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The aerodynamic characteristics of twin-separated parallel decks for long-span rail-cum-road bridges with various wind barriers clamped at railway girder are more complicated because of aerodynamic interference. Experimental investigations on aerodynamic coefficient and wind pressure coefficients of twin girders under different incoming flow directions were conducted using wind tunnel tests. Three different heights (H) varying from 2 m to 4 m and four different ventilation ratios (R) varying from 20% to 50% for wind barriers were examined. Results indicated that the aerodynamic coefficients were affected significantly by the incoming wind direction, which must be considered, and the railway wind barrier affected the aerodynamic characteristics of the railway girder when it is located both upstream and downstream, but the laws are not the same. Due to the aerodynamic interference effect of the twin parallel girders, the aerodynamic characteristics of the adjacent highway girders were also affected by the wind barrier along the railway girder, especially when the highway girders were located downstream. While, the highway girders were less affected when located upstream. The influence of wind barrier height and ventilation ratios on the adjacent highway girders was completely different. Most importantly, the parameters optimization of wind barriers clamped at railway girders should be determined after a comprehensive evaluation of the aerodynamic characteristic of both the railway and highway girders. [ABSTRACT FROM AUTHOR]

Abstract Computational fluid dynamics (CFD) was used to reproduce wind fields around a twin-box girder. Wind tunnel tests and field measurements were conducted to verify the accuracy of the CFD results. Variations in wind speed at different heights and crosswind reduction effects with different barriers were also examined using CFD simulation; the barriers had significant reduction effects. The reduction effectiveness was closely related to the barrier height and position; porosity was also a crucial factor. The wind speed profiles of a twin-box girder and a single box girder were analysed to determine why the wind speeds above the downstream deck were lower than above the windward deck of the twin-box girder. The results show that the incoming flow leaked downward through the slotted parts of the bridge and formed regulation vortices. Wind speeds were lower above the downstream deck than above the upstream deck as a result of leakage effects. The gap width also influenced the wind environment around the bridge deck.

Computational fluid dynamics (CFD) was used to reproduce wind fields around a twin-box girder. Wind tunnel tests and field measurements were conducted to verify the accuracy of the CFD results. Variations in wind speed at different heights and crosswind reduction effects with different barriers were also examined using CFD simulation; the barriers had significant reduction effects. The reduction effectiveness was closely related to the barrier height and position; porosity was also a crucial factor. The wind speed profiles of a twin-box girder and a single box girder were analysed to determine why the wind speeds above the downstream deck were lower than above the windward deck of the twin-box girder. The results show that the incoming flow leaked downward through the slotted parts of the bridge and formed regulation vortices. Wind speeds were lower above the downstream deck than above the upstream deck as a result of leakage effects. The gap width also influenced the wind environment around the bridge deck. [ABSTRACT FROM AUTHOR]

In this study, wind tunnel tests were used to study the effect of changes in the length of a wind barrier on the aerodynamic performance of a train with single-sided and double-sided wind barriers. The results showed that in the condition of a doublesided wind barrier, as the length of the wind barrier increased, the pressure change on the windward side of the train was significantly smaller than that of the single-sided wind barrier. When the length of the wind barrier is less than 21.67 H (H is the height of the train), in the condition of the two types of wind barrier, the direction of the side force coefficient is opposite to the direction of the incoming flow. As the length of the wind barrier changes, the drag coefficient with the double-sided wind barrier is obviously more stable than that with the single-sided wind barrier. For the drag coefficient and lift coefficient, under the condition of double-sided wind barrier, when the length of the wind barrier is greater than 23.65 H, the change amplitude is lower than that of the single-sided wind barrier. For the running safety of the train, it is conservative and approximately accurate at the single-sided barrier length of 25.63 H and double-sided barrier length of 23.65 H. [ABSTRACT FROM AUTHOR]

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Aerodynamic characteristics of vehicles are directly related to their running safety, especially for the high-sided vehicles. In order to study the aerodynamic characteristics under multiple sheltering conditions, a complex large scale (1:20.4) truss model and three high-sided vehicles including articulated lorry, travelling bus and commercial van models with the same scale were built. The aerodynamic coefficients under various sheltering effects of wind barriers with different heights and porosities, bridge tower and the vehicle on the adjacent lane were measured. According to the results, wind barriers can effectively reduce wind speed behind them, thus decreasing the wind load acting on the vehicle, which causes the decrease of the aerodynamic response of all three vehicles. However, the influence at the leeward side is limited due to installation of central stabilizers. When the vehicle passes through the bridge tower, a sudden change occurs, the aerodynamic coefficients decrease and fluctuate in varying degrees, especially for the commercial van. When the vehicle moves in different lanes behind the bridge tower, the sheltering effect of the tower on the aerodynamic coefficient in Lane 1 is much greater than that in Lane 2. With regard to the interference between two vehicles on the adjacent lanes, the relative windward area between the test vehicle and the interference vehicle greatly affects the aerodynamics of the test vehicle.

