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Design concepts of an aircraft wing: composite and morphing airfoil with auxetic structures

P R BUDARAPU,Sudhir Sastry Y B,R NATARAJAN

《结构与土木工程前沿(英文)》 2016年 第10卷 第4期   页码 394-408 doi: 10.1007/s11709-016-0352-z

摘要: This paper is categorized into two parts. (1) A frame work to design the aircraft wing structure and (2) analysis of a morphing airfoil with auxetic structure. The developed design frame work in the first part is used to arrive at the sizes of the various components of an aircraft wing structure. The strength based design is adopted, where the design loads are extracted from the aerodynamic loads. The aerodynamic loads acting on a wing structure are converted to equivalent distributed loads, which are further converted point loads to arrive at the shear forces, bending and twisting moments along the wing span. Based on the estimated shear forces, bending and twisting moments, the strength based design is employed to estimate the sizes of various sections of a composite wing structure. A three dimensional numerical model of the composite wing structure has been developed and analyzed for the extreme load conditions. Glass fiber reinforced plastic material is used in the numerical analysis. The estimated natural frequencies are observed to be in the acceptable limits. Furthermore, the discussed design principles in the first part are extended to the design of a morphing airfoil with auxetic structure. The advantages of the morphing airfoil with auxetic structure are (i) larger displacement with limited straining of the components and (ii) unique deformation characteristics, which produce a theoretical in-plane Poisson’s ratio of −1. Aluminum Alloy AL6061-T651 is considered in the design of all the structural elements. The compliance characteristics of the airfoil are investigated through a numerical model. The numerical results are observed to be in close agreement with the experimental results in the literature.

关键词: wing design     aerodynamic loads     morphing airfoil     auxetic structures     negative Poisson’s ratio    

Numerical analysis of aerodynamic noise radiated from cross flow fan

CHEN Anbang, LI Song, HUANG Dongtao

《能源前沿(英文)》 2008年 第2卷 第4期   页码 443-447 doi: 10.1007/s11708-008-0063-9

摘要: The flow field in a cross flow fan was simulated by solving the 2-D unsteady Reynolds-averaged Navier-Stokes equations. The calculated pressure fluctuations of the blades, the vortex wall, and the rear wall were then used as noise sources to calculate the sound field. The Ffowcs Williams-Hawkings (FW-H) equation was employed to predict the noise field caused by these sources. The predictions show that the rear wall and the vortex wall sources contribute significantly to the total noise and that both the predicted aerodynamic performance and noise agree well with the experimental results.

关键词: predicted aerodynamic     Williams-Hawkings     calculated pressure     aerodynamic performance     unsteady Reynolds-averaged    

Experimental study of wind loads on gable roofs of low-rise buildings with overhangs

Peng HUANG, Ling TAO, Ming GU, Yong QUAN

《结构与土木工程前沿(英文)》 2018年 第12卷 第3期   页码 300-317 doi: 10.1007/s11709-018-0449-7

摘要:

Gable roofs with overhangs (eaves) are the common constructions of low-rise buildings on the southeastern coast of China, and they were vulnerable to typhoons from experience. The wind pressure distributions on gable roofs of low-rise buildings are investigated by a series of wind tunnel tests which consist of 99 test cases with various roof pitches, height-depth ratios and width-depth ratios. The block pressure coefficients and worst negative (block) pressure coefficients on different roof regions of low-rise buildings are proposed for the main structure and building envelope, respectively. The effects of roof pitch, height-depth ratio, and width-depth ratio on the pressure coefficients of each region are analyzed in detail. In addition, the pressure coefficients on the roofs for the main structure and building envelope are fitted according to roof pitch, height-depth ratio and width-depth ratio of the low-rise building. Meanwhile, the rationality of the fitting formulas is verified by comparing the fitting results with the codes of different countries. Lastly, the block pressure coefficients and worst negative pressure coefficients are recommended to guide the design of low-rise buildings in typhoon area and act as references for the future’s modification of wind load codes.

