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Cross-wind effects on road and rail vehicles

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Abstract

This paper presents a review of recent research that has been carried out on the cross-wind effects on road and rail vehicles. After a brief introduction to the issues involved, the risk analysis framework is set out. All risk analysis methods require some knowledge of cross-wind aerodynamic force and moment coefficients, and methods of obtaining these through full scale and wind tunnel testing and through Computational Fluid Dynamics methods are then described. The picture of the flow fields around vehicles that is suggested by these measurements and calculations is then presented, and the steady and the unsteady aerodynamic force characteristics described. The detailed methodology for using this information to predict accident risk is then set out, including details of the vehicle dynamics system models that can be used. Finally potential alleviation methods are described and suggestions made for further works.

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... This reality brought new concerns to the railway engineering community, since the likelihood of a train being over a bridge during the occurrence of hazards that might compromise its running safety increased significantly. Hence, events such as the derailment of the Shinkansen HS train when it was running at 200 km/h over a viaduct during the Niigata Ken Chuetsu earthquake in October 2004 [4] or the several overturning derailments caused by strong crosswinds reported by [5] provided the motivation for further research regarding the assessment of the running safety of trains moving over viaducts and bridges. ...
... To achieve this, the wind and mechanical engineers follow two main approaches: i) through wind tunnel tests; or ii) through Computational Fluid Dynamics (CFD) analysis. On this basis, significant contributions addressing the determination of aerodynamic coefficients of trains with wind tunnel tests have been made by research groups from the Politecnico di Milano and the University of Birmingham and [5,68,69,85], among others [86][87][88]. Regarding CFD, several recent works have been reported, for example in [89][90][91]. ...
Article
Train running safety is a major concern among railway engineers, since a derailment may cause significant personal and material damages. This problem becomes more important if the derailment occurs on bridges, especially at high ¬¬speeds, where the consequences may be even worse. The sudden development of high speed (HS) railway networks that occurred at the end of the 20th century and beginning of the 21st century demanded the construction of new lines with large curve radii in order to fulfill the design requirements of this type of transport. By adding this fact to the orography constraints and, in some cases, to constraints related with the lack of construction area and with the high costs of expropriation, several HS lines started to be developed with more than 75 % of their length built over viaducts and bridges. Naturally, this relatively new reality led to a significant increase in the probability of a train being exposed to natural hazards that might jeopardize its stability when it is running over an elevated structure. Hence, this paper aims to present a comprehensive literature review of the problematic associated with the train running safety assessment on bridges. The existing normative criteria from different regions of the world related to this topic are summarized in a first stage. Then, the paper gives a brief description of the available train bridge interaction models needed to explicitly assess the traffic stability, followed by a presentation of the running safety indexes used to assess the derailment risk. Finally, the available applications regarding the traffic stability against different sources of excitation are systematically reviewed and guidance to future research work on this topic is provided.
... The investigation of railway vehicles aerodynamics is of great importance both for economic and safety reasons; in fact, knowing the wind loads acting on a train-set allows, on the one hand, to address energy consumption issues and, on the other hand, to study the aerodynamic stability of the train. In this field, research has been mainly focused on passenger trains as they travel at higher speeds and are much lightweight with respect to freight trains (Baker et al., 2009;Baker, 2013;Cui et al., 2014;Dorigatti et al., 2015;Paradot et al., 2015;Premoli et al., 2016). ...
... The convoy composition was chosen in order on the basis of a tradeoff between the minimum Re number required by the EN 14067-6 (Re ¼ 2.5 10 5 ) and the minimum number of vehicles necessary to correctly account for the boundary conditions to evaluate the crosswind performance of a railway vehicle (Baker et al., 2009;Baker, 2013). The selected solution complies with the requirements of the international standards (TSI 232/2008 and EN 14067-6) for the evaluation of the aerodynamic coefficients useful for the crosswind analysis, which is the main objective of the present paper. ...
