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To address the challenges in predicting the aeroelastic phenomenon and the resulting wind-induced forces on slender bridges, a real-time aeroelastic hybrid simulation (RTAHS) system was developed. The RTAHS system directly measures the aerodynamic and aeroelastic forces through load cells. It controls the next step's position of the deck section model with linear motors by solving the governing equations of motion in real time. Given the complex shape of a bridge deck section geometry, load cells are chosen for force measurement instead of as pressure sensors. In the previous RTAHS system proposed by the authors, the inertial forces of a rectangular section model were eliminated from the measured forces under the assumption of the model's rigid-body motion. However, when conducting RTAHS experiments with a realistic bridge deck section model, increasing the mass ratio between the mass of the model and the target mass input to the hybrid system results in unstable vibrations. This instability is primarily attributed to forces generated by the model's flexibility. This study developed an improved RTAHS system, which took into account the inertial forces arising from the nonrigid motion of the flexible bridge deck section model. An accelerometer was additionally installed at the midpoint of the model, and the inertial forces caused by the nonrigid behavior were compensated using a calibration factor derived from impact hammer tests. This approach was validated by comparing the spring-supported experiments conducted on a realistic bridge deck section model. [ABSTRACT FROM AUTHOR]

Historical wooden pagodas are found in several Asian countries and are considered priceless world heritage values due to their majestic appearance and exquisite manufacturing techniques. Over time, the structure may occur inclination due to the wind action. This study presents a nondestructive method based on trees that can reduce wind pressures and loads on the wooden pagoda. The methodology was applied to the Yingxian wooden pagoda in China, a site of great historical interest. The feasibility and effectiveness of the methodology were validated through wind tunnel tests. A refined model of the wooden pagoda, with a scale ratio of 1∶50 , was fabricated and tested. Wind pressure coefficients and shelter effects of the pagoda with and without trees were analyzed. Additionally, wind base loads and reduction rates of pagoda with various tree arrangements are calculated and discussed, and the suggested tree arrangements are proposed. Though the discussion of the study, the study shows that the proposed nondestructive method can effectively reduce wind loads and actions with an average reduction rate of 12%. The height of the trees significantly affects the shelter effect of the tree blockings. This study provides a useful reference for protecting historical pagodas with similar profiles. [ABSTRACT FROM AUTHOR]

The wind-resistant performance of cable-stayed bridges under construction deteriorates sharply as the cantilever length increases, and the arrangement of the temporary pier is an effective measure to improve aerodynamic stability. To investigate the effect of the temporary pier on buffeting response of a long-span three-tower cable-stayed bridge under construction, the nonlinear buffeting analysis and wind tunnel test of aeroelastic model methods are adopted in this paper. The influence of the type and arrangement positions of temporary piers on mean wind response and the nonlinear buffeting response of double-cantilever construction are studied, and the arrangement of the temporary pier is optimized based on the buffeting response. The results show that the reduction rates of the RMS of the torsional moment at the tower bottom and the lateral buffeting displacement at the girder end with the rigid pier are 35.6% and 59.2% compared to those without the temporary pier. Further, the buffeting response will decrease as the distance between the rigid pier and the tower increases in the state. On the contrary, in the double-cantilever construction state before the constraint of temporary piers, the buffeting response will become significant as the distance increases. Therefore, it is necessary to consider the buffeting response under two construction states when optimizing the arrangement position of the temporary pier. [ABSTRACT FROM AUTHOR]

Wind energy is essential for sustainable energy development, providing a clean and reliable energy source through the wind turbine. However, the vortices and turbulence generated as wind passes through turbines reduce wind speed and increase turbulence, leading to significant power losses for downstream turbines in wind farms. This study investigates wake characteristics in wind turbines by examining the effects of different scale ratios on wake dynamics, using both experimental and numerical approaches, utilizing scaled-down models of the Aeolos H-20 kW turbine at scales of 1:33, 1:50, and 1:67. The experimental component involved wind tunnel tests in an open-circuit tunnel with adjustable wind speeds and controlled turbulence intensity. Additionally, Computational Fluid Dynamics (CFD) simulations were conducted using STAR-CCM+ (Version 15.06.02) to numerically analyze the wake characteristics. Prior to the simulation, a convergence test was performed by varying grid density and y+ values to establish optimized simulation settings essential for accurately capturing wake dynamics. The results were validated against experimental data, reinforcing the reliability of the simulations. Despite minor inconsistencies in areas affected by tower and nacelle interference, the overall results strongly support the methodology's effectiveness. The discrepancies between the experimental results and CFD simulations underscore the limitations of the rigid body assumption, which does not fully account for the deformation observed in the experiment. [ABSTRACT FROM AUTHOR]

