Effect Of Wind Barriers Research Articles

Experimental and numerical study on the local crosswind environment of a wide streamlined bridge deck equipped with wind barriers at different angles of attack

In this study, the effects of wind barriers on the crosswind environment of vehicle safety on a long-span bridge with a streamlined bridge deck were investigated at different angles of attack (AOA). The profiles of the mean and the root mean square (RMS) of the wind pressure coefficients above different traffic lanes were obtained through synchronous pressure measurements. The mean pressure fields around the bridge decks were investigated by computational fluid dynamics (CFD) simulations. The crosswind environment of vehicle safety between the deck with railings and the deck with wind barriers was compared and analyzed in detail at different AOA. The results showed that the wind barriers produce a thicker separation shear layer above the bridge deck and result in a larger negative pressure region in comparison with the case with railings. This leads to a notable reduction in the mean wind pressure coefficients above the deck. The increase in the AOA enhances the above-mentioned reduction effect. It was also found that the wind barriers significantly increase the RMS of the wind pressure coefficients above the deck compared with the railings. The increase in the AOA inhibits this enhancement effect. The results of the equivalent mean pressure coefficients show that the wind barriers reduce the vehicle sideslipping risk more effectively than the vehicle overturning risk. It was also found that the effect of the wind barriers on the reduction of the overturning risk is more sensitive to the change in AOA than the effect on the reduction of the vehicle sideslipping risk.

The Effect of wind barriers on the local wind field on a bridge deck

Abstract The adverse effect of crosswinds on road vehicles on a bridge deck or traffic lanes is of increasing concern. Local flow characteristics depend on the bridge's architecture and wind barriers are commonly used to alleviate wind-induced instability for vehicles. Terrain orography is another dominant factor. This study uses a terrain model with a coastal bridge (Chen-Kung Bridge, Penghu, Taiwan). The bridge is located between a reservoir and the Taiwan Strait. Numerous accidents have occurred due to strong monsoon winds in autumn and winter. In wind tunnel experiments, an atmosphere boundary layer is established and the test conditions (wind speed and wind incidence) are taken from local meteorological data. The effect of the height of solid wind barriers on local wind direction and speed is determined. The results can be used to remodel wind barriers to increase safety for road vehicles.

Effects of wind barriers on the aerodynamic characteristics of twin-separated parallel decks for a long-span rail-cum-road bridge

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.

Effects of wind barriers on VIV performances of twin separated parallel decks for a long-span rail-cum-road bridge

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.

Effects of wind barriers on the aerodynamic characteristics of bridge-train system for a road-rail same-story truss bridge

Effects of wind barriers on the aerodynamic characteristics of bridge-train system for a road-rail same-story truss bridge

Analysis of the effects of wind barrier on driving safety and comfort of vehicles on long-span bridges under crosswinds

The installation of wind barriers is generally considered able to improve traffic safety on bridges. Conventionally, the effects of wind barriers are evaluated through the aerodynamic characteristics or dynamic responses of vehicles. In this study, the effects of wind barriers are numerically investigated from the driving safety and comfort perspectives for the first time. The methodology for dynamic analysis of wind–vehicle–bridge (WVB) coupled system is firstly present. Then, the evaluation indexes for driving safety and comfort of vehicles are proposed. A series of wind-tunnel experiments are conducted, and corresponding numerical calculations are performed to discuss the influence of wind barrier parameters i.e., height and opening ratio. Through dynamic responses derived from the calculation results, it is confirmed that: (1) the lateral dynamic responses for both vehicles and bridges considerably increase under winds excitation; (2) the installation of wind barriers can effectively prevent traffic accidents on a bridge, and is thus an effective windproofing measure; (3) however, this method is not beneficial to the bridge structure in terms of stresses and significantly increases the overall vibration value total value (OVTV) of vehicles, which is not conducive to the driving comfort of vehicles on the bridge.

Effects of Wind Barriers on Wind Fields and Vehicle Stability on Bridges

To explore the influence of bridge wind barriers, with their specific opening shapes and arrangements, on bridge deck wind fields and vehicle driving stability under different crosswinds, five bridge wind barrier schemes were designed. For two incoming wind speeds, the wind speed at different heights over three traffic lanes and the aerodynamic six-component force of the vehicle model were measured, and the influence of the wind barrier parameters on the vehicle driving stability was analyzed. The equivalent wind speed reduction coefficient of the wind barrier was compared with the dimensionless coefficients of the aerodynamic side force, roll moment, and aerodynamic lift to verify the accuracy of the shielding effect evaluation indices. The final conclusions provide a useful reference for designing bridge wind barriers.

