Train-induced Wind Research Articles

Effects of canyon wind speed and angle on the aerodynamic performance of a high-speed train passing through canyon tunnel–bridge–tunnel infrastructure

A significant airflow acceleration effect generated by canyon terrain and the bridge poses a serious threat to the safety of train operation in the canyon wind zone. The scale-resolving hybrid turbulence model and overset mesh technology have been employed to investigate the aerodynamic performance of the train traversing a tunnel–bridge–tunnel infrastructure under the canyon wind. Meanwhile, the mechanism of aerodynamic load variation is explored in combination with the characteristics of wind field distribution. The results indicate that the wind speed reaching the windward track of the bridge is about twice the wind speed of far-field inflow. The air within both tunnels will be sucked toward the center of the canyon. The accelerated flow area outside the tunnel portal leads to sudden changes in the lateral force and overturning moment of the train, with the most significant occurring in the head car. The peak of the lateral force and overturning moment coefficients are the highest at wind angles of approximately 60° and 120°, while smaller at 90°, exhibiting an overall approximate “M-shaped” variation pattern. The peak of the sudden change in lift coefficient is later than that of the lateral force coefficient, indicating a lag phenomenon. The direction of vortex shedding is roughly the same as the direction of the composite velocity of train-induced wind and canyon wind, except at the tunnel portal. The research results can provide a reference for the safety of train operation and the design of wind barrier facilities in canyon areas.

Analysis of concrete damage at anchorage end of the high-speed railway bridge sound barrier under the 400 km/h train-induced wind loads

The sound barrier installed on high-speed railway bridges withstands repeated train-induced wind load, which may lead to concrete damage at its anchorage end. This paper focuses on the assessment of concrete static damage at the sound barrier anchorage end under train-induced wind loads. The nonlinear finite element model of the sound barrier anchorage system is established to analyze the stress distribution, strain distribution and static damage of concrete structure at the anchorage end under 400 km/h train-induced wind loads in respect of different bolt preloads. The simulated results illustrate that both mortar and concrete near bolt holes suffer a certain degree of tensile and compressive damage. The maximum tensile and compressive damage factor values for mortar and concrete are 0.930, 0.643 and 0.892, 0.434 respectively. In addition, the effects of train-induced wind load on the internal force of the sound barrier anchorage take nearly no account, with a maximum of only 0.68 %. The results indicate that bolt preload is the most significant factor for concrete static damage, while the train-induced wind load appears negligible. An appropriate bolt preload can avoid the concrete static damage of the sound barrier anchorage end, and guarantee the structural stability of the sound barrier.

Wind Load Model and Response Spectra of Overbridges Subjected to Train-Induced Wind Loads

The vibration of pedestrian overbridges due to train-induced wind loads (TIWLs) during the passage of a high-speed train threatens the overbridge safety and causes pedestrian discomfort. To incorporate the structural dynamic magnification effect on overbridges under TIWLs in the design process, a framework to calculate the structural dynamic response, equivalent static TIWLs and response spectra of overbridges is established. A new simplified TIWL model with a “three-segment” wind pressure time history described by harmonic functions is proposed. This model facilitates the acquisition of analytical solutions for the structural dynamic response, streamlining the analysis process. The dynamic response and equivalent static TIWLs based on dynamic magnification factors (DMFs) of overbridges are obtained from the analytical method. The DMFs are primarily affected by the structural natural frequency and the characteristic frequency of TIWLs. Furthermore, based on the analytical solution of the overbridge dynamic response, parametric analysis is performed, and the response spectra representing the dynamic displacement and acceleration of overbridges are developed. The response spectra can be used to quickly calculate the displacement, internal force, and acceleration of the overbridges during engineering applications, which is more convenient but slightly less accurate than the analytical method.

Aerodynamic characteristics of fully enclosed sound barrier induced by the passing trains with 400 km/h