Article
The paper investigates the response to crosswind of a high-speed freight train for intermodal transportation, through wind tunnel tests. A 1:20 model of a freight train composed by an engine and two flat-car vehicles was instrumented with force balances to measure the aerodynamic coefficients of the flat-car plus container assembly and of the container alone. Aerodynamic coefficients strongly affects the train stability and the anchorage limits of the container itself. During the wind tunnel tests, eight different loading configurations were considered and aerodynamic coefficients were determined for yaw angles (i.e. angle between train and wind) ranging from 0° to 90°. Experimental results show the benefits in terms of drag reduction due to the presence of a laden vehicle upstream. As far as the rollover risk is concerned, the less critical condition is found for a vehicle preceded by a fully laden wagon and followed by an empty one. More in particular, at low yaw angles, the worst condition for a vehicle occurs when the wagon ahead is empty while, for yaw angles between 45° and 55°, which are the most critical for ‘low speed’ trains, the differences with respect to the other configurations reduce significantly.
... The instantaneous wind velocities exceeding 20-25 m/s are considered high risk for train operation, especially in exposed places such as bridges and embankments. The critical cross-wind speed for road vehicles may be lower [24,[28][29][30][31]. • Several strategies can be used to successfully reduce the vehicle overturning moment in cross-wind successfully. ...
... The instantaneous wind velocities exceeding 20-25 m/s are considered high risk for train operation, especially in exposed places such as bridges and embankments. The critical cross-wind speed for road vehicles may be lower [24,[28][29][30][31].  Several strategies can be used to successfully reduce the vehicle overturning moment in cross-wind successfully. ...
Article
Full-text available
The article presented the issue of securing semi-trailer trucks and trailers during their transport using intermodal railway wagons as a part of combined transport. This issue was analysed in different operational conditions related to loading level, cross-winds influence, inertia forces due to the emergency braking, and track curvature. According to general rules of loading and securing cargo, described in the internal and UIC regulations, the transported load should be positioned and secured with minimised risk of undesirable displacement or rolling over during transport. Basic analysis showed that adverse conditions such as strong winds or emergency braking may require adequate additional cargo protection. The lack thereof may result in a severe accident or damage to the transported vehicle or the nearby structures. The presented results for generic road and railway freight vehicles showed that the required anti-rollover torque for a semi-trailer mounted on the railway wagon platform may differ considerably (almost four times at the same maximum tested airflow speed) depending on the conditions related to aerodynamic and inertia influence. The potential weaknesses of the analysis relate to the impracticality of experimental tests for roll-over (or derailment) events under high levels of cross-wind, due to economic and safety reasons. The analysis can be extended in the future by including unsteady aerodynamic forces and a full-vehicle model based on the multi-body method for a specific design solution.
... Crosswinds can significantly change the lateral aerodynamic performance of a train, which creates a risk of overturning. There have been many accidents involving trains as well as road vehicles recorded in different regions of the world (Baker et al., 2009). These have led to the development of a number of standards, such as the EN (European Standard, 2010). ...
Article
The present work focused on the aerodynamic performance of double unit trains (DUT) and traditional single unit trains (SUT) under crosswinds. The aerodynamic coefficient as well as the characteristics of the time-averaged and instantaneous flow of the SUT and DUT were calculated using the improved delayed detached eddy simulation (IDDES) method for 1/8th scale models. The numerical results were verified by wind tunnel tests. The time-averaged flow pattern on different cross-sections and horizontal planes were compared for the SUT and DUT. The pressure coefficients on the loops of different cars were also analyzed quantitatively. The vortices around the SUT and DUT were visualized, and the frequency characteristics of each car of the SUT and DUT were computed. The coupling region changed the forces on the train and increased the overall drag of the train. Faster vortex development was found on the last three cars of the DUT. Furthermore, a higher velocity belt was generated by the gap of the coupling region. The coupling region gave a significant influence of the power spectrum densities (PSD) on the last four cars and a relatively slight impact on the first two cars.
... Crosswind stability has long been a key consideration concerning the aerodynamic shape design and railway operation (Baker et al., 2009). The running stability and safety of the rolling stocks deteriorate significantly when exposed to a strong crosswind environment, especially with the increase of the train speed and reduced vehicle weight that we see nowadays (Dorigatti et al., 2015;Krajnović et al., 2012;Munoz-Paniagua et al., 2017;Tian, 2019). ...