With the increase in span, the flexibility and sensitivity to aerodynamic damage of bridges significantly increase. However, current research studies primarily focus on analyzing the single environment, leaving the safety and durability of bridges under extreme weather relatively understudied, such as snowdrift. This study selects four typical box girder bridges as test models to conduct wind tunnel tests. By analyzing similarity principles and particle properties, polyethylene particles are chosen as the test medium, and their simulation accuracy is validated using a step-type flat roof model. The study then explores wind-induced snow redistribution on the surfaces of the four box girder bridges under different horizontal wind speeds, initial particle heights, and wind attack angles. The results demonstrate that as the surface configurations of the test models become more complex, the particle redistribution becomes more chaotic. Among the three test conditions, the wind attack angle exerts the greatest influence, followed by horizontal wind speed and initial particle height. Notably, the dimensionless redistribution coefficients of particles on the surface of the large-span highway box girder bridge show the largest differences under these test conditions, with average differences and maximum differences reaching 50.3% and 63.5%, respectively, for different wind attack angles. These findings provide data support for the investigation of the safety and durability of real bridges under extreme weather conditions. [ABSTRACT FROM AUTHOR]

Copyright of Journal of South China University of Technology (Natural Science Edition) is the property of South China University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With global urbanization accelerating, high-rise buildings have become a common feature in the urban landscape, especially in coastal cities, where they encounter unique wind-load challenges. This study aims to quantify the structural response and occupant comfort of a high-rise residential building under wind-induced accelerations by integrating wind tunnel testing with finite element analysis (FEA). The research focuses on critical response parameters, including displacement, acceleration, and stress, to evaluate the building's performance. Wind tunnel tests provided detailed wind pressure distribution data across the building's surface, while multi-degree-of-freedom and finite element models facilitated precise numerical simulations. The findings highlight a significant directional and temporal variability in wind-load responses, with the most pronounced effects observed at a wind-direction angle of 105° relative to the building's front-facing axis (0°). The study confirms that the combined application of wind tunnel tests and FEA offers a comprehensive approach to understanding wind-induced responses, essential for the scientifically accurate and effective design of high-rise structures. [ABSTRACT FROM AUTHOR]

A small-scale supersonic flight experiment vehicle named OWASHI is being developed at Muroran Institute of Technology as a flying testbed for verification of innovative technologies for high-speed atmospheric flights. Drag reduction in the transonic and supersonic regimes is quite crucial for attainability of its supersonic flights. This study aims to obtain configuration modification for transonic drag reduction on the basis of the so-called area rule. In order to prevent accumulation of compression waves, various profiles of the bottleneck and the bulge are designed by using arcs with constant and large radii and spline curves approximating them. Their effects are assessed through CFD analysis, wind tunnel tests, and wave drag analysis. As a result, an area-rule-based configuration with a sharpened conical nose and a large-radius bottleneck achieves significant drag reduction in a transonic Mach range, as well as 57-count (57 × 10−4) reduction at the design Mach number of 1.1. However, the drag reduction effects of bulges are small and apparent only in a narrow Mach range. On the other hand, in the practical vehicle configuration, rearward fuselage extension shows a large amount of drag reduction, whereas the addition of an intake cancels the drag reduction effects of area-rule-based configurations. [ABSTRACT FROM AUTHOR]

This study aims to comprehensively investigate the dynamic characteristics of the tower of a scaled wind turbine model through wind tunnel tests. A model was scaled from the NREL 5 MW prototype wind turbine with a geometric scale ratio of 1/75, based on the similarity rules in thrust coefficient and dynamic characteristics. A series of wind tunnel tests were carried out on the scaled wind turbine model under different operating conditions and parked conditions with different yaw angles, and the modal parameters of the scaled model were identified by the stochastic subspace identification method and rotor stop tests. It was found that the vibration response of the tower in the fore–aft direction achieved its maximum value when the yaw angle was 90° with feathered blades, while the tower vibration response in the side–side direction was relatively severe with the yaw angle ranging from 10° to 50°. These observations are found to be well aligned with the aerodynamic characteristics of the airfoil. Moreover, the experimental results indicate that the scaled wind turbine model can reflect the vibration responses of its full-scale counterpart in the fore–aft direction. The natural frequencies and mode shapes of the scaled model can be accurately identified by different methods, but the identified damping ratios are relatively scattered. [ABSTRACT FROM AUTHOR]

Hailstorms, characterized by their intensity, are often accompanied by strong winds and heavy rain, posing significant destructive potential. Data indicate that the economic losses caused by hail to buildings, particularly solar panels, have been increasing annually. However, research on the hail resistance of photovoltaic panels has predominantly focused on the isolated effects of hail impacts and wind loads, neglecting the coupling effects between wind and hail. In this study, a device was designed to couple both wind and hail. The effects of turbulence, hail size, and velocity on hail impact behavior were systematically studied and quantified. A predictive formula for the peak load of hail impact on structures was established. The results indicate that the impact of turbulence on hail is significant. When turbulence intensity varies with hail velocity, hail impact force increases as turbulence decreases and hail velocity increases. When both turbulence and hail diameter vary, the impact force of smaller hailstones shows less variation with increasing turbulence. According to variance analysis, hail velocity is the most significant factor affecting hail impact, followed by hail diameter and finally turbulence. The regression equation is given by F = - 0.624 I u + 5116.25 D + 7.85 V hail - 259.709 , where F represents the peak impact force in Newtons (N), I u denotes the turbulence intensity, D is the hail diameter in meters (m), and V hail is the hail velocity in meters per second (m/s). [ABSTRACT FROM AUTHOR]