The fully enclosed sound barrier (FESB) has excellent sound reduction effect, but the relatively closed space will make train-induced wind effect more obvious. This study aims to quantify the aerodynamic characteristics on FESB during the trains passing through using a computational fluid dynamic (CFD) method, considering the effects of opening spacing ΔH, train length, and trains passing each other. An overset grid approach is applied to stimulate the relative motion between the train and the FESB, which is verified by correlated test data. The results demonstrate that compression and expansion waves induced by passing trains are the primary sources of pressure fluctuations within the FESB. Implementing a pressure relief scheme with a top opening, which modifies the propagation law of pressure fluctuations inside the FESB, can effectively mitigate the train-induced aerodynamic effects on the structure. Moreover, the head-wave effect on the FESB is less affected by the train length in such schemes. When the opening spacing ΔH value exceeds 1.5 m, the peak-to-peak pressure ΔPH induced by a train passing by gradually reaches a stable state, and there exists a perfectly negative exponential relationship between the aerodynamic force per unit length of FESB and the opening spacing ΔH. However, the train-induced aerodynamic effect on the FESB is amplified when two trains pass each other. In pressure relief scheme with ΔH of 1.5 m, compared to the ΔF observed on the near and far line sides during a single train passing by, those obtained during trains meeting operation are found to be 0.66 times and 2.64 times higher.

CFD model for airflow in a subway station compared to on-site measurements: The challenges of as-built environment

Understanding the contribution of piston effect and train-induced airflow to the ventilation of underground subway stations is essential to design efficient ventilation systems. To this aim, numerical models using computational fluid dynamics (CFD) have been used to recreate existing stations with a number of simplifying assumptions. However, the large variety of station configurations as well as types of sources influencing the airflow makes the generalization to other cases difficult. This study intends to predict numerically the train-induced wind affecting the climate of subway stations perceived on the platforms, and a comparison of these numerical predictions with field tests in an actual station is provided and extensively discussed.A simplified geometry of a station, where the ventilation is mainly realized by the piston effect caused by the train movement, is used to implement a scenario of a train passing through the station, with dynamic meshing techniques, and background wind is included in one configuration. Experimental measurements at 9 locations along the station's platform, repeated in order to improve statistical accuracy and the reproducibility of the results, provide data that can be compared with the corresponding numerical simulation. Numerical to experimental comparison is based on quantification of the peaks due to ingoing and outgoing trains through parameters like peak value, skewness and kurtosis. It is found that the main features of the airflow are well captured by the model, but the differences observed also highlight the challenges of simulating the as-build environment. Several non-dimensional metrics proposed in this paper can be used for comparison with other papers, so that a validated numerical model can be a relevant tool to calculate different velocity scenarios for trains and within different station architectures, supporting the design of ventilation systems to improve the comfort and safety of passengers.

A Lightweight Optimization Study for Large Capacity Dry-Type On-board Traction Transformer of EMU Based on CFD and RSM

Using the dry-type on-board traction transformer cooled by train-induced wind is an effective way to realize the lightweight of on-board equipment. However, the existing small capacity fan cooled dry-type on-board traction transformer cannot meet the power requirements of the high-speed electric multiple unit. For the large capacity dry-type on-board traction transformer, the lack of mathematical models that can reflect the relationship between hotspot temperature and design parameters limits its development. This paper aims to propose an optimization method for large capacity dry-type on-board traction transformer. First, the user-defined function based computational fluid dynamics modelling method for dry-type on-board traction transformer is proposed and validated to accurately obtain the winding hotspot temperature. Then, the response surface models of winding hotspot temperature are firstly proposed based on the response surface methodology. Finally, the lightweight optimization of a 6.3 MVA dry-type on-board traction transformer is completed, and the influence of design parameters on the weight reduction is studied. Under the conservative optimization strategy, the total weight of dry-type on-board traction transformer is reduced to 3650.40 kg, which is reduced by 38.55% compared with the oil cooled on-board traction transformer with the same rated capacity. This paper provides an efficient and feasible method and regular guidance for the lightweight optimal design of dry-type on-board traction transformer, and the obtained response surface models can be used for the optimization of similar dry-type on-board traction transformer under different specific needs.

Aerodynamic impact of train-induced wind on a moving motor-van

Aerodynamic impact of train-induced wind on a moving motor-van

태풍과 고속열차 운행에 의한 지상역사 승강장 스크린도어의 풍압 수치해석 연구

In the present study, the wind pressure acting on the platform screen door is investigated numerically by a train-induced wind and a typhoon. The dual island platform on a ground-level station was considered as a computational domain. To make a stable simulation, detailed buildings and station structures were modeled in a 2 km long, 1 km wide and 200 m hight computational domain. The high-speed train and station were modeled as detail as possible, and the actual train operation was considered to build similar analysis conditions. The overset mesh method was adopted to consider the high-speed train

