Critical Wind Speed Research Articles

Wind Stability Analysis of 4000m-Span Suspension Bridge with Carbon Fiber Spatial Cable System

In order to solve problems of the low utilization ratio of the material of main cable and wind instability of suspension bridges with super-long-span steel main cables, ANSYS is used in this paper to establish models of a spatial cable suspension bridge and a parallel cable suspension bridge respectively. The dynamic mode, static wind stability and flutter stability of the models are compared by the software. The results show that the spatial suspension bridge has tensional vibration appearing much later, a higher frequency of the cable system, and a higher critical wind speed and a higher critical wind speed for the flutter, compared with the parallel cable suspension bridge. Therefore, the spatial suspension bridge has better wind stability.

Wake-induced vibrations of iced pin joint hangers of suspension bridges based on wind tunnel test and new method of transiting test

The wind-induced vibration of suspension bridge hangers may be due to hanger icing. This study presents a new test method named transiting test method, combining with the section model wind tunnel test, to investigate the wake-induced vibrations of iced pin joint hangers under limited conditions. Results reveal that according to wind tunnel test and DenHartog galloping theory, the attack angle of 3° is the angle at which the wake galloping of iced pin joint hangers is most likely to occur. The driving wind field is stable in the transiting test and exhibits relatively minimal interference from the external factors under limited conditions. The predominant frequencies of vehicular vibration in the transiting test exhibit no marked relation with the fundamental frequency of the model, thereby demonstrating transiting test can satisfy the requirements of wind-resistant research on iced pin joint hangers. The wake galloping-reduced wind speed of iced pin joint hangers with D-shaped ice and a 30 mm icing thickness is 165, and the leeward iced hanger is vulnerable to endurance failure. The wake galloping critical wind speed of pin joint hangers with icing is lower than that without icing. The findings have important implications for the wind-resistance of suspension bridges with pin joint hangers.

Wind-induced symmetric and asymmetric static torsional divergence of flexible suspension bridges

Two types of wind-induced static torsional divergence of suspension bridge structures are addressed in this work in terms of analytic and numerical approaches. The vertical stiffness of a single cable, torsional stiffness of the cable system, bridge deck, and negative aerodynamic stiffness are analyzed via generalized models simplified by ignoring bridge towers’ deformation. It is found that the main cable system’s symmetric torsional stiffness can be one order of magnitude larger than its asymmetric counterpart. The bridge deck’s symmetric torsional stiffness is only a quarter of its asymmetric counterpart. The aerodynamic torsional stiffness, on the other hand, is found to be independent on the symmetrical characteristic of the structure’s deformation. The generalized models show that, while the asymmetric torsional stiffness is unaffected by the structure’s vertical deflection, the symmetric torsional stiffness is subject to a critical vertical deflection, beyond which the part of stiffness contributed by the cable system vanishes and the whole system’s stiffness degrades to a very low level contributed uniquely by the bridge deck. The finite element simulations indicate that, because of the degradation nature of the symmetric torsional stiffness, the wind-induced symmetric static torsional divergence may emerge ahead of the asymmetric one even in the case of the symmetric stiffness being much greater than the asymmetric stiffness. The numerical simulations indicate that asymmetric divergence is characterized by ‘twist-locking’ phenomenon, signified by two half-spans’ abrupt rotating to opposite directions and swift tighten up of the tension in main cables. The numerical results also show that increase in the deck’s torsional stiffness not only enhances the critical wind speed of static torsional divergence, but also shifts the pattern of instability from asymmetric to symmetric divergence.

Effect of car-body initial dynamic sway on overturning before high-speed trains negotiate wind speed variations

A new phenomenon has occurred during a full-scale test in which the maximum overturning coefficient did not appear at the maximum wind speed or the highest operating speed when a train negotiates wind speed variations along a section of railway. This study focused on this challenge, and conducted an experimental-numerical study of the relationship between the car-body initial dynamic sway and the operational safety during wind speed abrupt changes. The results revealed that the car-body initial dynamic-sway states (i.e., amplitude and speed) before a train passed through sections where the wind speed changed abruptly were the primary causes of this new phenomenon, and the effect of the car-body initial dynamic sway on the train’s overturning safety was greater than derailment safety. Furthermore, the probability of an increase in overturning risk was greater than the probability of a decrease in risk when the train negotiated the sections where wind speed changed abruptly with different initial dynamic-sway states of the car-body. As a result, we suggested a probability critical wind speed curve for the train’s ability to negotiate abrupt changes in wind speed, which provides a reference for developing a more reasonable train operation scheme in complex conditions.