Article
Crosswind stability of rolling stocks running on an embankment has been a key focus for decades, stemmed from the high overturning risks under crosswind. The correct reproduction of the embankment layout in a wind tunnel is therefore of great significance for estimating the train's aerodynamics and running safety. In this study, four different 6-m-high embankment layouts are proposed to replicate realistic wind tunnel configurations with the improved detached eddy simulation (IDDES) method. These helped to estimate the aerodynamics of a leading vehicle when subjected to a block wind profile of 45 m/s at the typical yaw angle of 30°. Furthermore, a static wind tunnel test with a 1:20 scaled train/embankment model enabled the validation of the numerical algorithm. The overall results indicate that all the aerodynamic coefficients of the leading vehicle mounted on the leeward track of the embankment top, decrease rapidly with the extending length of the upstream embankment. Similar aerodynamic performance appears on scenarios such as wall-to-wall (W2W) and partially wall-to-wall (P–W2W), which highlight equivalences between W2W and P–W2W under yaw effects. However, those particular scenarios considerably underestimate the aerodynamic coefficients compared with a more realistic scenario based on open domain (OD) and motion boundaries. Therefore, the conservative assessment of the vehicle aerodynamic characteristics based on the finite-length-embankment in a wind tunnel test could be taken into consideration for determining the running safety.
... As for train derailment, considerable works are reported on the derailment for main track rail, which is related to track defects, earthquakes, crosswinds and impacts [25][26][27][28][29][30][31][32][33][34][35]. The authors [36,37] also derived the limit value of wheel flange climbing derailment under the quasi-static condition, which can provide a theoretical basis for simulating dynamic derailment. ...
Article
Full-text available
Wheel flange climb derailment of vehicles in railway turnouts is a serious safety issue. In particular, derailment accidents in smaller turnouts, caused by poor track alignment before the turnout or structural degradation, are becoming more and more frequent. Most of the previous research on derailment has focused on main track areas, while the dynamic derailment mechanism for turnouts is still not clear. For this reason, a field derailment investigation of freight wagons in No.6 symmetrical turnouts is presented in this paper. Taking this into consideration, a half-car multi-body dynamics model and flexible turnout model, subject to wheel flange climb derailment, has been established. In addition, a field test for wheel-rail interaction was carried out to verify the dynamic model. This model is capable of revealing derailment evolution of the front and rear wheelset for a bogie under critical derailment conditions. The influence of several sensitive parameters of the derailment model on critical derailment behavior has been carried out. Results show that the simulation results of the wheel climb derailment are very consistent with the filed investigation, and the safety of the bogie depends on the status of both front and rear wheelset. This work is a world first in providing a solid understanding of dynamic derailment behavior and motion posture, giving guidance on the prevention of wheel flange derailment in turnout areas.
... When a crosswind exists, the running train is subjected to a speed limit [1], which has a significant effect on carrying efficiency. Operational protection is also threatened by the crosswind [2]. In fact, many derailment accidents due to crosswinds have been reported around the world, such as in China [3,4], Japan [5,6], and the UK [7,8]. ...
Article
Full-text available
High-speed trains serving in a crosswind region are bearing more significant safety risks. Based on the three-dimensional (3D) Unsteady Reynolds-Averaged Navier–Stokes (URANS) turbulence model, a Computational Fluid Dynamics (CFD) computational work was conducted in the present study to predict the transient aerodynamic load of the train. The transient aerodynamic load was then employed as the input of the dynamic system to perform a dynamic analysis of running safety. Noticeable changes in the aerodynamic coefficients were found when the train entered and left the crosswind region due to the dramatic change in flow patterns. The original posture also provided significant changes to the train’s aerodynamic responses. A slightly larger maximum derailment coefficient was found on the first bogie of the leading car with a preset posture. There were obvious differences in the displacement characteristics of the three cars in the lateral direction and the rolling rotation, and the magnitude of the posture changes decreased from the leading car to the trailing car. The train with the consideration of posture was proven to withstand weaker crosswinds.
... The past decade has witnessed a rapid development of high-speed trains worldwide, with a significant increase in train speed, train accidents, like derailment and overturning, have been reported and studied at a higher frequency than ever before because these trains are more sensitive to the effects of strong winds (Diedrichs et al. 2007, Krajnovic 2008, Baker et al. 2009, Yao et al. 2018, Tian, 2019, Guo et al. 2020a, 2019, 2021. Moreover, the trains need to run on different substructures (e.g., flat ground, cuttings and embankment) because of complex and changeable terrain. ...