The propeller performance of small loitering munition is easily affected by the smaller blade size and lager hub ratio. A loitering munition encountered the problems of propeller speed is too high, and the endurance is not enough, the propeller wind tunnel test, the calculation results and flight performance are different. Aiming at the problem of inconsistent calculation results, the numerical simulation of the experimental subject was carried out. The result shows that the propeller hub produces a large negative thrust and torque, which is the most important factor leading to a significant decrease in propeller efficiency and increase in propeller speed. According to the calculation results, the formula of the hub thrust and torque correction and the propeller optimization design are given. In view of the large difference between the wind tunnel test efficiency value and flight performance, the propulsion system wind tunnel test was carried out, the problem of incoming flow interference is solved and accurate experimental results are obtained. In order to improve propeller efficiency, a propeller calculation model is derived based on propeller vortex theory, the optimization design of propeller aerodynamic profile is carried out by using genetic algorithm toolbox, with the efficiency of propeller at cruise as objective, the thrust and maximum counter torque in climb as constraints. The design results are verified by the wind tunnel test of the propulsion system. Experimental results show that the optimized design is effective, and the propeller efficiency is increased by 17.2% at cruise. [ABSTRACT FROM AUTHOR]

As the velocity of a train increases, the corresponding air pumping power consumption of the brake discs increases proportionally. In the present experimental study, a standard axle-mounted brake disc with circumferential pillars was analyzed using a 1:1 scale model and a test rig in a wind tunnel. In particular, three upstream velocities were selected on the basis of earlier investigations of trains operating at 160, 250, and 400 km/h, respectively. Moreover, 3D steady computational fluid dynamics (CFD) simulations of the flow field were conducted to compare with the wind tunnel test outcomes. The results for a 3-car train at 180 km/h demonstrated: (1) good agreement between the air resistance torques obtained from the wind tunnel tests and the related numerical results, with differences ranging from 0.95% to 5.88%; (2) discrepancies ranging from 3.2 to 3.8 N · m; (3) cooling ribs contributing more than 60% of the air resistance torque; (4) the fast rotation of brake discs causing a significantly different flow field near the bogie area, resulting in 25 times more air pumping power loss than that obtained in the stationary brake-disc case. [ABSTRACT FROM AUTHOR]

In this research, an experimental study of thermal-hydraulic performance of bi-metallic (Al-Cu) plate fin heat sink (PFHS) under forced convection in wind tunnel is investigated. The key parameters such as pressure drop, Reynolds and Nusselt numbers, heat transfer coefficient, thermal resistance, power pumping and profit factor have studied. Then the PFHS has simulated and the results have validated with test. A good agreement is seen in the results of pressure drop between test and simulation. The results show an increase of performance of the applied bi-metal sink compared with similar single aluminum one in available literature. Finally, in order to improve the thermal behavior of PFHS, porous materials have been used in numerical simulation. Because of using a porous layer in the fin spaces, the pressure drop has been increased in comparison with the normal state. Thus, pumping power has increased which means the more energy consumption is needed for the cooling process so the profit factor is decreased. On the other hand, the amount of thermal resistance is decreased by 12% compared with bi-metallic PFHS without porous materials. The results of this study could be used as the fundamental of the future researches. [ABSTRACT FROM AUTHOR]

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The development of rail transport necessitates expanding environmentally friendly infrastructure. However, specific challenges arise in desert and sandy regions. One innovative solution to manage the effects of windblown sand on desert railways is the use of hump slab track superstructure. This paper develops a solid–fluid aerodynamic model based on ANSYS Fluent 2021 R2 software to simulate the hump slab track during a sandstorm. The model is validated through wind tunnel testing. A case study of a railway sandstorm in the Shuregaz region of Iran is presented, evaluating various sandstorm parameters and hump heights to determine their impact on sand concentration and particle velocity within the sand transit channels. The results indicate that increasing the sand particle diameter (from 150 to 250 µm) leads to higher sand concentration (up to 40%) and lower sand movement velocity (up to 28%). These results have been observed with a higher incremental approach concerning the sand flow rate. Conversely, increasing sandstorm velocity (from 10 to 30 m/s) decreases sand concentration and increases sand movement velocity up to 80% and 150%, respectively. Additionally, a 25 cm hump height significantly enhances sand passage by creating larger channels. [ABSTRACT FROM AUTHOR]