关键词: low-rise building     gable roof     wind loads     wind tunnel test     block pressure coefficient     load code    

Flutter control effect and mechanism of central-slotting for long-span bridges

YANG Yongxin, GE Yaojun, XIANG Haifan

《结构与土木工程前沿(英文)》 2007年 第1卷 第3期   页码 298-304 doi: 10.1007/s11709-007-0039-6

摘要: The flutter control effect and mechanism of central-slotting, which have gradually been adopted in the design and construction of long-span bridges as an effective flutter controlling measure, were investigated with theoretical analysis and wind tunnel test. Five basic girder cross-sections representing five typical aerodynamic configurations were selected and central-slotted with two different slot widths. Then, a series of sectional model tests and theoretical analyses based on the two-dimensional three-degrees-of-freedom coupling flutter analysis method (2 dimension-3 degrees of freedom method, 2d-3DOF method) were carried out to investigate the aerodynamic performance, flutter mechanism and flutter modality of the five basic sections and their corresponding central-slotted sections. The results show that central-slotting can not always improve the aerodynamic stability of bridge structure. The control effect of central-slotting depends on the aerodynamic configuration of the original girder section and the corresponding central-slotting width. If the original section is inappropriate or the slot width is unsuitable, central-slotting will even deteriorate the structural flutter performance. Theoretical investigations indicated that the differences in flutter control effects come from the different formation and evolution of aerodynamic damping, and flutter modality especially the participation level of heaving motion also has a significant influence on the control effect of central-slotting.

关键词: aerodynamic configuration     aerodynamic performance     flutter mechanism     aerodynamic stability     theoretical analysis    

Aerodynamic stability evolution tendency of suspension bridges with spans from 1000 to 5000 m

《结构与土木工程前沿(英文)》 doi: 10.1007/s11709-023-0980-z

摘要: Aerodynamic instability owing to aerostatic and flutter-related failures is a significant concern in the wind-resistant design of long-span suspension bridges. Based on the dynamic characteristics of suspension bridges with spans ranging from 888 to 1991 m, we proposed fitted equations for increasing spans and base frequencies. Finite element models of suspension bridges with increasing span from 1000 to 5000 m were constructed. The structural parameters were optimized to follow the fitted tendencies. To analyze the aerodynamic instability, streamlined single-box section (SBS), lattice truss section (LTS), narrow slotted section (NSS), and wide slotted section (WSS) were considered. We performed three-dimensional (3-D) full-mode flutter analysis and nonlinear aerostatic instability analysis. The flutter critical wind speed continuously decreases with span growth, showing an unlimited approaching phenomenon. Regarding aerostatic instability, the instability wind speed decreases with span to approximately 3000 m, and increases when the span is in the range of 3000 to 5000 m. Minimum aerostatic instability wind speed with SBS or LTS girder would be lower than observed maximal gust wind speed, indicating the probability of aerostatic instability. This study proposes that suspension bridge with span approximately 3000 m should be focused on both aerostatic instability and flutter, and more aerodynamic configuration optimistic optimizations for flutter are essential for super long-span suspension bridges with spans longer than 3000 m.

关键词: suspension bridge     super long-span     finite element model     aerodynamic instability     aerodynamic configuration    

Experimental study of aerodynamic interference effects on aerostatic coefficients of twin deck bridges

Zhiwen LIU , Zhengqing CHEN , Gao LIU , Xinpeng SHAO ,

《结构与土木工程前沿(英文)》 2009年 第3卷 第3期   页码 292-298 doi: 10.1007/s11709-009-0048-8

摘要: The aerodynamic interference effects on aerostatic coefficients of twin deck bridges with large span were investigated in detail by means of wind tunnel test. The distances between the twin decks and wind attack angles were changed during the wind tunnel test to study the effects on aerodynamic interferences of aerostatic coefficients of twin decks. The research results have shown that the drag coefficients of the leeward deck are much smaller than that of a single leeward deck. The drag coefficients of a windward deck decrease slightly compared with that of a single deck. The lift and torque coefficients of windward and leeward decks are also affected slightly by the aerodynamic interference of twin decks. And the aerodynamic interference effects on lift and torque coefficients of twin decks can be neglected.