Study on the smoke propagation characteristics of metro tunnel fire under the effects of piston wind

Metro trains running in tunnels cause piston wind, and when a metro train stops in a tunnel due to a fire, the effect of the piston wind on smoke propagation characteristics cannot be ignored. In this paper, a theoretical model based on the unsteady flow theory of the Bernoulli equation was established to describe the change in piston wind speed under fire conditions. The characteristics of the smoke propagation in tunnel fires under the effect of the piston wind were analysed by means of numerical simulation. The result indicates that the piston wind has a significant effect on the characteristics of smoke distribution. In a longitudinally ventilated tunnel, whether the direction of piston wind is the same as that of longitudinal ventilation could seriously affect the control of fire smoke. When the direction is the same, the piston wind could enhance the smoke control effect of the longitudinal ventilation. Otherwise, the smoke control effect could be significantly diminished, and the smoke control by the critical wind speed of longitudinal ventilation would fail. The findings could contribute to a better understanding of the characteristics of tunnel fire to control smoke spread under the influence of piston wind.

Correlation Analysis of Bridge Flutter Critical Wind Speed and Three-Component Force Coefficient Based on Grey Correlation Method

Based on the grey correlation theory, analyze the correlation between the three typical main girder section flutter critical wind speed and three-component force coefficient of long-span bridge truss section, closed steel box girder section, and slotted steel box girder section. Provide a reference for establishing the prediction model of the flutter critical wind speed estimated from the static wind load, It is convenient to quickly and accurately judge the stability of bridge flutter. The analysis results show that the lift coefficient, the lift moment coefficient and their derivatives have a good correlation.

Wind-induced vibrations and suppression measures of the Hong Kong-Zhuhai-Macao Bridge

A series of wind tunnel tests, including 1:50 sectional model tests, 1:50 free-standing bridge tower tests and 1:70 full-bridge aeroelastic model tests were carried out to systematically investigate the aerodynamic performance of the Hong Kong-Zhuhai-Macao Bridge (HZMB). The test result indicates that there are three wind-resistant safety issues the HZMB encounters, including unacceptable low flutter critical wind speed, vertical vortex-induced vibration (VIV) of the main girder and galloping of the bridge tower in across-wind direction. Wind-induced vibration of HZMB can be effectively suppressed by the application of aerodynamic and mechanical measures. Acceptable flutter critical wind speed is achieved by optimizing the main girder form (before: large cantilever steel box girder, after: streamlined steel box girder) and cable type (before: central cable, after: double cable); The installations of wind fairing, guide plates and increasing structural damping are proved to be useful in suppressing the VIV of the HZMB; The galloping can be effectively suppressed by optimizing the interior angle on the windward side of the bridge tower. The present works provide scientific basis and guidance for wind resistance design of the HZMB.

A Multi-Objective Optimization Framework for Anti-Galloping of UHV Transmission Lines Using MTTMD Based on Weighted Satisfaction

Conductor galloping is known to be a complicated phenomenon as different aerodynamic characteristics, galloping mechanisms are involved. To tackle the galloping problem of ultra-high-voltage transmission lines, this study designs a torsional tuned mass damper (TTMD) with eddy current mechanism. For a full-span iced conductor with multiple TTMDs (MTTMD), motion equations of galloping are derived and discretized using the Galerkin method. A multi-objective optimization framework using genetic algorithm for anti-galloping of conductors is proposed. The optimization objectives include critical wind speed at galloping initiation, galloping amplitude and damper stroke, which cover the wind conditions with frequent occurrence and large galloping amplitude. By using satisfaction function and weighting factor for each objective, the multi-objective optimization problem is transformed into a single objective optimization problem. For the weighting factors, the Analytic Hierarchy Process and random sampling method are employed to simulate the expert decision-making process with high efficiency, and reasonable ranges of the weighting factors are available for selection. The results of a numerical study show that the MTTMD with optimum design can achieve satisfying anti-galloping effectiveness on the bundled conductor, significantly increasing critical wind speed and suppressing the galloping amplitude. The robustness of the optimization method is also verified.