In this study, we developed a wind load calculation program (WCP) capable of predicting wind loads with relative precision during the preliminary design phase. First, wind tunnel tests were conducted to identify the essential factors necessary for calculating wind loads and the variables influencing these factors. Square building shapes were considered, and the wind force coefficients and power spectral density were measured by combining four ground roughness values, eleven side ratios ( D / B ), four aspect ratios ( H / B D ), and wind directions ranging from 0° to 90°. The wind power coefficient and the spectral coefficient were formulated so that the wind load could be calculated according to various conditions. The WCP computations were based on the calculation of the load combination coefficient using the resonant wind load. Finally, the wind loads obtained from the wind tunnel tests were compared with those predicted by the WCP using an actual project model (inner-core (A) and outer-core (B) types). Building A yielded similar WCP and wind tunnel experimental responses when subjected to wind and laminar wind loads. Additionally, Building B yielded a larger error than that of Building A, but similar results were obtained when buildings were subjected to combination and laminar wind loads. [ABSTRACT FROM AUTHOR]

Aircraft secondary flow systems are small-flow circulation devices that are used for thermal and cold management, flow control, and energy generation on aircraft. The aerodynamic characteristics of main-flow-based inlets have been widely studied, but the secondary-flow-based small inlets, jets, and blowing and suction devices have seldom been studied. Two types of secondary flow systems embedded in a supersonic aircraft wing, a ram-air intake and a submerged intake, are researched here. Firstly, wind tunnel tests under subsonic, transonic, and supersonic conditions are carried out to test the total pressure recovery and total pressure distortion. Secondly, numerical simulations are used to analyze the flow characteristics in the secondary flow systems. The numerical results are validated with experimental data. The calculating errors of the total pressure recovery on the ram-air and submerged secondary flow systems are 8% and 10%, respectively. The simulation results demonstrate that the total pressure distortion tends to grow while the total pressure recovery drops with the increasing Mach number. As the Mach number increases from 0.4 to 2, the total pressure recovery of the ram-air secondary flow system decreases by 68% and 71% for the submerged system. Moreover, the total pressure distortion of the ram-air and submerged secondary flow systems is increased by 19.7 times and 8.3 times, respectively. Thirdly, a detailed flow mechanism is studied based on the simulation method. It is found that the flow separation at the front part of the tube is induced by adverse pressure gradients, which primarily determine the total pressure recovery at the outlet. The three-dimensional vortex in the tube is mainly caused by the change in cross-sectional shape, which influences the total pressure distortion. [ABSTRACT FROM AUTHOR]

This study examines the aerodynamic performance and surface pressure distribution features of circular and helical fillet stay cables when subjected to wind using wind tunnel testing. The research seeks to clarify the aerodynamic performance disparities between conventional circular stay cables and helical fillet cables, providing valuable insights into their appropriateness for cable-supported structures exposed to windinduced vibrations. The study initially investigates the aerodynamic efficiency of circular and helical fillet cables. Afterward, the wind tunnel captures the distribution of surface pressure on both cable surfaces. The findings suggest that circular stay cables may undergo cable dry galloping, whereas helical fillet cables demonstrate stability when subjected to wind forces. Furthermore, there are noticeable differences in the surface pressure distribution patterns between circular stay cables and helical fillet cables. Circular stay cables provide a symmetric distribution of pressure, with uniform pressure magnitudes along their surfaces, forming a symmetric pattern. On the other hand, helical fillet cables exhibit modified airflow patterns, leading to asymmetric pressure on the cable surface. Furthermore, the dry galloping observed in circular cables is attributed to the presence of low-frequency components. In contrast, helical fillet cables exhibit a more regulated incidence of low-frequency vortices, making them less prone to wind-induced vibrations. [ABSTRACT FROM AUTHOR]

Purposes This research has been carried out to investigate the wind load characteristics of dual-slope solar panels. Methods Wind tunnel tests with rigid models were conducted to investigate the effects of wind direction, inclination angle, and panel spacing on the surface wind pressure distributions and shape coefficients of dual-slope solar panels. The experimental results were compared with recommended values specified in three national standards including China, America, and Japan, and the shape coefficients were then suggested. Findings The results show that the extreme value of local shape coefficient occurs at the corner of windward edge of the solar panel at the wind direction of 15°. The most unfavorable wind direction for the overall shape coefficient of dual-slope solar panels is 0°, and the wind loads on the panel increase as the inclination angle increases. For solar panels with large inclination angles, the spacing has a significant influence on the wind loads acting on the structures, and the windward panel is more sensitive to spacing than the leeward panel. When the inclination angle is greater than 15°, the overall shape coefficient of the leeward panel is higher than the specification value for the structure with similar shape as the dual-slope solar panel, as given in the “Load code for the design of building structures” of China.