Dynamic Response of Transmission Lines Crossing High-Speed Railway

Transmission lines crossinghigh-speed railways are prone to cable rupture accidents, due to the frequent effects of train-induced wind. In this work, we propose a numerical simulation method for the dynamic response of transmission line caused by high-speed train, and validate it by field testing. We investigate the action mechanism of train-induced wind on transmission lines and the time domain responses of cables. Meanwhile the influences of different parameters are discussed, including train speed, train length, span length, and height of transmission lines. It shows that the response caused by the passing of high-speed trains lasts for tens of seconds, and the cumulative damage caused by train induced wind should not be ignored. Increasing the height of transmission line, changing the span length, or installing damping devices can effectively overcome the line vibration or mitigate its impact. The proposed method can help to improve the structure design of transmission lines crossing high-speed railway and can also be used for the design and optimization of damping devices.

Modeling Method for Thermal Field of Turbulent Cooling Dry-Type On-Board Traction Transformer in EMUs

Adopting dry-type on-board traction transformer (OBTT) is one of the main ways to reduce the weight of electric traction systems, and its thermal characteristics are crucial for the safe operation of high-speed electric multiple units (EMUs). However, the existing thermal modeling methods either cannot realize the fast calculation of thermal characteristics of dry-type OBTT, or cannot accurately obtain the turbulence heat-transfer intensity when using the high-speed train-induced wind cooling. This article proposes an efficient method for dry-type OBTT thermal characteristics calculation. First, the thermal network of the winding area is proposed considering the thermal developing region of the air duct and the heat flow in the insulation paper between conductors. Then, the effects of key parameters on convective heat-transfer intensity are obtained by computational fluid dynamics (CFD) parametric sweeps, and then a novel local Nusselt number correlation for accurately calculating the turbulent convective thermal resistance is proposed. Finally, validation is performed with an experimental setup. The experimental results show that the computationally efficient thermal network model proposed in this article can quickly obtain the winding temperature distribution and the location of the hot-spot temperature. Moreover, the thermal analysis of a 6.3 MVA dry-type OBTT was conducted using the proposed modeling method.

Aerodynamic loads and bridge responses under train passage: case study of an overpass steel box-girder cable-stayed bridge

Increased train speeds have led to significant train-induced wind problems. This paper describes a numerical study of the aerodynamic loads produced when a train passes under a bridge and the bridge dynamic response based on a steel box-girder cable-stayed bridge. The results indicate that the wind pressure on the bottom plate and the maximum lift on the beam sections increase as the train speed increases or as the clearance under the bridge decreases. Changes in the intersection angle are found to have a greater impact on the 1/4-span and 3/4-span regions. The effects of the various influencing factors are basically the same in the construction and operation stages. As the train speed increases or the clearance under the bridge decreases, the bridge responses exhibit an upward trend. As the intersection angle decreases, the vibration displacement tends to increase, but the effects on the vibration acceleration and maximum counter-force of the temporary pier are not consistent. Compared with the construction stage, the dynamic responses of the main girder are smaller in the operation stage due to the larger overall rigidity and the support constraints. In the parameter ranges investigated in this study, the absolute values of maximum vertical bridge vibration displacement and acceleration decrease from 4 to 16 mm and from 85 to 400 mm/s2, respectively, in the construction stage to 1–5 mm and 42–174 mm/s2 in the operation stage. Moreover, the counter-force falling on the temporary pier after the main girder turns does not exceed the 2000-kN positive force or 300-kN negative force limits. In the operation stage, the bridge vibration responses will not affect the comfort of pedestrians.

Aerodynamic performance of traveling road vehicles on a single-level rail-cum-road bridge under crosswind and aerodynamic impact of traveling trains

ABSTRACT Crosswind and train-induced wind are major factors influencing the aerodynamic performance of vehicles on single-level rail-cum-road bridges. Based on computational fluid dynamics (CFD) technology, this work developed a numerical model to discuss relevant issues. The flow features of the vehicle-bridge system, the influence of different lanes and vehicles are explored, and the superposition of crosswind and train-induced wind has been analyzed. The results indicate that the crosswind and train-induced wind superpose near the windward side of the concrete wall, producing two high-pressure and low-pressure zones, which are the primary cause of the aerodynamic variations on nearby vehicles. The crosswind decreases the variation amplitude of side force, rolling moment and yawing moment for 10% ∼ 20%, but the influence on the lift force and pitching moment is not significant. Therefore, the aerodynamic forces of the vehicle while meeting the train at different wind speeds can be obtained by superposing the aerodynamic variation caused by the moving train and the aerodynamic forces at its sole-traveling state, which are conservative and can provide references for actual engineering.