Wind as an atmospheric element has some annoying aspects, therefore, controlling it and reducing its speed is one of the most important matters, which should be examined in landscape engineering. Natural windbreaks such as rows of trees with different gap distances between them are used to decrease wind velocity. The current study numerically investigates the effect of trees with irregular canopy form on wind speed reduction in urban open spaces and green belts. The computational fluid dynamics (CFD) is used to simulate airflow through the trees as 3D forms. Quercus sp. is chosen as a typical tree with irregular crown shape. The influence of some criteria such as; 1. Number of tree rows, 2. Gaps between trees, 3. Trees arrangement patterns, and 4. Height levels on wind speed reduction are examined at this study. According to the results, the best reduction is observed for the heights above 5 meters with 0.50 m gap distance between trees. The results also reveal that rectangular two-row arrangement of trees with irregular forms is more effective than the other arrangements in reducing wind velocity. [ABSTRACT FROM AUTHOR]

Due to the acceleration effect of the wind by the special geographical location of the canyon bridge-tunnel junction, the traffic safety and stability of this section are difficult to be guaranteed, resulting in frequent traffic accidents. In order to ensure the safety and comfort of vehicles driving on this section, the numerical simulation method based on CFD is adopted to establish the numerical model of the canyon bridge-tunnel junction. The acceleration of the incoming wind speed in the bridge-tunnel junction with a guardrail that is 0.8 m high is analyzed from different canyon spacings, wind directions and heights from the bridge deck. Based on the characteristics of wind field above the bridge deck, two kinds of gradient wind barriers—trapezoidal and stepped—are proposed, and their wind reduction effects and turbulence intensity changes are analyzed. Then the aerodynamic performances of running vehicle are compared. The results show that the stepped wind barrier with 50% porosity and rectangular section railings has the best wind reduction effects, and can noticeably improve the comfort of driving. The aerodynamic coefficients of vehicle are lower with stepped wind barrier. [ABSTRACT FROM AUTHOR]

This study investigated the impact of wind barriers and installation configuration on soiling of photovoltaic arrays. Soiling parameters including wind speed, tilt angles and dust particle sizes were investigated. Computational fluid dynamics was used to simulate airflow characteristics leading to the estimation of soiling on the photovoltaic array. The shading effects caused by the deposited dust particles, and the barrier height and position were also investigated. It was found that increasing the barrier height reduces soiling, but it also caused partial shading of the photovoltaic array, thus causing more reduction in the irradiance received. Increasing the barrier distance increased the amount of deposited particles on the collectors due to turbulent eddies forming behind the barrier. It was concluded that the use of barriers is an effective way of mitigating dust deposition and up to 25% of the total released dust particles were trapped by the barrier situated at 3 m from the solar collectors. Optimization to maximize the energy generated revealed a 2.81% increase in energy compared to an installation without a barrier. The best configuration of the solar collectors and the barrier was 0.932 m for barrier height, 3.9 m for barrier distance and a tilt of 21.11°. • CFD used to predict soiling on different barrier and PV installation configurations. • Total shading is computed using deposited dust and shading effect of wind barriers. • Tilt, barrier height, barrier distance, wind speed, dust particle size on soiling analyzed. • Optimization carried out to minimize shading whilst maximizing the energy generated. • Empirical model for energy prediction developed. [ABSTRACT FROM AUTHOR]