Abstract Hailstorms, characterized by their intensity, are often accompanied by strong winds and heavy rain, posing significant destructive potential. Data indicate that the economic losses caused by hail to buildings, particularly solar panels, have been increasing annually. However, research on the hail resistance of photovoltaic panels has predominantly focused on the isolated effects of hail impacts and wind loads, neglecting the coupling effects between wind and hail. In this study, a device was designed to couple both wind and hail. The effects of turbulence, hail size, and velocity on hail impact behavior were systematically studied and quantified. A predictive formula for the peak load of hail impact on structures was established. The results indicate that the impact of turbulence on hail is significant. When turbulence intensity varies with hail velocity, hail impact force increases as turbulence decreases and hail velocity increases. When both turbulence and hail diameter vary, the impact force of smaller hailstones shows less variation with increasing turbulence. According to variance analysis, hail velocity is the most significant factor affecting hail impact, followed by hail diameter and finally turbulence. The regression equation is given by $$F = - 0.624I_{{\text{u}}} + 5116.25D + 7.85V_{hail} - 259.709$$ F = - 0.624 I u + 5116.25 D + 7.85 V hail - 259.709 , where $$F$$ F represents the peak impact force in Newtons (N), $$I_{{\text{u}}}$$ I u denotes the turbulence intensity, $$D$$ D is the hail diameter in meters (m), and $$V_{hail}$$ V hail is the hail velocity in meters per second (m/s).

Glass curtain walls, while broadly used as a building facade, are vulnerable to extreme winds. Curtain-wall failures in major wind events lead to substantial economic losses, and wind-induced vibration is often a major contributing factor to such failures. The main objectives of this study are to (i) present high-fidelity numerical modeling techniques to reproduce the wind-induced dynamic behavior of building facades, specifically focusing on a single-skin curtain-wall system, and (ii) highlight the impact of the interaction between facade and building structure on the wind-induced dynamic behavior of the curtain-wall system. The developed finite-element model is calibrated for a particular wind scenario tested at the Natural Hazards Engineering Research Infrastructure (NHERI) Wall of Wind Experimental Facility (WOW EF) at Florida International University (FIU), and subsequently validated to assess whether it can realistically reproduce the dynamic behavior in different scenarios involving various wind speeds and directions. This study also uncovers that the interaction between the facade and the building structure plays an important role in governing the wind-induced dynamic behavior of the curtain wall. In addition, this study finds that the presence of a vertical protrusion, attached to the facade for architectural reasons, may negatively impact the wind-induced dynamic response of the curtain wall, with this impact being influenced by the interaction between facade and structure. This study reports the significant discoveries, contributing new insights to facade design and the engineering industry. [ABSTRACT FROM AUTHOR]

Wind tunnel tests or computational fluid dynamics (CFD) simulations of the aeroelastic model of a bridge deck section are currently used to make sure that significant vortex-induced vibration (VIV) of a long-span bridge will not occur after the bridge is put into operation. However, significant VIV still occurred in several long-span bridges in operation, indicating that the currently used wind tunnel tests and CFD simulations have some drawbacks or uncertainties. This study aims at establishing a digital twin by interacting CFD simulation with wind tunnel test for accurately and efficiently predicting the VIV response of a bridge deck. The measurement information of VIV of the deck section is collected from the wind tunnel test and fused with the CFD simulation. The optimisation for reducing uncertainties existing in wind tunnel test and CFD simulation is then carried out to make the CFD simulation as a digital twin. The digital twin is finally used to investigate the blockage effect of wind tunnel test and give an accurate and efficient prediction of VIV of the bridge deck. The flat closed-box steel deck section used in the Xiangshan Harbor cable-stayed bridge is selected as a case study. The results from the case study show that the digital twin can be established and used for an accurate and efficient prediction of VIV of the bridge deck section. [ABSTRACT FROM AUTHOR]

Computational fluid dynamic (CFD) has not been widely accepted as a design tool in current wind‐resistant structural design practices due to its contentious accuracy. To promote the application of CFD in wind‐resistant structural design, the accuracy of CFD should be comprehensively validated. However, most previous validation studies were focused on isolated generic or regular‐shaped buildings. This paper evaluates the accuracy of large eddy simulation (LES) in predicting the wind loads on a 600‐m‐high supertall building with a complex appearance in a realistic urban area against wind tunnel test results. The aerodynamic characteristics obtained from the LES and the wind tunnel test are compared and analyzed in detail, including wind pressure and force coefficients, wind force spectra, base moments, and correlations of the wind loads. This study aims to assess the performance and potential as well as the strengths and weaknesses of CFD in predicting wind loads on high‐rise buildings in an urban environment and promote its application to the wind‐resistant design of skyscrapers. [ABSTRACT FROM AUTHOR]

Due to the influence of the three-dimensional (3D) effect, the identification accuracy of 3D aerodynamic admittance functions (AAFs) would inevitably be influenced by the ratio of turbulent integral scale to model dimension (dimensionless integral scale). For this, the two-dimensional (2D) AAFs of a streamlined bridge deck in different turbulent flow fields are experimentally investigated, wherein the 2D AAF is determined by separating out the 3D effect from the 3D AAF. Consistent with the previous studies, the 3D AAFs exhibit significant flow field dependence, and are less than the Sears function in low-frequency range. Different from the 3D AAF, the 2D AAFs obtained in two turbulent flow fields are higher than the Sears function and have a good consistency in various turbulent flows. It can be therefore considered that the identification accuracy of 2D AAF of a streamlined bridge deck is not related to the dimensionless integral scale, which might avoid the possible deviation caused by the mismatch of integral scale in the wind tunnel test. An empirical formula for the 2D AAF of a streamlined bridge deck is then proposed by fitting the experimental data. In addition, to further examine the validity of above conclusion, a comparison between the 3D AAFs of a streamlined bridge deck measured in other wind tunnel tests and the predictions calculated with the present 2D AAF is also made. [ABSTRACT FROM AUTHOR]