CFD model to assess parameters influencing piston wind in a subway tunnel and station

Quantifying the train-induced wind affecting the climate of subway stations can be applied to improve underground networks air quality. In this paper, numerical simulations of train-induced airflow in a subway station are performed, using a CFD model with dynamic meshing techniques. A preliminary study is done in a double-track tunnel with blockage ratios of 0.30, 0.37 and 0.46 with a train running at constant speed in the order of 10 m/s. The tunnel length necessary to obtain a stable flow around the train body is determined, and this upstream tunnel length is included in a subway station model. Two different architectures and three train speeds are simulated, and the effect of these configurations on the station airflow is evaluated through the air velocity and the mass flow rate at a location on the platform. The results evidence an increase in air circulation with blockage ratio and train speed.

Coupling vibration response analysis of wind-train-bridge system considering the train-induced wind effect

Considering the wind loads and track irregularity as external excitation, the wind-train-bridge dynamic analysis model considering the longitudinal freedom of train is established in the present study. In the model, the wind load of train-bridge system under the train-induced wind field and the combined wind field is obtained by employing Computational Fluid Dynamics (CFD) method. With the CRH2 high-speed train and a 10-span simply-supported box girder bridge as an example, the whole history of the train running on the bridge under the combined effect of train-induced wind and crosswind is simulated to analyze the dynamic response of the train-bridge system. In addition, the operational safety indicators of the train are evaluated. According to the obtained results, the dynamic response of vehicles and bridges increases with the train speed without the consideration of the crosswind. In the combined wind field, the train-induced wind exerts a greater impact on the dynamic response of the vehicle, but has a less influence on that of the bridge simultaneously. Moreover, the influence of wind velocity is greater than that of train speed. When the wind-train-bridge dynamic response analysis is carried out based on traditional methods, the calculated wind load of the train-bridge system is too high, making the calculated responses too large to be consistent with actual values.

Effect of Train-Induced Wind on the Transmission of COVID-19: A New Insight into Potential Infectious Risks.

The unprecedented COVID-19 pandemic has caused a traffic tie-up across the world. In addition to home quarantine orders and travel bans, the social distance guideline of about six feet was enacted to reduce the risk of contagion. However, with recent life gradually returning to normal, the crisis is not over. In this research, a moving train test and a Gaussian puff model were employed to investigate the impact of wind raised by a train running on the transmission and dispersion of SARS-CoV-2 from infected individuals. Our findings suggest that the 2 m social distance guideline may not be enough; under train-induced wind action, human respiratory disease-carrier droplets may travel to unexpected places. However, there are deficiencies in passenger safety guidelines and it is necessary to improve the quantitative research in the relationship between train-induced wind and virus transmission. All these findings could provide a fresh insight to contain the spread of COVID-19 and provide a basis for preventing and controlling the pandemic virus, and probe into strategies for control of the disease in the future.

Numerical simulation on aerodynamic characteristics of moving van under the train-induced wind

Constructing combined highway–railway bridge brings concerns regarding the aerodynamic interference between train and road vehicle. Research on the interaction mechanism can help calculate the vehicle response for the assessment of travelling safety. In this work, computational fluid dynamics (CFD) verified by a moving model test was applied on researching the aerodynamic characteristics of a moving van under the influence of train-induced wind. Two processes - encounter process (train and van drive towards each other) and chase process (train surpasses the van), are compared. The aerodynamic forces and pressure distribution of the van as well as the flow fields around the vehicles during the interaction are analyzed coherently. The results reveal that the adjacent positive and negative pressure zones around the nose and tail of the train bring moving and centralized high-pressure zone on the van's flank and generate significant aerodynamic variations, each variation contains at least two peak/valley values, and the middle carriage provide a stable transition between. Different superposition effect of the pressure zones results in difference between the encounter process and chase process, the variation trend of drag force and lift in the two processes are similar while the encounter has larger variation amplitude, in terms of pitching moment and yawing moment, more inversions of force happen in the encounter process but the variation amplitude is smaller. When the van runs near the nose of the train in the encounter, it gets the largest variation of drag force, lift force and rolling moment, while the largest variation of yawing moment and pitching moment happens when it runs near the nose of the train in the chase process.