Wind-induced vibration response analysis of Chinese solar greenhouses

Chinese solar greenhouses (CSG) are widely used in agricultural and horticultural industries in China. With the characteristics of lightweight, small stiffness and high flexibility, CSG are sensitive to wind loads. In this study, based on Davenport wind spectrum, the fluctuating wind speed time histories were simulated by harmony superposition method. The wind-induced vibration response of a 12 m span CSG was investigated by using ANSYS in time domain. The time histories of stress and displacement were obtained. The results show that both the stress and displacement under instantaneous wind loads are obviously larger than those under the corresponding mean wind loads. The most dangerous section appears near the front foot of the CSG structure. The critical wind speeds for dynamic and static instability are 38.7 and 58.5 m/s, respectively. Finally, a recommended nodal displacement wind vibration coefficient is given for practical structures. The analytical results can provide a reference for dynamic analysis and wind resistance design of CSG structures in the future.

Effects of installation position of fin-shaped rods on wind-induced vibration and energy harvesting of aeroelastic energy converter

The influence of fin-shaped rod (FSR) with different installation positions on wind-induced vibration and energy harvesting of a cylinder-based aeroelastic energy harvester are studied by experiments and simulations. Two FSRs are installed symmetrically on the surface of a circular cylinder, and the coverage angle of each FSR is 20°. The installation position of FSRs on the cylinder is represented by the placement angle, θ, which varies in the range of ±160°. And the tested wind speed range is 0–6.8 m s−1. The results show that FSRs change the position of the separation point of the boundary shear layers, further affect the formation and shedding of vortices. Then the force on the cylinder changes, which causes the energy harvester to produce different vibration responses and energy outputs. When 0° < θ < 70°, back-to-back vortex-induced vibration (VIV) and galloping can be observed for FSR-cylinder, and the output power increases with the increase of wind speed, the maximum output voltage and power reach 18.1 V and 1.645 mW. For 70° ⩽ θ < 120°, the vibration of FSR-cylinder is suppressed, which is not conducive for energy harvesting. When 120° < θ ⩽ 160°, the vibration of FSR-cylinder firstly experiences VIV and then galloping occurs after reaching the critical wind speed.

Machine learning strategy for predicting flutter performance of streamlined box girders

Engineers often heavily rely on wind tunnel tests or computational fluid dynamics (CFD) to evaluate the flutter performance of bridges in their preliminary design, which is costly and time-consuming. To quickly obtain the critical flutter wind speed of streamlined box girders in the preliminary design, a machine learning (ML) strategy was proposed in this paper. A big dataset was built by testing critical flutter wind speeds of 30 sectional models of streamlined box girders with and without railings at 5 angles of attack through free vibration wind tunnel tests. The flutter predicting models, taking geometric information and dynamic parameters as inputs, were built based on four widely-used ML algorithms, i.e., support vector regression (SVR), neural network (NN), random forest regression (RFR), and gradient boosting regression tree (GBRT). It is shown that the NN and GBRT models exhibit the highest prediction accuracy for the girders regardless of railings, respectively. A comparative study revealed that the ML models were superior over those simplified formulas for flutter estimation including the Van der Put formula, Selberg formula, and Haifan Xiang formula. A case study was also given to demonstrate the practical application of the proposed method. These ML models provide an efficient supplement to wind tunnel tests and CFD simulations for flutter predictions of streamlined box girders in the preliminary design.

Exploring and quantifying the relationship between instantaneous wind speed and turbidity in a large shallow lake: case study of Lake Taihu in China.

Sediment resuspension is critical to the internal nutrient loading in aquatic systems. Turbidity is commonly used as an indicator for sediment resuspension and is proved to be highly correlated to wind speed in large shallow lakes. A field observation of wind speed and turbidity was conducted using a portable weather station and a YSI 6600V2-2, and an observation lasting for 39days was evaluated in this study (the data points with wind speed > 4m/s account for 75%). The daily average values (DA dataset) as well as daily maximum (MX dataset) and minimum values (MI dataset) were calculated from the instantaneous observations (IN dataset). Correlations in IN dataset were deduced based on machine learning methods and were compared to those obtained from DA, MI, and MX datasets. Furthermore, the correlation in IN dataset was analyzed by using two statistical methods, and from the view of statistical the turbidity is regarded as a variable. Results indicate that the correlations in IN datasets follow the exponential function or power function pattern with a critical wind speed of 6m/s, Regression on IN dataset revealed that linear regression model had the best performance on predicting the turbidity in test dataset and no significant differences are observed between exponential function and power function pattern. Correlations in DA and MX datasets exhibit higher maximal information coefficient (MIC) than IN dataset and error of turbidity prediction introduced by using these correlations in IN dataset is within the tolerance level. Statistical analysis on the IN dataset shows that a strong relationship exists among the wind speed and expectation of turbidity with a MIC over 0.99, and follows the exponential function or the power function as well with a different critical wind speed of 4m/s. Over 95% data points fall in the predicted intervals of turbidity for both methods, suggesting a high predicting accuracy.