In order to study the wind field characteristics of canyon topography, firstly, the wind pressure or wind speed correction about the canyon topography in the four standards were compared. Secondly, taking a generalized canyon topography with a V-shaped symmetrical slope as the research object, the wind speed distribution law of the canyon topography's cross section direction and along the canyon strike were investigated through wind tunnel test, and the impact of wind direction on the canyon topography's wind speed distribution was also discussed. The findings demonstrate that there are few laws governing the correction of wind speed in canyon abroad, where the correction coefficient is set from 1.07 to 1.22 in Chinese standards. The wind speed correction coefficients are essentially symmetrical along the center axis of the canyon topography at 0º wind direction. Within the range of the test height, the acceleration area along the canyon is gradually narrowed, the deceleration area is gradually enlarged, and the maximum value of the wind speed correction coefficients are gradually reduced, and the extreme values all appear in the "HIZX" cross section, with the values are 1. 345 and 0. 456 respectively. At the wind direction of 0° and 15°, along the canyon, the wind speed correction coefficients are seemed as "vortex" and "hill", respectively, and the location of deceleration area is different. At the bottom of the canyon, the wind speed acceleration impact is very limited, which only occurs close to the wind inlet location of the canyon, and the highest wind speed correction coefficient is less than 1. 22 that value set in Chinese standards. [ABSTRACT FROM AUTHOR]

The sting support faces an issue of being prone to resonance due to its low-damping characteristics, which will compromise the accuracy of test data in wind tunnel experiments. Magnetorheological damper (MRD)-based tail support (MRSS) features varying stiffness and damping abilities, enabling it to suppress the vibration with random, time-variation characteristics in a self-adaptive way, and it also exhibits excellent fail–safe properties. This work aims to validate its controllability and fail–safe property in a wind tunnel environment. First, the natural frequency, root mean square (RMS), and power spectral density (PSD) of the designed MRSS’ response for random excitation were theoretically analyzed. Then, wind tunnel experiments were conducted to test the response under different attack angles, wind speeds, and test currents. Subsequently, the controllability and fail–safe property were demonstrated by analyzing the aircraft model response. Also, the variable stiffness and damping properties of MRD behind the observed phenomena were revealed based on the theoretical analysis. Results demonstrate that as the input current increases and the MRD’s stiffness continues to increase, the damping initially increases and then decreases. Increasing wind speed leads to a decrease in the MRD’s stiffness. Additionally, approximately 50% reduction in RMS and a multi-modal response attenuation was achieved. [ABSTRACT FROM AUTHOR]

Wind turbine towers are growing taller to obtain larger thrust load and capture more wind energy at higher elevations. To address the excessive vibration problem of conventional steel tube (ST) towers, a concrete-filled double-skin tubular (CFDST) tower can be a great alternative owing to the advantages of excellent mechanical properties and cost efficiency, especially for tall and slender wind turbines. This paper developed a theoretical model of the CFDST-based wind turbine system by combining the Lagrangian method with the Galerkin method. Subsequently, the analytical solutions of both fundamental frequency and cross-wind displacement response were obtained. The wind tunnel tests of scaled CFDST and ST wind turbine systems, with variations in hollow ratio, tube length, and wind speed, were used to verify the proposed model. The predicted results from the analytical model showed reasonable agreement with the test results. Finally, the validated analytical solutions were employed to further analyze the influence of hollow ratio, length-to-diameter ratio, and tip-mass ratio. This study makes a contribution to the integration analysis of the CFDST-based wind turbine system in theory and experiment, and develops a simplified method to predict its dynamic behavior. [ABSTRACT FROM AUTHOR]

