zheng Shan Li Xiaomin Ma Bangxiao Mao Junxiong Zhang School of Civil Aviation Northwestern Polytechnical UniversityXi’an 710072PR China research&Development institute of northwestern polytechnical university in Shenzhen Shenzhen 518057PR China yangtze river delta research institute of northwestern polytechnical university Suzhou 215400PR China National Equipment New Material&Technology(Jiangsu)Co. LtdSuzhou 215400PR China Beijing Xinfeng Aerospace Equipment Co. LtdBeijing 100854PR China School of Textile and Clothing Nantong UniversityNantong 226019PR China

The well-designed composite with satisfactory electromagnetic microwave absorption at high temperatures remains a serious challenge.Herein,we fabricated a resorcinol-formaldehyde/silica dioxide composite aerogel(RF/SiO_(2))with a three-dimensional network structure using sol-gel,atmospheric pressure drying technique as well as heat-treated processes to achieve enhanced microwave absorption capabilities in the low frequency range.The pristine RF/SiO_(2)aerogel presented a typical micropores structure with a surface area,porous volume,and density of 146.82 m^(2)/g,62.40%,and 0.28 cm^(3)/g,respectively.Remarkably,the RF/SiO_(2)aerogel showed an effective absorption bandwidth of 3.56 GHz and a minimum reflection loss value of-46.10 d B at 2.25 mm after being heat-treated at 1500°C,while the maximum effective absorption bandwidth was 3.60 GHz at 2.30 mm.The intricate three-dimensional networks possessed remarkable impedance matching,multiple attenuation mechanisms,interfacial polarization,and dielectric loss,which were attributed to the exceptional ability to absorb electromagnetic microwaves.It offered a fresh approach to creating adaptable and effective microwave absorption materials in military defense.

关键词： RF/SiO_(2) Aerogel Heat-treated Microwave absorption

来源：

维普期刊数据库博看期刊

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Effect of Incoming Vortex on Secondary Flows in Turbine Cascades with Planar and Non-Axisymmetric Endwall

引用

Journal of Thermal Science 2024年第1期33卷 138-157页

作者： CAO Zhiyuan WANG Chuxuan SONG Zhigao GAO Xi ZHAO Wei LIU Bo School of Power and Energy Northwestern Polytechnical UniversityXi'an 710072China National Key Laboratory of Science and Technology on Aerodynamic Design and research Northwestern Polytechnical UniversityXi'an 710072China institute of Engineering Thermophysics Chinese Academy of SciencesBeijing 100080China School of Aeronautics and Astronautics University of Chinese Academy of SciencesBeijing 100080China

Non-Axisymmetric Endwall Profiling(NAEP) is commonly utilized in turbines to eliminate secondary flows.Nevertheless,most of the NAEP methods consider a single-blade row environment without incorporating the effect of the stage environment.This paper aims to investigate the influence mechanism of the incoming vortex on the endwall secondary flow structures of NAEP in a highly loaded turbine cascade.To model the incoming vortex in a stage environment,this study considers a half-delta wing as the vortex generator at the upstream of the turbine cascade.The NAEP is then carried out for a highly loaded turbine cascade with an in-house numerical optimization design platform subject to no incoming vortex.Numerical simulation is also carried out under the influence of the incoming vortex for the turbine cascades with both planar and non-axisymmetric endwall.This paper furthers investigated the pitchwise effect of the incoming vortex on the near endwall secondary flow.The results indicate that the NAEP effectively improves the endwall secondary flow of the turbine cascade,where the total pressure loss coefficient and the secondary kinetic energy(SKE) are reduced by 7.3%,and 45.7%,respectively.It is further seen that with the incoming vortex,the NAEP achieves a considerable control effect on the endwall secondary flow of the turbine cascade.With incoming vortex,the NAEP can still achieve considerable control effect on the endwall secondary flow of the turbine cascade;the averaged reductions of loss coefficient and SKE are 7.8% and 14.2%,respectively.Under some pitchwise locations,incoming vortex can suppress the convection of cross-passage flow toward the suction corner greatly and reduce the loss coefficient of the baseline cascade.The incoming vortex at 4/7 pitch impinged right at the blade leading edge,leading to the generation of low-momentum fluid,which increased the size and the strength of the horseshoe vortex.Under all the pitchwise locations,NAEP can suppress the secondary vortices,e.g.,the passage vortex and the c