Article
This paper studied the case of high-speed train running from flat ground to bridges and into/out of tunnels, with or without crosswind based on the Computational Fluid Dynamics (CFD) method. First, the flow structure was analyzed to explain the influence mechanisms of different infrastructures on the aerodynamic characteristics of the train. Then, the evolution of aerodynamic forces of the train during the entire process was analyzed and compared. Additionally, the pressure variation on the train body and the tunnel wall was examined in detail. The results showed that the pressure coefficient and the flow structure on both sides of the high-speed train were symmetrical for no crosswind case. By contrast, under crosswind, there was a tremendous and immediate change in the pressure mapping and flow structure when the train passing through the bridge-tunnel section. The influence of the ground-bridge transition on the aerodynamic forces was much smaller than that of the bridge-tunnel section. Moreover, the variation of aerodynamic load during the process of entering and exiting the bridge-tunnel sections was both significant. In addition, in the case without crosswind, the change in the pressure change in the tunnel conformed to the law of pressure wave propagation, while under crosswind, the variation in pressure was comprehensively affected by both the train and crosswind in the tunnel.
... As derailment accidents by strong winds have become serious, the risks of derailment by winds are evaluated by criteria given in standards like EN (European Standard), JIS (Japanese Industrial Standards) at the design stage of railway vehicles. In Europe, the safety of cross-winds by CWC (characteristic wind curves) in EN standard has usually been evaluated [6,7], and the EN and UIC regulations provide a model for wind forces acting on a vehicle under various conditions such as a wind force of Chinese hat type and wind pressure acting on a vehicle when entering a tunnel, as shown in Figure 2 [8,9]. Since the 1970s in Japan, Masharu Kunieda [10] proposed Kunieda's formula to evaluate the risk of derailment by cross-wind because derailment accidents had been frequently caused by strong cross-winds. ...
Article
Full-text available
In this paper, theoretical derailment equations for cross-wind with frequency were derived to assess running safety. For a KTX (Korean high-speed train) unit, the wheel unloading ratios, which are the criteria for evaluating derailments in UIC (International union of railways) and TSI (Technical Specification for Interoperability) regulations, were calculated through the formula under the driving regulations according to cross-wind speeds, and the theoretical results were compared and evaluated through a multibody dynamics (MBD) simulation. In addition, the wheel unloading ratios were calculated for various frequencies of cross-winds. As a result of the formula and MBD, the wheel unloading ratios were shown to increase rapidly regardless of the dampers in suspension when the cross-wind frequency and the natural frequency of a vehicle were in agreement. Finally, we calculated the changes of wheel unloading ratio for different track gauges and found that these theoretical equations could calculate more accurate results than the existing Kunieda’s formula. The formula derived in this study has the advantage of considering various variables, such as fluctuant cross-winds, rail irregularities, and derailment behaviors, which were not considered in previous studies or Kunieda’s formula. It could be used for setting suspensions or railway vehicle specifications in the initial design stage.
... Scholars have summarized the history of curve linear design in the United States from the two aspects (e.g., flat and vertical curves), especially the setting of easement curves [18,19]. In terms of traffic safety in adverse weather, scholars obtained basic data on the operation of high-side bus under crosswinds through wind tunnel tests of 1:50 car models and studied the aerodynamic response of crosswinds to trucks [20][21][22]. Scholars also analyzed the relationship between the rain accident rate and the lock brake coefficient. The conclusion showed the nonlinear relationship between the accident rate on wet roads and anti-skid performance [23]. ...
Article
Full-text available
To study the side slip and rollover threshold of large bus in slope–curve section under adverse weather, factors that affect the safety of large buses that run in slope–curve section, such as rain, snow, cross-wind environmental factors, and road geometry, were analyzed to obtain the friction coefficient of the road surface under different rainfall and snowfall intensities through field measurements and to determine the six-component force coefficient of wind that acts on large buses through wind tunnel tests. The force analysis of large bus in slope-curve section was carried out, and the mechanical equations of large bus under the limit conditions of sideslip and rollover in slope-curve section were established. TruckSim simulation test platform was used to establish a three-dimensional road model and large bus mechanical model at a design speed of 100 km/h. Input parameters, such as cross-wind speed and road friction coefficient, simulate the impact of wind-rain/snow coupling. Under the combined action of wind-rain/snow, the operation test of large bus in slope-curve section was carried out, and the key parameters and indicators of the sideslip and rollover of large bus in slope-curve section were outputted and analyzed. The sudden change point of lateral acceleration is the judging condition for sideslip of large bus in slope-curve section under different road friction coefficient (0.2–0.7), changing from 0.15m/s 2 and stabilizing to 0.52 m/s 2 , and a 0N vertical reaction force of the inner tire is the critical judging condition for rollover under road friction coefficient0.8, and the operating speed thresholds were proposed under different road friction coefficient. This study is expected to provide theoretical support for the speed limit of large bus in slope-curve section under adverse weather.