Effects of wind barriers on running safety of trains for urban rail cable-stayed bridge

Considering the wind barriers induced aerodynamic characteristic variations of both bridge deck and trains, this paper studies the effects of wind barriers on the safety and stability of trains as they run through an urban rail transit cable-stayed bridge which tends to be more vulnerable to wind due to its relatively low stiffness and lightweight. For the bridge equipped with wind barriers of different characteristics, the aerodynamic coefficients of trains and bridge decks are obtained from wind tunnel test firstly. And then, the space vibration equations of the wind-train-bridge system are established using the experimentally obtained aerodynamic coefficients. Through solving the dynamic equations, one can calculate the dynamic responses both the trains and bridge. The results indicate that setting wind barriers can effectively reduce the dynamic responses of both the trains and bridge, even though more wind forces acting on the bridge are caused by wind barriers. In addition, for urban rail transit cable-stayed bridges located in strong wind environment, the wind barriers are recommended to be set with 20% porosity and 2.5 m height according to the calculation results of cases with wind barriers porosity and height varying in two wide ranges, i.e., 10% - 40% and 2.0 m to 4.0 m, respectively.

Effect of wind barriers on the flow field and aerodynamic forces of a train–bridge system

This paper investigates the effect of a wind barrier on the aerodynamic performance of a train–bridge system under crosswind using a numerical simulation method. The studied bridge is a long-span cable-stayed bridge with a flat steel box girder, located in Chongqing, China. The flow field around the train–bridge system with and without a wind barrier is numerically simulated. Wind barrier porosities varying from 10 to 60% are evaluated. The tricomponent coefficients of the train, bridge, and train–bridge system are obtained and investigated in detail. The effect of the wind barrier on the aerodynamics of the train–bridge system is revealed through the determination of the aerodynamic forces, pressure mapping, and flow visualization. The results show that a wind barrier successfully decreases the mean velocity above the girder and consequently decreases the drag force and moment on the train; however, the wind barrier also significantly increases the drag force on the girder. Therefore, installation of a wind barrier improves the running safety of the train but is detrimental to the wind resistance of the bridge. Additionally, the efficiency of the wind barrier depends on the porosity. A lower porosity improves the train safety but is more detrimental to the bridge safety. An optimal wind barrier porosity of 30% is obtained based on the aerodynamic forces of both the train and the bridge. Compared to a train–bridge system without a wind barrier, the drag force and moment on the train decrease by 66.1 and 62.9%, respectively; the drag force on the bridge girder increases to 0.86, and the drag force on the train–bridge system equals that without the wind barrier.

Flutter and galloping of cable-supported bridges with porous wind barriers

Wind-tunnel experiments are carried out to analyze the influence of wind-barrier porosity and height on aerodynamic and aeroelastic characteristics of wide long-span cable-supported bridges. The experiments are carried out on sectional models of the Golden Gate Bridge (USA), Kao-Pin Hsi Bridge (Taiwan), and Great Belt Bridge (Denmark). The bridge-deck section models are equipped with the wind-barrier models at the windward (leading) edge of the studied sections. The experimental results indicate that the effects of wind barriers on galloping sensitivity of studied bridge decks are rather negligible, while bridge decks become quite prone to flutter for wind barriers placed at their windward edge. These trends are more exhibited for more-solid wind barriers. The effects of increasing wind-barrier height are not unambiguous, as they are simultaneously influenced by the aerodynamic shape of bridge decks as well.

Numerical simulation of the protective effect of railway wind barriers under crosswinds

Computational fluid dynamics (CFD) was employed for the simulation of a train model subjected to crosswinds. The numerical model was validated by comparing the flow structures and aerodynamic coefficients. A discussion of the protective effects of wind barriers at yaw angles in the range 0 < β ≤ π/4 is provided, along with an analysis of the flow distribution, and a proposal for a transformation of aerodynamic coefficients in the presence of wind barriers. The results show that the protective effect of a wind barrier for end nose are different for various yaw angle; the separation lines of the end nose at the leeward side of the vehicle bottom shift to windward in the presence of a wind barrier. The coefficients obtained through this transformation are found to be applicable for the side drag and lift coefficients of the head nose, which were obtained through numerical simulation, and are larger than the coefficients of the end nose at a majority of yaw angles. The yaw angle has a little effect on the absolute errors of the transformation for the end nose. The wind-reduction factor and absolute errors can be used to evaluate the protective effects of railway wind barriers to avoid the appearance of the different protective effect in a wind barrier.

The effect of wind barriers on airflow in a wind tunnel

Porous wind barriers are widely used and proven more efficient than solid barriers. In this study, the shelter quality of wind barriers of different porosity, row space and row number was compared based on wind-tunnel measurements. The 14 cm-high (H) scaled models of wind barriers were placed perpendicularly to the wind direction in the wind tunnel, and rough elements were placed upwind of the models to obtain a reasonable self-simulation zone and Reynolds number. The results show that the airflow field changes little in the area above one-row wind barriers. In the area below the models, the airflow field is rearranged into four energy regions. The best shelter effect achieved downwind is always obtained using a 0.35-porosity wind barrier, so we suggest the optimal porosity of 0.3–0.4 for wind barriers in sand-control engineering. The shelter effect comparison of two-row 0.35-porosity wind barriers indicates that 6 H is the optimum row space. Two-row and three-row wind barriers obviously provide better shelter than one-row barriers. Therefore, we suggest 5–7 H as the optimal row spacing for multi-row wind barriers. Our results indicated good agreement with previous studies regarding porosity, row number and row space, with some exceptions about wind barrier design regarding porosity.