关键词： non-axisymmetric endwall secondary flow incoming vortex passage vortex stage environment

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Review on ultra-lightweight flapping-wing nano air vehicles:Artificial muscles,flight control mechanism,and biomimetic wings

引用

Chinese Journal of Aeronautics 2023年第6期36卷 63-91页

作者： Liang WANG Bifeng SONG Zhongchao SUN Xiaojun YANG School of Aeronautics Northwestern Polytechnical UniversityXi'an 710072China research&Development institute of northwestern polytechnical university in Shenzhen Shenzhen 518057China yangtze river delta research institute Northwestern Polytechnical UniversityTaicang 215400China

Flying insects are capable of flapping their wings to provide the required power and control forces for flight.A coordinated organizational system including muscles,wings,and control architecture plays a significant role,which provides the sources of inspiration for designing flapping-wing vehicles.In recent years,due to the development of micro-and meso-scale manufacturing technologies,advances in components technologies have directly led to a progress of smaller Flapping-Wing Nano Air Vehicles(FWNAVs)around gram and sub-gram scales,and these air vehicles have gradually acquired insect-like locomotive strategies and capabilities.This paper will present a selective review of components technologies for ultra-lightweight flapping-wing nano air vehicles under 3 g,which covers the novel propulsion methods such as artificial muscles,flight control mechanisms,and the design paradigms of the insect-inspired wings,with a special focus on the development of the driving technologies based on artificial muscles and the progress of the biomimetic wings.The challenges involved in constructing such small flapping-wing air vehicles and recommendations for several possible future directions in terms of component technology enhancements and overall vehicle performance are also discussed in this paper.This review will provide the essential guidelines and the insights for designing a flapping-wing nano air vehicle with higher performance.

关键词： Actuators Artificial muscle Biomimetic wings Flapping wing Flight control mechanism Nano Air Vehicles(NAVs)

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Lift performance enhancement for flapping airfoils by considering surging motion

引用

Chinese Journal of Aeronautics 2022年第9期35卷 194-207页

作者： Tao WU Bifeng SONG Wenping SONG Wenqing YANG Dong XUE Zhonghua HAN School of Aeronautics Northwestern Polytechnical UniversityXi'an 710072China research&Development institute of northwestern polytechnical university in Shenzhen Shenzhen 518057China yangtze river delta research institute of northwestern polytechnical university Taicang 215400China

The flapping motion has a great impact on the aerodynamic performance of flapping wings. In this paper, a surging motion is added to an airfoil performing pitching-plunging combined motion to figure out how it influences the lift performance and flow pattern of flapping airfoils.Firstly, the numerical methods are validated by a NACA0012 airfoil pitching case and a NACA0012 airfoil plunging case. Then, the E377m airfoil which has typical geometric characteristics of the bird-like airfoil is selected as the calculation model to study how phase differences φ1 between surging motion and plunging motion affect the aerodynamic performance of flapping airfoils. The results show that the airfoil with surging motion has comprehensively better lift performance and thrust performance than the airfoil without surging motion when 15°< φ1< 90°. It is demonstrated that surging motion has a powerful ability to improve the aerodynamic performance of flapping airfoil by adjusting φ1. Finally, to further explore how flapping airfoil improves lift performance by considering surging motion, the flapping motions of E377m airfoil with the highest lift coefficient and lift efficiency are obtained through trajectory optimization. The surging motion is removed in the highest lift case and highest lift efficiency case respectively, and the mechanism that surging motion adjusts the aerodynamic force is analyzed in detail by comparing the vortex structure and kinematic parameters. The results of this paper help reveal the aerodynamic mechanism of bird flight and guide the design of Flapping wing Micro Air Vehicles(FMAV).