Temperature field and anti-freezing system for cold-region tunnels through rock with high geotemperatures

The tunnels of the Sichuan-Tibet railway reach altitudes of above 4200 m and have very deep burial depths; thus, serious freeze and heat damage will be encountered during the long-term usage of these tunnels. Taking the Zilashan Tunnel as an example, the dynamic change in the temperature field during tunnel operation was studied by using a transient heat transfer model that coupled convection and conduction. The results show that a high geotemperature fails to directly eliminate freeze damage of the tunnel entrance. The temperature of the tunnel section with a low original geotemperature changes periodically, and the train-induced wind dramatically affects the temperature field. After long-term operation, the surrounding rock a certain distance from the tunnel wall in the radial direction maintains the original high geotemperature, serving as a stable heat source. To prevent and control the freeze damage of tunnels and utilize the high geotemperatures, an efficient and energy-saving anti-freezing system was proposed using an air-source heat pump in a heat extraction tunnel. The calculation method of the anti-freezing system was proposed, and the effect of the length of the extraction tunnel on the air temperature and coefficient of performance (COP) was also studied. The total heat consumption required for freeze damage prevention was obtained. Considering the energy loss of the transmission system, the maximum heating load of Zilashan Tunnel’s heating system was determined to be 37.23 kW. In addition, it is suggested that the length of the extraction tunnel is 60 m, and the resulting COP of the air-source heat exchanger is 4.75. These research results can support anti-freezing design for cold-region tunnels through rock with high geotemperatures.

Effect of High-Speed Train-Induced Wind on Trackside UAV Thrust Near Railway Bridge

Imaging devices attached to unmanned aerial vehicles (UAVs) are used for crack measurements of railway bridges constructed for high-speed trains. This research aims to investigate track-side wind induced by high-speed trains and its effect on UAV thrust near the railway bridge. Furthermore, the characteristics of train-induced wind in three axial directions along a track, wind velocity, and the effect of train-induced wind on the UAV thrust were analyzed. This was achieved by installing 3-axis ultrasonic anemometers and a UAV thrust measurement system on top of a PSC box girder bridge. The changes in the train-induced wind velocity were monitored along the train travel, width, and height directions. The train-induced wind was measured at distances of 0.8, 1.3, 2.3, and 2.8 m away from the train’s body to analyze wind velocity based on distance. It was found that the maximum wind velocity decreased linearly as the distance from the train’s body increased. The UAV thrust increased by up to 20% and 60%, owing to train-induced wind when the leading and trailing power cars of a high-speed train passed, respectively. Thus, it is necessary to conduct further research to develop robust control and a variable pitch-propeller that can control thrust.

A Numerical Study Toward Harvesting Power From Train Slipstream Using Savonius Rotor

AbstractA novel and strategic green energy production method that utilizes relative wind generated from moving vehicles is presented. A speeding train generates an enormous wake of wind around it, which stocks a substantial amount of kinetic energy. In this study, this freely accessible wind power is harvested by installing a modified savonius wind turbine within the slipstream region of the train. A computer-oriented fluid-solid integrate simulation of wind turbine propelled by train-induced wind is performed by executing all physically realistic boundary conditions. The numerical study is based on open-source CFD toolbox openfoam, and the results were validated against benchmark experimental study. Parametric sensitivity analysis such as optimal turbine performance within the slipstream regime, torque prediction from express trains, two opposite crossing trains, tunnel condition, and turbine wind turbine clusters arrangement has been reported. This study enhances the understanding of the power generation by the turbine from the train slipstream which is not reported in any open literature as far as the authors’ present knowledge goes.

Research on aerodynamic optimization of high-speed train’s slipstream

Slipstream severely affects the safety of trackside workers and equipment. With use of profile superimposition method and vehicle modeling method, parametrization of the whole train is carried out. Then, a slipstream optimization study has been performed, taking components of slipstream in different directions at the standard heights, the drag coefficient of the whole train and the volume of the driving cab as the design objectives. For each design objective, one unique ϵ-TSVR surrogate model has been constructed. Six final Pareto sets have been obtained on the base of six groups of different fitness functions by using multi-objective particle swarm method. Results reveal that the volume of the driving cab keeps almost the same, compared to the original shape. The velocity components of train-induced wind at the positions 0.2 and 1.4 m above the top of the rail, and the drag coefficient of the train are reduced by 11.6%, 33.9%, 24.7%, 25.9% and 13.0% respectively. Sensitivity analysis reveals that the length of the streamline, the height of the train and the width of the train influence significantly on the aerodynamic performance, and the train with a tall and thin streamline will benefit in reducing the slipstream and aerodynamic drag.