关键词: twin decks     aerodynamic interference effects     aerostatic coefficients     wind tunnel test    

New response surface model and its applications in aerodynamic optimization of axial compressor blade

LIU Xiaojia, NING Fangfei

《能源前沿(英文)》 2008年 第2卷 第4期   页码 541-549 doi: 10.1007/s11708-008-0077-3

摘要: A parametric method for the axial compressor 2D blade profiles is proposed in which the blade geometries are defined with the parameters commonly used for blade definition, which ensures that the geometric significance is clear and an unreasonable blade profile is not generated. Several illustrations are presented to show the fitting precision of the method. A novel response surface model is proposed which regards the objective distribution function in the vicinity of a sample as normal school, and then generates the response surface function in the whole design space by a linear combination of distribution functions of all the samples. Based on this model, a numerical aerodynamic optimization platform for the axial compressor 2D blade profiles is developed, by which aerodynamic optimization of two compressor blade profiles are presented.

关键词: definition     objective distribution     fitting precision     combination     numerical aerodynamic    

Aerodynamic interference effects and mitigation measures on vortex-induced vibrations of two adjacent

Xiaoliang MENG, Ledong ZHU, Zhenshan GUO

《结构与土木工程前沿(英文)》 2011年 第5卷 第4期   页码 510-517 doi: 10.1007/s11709-011-0129-3

摘要: By examining the two neighboring Haihe Bridges with semi- and full-closed bridge decks, the aerodynamic interference between the two decks on the vortex-induced vibration (VIV) and the corresponding aerodynamic mitigation measures are investigated via a series of wind tunnel tests with a spring-suspended sectional model aided with computational fluid dynamics (CFD) method. The results show that the VIV responses of both bridges can be significantly affected by the aerodynamic interference and that the extent of the influence varies with the shapes of the windward and leeward decks. The VIV amplitudes of the windward bridge are often fairly close to those of the single bridge. However, those of the leeward bridge are magnified substantially by aerodynamic interference if the same structural and aerodynamic configurations are adopted for the two bridges. Otherwise, the VIV responses are not significantly increased and may even be reduced by the aerodynamic interference if different configurations are employed for the two bridges. Furthermore, an effective combined measure of adding wind barriers and sharpening the wind fairing noses of the two box decks is presented for mitigating both the vertical and torsional VIV responses of the windward and leeward bridges.

关键词: separated parallel decks     vortex-induced vibration     aerodynamic interference     aerodynamic mitigation measure     semi-closed box deck     full-closed box deck    

Integration of renewable energies, flexible loads and storages into the German power grid: Actual situation

Harald SCHWARZ, Xiaoshu CAI

《能源前沿(英文)》 2017年 第11卷 第2期   页码 107-118 doi: 10.1007/s11708-017-0470-x

摘要: Starting from the late 1990’s, the German government decided to change the national electric power supply system dramatically. The main stimulating instrument was the German Law on Renewable Energies (Erneuerbare Energien Gesetz (EEG)), which guaranteed a fixed feed-in tariff to everyone who was willing to invest into renewable generation. Based on the year of commissioning, defined revenues per kWh were fixed for the next 20 years. Due to a very attractive over-funding, more than 1.5 million renewable generation units were connected to the German grid up to the end of 2015. According to the EEG, renewable generation units can feed to the grid wherever they are located and whenever they are able to produce. The old physical principle was and is still neglected, which clearly stated that generation always has to follow the demand—simply due to the limited availability of storages in the power system. Only in cases, when temporarily renewable overproduction exceeds the tolerable loading of lines or transformers respectively endangers the system stability in total, are German grid operators allowed to announce curtailments by emergency measures. Even in such cases, the “not produced energy” from renewable sources has to be funded. Although the installed capacity from renewables is much higher than the peak load in Germany, it contributes only about 32% to German average annual energy. Unfortunately, the regional distribution of renewable generation and load is very different, e.g. in the northeast of Germany, this Renewable Energy (RE)-ratio meanwhile exceeds 100% due to the high RE-penetration and low load. High transits of renewable overproduction from the north to the south will be necessary at nearly every day per year. Therefore, a tremendous change is needed within the German power grid. This paper will give a first overview followed by several others, describing possible solutions on how to overcome this critical situation.