Research on the Design of Disaster Prevention Plan for 22km Ultra-long Highway Tunnel with Multiple Intersections

The Tianshan Shengli Tunnel is currently the longest high-altitude highway tunnel. In order to ensure the safe operation of the tunnel, the SES software is used to investigate the wind speed laws in the tunnel, and the tunnel is divided into 16 disaster prevention sections based on the shaft and critical wind speed. The principles of disaster prevention and rescue of Tianshan Shengli Highway Tunnel are given, and the emergency treatment process of tunnel disaster prevention and rescue is given. The disaster prevention and rescue plan of Tianshan Shengli Tunnel from fire occurrence, personnel and vehicle evacuation, and fire treatment are discussed in detail.

ДИАГНОСТИКА ВОЗНИКНОВЕНИЯ ПЫЛЬНЫХ (ПЕСЧАНЫХ) БУРЬ С ИСПОЛЬЗОВАНИЕМ ЭМПИРИЧЕСКИХ ДАННЫХ

When forecasting dust/sand storms, it is extremely important to determine meteorological conditions favoring the wind-induced lifting of particles, especially critical wind speed above which the separation of particles from the surface occuru. The results of comparison of dust storm diagnosis skill using five methods for the determination of critical wind speed are presented. The methods are validated using the weather station observation series for 10 years (2010-2019).

SSO risk evaluation for grid-connected PMSG-based wind farm based on sequential Monte Carlo simulation

In a grid-connected wind farm based on permanent magnet synchronous generators (PMSGs), the wind speed and the number of operating PMSGs are the two most important influencing factors with stochastic nature on subsynchronous oscillation (SSO) from the point view of the farm. This paper proposes a method of unstable SSO risk evaluation for grid-connected PMSG-based wind farm based on sequential Monte Carlo simulation (SMCS). The determination of critical wind speed (CWS) of SSO and the sequential simulation strategy of wind speed states and PMSG states in a wind farm at the same wind speed (S-WF) as well as in a wind farm at different wind speeds (D-WF), are studied. Five indices evaluating the expectation, duration, frequency and energy loss of SSO risk are proposed. Moreover, a strategy to reduce SSO risk by adjusting the cut-in wind speed is discussed. The effectivenesses of the discussed issues in the paper are proved by the case studies of a 750-PMSG wind farm based on the actual wind speed data collected.

Suppression of Bridge Flutter Using Suction Control

To verify the effectiveness of the suction‐based method for improving flutter stability of long‐span bridges, the forced vibration experiments for extracting the flutter derivatives of a section model with and without suction were performed, and the corresponding critical flutter wind speeds of this structure were calculated out. It is shown by the experiment that the flutter stability of the bridge depends on suction configuration. As the suction holes locate at the leeward side of the model, the critical flutter wind speed can attain maximum under the same suction velocity. In the analytical results, it is remarkably effective that the suction control improves the long‐span bridge flutter stability.

Temperature Compensation Method for Infrared Detection of Live Equipment under the Interferences of Wind Speed and Ambient Temperature

Infrared thermal imaging technology plays an important role in evaluating the operating condition of electrical equipment. This article focuses on two critical environmental factors, namely, wind speed and ambient temperature. They interfere with infrared detection and fault diagnosis by affecting the actual temperature of the fault area. In this article, we use the principle of heat transfer to explore the affected conditions and the changing laws of diagnostic indicators. We provide a solution for diagnosing the live equipment fault area after compensating for the infrared temperature. Both the simulation and experimental results show that the method can obtain the temperature of the equipment fault area under different environmental conditions for different electrical equipment failures when they meet the temperature compensation conditions. The method can eliminate the influences of wind speed and ambient temperature on the results of infrared temperature measurement and achieve a unified solution to the problem of multiple types of electrical equipment. This breaks through the barriers of infrared temperature measurement applications limited by the on-site environmental conditions. The proposed method can serve to further improve the existing evaluation standards. The results of the article are useful for troubleshooting equipment and improving the accuracy of the infrared diagnosis of live equipment.