... With developments of the lighter and faster modern railway trains (Suzuki, 2016), crosswinds have emerged as one of the most important factors affecting train safety (Cooper, 1980;Baker, 2009;Zhuang and Lu, 2015). When train speed exceeds 200 km/h and the crosswind speed is greater than 30 m/s, the train is most likely to derail or overturn (Hoppmann et al., 2002;Fujii et al., 1999). ...
Article
Sudden changes in the aerodynamic loads acting on trains can result in derailment or overturning. The impacts of infrastructure scenarios on the aerodynamic performance of trains are significant. When high-speed trains travel from one infrastructure scenario to another one, the aerodynamic loads and flow field will change suddenly. It is a commonly in western China for HSTs to exit a tunnel with crosswinds. In order to investigate the aerodynamic loads and the flow evolution, a three-dimensional, compressible, unsteady Reynolds Averaged Navier-Stokes method was utilized to simulate the process of a train exiting a tunnel under crosswinds. Results show that the flow field and the pressure varied significantly in the horizonal plane while the train exited the tunnel under crosswinds. In addition, the aerodynamic loads of each carriage which varied abruptly resulted in complex dynamic responses of the train including lateral variation, snake-like locomotion, and pitching motion. Furthermore, the variation magnitudes of ΔCside, ΔClift, and ΔCRM for the head carriage were 4.1, 2.2 and 1.6 times for the middle carriage, and 7.9, 8.1 and 8.2 times for the rear carriage. Therefore, the aerodynamic performance of the head carriage was the worst and the risk of accidents was the highest under crosswinds.
... Jeon et al. [10] suppressed the carbody swaying of the Korean high-speed train HEMU-430X at 1-2 Hz by optimising the installation position of the yaw damper. Finally, Baker et al. [11] considered crosswind effects as significant factors causing carbody swaying and evaluated their safety in detail. ...
Article
Full-text available
Carbody chattering is an abnormal vibration that severely deteriorates the ride quality of a railway vehicle. However, systematic studies on the mechanisms and control methods of carbody chattering are inadequate. Hence, in-situ tests, wheel and rail profile tests, modal parameter tests, and root locus analyses were conducted for an electric multiple-unit train to study the carbody chattering mechanism. Results show significant concave wear on wheel treads that have not yet met their wheel-turning mileages. When the vehicle moves from a carbody non-chattering to a chattering section, the wheel–rail contact positions are scattered and jumping is observed; then, the wheel–rail contact conicity increases rapidly, causing the modal damping ratio of the bogie hunting motion to reduce to 0, the bogie to change from stable to critical-unstable state, and bogie hunting motion frequency to increase close to the modal frequency of the carbody diamond-shaped deformation, thereby triggering synchronous movement. This amplifies the modal vibration, causing carbody chattering. Therefore, three control methods are proposed for carbody chattering—turning worn wheels; grinding rail profiles in the carbody chattering section; and synchronous optimisation of the primary longitudinal and lateral positioning stiffness, node stiffness, and damping coefficient of the yaw damper—according to the multi-objective synchronisation optimisation method to improve operational stability and ride quality. Test results show that all three methods effectively control carbody chattering; compared to the original vehicle, the amplitude of carbody chattering acceleration at 10 Hz can be reduced by 90%, 40% and 60% for the three methods.
... However, for cases with large flow separations and vortex shedding, transient simulations that reflect the unsteady nature of turbulence should be adopted. Although the RANS formulation can be used to perform transient simulations, i.e., the unsteady RANS (URANS) simulations, Baker et al. [40] suggest that URANS might smooth the fluctuation caused by vortices as the velocity field is time-averaged. A more accurate approach is the large-eddy simulation (LES), which was originally developed by Smagorinsky [41] to study unsteady atmospheric motions. ...