关键词: grid integration     renewable energies     system stability     storages     flexible loads     new market design    

Possible role of power-to-heat and power-to-gas as flexible loads in German medium voltage networks

Mark KUPRAT, Martin BENDIG, Klaus PFEIFFER

《能源前沿(英文)》 2017年 第11卷 第2期   页码 135-145 doi: 10.1007/s11708-017-0472-8

摘要: Germany’s energy transition triggered a rapid and unilateral growth of renewable energy sources (RES) in the electricity sector. With increasing shares of intermittent RES, overcapacities during periods of strong wind and photovoltaic electricity generation occur. In the face of insufficient transmission capacities, due to an inhibited network extension, the electricity generation has to be curtailed. This curtailment of RES leads to economic losses and could be avoided through flexible loads. As an option to cope with those problems, the technologies of power-to-gas (PtG) and power-to-heat (PtH) are presented in this paper. First, the alkaline electrolyzer (AEL), polymer electrolyte membrane electrolyzer (PEMEL), and solid oxide electrolyzer cell (SOEC) are investigated regarding their operational parameters. Second, the electric boiler, electrode heating boiler, and heat pumps are considered. Ultimately, the network-supporting abilities and the potential to provide ancillary services, such as control power, load sequence operation, cold start and part load capability, are compared among one another.

关键词: power-to-gas     power-to-heat     flexible loads     ancillary services     coherent energy systems    

Aerodynamic impact of train-induced wind on a moving motor-van

Jiajun HE; Huoyue XIANG; Yongle LI; Bin HAN

《结构与土木工程前沿(英文)》 2022年 第16卷 第7期   页码 909-927 doi: 10.1007/s11709-022-0833-1

摘要: The newly-built single-level rail-cum-road bridge brings the issue of the aerodynamic impact of train-induced wind on road automobiles. This research introduced a validated computational fluid dynamics (CFD) model regarding this concern. Such an aerodynamic impact mechanism was explored; a relationship between the transverse distance between train and motor-van (hereinfafter referred to as van) and the aerodynamic effects on the van was explored to help the optimization of bridge decks, and the relationship between the automobile speed and aerodynamic variations of a van was fitted to help traffic control. The fitting results are accurate enough for further research. It is noted that the relative speed of the two automobiles is not the only factor that influences the aerodynamic variations of the van, even at a confirmed relative velocity, the aerodynamic variations of the van vary a lot as the velocity proportion changes, and the most unfavorable case shows an increase of over 40% on the aerodynamic variations compared to the standard case. The decay of the aerodynamic effects shows that not all the velocity terms would enhance the aerodynamic variations; the coupled velocity term constrains the variation amplitude of moments and decreases the total amplitude by 20%–40%.

关键词: rail-cum-road bridge     aerodynamic impact     train-induced wind     CFD     aerodynamic force     quantitative analysis     fitting    

Possible role of power-to-vehicle and vehicle-to-grid as storages and flexible loads in the German 110

Erik BLASIUS

《能源前沿(英文)》 2017年 第11卷 第2期   页码 146-154 doi: 10.1007/s11708-017-0475-5

摘要: The sectoral coupling of road traffic (in form of E-Mobility) and electrical energy supply (known as power-to-vehicle (P2V), vehicle-to-grid (V2G) is discussed as one of the possible development concepts for the flexible system integration of renewable energy sources (RES) and the support of the objectives of the German energy transition (aka. Energiewende). It is obvious that E-mobility, which shall produce as few emissions as possible, should be based on the exclusive use of renewable energies. At the same time, the E-mobility can help to reduce the negative effects of the grid integration of RES to the distribution grids. However, this assumes that the electric vehicles are smart integrated to the grids where they charge, meaning that they must be able to communicate and be controllable. Because per se unplanned and uncontrollable charging processes are harmful for the grid operation, especially if they occur frequently and unexpected in similar time periods, the effects can hardly be controlled and can lead to serious technical problems in practical grid operation. This paper provides an insight into the current development of E-mobility in Germany. The insight will be matched with the German development of the RES. By the combination of both sectors, the possible role of the E-mobility for the distribution grid will be depicted, which can have positive and negative aspects.