Vibration causes compressor rotor blade failure that affects aeroengine safety. Therefore, a plane cascade model of rotor blades was developed to capture the vibration phenomenon. The blade vibration, vortex shedding, and aerodynamic noise were measured. The results indicate that flow and noise induce a natural vibration mode, resulting in torsional vibration fatigue damage. The frequency of trailing edge vortex shedding is consistent with the frequency of tip clearance leakage vortex pulsation and is close to the second-order modal frequency of the blade, which induces torsional vibrations. The triple frequency of the background noise peak frequency in the wind tunnel is consistent with the first standing wave acoustic resonance modal frequency of the cascade experimental section duct and is close to the third-order natural modal frequency of the blade, which induces bending and torsional vibrations. This research provides guidance for the study of rotor blade multifield coupling-induced vibration. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Southeast University / Dongnan Daxue Xuebao is the property of Journal of Southeast University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A long-span double-deck steel truss suspension bridge is easy to produce vortex-induced vibration (VIV) at low air velocity, which affects bridge service life. Additional aerodynamic measures play a role in suppressing VIV by changing the aerodynamic shape, which is a common control method. As the main aerodynamic measure to suppress the VIV response, wind fairing is widely used in engineering practice. In order to obtain the optimal additional position and shape parameters of the fairing, Huangjuetuo Yangtze River Bridge is the research target. Through the combination of a wind tunnel test and numerical simulation, the VIV response of the original and fairing section is studied. Based on data analysis, it is revealed that these additional fairings to the upper chord can significantly reduce the VIV response. When the shape parameters of the fairing are h/D = 1/4 and l/D = 1, the VIV inhibition efficiency is the highest, which can reach 65.51%. By analyzing the flow distribution, it can be seen that VIV is caused mainly by vortex separation in the upper bridge board area. Although this wind fairing does not change the original vortex shedding forms, it changes the first separation point and movement direction of the airflow, making the vortex scale generated by the airflow smaller and the vorticity lower, thus effectively suppressing VIV. [ABSTRACT FROM AUTHOR]

A multibladed drag-based Vertical Axis Wind Turbine (VAWT) was developed and its startup dynamics evaluated using wind tunnel tests. The experimental data obtained for the time-based angular position of the rotor shaft at Aberdeen's average wind speed of 6 m/s show an initial rapid acceleration of the VAWT due to the drag force being exerted on the rotor blades. This acceleration becomes more gradual until the VAWT reaches its peak rotational speed of 85 rpm in 30 s, which corresponds to an operating tip speed ratio (TSR) of 0.42. The operating TSR of the VAWT was found to be 27% higher than previously reported in numerical studies. [ABSTRACT FROM AUTHOR]

The vibrissae of harbor seals exhibit a distinct three-dimensional structure compared to circular cylinders, resulting in a wave-shaped configuration that effectively reduces drag and suppresses vortex shedding in the wake. However, this unique cylinder design has not yet been applied to wind power technologies. Therefore, this study applies this concept to the design of downwind wind turbines and employs wind tunnel testing to compare the wake flow characteristics of a single-cylinder model while also investigating the output power and wake performance of the model wind turbine. Herein, we demonstrate that in the single-cylinder test, the bionic case shows reduced turbulence intensity in its wake compared to that observed with the circular cylinder case. The difference in the energy distribution in the frequency domain behind the cylinder was mainly manifested in the near-wake region. Moreover, our findings indicate that differences in power coefficient are predominantly noticeable with high tip speed ratios. Furthermore, as output power increases, this bionic cylindrical structure induces greater velocity deficit and higher turbulence intensity behind the rotor. These results provide valuable insights for optimizing aerodynamic designs of wind turbines towards achieving enhanced efficiency for converting wind energy. [ABSTRACT FROM AUTHOR]

Free-play-induced nonlinear dynamic behavior has been one of the most important topics of aeroelastic research in recent decades. In this paper, the describing function (DF) method is developed to investigate the complex dynamic response of a popular all-movable horizontal tail with free-play. Piecewise expressions for the time history and phase portrait of limit cycle oscillation (LCO) are derived by the developed DF method, which is conducive to understand the mechanism of free-play-induced LCO. Another advantage of the developed DF method is the ability to predict the high-order harmonics, which cannot be realized by the classic DF method. A three-dimensional (3D) all-movable horizontal tail model with torsional free-play was designed and manufactured to implement wind tunnel tests via various initial parameters. A good agreement was found between the numerical and experimental results, which can demonstrate the effectiveness of the proposed method. The influence of the initial parameters of the all-movable horizontal tail on the LCO characteristics is analyzed by both numerical calculations and wind tunnel tests. The method and results in this paper can provide a significant reference for the design of all-movable horizontal tail versus the free-play-induced LCO. [ABSTRACT FROM AUTHOR]

The impact of urban construction on pedestrian level wind (PLW) has been extensively studied, which has mainly focused on ideal structures rather than real multiplex building layouts. Therefore, a series of wind tunnel tests were conducted on a real building complex to investigate the impacts of a newly built nearby high-rise building, added floors, passage width and a novelty zigzag building shape on the PLW. The findings showed that in converging layouts, PLW velocity can be increased up to 2.75 times by a nearby 230 m high-rise building, and it is reduced by 30% with a 30 m passage compared to a 10 m passage. Adding 38 m to a 65 m high building would increase PLW velocity by 1.95 times when compared to an isolated building and 2.4 times when compared to a building surrounded by others. Additionally, a modest impact on PLW velocity was observed with zigzag building shapes. This study highlights the PLW velocity that can be increased to a large extent with newly built high-rise buildings and adding floors, while increasing the passage width has the opposite effect. This study also offers insights into urban planning and building design to enhance wind comfort. [ABSTRACT FROM AUTHOR]