Article
Full-text available
Engineers, architects, planners and designers must carefully consider the effects of wind in their work. Due to their slender and flexible nature, long-span bridges can often experience vibrations due to the wind, and so the careful analysis of wind effects is paramount. Traditionally, wind tunnel tests have been the preferred method of conducting bridge wind analysis. In recent times, owing to improved computational power, computational fluid dynamics simulations are coming to the fore as viable means of analysing wind effects on bridges. The focus of this paper is on long-span cable-supported bridges. Wind issues in long-span cable-supported bridges can include flutter, vortex-induced vibrations and rain–wind-induced vibrations. This paper presents a state-of-the-art review of research on the use of wind tunnel tests and computational fluid dynamics modelling of these wind issues on long-span bridges.
... Based on the latest study conducted by Soares [29], differential reliability and performance of turbulence models are applied in CFD software to determine the aerodynamic features of vehicle and passenger cars. As for airflow and aerodynamics simulation, three different CFD techniques are employed, Reynolds-Averaged Navier-Stokes (RANS), unsteady RANS (URANS), and Large Eddy Simulation (LES) [30][31][32][33][34][35]. The Reynolds-Averaged Navier-Stokes (RANS) solves time-averaged steady-state Navier-Stokes equations while the unsteady RANS numerically solves unsteady Navier-Stokes equation [36][37][38]. ...
Article
Full-text available
The aerodynamic characteristics of a vehicle play a vital role in steering stability, performance, comfort, and safety of a car. The fuel efficiency of a vehicle is determined by the performance of the internal combustion engine and the aerodynamic design of the body. One of the most important aspects of automobile design is aerodynamic styling. A vehicle with low drag resistance provides advantages in terms of cost and efficiency. This article will review design characteristics and implementation of various specific reference models on drag issues using Computational Fluid Dynamics (CFD) techniques. The benefits and limitations of these models are analysed, and the validity of results in developing guidelines to improve the performance and stability of cars are described. This review paper covers significant studies that utilise the CFD model and simulation on a simplified vehicle model using various turbulence models to generate drag coefficient. Characteristics and impacts of various vehicle design models with and without external factors such as side mirrors and door handles are also discussed. Results obtained from the research focuses on the physics flow structures such as static pressure contours, are presented for the three types of car model geometry. The simplified generic models are more efficient and advocated to apply compared to the specific model geometry based on the result acquired by the latest studies. Simplified generic models are preferred due to their cost-effectiveness, procurement of optimum time, and better simulation effects. Moreover, the study also demonstrates the importance of having a car with suitable turbulence models that are appropriate to be applied for simulations in terms of its applicability, time effectiveness, and cost.
... As for train derailment, considerable works are reported on the derailment for main track rail, which is related to track defects, earthquakes, crosswinds and impacts [25][26][27][28][29][30][31][32][33][34][35]. The authors [36,37] also derived the limit value of wheel flange climbing derailment under the quasi-static condition, which can provide a theoretical basis for simulating dynamic derailment. ...
... As for train derailment, considerable works are reported on the derailment for main track rail, which is related to track defects, earthquakes, crosswinds and impacts [25][26][27][28][29][30][31][32][33][34][35]. The authors [36,37] also derived the limit value of wheel flange climbing derailment under the quasi-static condition, which can provide a theoretical basis for simulating dynamic derailment. ...
Article
Wheel flange climb derailment of vehicles in railway turnouts is a serious safety issue. In particular, derailment accidents in smaller turnouts, caused by poor track alignment before the turnout or structural degradation, are becoming more and more frequent. Most of the previous research on derailment has focused on main track areas, while the dynamic derailment mechanism for turnouts is still not clear. For this reason, a field derailment investigation of freight wagons in No.6 symmetrical turnouts is presented in this paper. Taking this into consideration, a half-car multi-body dynamics model and flexible turnout model, subject to wheel flange climb derailment, has been established. In addition, a field test for wheel-rail interaction was carried out to verify the dynamic model. This model is capable of revealing derailment evolution of the front and rear wheelset for a bogie under critical derailment conditions. The influence of several sensitive parameters of the derailment model on critical derailment behavior has been carried out. Results show that the simulation results of the wheel climb derailment are very consistent with the filed investigation, and the safety of the bogie depends on the status of both front and rear wheelset. This work is a world first in providing a solid understanding of dynamic derailment behavior and motion posture, giving guidance on the prevention of wheel flange derailment in turnout areas.
