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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

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Comparisons of bridges flutter derivatives and generalized ones

Fuyou XU , Zhe ZHANG , Cailiang HUANG , Airong CHEN ,

《结构与土木工程前沿（英文）》 2009年第3卷第3期页码 272-278 doi: 10.1007/s11709-009-0042-1

摘要： The causes of the nonlinearity of self-excited aerodynamic force of bridge are interpreted from such two aspects as amplitude and wind velocity. The concept of “generalized flutter derivative” is proposed, and its physical meaning is illustrated. The graphs of the generalized flutter derivatives of plate and Sutong Bridge section model are plotted. The characteristics of all generalized flutter derivatives are compared and analyzed, and their superiorities are verified. The results indicate that the physical meaning of generalized flutter derivatives are more explicit compared to the traditional ones. It is more convenient to understand the nonlinearity properties of self-excited aerodynamic force of bridge according to the generalized flutter derivatives graphs with the wind velocity as the horizontal coordinate.

关键词： bridge flutter derivative generalized flutter derivative self-excited aerodynamic force Sutong Bridge

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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

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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

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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

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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

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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

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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

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Modeling limit force capacities of high force to volume lead extrusion dampers

《结构与土木工程前沿（英文）》 2021年第15卷第3期页码 609-622 doi: 10.1007/s11709-021-0724-x

摘要： Lead extrusion dampers are supplemental energy-dissipation devices that are used to mitigate seismic structural damage. Small volumetric sizes and high force capacities define high-force-to-volume (HF2V) devices, which can absorb significant response energy without sacrificial damage. However, the design of such devices for specific force capacities has proven difficult based on the complexities of their internal reaction mechanisms, leading to the adoption of empirical approaches. This study developed upper- and lower-bound force capacity estimates from analytical mechanics based on direct and indirect metal extrusion for guiding design. The derived equations are strictly functions of HF2V device geometric parameters, lead material properties, and extrusion mechanics. The upper-bound estimates from direct and indirect extrusion are denoted as (F_UB,1, F_UB,2) and (F_UB,3, F_UB,4), respectively, and the lower-bound estimates are denoted as (F_LB, F_LB,1) based on the combination of extrusion and friction forces. The proposed models were validated by comparing the predicted bounds to experimental force capacity data from 15 experimental HF2V device tests. The experimental device forces all lie above the lower-bound estimates (F_LB, F_LB,1) and below the upper-bound estimates (F_UB,1, F_UB,2, F_UB,4). Overall, the (F_LB, F_UB,2) pair provides wider bounds and the (F_LB,1, F_UB,4/F_UB,1) pair provides narrower bounds. The (F_LB,1, F_UB,1) pair has a mean lower-bound gap of 36%, meaning the lower bound was 74% of the actual device force on average. The mean upper-bound gap was 33%. The bulge area and cylinder diameter of HF2V devices are key parameters affecting device forces. These relatively tight bounds provide useful mechanics-based predictive design guides for ensuring that device forces are within the targeted design range after manufacturing.

关键词： extrusion lead dampers upper and lower bound analytical modelling limit force

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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

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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

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Parametric oscillation of cables and aerodynamic effect

Yong XIA, Jing ZHANG, Youlin XU, Yozo FUJINO,

《结构与土木工程前沿（英文）》 2010年第4卷第3期页码 321-325 doi: 10.1007/s11709-010-0028-z

摘要： This paper addresses the aerodynamic effect on the nonlinear oscillation, particularly parametric vibration of cables in cable-stayed bridges. A simplified 2-DOF model, including a beam and a stayed cable, is formulated first. Response of the cable under global harmonic excitation which is associated with wind speed is obtained using the multiple scales method. Via numerical analysis, the stability condition of the cable in terms of wind speed is derived. The method is applied to a numerical example and a long-span bridge to analyze its all stay cables. It is demonstrated that very large vibration at one of the longest cables in the middle span of the bridge can be parametrically excited when the wind speed is over around 210 km/h (58.5 m/s).

关键词： parametric vibration cables cable-stayed bridge nonlinear vibration

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Characterization of aerodynamic performance of wind-lens turbine using high-fidelity CFD simulations

Islam HASHEM, Aida A. HAFIZ, Mohamed H. MOHAMED

《能源前沿（英文）》 2022年第16卷第4期页码 661-682 doi: 10.1007/s11708-020-0713-0

摘要： Wind-lens turbines (WLTs) exhibit the prospect of a higher output power and more suitability for urban areas in comparison to bare wind turbines. The wind-lens typically comprises a diffuser shroud coupled with a flange appended to the exit periphery of the shroud. Wind-lenses can boost the velocity of the incoming wind through the turbine rotor owing to the creation of a low-pressure zone downstream the flanged diffuser. In this paper, the aerodynamic performance of the wind-lens is computationally assessed using high-fidelity transient CFD simulations for shrouds with different profiles, aiming to assess the effect of change of some design parameters such as length, area ratio and flange height of the diffuser shroud on the power augmentation. The power coefficient ( ) is calculated by solving the URANS equations with the aid of the SST model. Furthermore, comparisons with experimental data for validation are accomplished to prove that the proposed methodology could be able to precisely predict the aerodynamic behavior of the wind-lens turbine. The results affirm that wind-lens with cycloidal profile yield an augmentation of about 58% increase in power coefficient compared to bare wind turbine of the same rotor swept-area. It is also emphasized that diffusers (cycloid type) of small length could achieve a twice increase in power coefficient while maintaining large flange heights.

关键词： shroud diffuser-augmented wind turbine (DAWT) Betz limit aerodynamics computational fluid dynamics (CFD)

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Quality control based on electrode displacement and force in resistance spot welding

Chuntao JI, Lipeng DENG

《机械工程前沿（英文）》 2010年第5卷第4期页码 412-417 doi: 10.1007/s11465-010-0114-x

摘要： The behaviors of electrode displacement and force during spot welding under various conditions, such as different weld currents, electrode forces, and welding times, were studied. Tests were conducted on a 170?kVA MFDC spot welder. Data were collected via a multichannel high-speed data acquisition system and were analyzed with MATLAB. Behaviors of 5182 aluminum and mild steel in spot welding were compared. Results show that nugget expansion rate does not reach zero for aluminium as it does for mild steel as nugget grew to a certain size. A linear relationship is found between the nugget size and maximum expansion that facilitates online weld quality evaluation. An electrode force peak is observed and believed relevant to the sufficient nugget size.

关键词： aluminum electrode displacement electrode force nugget size data acquisition

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Visualization of force networks in 2D dense granular materials

Jianguo LIU, Qicheng SUN, Feng JIN,

《结构与土木工程前沿（英文）》 2010年第4卷第1期页码 109-115 doi: 10.1007/s11709-010-0003-8

摘要： Dense granular matter is a conglomeration of discrete solid and closely packed particles. As subjected to external loadings, the stress is largely transmitted by heavily stressed chains of particles forming a sparse network of larger contact forces. To understand the structure and evolution of force chains, a photoelastic technique was improved for determining stresses and strains in the assemblies of photoelastic granular disks in this paper. A two-dimensional vertical slab was designed. It contains 7200 polydispersed photoelastic disks and is subjected to a localized probe penetrating at the top of the slab to mimic the cone penetration test. The interparticle contact force distribution was found a peak around the mean value, a roughly exponential tail for greater force and a dip toward zero for smaller force. The force chain network around the probe tip was depicted, and the contact angle distribution of particles in force chains was found to be well aligned in the directions of major principal stress.

关键词： granular matter force chain multiscale modeling