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In aeolian sand movement, the vertical distribution of sand particle size is intricately linked to sand flux, wind–sand flow field and dune development. In the present study, the distribution characteristics of sand grains in four particle size ranges at nine heights were investigated through sand blowing tests at five different reference wind speeds. The correlation between sand particle size and wind speed indicates that when the particle size was ≥0.35 mm, there was a linear variation of mass percentage with wind speed. When the particle size was <0.35 mm, when Z ≤ 0.15 m, a linear variation of mass percentage with wind speed was found; when Z > 0.15 m, an exponential modification in mass percentage with wind velocity was observed for sand grains falling within this specific range of particle sizes. The correlation between sand particle size and height indicates that when the reference wind speed was ≥15 m/s, the mass percentage of sand particles varied linearly with height. When the reference wind speed was ≤13.5 m/s, the mass percentage of sand grains with particle size in the 0.25–0.35 mm range increases first and then decreases with increasing height. The present results can provide a reference for subsequent research on the aerodynamic characteristics of wind–sand flow fields and on the mechanism of dune formation. [ABSTRACT FROM AUTHOR]

Featured Application: The study can further guide the application of vortex isolation plates in wind-induced vibration of twin-box girders. Twin-box girders are a good option for long-span cable-bearing bridges due to their excellent stability. Nonetheless, the girder's slots may generate vortex-induced vibrations (VIVs). Fortunately, appropriate aerodynamic measures can effectively suppress the VIVs in twin-box girders while reducing costs. To examine the effects of vortex isolation plates with varying aperture diameters and opening ratios on the VIVs, a segment model wind tunnel test was conducted. The results demonstrated that a reduction in the opening ratio improved the performance under heaving VIVs, but there was no discernible trend under torsional vibrations. It was also discovered that the opening size significantly influences the length of the lock-in region of torsional vibrations. Furthermore, heaving VIVs have a substantial correlation with both of the girder's boxes, while torsional vibrations are mostly connected with the downstream section. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Xi'an Jiaotong University is the property of Editorial Office of Journal of Xi'an Jiaotong University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Wind tunnel tests and numerical simulations are the mainstream methods to study the wind-induced vibration of structures. However, few articles use statistical parameters to point out the differences and errors of these two research methods in exploring the wind-induced response of membrane structures. The displacement vibration of a saddle membrane structure under the action of wind load is studied by wind tunnel tests and numerical simulation, and statistical parameters (mean, range, skewness, and kurtosis) are introduced to analyze and compare the displacement data. The most unfavorable wind direction angle is 0° (arching direction). The error between experiment and simulation is less than 10%. The probability density curve has a good coincidence degree. Both the test and simulation show a certain skewed distribution, indicating that the wind-induced vibration of the membrane does not obey the Gaussian distribution. The displacement response obtained by the test has good stability, while the simulated displacement response has strong discreteness. The difference between the two research methods is quantitatively given by introducing statistical parameters, which is helpful to improve the shortcomings of wind tunnel tests and numerical simulations. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Icing is a common physical phenomenon, and the icing of wind turbine blades can significantly affect the performance of wind turbines. Therefore, researching methods to prevent icing is of great significance, and the coating method of anti-icing is an effective way to delay icing, with advantages such as low energy consumption and easy implementation. In this study, using the coating method as the background, tetradecane phase change microcapsules were prepared, with a melting enthalpy of 90.8 J/g and a crystallization enthalpy of 96.3 J/g, exhibiting good coverage and energy storage efficiency. After mixing tetradecane phase change microcapsules (PCMS) with polyurethane coating (PUR) and coating them on wind turbine blades, after a 5 min icing wind tunnel test, the coating could significantly delay the icing on the blade surface, with the highest anti-icing rate reaching 60.41%. This indicates that the coating has a good anti-icing effect and provides basic research data for exploring new anti-icing methods. [ABSTRACT FROM AUTHOR]

Offshore wind turbines operating in frigid and humid climates may encounter icing on the blade surface. This phenomenon adversely impacts the aerodynamic efficiency of the turbine, consequently diminishing power generation efficacy. Investigating the distribution characteristics of icing on the blade surface is imperative. Hence, this study undertook icing wind tunnel tests on segments of DU25 airfoil, a prevalent type for offshore wind turbines, to examine such characteristics as different chord lengths and angles of attack. The results show a simultaneous increase in the blade icing area and growth rate of the net icing area with augmenting the chord length and angles of attack. The total icing area rate decreases by a factor of two when the chord length is doubled. The relative positioning of icing and the average icing thickness remain consistent across the airfoil blades with varying chord lengths. Comparing the icing shapes on blades of varying scales shows a similarity ranging from 84.06% to 88.72%. The results of this study provide insight into the icing characteristics of offshore wind turbines. [ABSTRACT FROM AUTHOR]

Copyright of Ordnance Industry Automation is the property of Editorial Board for Ordnance Industry Automation and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)