关键词： Aerodynamics Flapping airfoils Surging motion Trajectory optimization Unsteady flow

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Unsteady characteristic research on aerodynamic interaction of slotted wingtip in flapping kinematics

引用

Chinese Journal of Aeronautics 2022年第4期35卷 82-101页

作者： Dan LIU Bifeng SONG Wenqing YANG Dong XUE Xinyu LANG School of Aeronautics Northwestern Polytechnical UniversityXi'an 710072China yangtze river delta research institute.northwestern polytechnical university Taiccing 215400China research&Development institute of northwestern polytechnical university in Shenzhen Shenzhen 518057China

The slotted wingtip structure of birds is considered to be the product of improving flight efficiency in the process of evolution. It can change the vortex structure of wingtip and improve aerodynamic efficiency. This paper reports a numerical investigation of slotted wing configuration undergoing bio-inspired flapping kinematics(consisting of plunging and in-line movement)extracted from a free-flying bald eagle wing. The aim is to eluci-date the collective mechanism of the flow generated by slotted tips and the lift contribution of each tip. Specifi-cally, the objective of the study is to determine how changes in the wing spacing affect the resulting aerodynamic interaction between the slotted tips and how that affects the force generation and efficiency. Changes in the phase angle between the flapping motions of slotted tips, as well as the spacings among them,can affect the resulting vortex inter-actions. The rear tips often operates in the wake of the frontal tips and, meanwhile, the vortex generated by the movement of the rear tips promote the frontal tips.The interaction of vortices in time and space leads to wing-wing interference and the flow around slotted tips becomes complicated and unstable. The innovative study of wingtip slot in unsteady state leads us to find that the aerodynamic interaction among slotted tips makes the overall lift characteristic better than that of the unslotted wings. The slotted wing configuration can efficiently convert more energy into lift. As the flapping frequency increases, the collective feature of slotted wing with constantly changing gaps can be more advantageous to enhance lift-generation performance.

关键词： Aerodynamic interaction Aerodynamic mechanism Flapping Unsteady behavior Wingtip slots

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Analysis of friction‐related acoustic emission in bolted joint structures

引用

International Journal of Mechanical System Dynamics 2023年第4期3卷 383-396页

作者： Jiaying Sun Huiyi Yang Dongwu Li Chao Xu School of Astronautics Northwestern Polytechnical UniversityXi'anChina yangtze river delta R&D institute Northwestern Polytechnical UniversitySuzhouChina

A bolted joint may be in a state of continuous fretting friction and wear under random oscillatory loading,which makes the bolted joint prone to loosening.Therefore,it is essential to find a way to monitor the contact state of a bolted joint on time and handle it adeptly.Acoustic emission(AE)signals will be generated during the reciprocating friction of the bolted joint interface.Exploring the relationship between the frictional slip features and the acoustic emission characteristics under different bolt preloads can lay the foundation for using the acoustic emission techniques to monitor the pretightening state of bolted joints.This paper experimentally investigates the acoustic emission signals of a bolted joint structure during friction under different preloads,three repeated tests are implemented.The relationship between friction behavior and acoustic emission characteristics under different preloads is studied.The evolution of classical acoustic emission parameters and kinematic parameters with bolt preload levels is also analyzed.The 3‐D topography of the specimens after parametric tests is analyzed.The results show that the characteristics of both burst‐type and continuous‐type acoustic emission can reflect different friction behavior under different bolt preloads.The evolution curves of acoustic emission parameters changed under the interaction of both frictional kinematic parameters and bolt preload levels.For the 3‐D surface topography,the reciprocating friction shears the peaks and fills the surface valleys,and the topography of the scratched surface areas is redistributed.

关键词： acoustic emission bolted joints friction fretting wear hysteresis loops

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Dynamic Biaxial Compression of CFRP Laminates Using Electromagnetic Loading

引用

Acta Mechanica Solida Sinica 2022年第5期35卷 891-900页

作者： Huaipu Kang Jintao Liang Yi Li Hao Cui Yulong Li NPU yangtze river delta research institute Suzhou215400China School of Aeronautics Northwestern Polytechnical UniversityXi’an710072China School of Civil Aviation Northwestern Polytechnical UniversitySuzhou215400China