Wind barriers are nowadays commonly placed on bridges to protect vehicles from adverse cross-wind effects. In addition to this beneficial influence, wind barriers may adversely affect the bridge dynamic stability. This is particularly exhibited for long-span cable-supported bridges. It is therefore the scope of the present study to analyze the effects of wind barriers on aerodynamic and aeroelastic characteristics of bridge-deck sections of long-span cable-supported bridges together with the respective flow characteristics around bridge-deck sections. The focus is on various arrangements of wind barriers, i.e., (1) wind barriers placed at the windward bridge-deck edge only; (2) wind barriers placed at the leeward bridge-deck edge only; and (3) wind barriers placed at both windward and leeward bridge-deck edges. This was carried out experimentally on small-scale models in a boundary layer wind tunnel. Three typical bridge-deck section models were studied, i.e., Great Belt (Denmark), Kao-Pin Hsi (Taiwan), and Golden Gate (United States). The galloping susceptibility of the bridge-deck sections in all arrangements of wind barriers proved to be the same, as is the case for the empty bridge-deck sections without wind barriers; i.e., from this point of view, wind barriers do not adversely bridge dynamic stability. However, in configurations with the windward wind barrier only, as well as both windward and leeward wind barriers, the flutter susceptibility of the bridge-deck sections increases substantially; i.e., the critical flow velocity for the bridge flutter decreased significantly in comparison with the respective empty bridge-deck sections. For the leeward wind barrier only, the flutter susceptibility of the bridge-deck sections did not change and remained the same as it was for the empty bridge-deck sections. The empty bridge-deck sections do not exhibit any significant change concerning their susceptibility to flutter for various turbulence levels of the incoming freestream flow. The flutter susceptibility of cable-supported bridges equipped with wind barriers is lower in more turbulent incoming flows. The bridge decks with wind barriers are more resilient to flutter in more turbulent winds. Shear layers that separate from the top of the wind barrier may have an important role in the self-excited lift force and the pitch moment and, consequently, the dynamic behavior of bridge decks. [ABSTRACT FROM AUTHOR]

Traffic accidents on bridges occur occasionally and have attracted the wide attention of the whole society as well as world. Therefore, researching and exploring the wind environment on bridge deck is a significant and urgent incident, which is able to provide crucial reference for vehicle driving safety. In this paper, the wind environments on the bridge deck of twin-box girder with large scale of 1:20.4 are investigated through wide-ranging wind tunnel tests. During the tests, multiple wind barriers with different heights, porosities and opening forms are considered precisely. Also, the wind environments of truss girder are studied and compared in the process of experiment. Eventually, after handling with the data, analyzing the figures and comparing with other test results, the most significant disciplines are as follows: The wind environments of twin-box girder and truss girder are fairly various; the power spectrum and the wind velocity of twin-box girder are much larger, and there is a lag at the wind velocity stabilization point of truss structure. At the same time, while the parameters of wind barriers change, lower porosity creates lower wind velocity and lower power spectrum. And the height of the wind barriers affects the wind profiles a lot on the windward lanes and lower power spectrum. In addition, the effects of the opening form on windproof and power spectrum are relatively limited. [ABSTRACT FROM AUTHOR]

Due to the complex arrangement of structural components in the vicinity of bridge pylon zones, the wind environment above bridge decks is very complicated. A sudden change in wind speed exerts an adverse effect on vehicle control stability. In order to investigate the characteristics of the flow field in the vicinity of the bridge pylon, the wind environment near an inverted Y-shaped pylon is studied by experimental and numerical methods. From the flow visualization and the wind speed measurement in the wind tunnel and the numerical simulation created using Fluent software, specific patterns of the direction and magnitude of wind speed at a range of vehicle height above the bridge deck near the pylon zone were observed along the longitudinal direction. This distribution pattern of the wind environment can effectively guide the wind barrier arrangement near the bridge pylon zone. Combined with the two safety evaluation indicators proposed in this paper, the optimal arrangement scheme of wind barriers in the bridge pylon zone of Sutong Bridge is determined. This paper deepens the understanding of the wind environment near the pylon zone and proposes an evaluation method for the wind environment near the pylon zone, which can serve as the basis for wind barrier arrangement in similar research projects. [ABSTRACT FROM AUTHOR]