... As there has been a rapid development in high-speed railway systems in recent decades, the crosswind stability of trains has become a main concern [1][2][3][4]. In order to ensure a high-speed railway track's smoothness, the bridge mileage accounts for a large proportion.. ...
Article
Full-text available
Wind barriers can effectively reduce the risk of overturning and derailment of high-speed trains running on a bridge under crosswind. However, it can adversely affect the wind resistance of the bridge. There are few studies on the aerodynamic performance of curved wind barriers. In this paper, the effects of curved wind barriers with four curvatures (0, 0.2, 0.35, and 0.50) and different train-bridge combinations on the crosswind aerodynamic characteristics of a train-bridge system are investigated. The results show that the curved wind barrier can significantly reduce the wind speed below a certain height on the bridge deck. The curved wind barrier with small curvature can better reduce the aerodynamic force of the train; however, it greatly increases the aerodynamic force of the bridge. A wind barrier with a curvature of 0.35 is recommended because it takes into account the aerodynamic characteristics of the train and bridge at the same time. The porosity of a wind barrier greatly influences the aerodynamic performance of the train on the track of the windward side of the bridge, while the wind barrier has little effects on the train on the track of the leeward side of the bridge. The aerodynamic performance of the train on the track of the windward side of the bridge is less affected by whether or not a train on the track of the leeward side of the bridge is present.
... This is especially important in coastal areas with extreme weather conditions [2][3][4]. Vehicles with a higher center of gravity are more likely to roll over when there are strong crosswinds over a bridge [5,6], and the safety of vehicles passing over bridges is important [7,8]. ...
Article
Full-text available
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.
... When it comes to high speed vehicles, efforts to increase negative lift or downforce and thus the road holding capability of the vehicle are well documented [17]. Some work on identifying and stabilizing the dynamic states of a vehicle under crosswinds is also done, especially on bigger vehicles, such as buses and articulated heavy vehicles [18]. Recently, attempts have been made in accurate and robust mathematical modelling of the aerodynamic forces and coefficients to fit into full scale simulations [19][20]. ...
Conference Paper
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Under high speed and high lateral acceleration (i.e., high g) cornering maneuvers, the lateral tire-road forces are saturated, and the vehicle will lose its lateral stability. In order to increase the safety of road vehicles, various active safety systems have been proposed and developed. These active safety systems include active front/rear steering, torque vectoring, differential braking, active camber control, active roll moment control, etc. Essentially, all these active safety systems are manipulating the longitudinal/lateral forces and aligning torques at the contact patches of tire/road to improve the yaw and roll stability of road vehicles. With a given road condition and vehicle payload, the longitudinal/lateral forces and aligning torques due to the interfaces of tire/road are limited. A lot of severe road vehicle accidents frequently occur under cornering maneuvers at high speeds. Aerodynamic drag and downforce or lift increase significantly with vehicle speed. It is indicated that active aerodynamic control is effective for enhancing the lateral stability of high-speed vehicles. However, little attention has been paid to this research topic. This paper is intended to review the investigations conducted in the last two decades. It is seen that interesting vehicle aerodynamic control studies have been conducted, and numerous open problems need to be addressed.
... There are different external factors in the operation process of the HST, which will form different load boundaries when they are transformed into specific structures, thus changing the characteristics of the stress spectrum. These variables come from both the environment of the railway system [19] and train-operation modes [20]. Different geographical environments will directly affect the operation status of an HST, such as tunnels of the line [21,22] and natural winds [23,24]. ...
Article
Dynamic load histories of vulnerable fatigue sites in structures are of paramount importance for safety design, and such load–time histories with long duration are usually lumped together to a load spectrum for safety assessment. In this paper, long-term field tests involving several operation variables, including track types, operation speeds, passenger lines, trains and their in-service time, were carried out to obtain stress–time histories of the bogie frame of high-speed trains. By comparing the stress spectra from different operation conditions, we identified the correlation between operation variables and the characteristics of stress spectra. It was found that both track type and operation speed play a prominent role in the magnitudes of stress spectra. Combined with the segmented Weibull model, we quantified the impact of operation variables on damage and confirmed that the inflection stress in the segmented Weibull model can be used as a measure of track status. The results revealed in this report could help obtain a systematic understanding of the fatigue performance of structures of complex dynamic systems like high-speed trains.