The dynamic biaxial compression test for carbon-fiber-reinforced polymer(CFRP)laminates was carried out via synchronous electromagnetic loading in this study.During the experiments,four stress pulses transmitted along four incident bars,loading the square specimen simultaneously from four directions to keep the center of the specimen still.The dynamic mechanical behavior of CFRP was obtained employing the one-dimensional wave propagation theory,and the deformation and failure processes of the specimens were recorded by a high-speed camera.The effects of various biaxial stresses on the compressive strength were investigated in three biaxial and one uniaxial loading cases.For the CFRP laminates,the dynamic transverse compressive stress showed little effect on the longitudinal ultimate compressive strength.Numerical simulations were performed to understand the dynamic stress wave propagation.It showed that the employed loading device could guarantee good biaxial loading conditions until the ultimate failure of the specimens.This approach allows for the dynamic biaxial compression testing of various materials,which is of great significance in evaluating the dynamic impact performance of aeronautical composites.

关键词： Carbon-fiber-reinforced polymer(CFRP) Dynamic loading Biaxial testing Electromagnetic loading

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

A reduced order model for coupled mode cascade flutter analysis

引用

Chinese Journal of Aeronautics 2022年第10期35卷 176-182页

作者： Huang HUANG Xinkai JIA Jia REN Bochao CAO Dingxi WANG Xiuquan HUANG School of Power and Energy Northwestern Polytechnical UniversityXi'an 710072China yangtze river delta research institute of northwestern polytechnical university Taicang 215400China Department of Aeronautics and Astronautics Fudan UniversityShanghai 200433China

A Reduced Order Model(ROM)based analysis method for turbomachinery cascade coupled mode flutter is presented in this paper.The unsteady aerodynamic model is established by a system identification technique combined with a set of Aerodynamic Influence Coefficients(AIC).Subsequently,the aerodynamic model is encoded into the state space and then coupled with the structural dynamic equations,resulting in a ROM of the cascade aeroelasticity.The cascade flutter can be determined by solving the eigenvalues of the ROM.Bending-torsional coupled mode flutter analysis for the Standard Configuration Eleven(SC11)cascade is used to validate the proposed method.

关键词： Aerodynamic influence coefficients Chirp signal Coupled mode flutter Eigenvalue problem Reduced order model

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Modeling and flapping vibration suppression of a novel tailless flapping wing micro air vehicle

引用

Chinese Journal of Aeronautics 2022年第3期35卷 309-328页

作者： Siqi WANG Bifeng SONG Ang CHEN Qiang FU Jin CUI School of Aeronautics Northwestern Polytechnical UniversityXi'an 710072China yangtze river delta research institute of northwestern polytechnical university Taicang 215400China research&Development institute of northwestern polytechnical university in Shenzhen Shenzhen 518057China School of Aeronautic Science and Engineering Beihang UniversityBeijing 100083China

This paper establishes and analyzes a high-fidelity nonlinear time-periodic dynamic model and the corresponding state observer for flapping vibration suppression of a novel tailless Flapping Wing Micro Air Vehicle(FWMAV),named NPU-Tinybird.Firstly,a complete modeling of NPU-Tinybird is determined,including the aerodynamic model based on the quasi-steady method,the kinematic and dynamic model about the mechanism of flapping and attitude control,combined with the single rigid body dynamic model.Based on this,a linearized longitudinal pitch dynamic cycle-averaged model is obtained and analyzed through the methods of neural network fitting and system identification,preparing for the design of flapping vibration suppression observer.Flapping vibration is an inherent property of the tailless FWMAV,which arises from the influence of time-periodic aerodynamic forces and moments.It can be captured by attitude and position sensors on the plane,which impairs the flight performance and efficiency of flight controller and actuators.To deal with this problem,a novel state observer for flapping vibration suppression is designed.A robust optimal controller based on the linear quadratic theory is also designed to stabilize the closed-loop system.Simulation results are given to verify the performance of the observer,including the closed loop responses combined with robust optimal controller,the comparison of different parameters of observer and the comparison with several classic methods,such as Kalman filter,H-infinity filter and low-pass filter,which prove that the novel observer owns a fairly good suppression effect on flapping vibration and benefits for the improvement of flight performance and control efficiency.

关键词： Flapping vibration Flapping wing Linear quadratic theory Robust control State observer

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：