The vulnerability of soil by wind erosion using the wind erosion equation (WEQ) in geographic information systems (GIS) was demonstrated on the cadastral area of Přísnotice, southeast of the Czech Republic. Raster layers were created for input factors of WEQ and potential soil loss by wind was calculated using the Raster Calculator. Subsequently, map outputs showing the potential vulnerability of soil to wind erosion were made. In the first variant, where the protective effect of the barriers was not taken into account, the wind erosion intensity reached 47.6 t.ha-1.year-1. In the second variant, where the protective effect of the barrier was assumed, the loss of soil was lower, the maximum value was 4.7 t.ha-1.year-1. The soil loss limit was exceeded, even in a situation where a relatively high protective barrier effect has been proposed. The advantage of determining of wind erosion vulnerability using ArcGIS is that it is possible to identify particular parts of soil blocks from the map outputs, which are the most vulnerable. Similarly, it is possible to design a windbreak network and simulate its protective effect using ArcGIS. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the function of tree belts in reducing the aeolian transport of dust particles carrying pesticides. The study examined the importance of the buffer zones created by commonly planted trees (Eucalyptus camaldulensis, Pinus halepensis (pine) and Ceratonia siliqua (carob)). The methods include analyzing the quantity and the chemical composition of pesticides carried by aeolian dust particles from the intensively cultivated fields and orchards, where pesticides were applied, towards the tree belts nearby. Eighteen different chemicals used as insecticides, fungicides and herbicides, were found both in the agricultural fields and in the adjacent tree belts, suggesting an important function of the trees. This ecological service has rarely been taken into consideration by management policies of tree plantings in farmland areas. To integrate this service into agriculture, especially in the case of agricultural fields and orchards, which are adjacent to populated areas, planting tree belts should be positively considered as a means for reducing aeolian dust and air pollution, mainly in order to reduce leakage of pesticides, which are a cause for significant health concerns. [ABSTRACT FROM AUTHOR]

The problems on traffic safety caused by a lateral wind acting on railway vehicles are known and have been studied in the scientific literature. It is also known that the train speed increases the risk of derailment or overturning of the vehicle in a strong lateral wind event, especially with light vehicles such as the high speed trains. Some of the actions taken by public institutions of several countries to maintain the safety during the train travel with strong winds are the reduction of the train operation speed, during the lateral wind event, and the installation of wind barriers in certain high-speed line sections. On the deck of a high pier viaduct, the expected lateral winds are stronger because of the distance between the deck and the ground. On the other hand, on these laterally flexible bridges, the deck movements, induced by the wind, can affect traffic safety aggravating the problem, particularly when the deck presents a large exposed surface area, or wind barriers are used to reduce the wind direct impact on the train. In this article, the efficiency of the simultaneous use of wind barriers and tuned mass dampers at the top of the bridge piers is studied numerically, with a non-linear dynamic interaction train-bridge-wind model, in order to avoid the reduction of the train speed because of traffic safety and passengers’ comfort when turbulent winds are acting. [ABSTRACT FROM AUTHOR]

Due to the complex arrangement of structural components in the vicinity of bridge pylon zones, the wind environment above bridge decks is very complicated. A sudden change in wind speed exerts an adverse effect on vehicle control stability. In order to investigate the characteristics of the flow field in the vicinity of the bridge pylon, the wind environment near an inverted Y-shaped pylon is studied by experimental and numerical methods. From the flow visualization and the wind speed measurement in the wind tunnel and the numerical simulation created using Fluent software, specific patterns of the direction and magnitude of wind speed at a range of vehicle height above the bridge deck near the pylon zone were observed along the longitudinal direction. This distribution pattern of the wind environment can effectively guide the wind barrier arrangement near the bridge pylon zone. Combined with the two safety evaluation indicators proposed in this paper, the optimal arrangement scheme of wind barriers in the bridge pylon zone of Sutong Bridge is determined. This paper deepens the understanding of the wind environment near the pylon zone and proposes an evaluation method for the wind environment near the pylon zone, which can serve as the basis for wind barrier arrangement in similar research projects.

The main idea of a hinged-deck cross-section cable-stayed bridge appears with the need of increasing the capacity of a simple bridge by adding to lateral extension decks to the main deck. An experimental wind tunnel campaign to analyse the aeroelastic behaviour of a hinged-deck cross-section cable-stayed bridge has been performed. The bridge cross-section under study is formed by three parts: a central deck and two lateral extension decks joined to the central one using hinges and supported by their respective cable systems. The experimental model used is a reduced 6 degrees of freedom (DOFs) model for the elastic problem, which has previously proved to give good results concerning the bridge behaviour. The number of DOFs induces a new complexity in the oscillating motion of the bridge deck, compared to classical single deck 2 DOFs configurations. In this work, the aeroelastic tests performed at the UPM/IDR ACLA-16 wind tunnel facility to address the effect of wind barriers on the aeroelastic characteristics of the bridge section are reported. Nominal barriers are considered and compared with the case with no barriers. The effect of barrier porosity (wind barriers of the central deck and lateral decks) is also analysed. Stability ranges are reported in terms of reduced wind speed. The results show the large influence of the barriers in controlling the aeroelastic characteristics of the bridge. In some configurations, a large increase in bridge stability has been found due to the relevant effect of the barriers in changing the flow around the bridge. [ABSTRACT FROM AUTHOR]