FUNDAMENTAL EFFECT OF VIBRATIONAL MODE ON VORTEX-INDUCED VIBRATION IN A BRIMMED DIFFUSER FOR A WIND TURBINE

Abstract. A brimmed diffuser for a wind turbine, also known as a wind lens, is a ring-like short duct that is installed around a rotor. It gathers and accelerates wind to improve the power generation efficiency from the wind turbine, and this effect results from vortex shedding intentionally generated by the brim. However, periodic vortex shedding can induce a vibration in the wind lens structure, which could potentially harm it in the case where resonance occurs when the vortex shedding frequency corresponds to the natural frequency of the wind lens structure. In this study, we investigated the fundamental mechanism of the vortex-induced vibration (VIV) in the brimmed diffuser structure at the Reynolds number of 288. A 2D aeroelastic analysis was conducted, utilizing 2D computational fluid dynamics coupled with the equation of motion in modal space based on the 3D FEM analysis. The 2D aeroelastic analysis provided a reasonable estimation of the critical wind speeds for the actual VIV observed in the wind lens structure. Also, we clarified the vibrational modes critical to the VIV of the wind lens structure, which are the radial and rotational modes of the brimmed diffuser section. Both modes were accompanied by the circumferential bending oscillation of the support arms fixing the brimmed diffuser and were susceptible to the vortex shedding patterns.

Wind Resistant Analysis of 5000m Hyperbolic Parabolic Spatial Mixed Cable Suspension Bridge

Combined with the engineering background of a 5000-meter Strait Suspension Bridge, the configuration study of the hyperbolic parabolic space cable suspension bridge was carried out, and the ANSYS finite element analysis model was established to analyze and study the structural internal force and dynamic modal characteristics. The research shows that the hyperbolic parabolic space mixed cable suspension bridge has excellent spatial stiffness and wind stability performance, its torsional frequency and torsional frequency ratio are significantly improved, the critical wind speed of flutter is greatly improved. In order to further improve the wind stability of the hyperbolic parabolic space mixed cable suspension bridge, temporary wind resistance cable measures adopted during strong typhoons are proposed. This method can ensure that the 5000-meter-level hyperbolic parabolic space mixed cable suspension bridge has the ability to withstand 120 m / s rare extreme typhoons.

Estimating Wind Damage in Forested Areas Due to Tornadoes

Research Highlights: Simulations of treefall patterns during tornado events have been conducted, enabling the coupled effects of tornado characteristics, tree properties and soil conditions to be assessed for the first time. Background and Objectives: Treefall patterns and forest damage assessed in post-storm surveys are dependent on the interaction between topography, biology and meteorology, which makes identification of characteristic behavior challenging. Much of our knowledge of tree damage during extreme winds is based on synoptic storms. Better characterization of tree damage will provide more knowledge of tornado impacts on forests, as well as their ecological significance. Materials and Methods: a numerical method based on a Rankine vortex model coupled with two mechanistic tree models for critical wind velocity for stem break and windthrow was used to simulate tornadic tree damage. To calibrate the models, a treefall analysis of the Alonsa tornado was used. Parametric study was conducted to assess induced tornadic tree failure patterns for uprooting on saturated and unsaturated soils and stem break with different knot factors. Results: A power law relationship between failure bending moments and diameter at breast height (DBH) for the hardwood species provided the best correlation. Observed failure distributions of stem break and windthrow along the tornado track were fitted to lognormal distributions and the mean of the critical wind speeds for windthrow were found to be higher than that for stem break. Relationships between critical wind speed and tree size were negatively correlated for windthrow and positively correlated for stem break. Higher soil moisture contents and lower knot factors reduced the critical wind speeds. The simulations show varying tree fall patterns displaying forward and backward convergence, different tornado damage widths and asymmetry of the tracks. These variations were controlled by the relative magnitudes of radial and tangential tornado velocities, the ratio between translational speed and maximum rotational wind speed and the mode of failure of the trees. Conclusions: The results show the complexity of predicting tornadic damage in forests, and it is anticipated that this type of simulation will aid risk assessments for insurance companies, emergency managers and forest authorities.