关键词: P2V     V2G     grid integration     electric vehicles     distribution grid    

Numerical investigation of aerodynamic performance influenced by circumferentially pre-swirling coming

WANG Qikun, CHEN Kangmin

《能源前沿(英文)》 2007年 第1卷 第4期   页码 435-440 doi: 10.1007/s11708-007-0063-5

摘要: Numerical investigation is implemented on aerodynamic performance inside the crossover and de-swirling cascade of a multistage centrifugal compressor. The emphasis is put on the aerodynamic performance influenced by the circumferent

关键词: aerodynamic     investigation     centrifugal     de-swirling     circumferent    

Improvement of aerodynamic stability of suspension bridges with H-shaped simplified stiffening girder

Hiroshi KATSUCHI,Hitoshi YAMADA,Mayuko NISHIO,Yoko OKAZAKI

《结构与土木工程前沿(英文)》 2016年 第10卷 第1期   页码 93-102 doi: 10.1007/s11709-015-0311-0

摘要: Wind-tunnel study on the improvement of aerodynamic stability of simplified suspension-bridge girder structures was conducted with using a 1/40-scaled section model. Objective of the study is the development of an economically superior suspension bridge with 500–1,000 m center span length. The wind-tunnel test showed that an edge-girder type cross section exhibited large amplitude torsional vortex-induced vibration as well as torsional flutter at a low wind speed. Accordingly, aerodynamic countermeasures of open grating deck and triangular faring, and structural countermeasures of center stay, diagonal bracing and mass increase were tried to improve the aerodynamic stability. Finally, feasibility of the best combination to a full-scale bridge was examined by structural analysis.

关键词: suspension bridge     aerodynamics     simplified girder     wind-tunnel test    

Unified solution of limit loads of thick wall cylinder subject to external pressure considering strain

CHEN Changfu, XIAO Shujun, YANG Yu

《结构与土木工程前沿(英文)》 2007年 第1卷 第3期   页码 329-333 doi: 10.1007/s11709-007-0043-x

摘要: Based on the unified strength theory [1], a unified strength criterion for strain softening materials, such as concrete or rock, was derived, and the elastic and plastic limit loads of a thick-walled cylinder made of these materials subject to external pressure were also given. In addition, the influence of some factors on the limit loads of such cylinders as the ratio of the external radius to internal radius,/, the coefficient , which reflects the effect of medium principal stress and the normal stress of the relevant surface on the material destroy degree, the ratio of tensile strength to compressed strength of the material, , and the damage variable

标题 作者 时间 类型 操作

Design concepts of an aircraft wing: composite and morphing airfoil with auxetic structures

P R BUDARAPU,Sudhir Sastry Y B,R NATARAJAN

期刊论文

Numerical analysis of aerodynamic noise radiated from cross flow fan

CHEN Anbang, LI Song, HUANG Dongtao

期刊论文

Experimental study of wind loads on gable roofs of low-rise buildings with overhangs

Peng HUANG, Ling TAO, Ming GU, Yong QUAN

期刊论文

Flutter control effect and mechanism of central-slotting for long-span bridges

YANG Yongxin, GE Yaojun, XIANG Haifan

期刊论文

Aerodynamic stability evolution tendency of suspension bridges with spans from 1000 to 5000 m

期刊论文

Experimental study of aerodynamic interference effects on aerostatic coefficients of twin deck bridges

Zhiwen LIU , Zhengqing CHEN , Gao LIU , Xinpeng SHAO ,

期刊论文

New response surface model and its applications in aerodynamic optimization of axial compressor blade

LIU Xiaojia, NING Fangfei

期刊论文

Aerodynamic interference effects and mitigation measures on vortex-induced vibrations of two adjacent

Xiaoliang MENG, Ledong ZHU, Zhenshan GUO

期刊论文

Integration of renewable energies, flexible loads and storages into the German power grid: Actual situation

Harald SCHWARZ, Xiaoshu CAI

期刊论文

Possible role of power-to-heat and power-to-gas as flexible loads in German medium voltage networks

Mark KUPRAT, Martin BENDIG, Klaus PFEIFFER

期刊论文

Aerodynamic impact of train-induced wind on a moving motor-van

Jiajun HE; Huoyue XIANG; Yongle LI; Bin HAN

期刊论文

Possible role of power-to-vehicle and vehicle-to-grid as storages and flexible loads in the German 110

Erik BLASIUS

期刊论文

Numerical investigation of aerodynamic performance influenced by circumferentially pre-swirling coming

WANG Qikun, CHEN Kangmin

期刊论文

Improvement of aerodynamic stability of suspension bridges with H-shaped simplified stiffening girder

Hiroshi KATSUCHI,Hitoshi YAMADA,Mayuko NISHIO,Yoko OKAZAKI

期刊论文

Unified solution of limit loads of thick wall cylinder subject to external pressure considering strain

CHEN Changfu, XIAO Shujun, YANG Yu

期刊论文