Wind barriers are frequently used on the railway bridges to improve operational safety of high-speed trains. However, the effects of wind barriers along the railway on the separated decks' Vortex-induced vibration (VIV) for rail-cum-road bridges are not fully known, whose VIV characteristics are more complicated because of aerodynamic interference effect (AIE). A number of dynamic sectional model wind tunnel tests for VIV performance were carried out. Three different heights (H) varying from 2 m to 4 m and four different ventilation ratios (R) varying from 20% to 50% for wind barriers on railway decks were examined under two opposite incoming flow directions at a fixed spacing. Results indicated that twin separated decks' overall VIV performance are poor when the wind flows from the railway upstream to the highway downstream. The wind barrier on railway deck can weak the remarkable fluctuating wind pressure coefficients, change the correlation coefficients and reduce the contribution coefficients of local distribution aerodynamic forces to the overall aerodynamic forces. It was effective to suppress VIV of the railway deck, and it also had a greater impact on the adjacent highway deck. The VIV-suppress ability of wind barriers is determined by the parameters of H and R. The wind barriers with H = 3 m and R = 30% were recommended to satisfy the requirements of twin decks after a comprehensive evaluation. • The control effect of wind barriers installed on the railway for the VIV performances are investigated and in a wind tunnel. • H and R of the wind barrier affect its control effect. After a full analysis, wind barrier with optimal parameters are given. • Wind barriers can weaken the RMS wind pressure, change contribution coefficients, and destroy uniform frequencies of VIV. • Wind barriers installed on the railway can suppress VIVs of the railway upstream and the highway downstream. [ABSTRACT FROM AUTHOR]

This study provides evidence supporting the use of the update strategies for the support vector regression (SVR) model. Firstly, the fitting and interpolation method (FIM) is presented to select SVR parameters, and three infill strategies are adopted to search for update points. Secondly, the infill strategy and parameter selection method are illustrated by test functions that illustrate their dependability. The distribution of update points, the sample density and the proportion of update points are discussed. Finally, the adaptive SVR surrogate model is applied to optimize the protective effect of railway wind barriers. The result shows that the parameter selection method has high stability. On the whole, the accuracy of the adaptive SVR model using a suitable infill strategy will be improved with an increasing proportion of update points if the final number of training points is identical. The optimization result shows an optimal porosity of 0.117 when the height of the railway wind barrier is 2.05 m (full scale). [ABSTRACT FROM AUTHOR]

This paper reviews 5 existing models for predicting wind characteristics, namely the mean wind velocity and turbulence intensity, in the sheltered area of single or multi-row windbreaks. The paper briefly presents the mechanism of wind flow around windbreaks and then describes 5 models that predict the profiles of mean wind speed in the lee of windbreaks. These 5 models are the Schwartz model, the Engineering Sciences Data Unit (ESDU) model, the Středová model, the Hong model and the He model. The ESDU model can be used to estimate the mean horizontal wind speed profile and the turbulence intensity whilst the other 4 models are only capable of predicting the mean horizontal wind speed profile. By using existing wind speed datasets obtained from field measurements, laboratory tests and numerical simulations, the 5 models are assessed for their accuracy. It is found that the ESDU model is the most accurate for predicting the mean horizontal wind speed for flow regions behind a single windbreak. Behind multi-row windbreaks, the He model is found to provide the most accurate estimates of horizontal wind speed. In the case of predicting turbulence intensity, the ESDU model provides acceptable predictions, but unfortunately very limited data exist to validate these predictions. While the performance of these models is adequate, there is still much work to be done to further develop them and to address their current limitations. • Limited analytical or empirical models exist for predicting winds behind windbreaks. • Engineering Science Data Units model is the most accurate general model. • Different wind field models perform better in different regions behind fences. • No existing models perform adequately behind multi-fence wind breaks. [ABSTRACT FROM AUTHOR]