... The effects of crosswind on traffic and transportation are severe worldwide, and many accidents, including road and railway vehicle accidents, occur due to the impact of crosswind conditions every year (Baker et al., 2009). Therefore, studies on train aerodynamics under crosswind conditions have been conducted (Baker et al., 2004;Chen et al., 2018;Liu et al., 2018;Zhang et al., 2018). ...
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To reduce the impact of a mountain ridge on the crosswind flow field of a specific section of the Lanzhou-Xinjiang high-speed railway, a portion of the mountain ridge was removed to increase the distance from the windbreak. To verify the effects of this flow optimization measure, the wind speed and wind angle were tested in this mountain ridge region. In this paper, under the actual conditions of this specific case study, the average and transient wind characteristics were analyzed based on the test results. Then, based on the actual terrain model, using the computational fluid dynamics (CFD) method with two inlet boundary conditions, namely, constant wind and exponential wind, the results obtained from the two boundary conditions were validated. Furthermore, the visualized flow structures and wind speed distributions along the railway under both boundary conditions were compared. Finally, along the railway, the impacts of different terrain types on the flow field of the railway were compared.
... To achieve higher speeds, the car bodies of high-speed trains are constructed using light materials, and thus, they are easily influenced by crosswinds. Train overturning accidents due to strong winds are reported every year all over the world (Baker et al., 2009). Therefore, train aerodynamic performances under wind environments have been studied by many researchers using full-scale tests, wind tunnel tests, and various numerical simulation methods (Baker, 2002;Baker et al., 2004;Zhang et al., 2011Zhang et al., , 2018Gallagher et al., 2018). ...
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... There is a plethora of methods and models to estimate the risks due to railway asset failures, as well as the costs and effects on rail service due to failures and interventions. For example, [1][2][3][4][5][6][7][8][9][10][11][12] analyze the risk related to railways due to specific hazards. Many scholars have focused on the analysis of risk related to specific failure modes of the railway assets, e.g., [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. ...
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Railway managers identify and prioritize assets for risk-reducing interventions. This requires the estimation of risks due to failures, as well as the estimation of costs and effects due to interventions. This, in turn, requires the estimation of values of numerous input variables. As there is uncertainty related to the initial input estimates, there is uncertainty in the output, i.e., assets to be prioritized for risk-reducing interventions. Consequently, managers are confronted with two questions: Do the uncertainties in inputs cause significant uncertainty in the output? If so, where should efforts be concentrated to quantify them? This paper discusses the identification of input uncertainties that are likely to affect railway asset prioritization for risk-reducing interventions. Once the track sections, switches and bridges of a part of the Irish railway network were prioritized using best estimates of inputs, they were again prioritized using: (1) reasonably low and high estimates, and (2) Monte Carlo sampling from skewed normal distributions, where the low and high estimates encompass the 95% confidence interval. The results show that only uncertainty in a few inputs influences the prioritization of the assets for risk-reducing interventions. Reliable prioritization of assets can be achieved by quantifying the uncertainties in these particular inputs.
... In our future study, we will analyze the control performance along with various Nussbaum-type functions and extend the filter-based approximation approach to the event-triggered control of network systems. Additionally, the potential application of the proposed controller includes vehicle vibration control in the stochastic wind field [47] and the traction power collector system subjected to unknown irregularities [48]. ...
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... e wind-induced traffic accidents of road vehicles are a common occurrence, frequently reported around the world [1][2][3][4]. A postdisaster investigation indicates that the flow pressure and the aerodynamic loads acting on vehicles are the main cause of wind-induced traffic accidents. ...
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... However, crosswinds can cause serious shake and even a risk of overturning. Related accidents have been reported in different countries (Baker et al., 2009;Liu et al., 2015). As a result, there have been many studies of the aerodynamic performance of trains under crosswinds, e.g. by Baker (2013); Chen et al. (2019a); Gallagher et al. (2018); Guo et al. (2019); Guo et al. (2020); Hemida and Krajnovi c (2010); Krajnovic et al., (2012); Muñoz-Paniagua and García (2019). ...
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Wind tunnel tests and the improved delayed detached eddy simulation (IDDES) were carried out to study the aerodynamic characteristics of a train with a wind barrier in different lengths. The results were obtained at 20° and 30° yaw angles, which are the highest realistic values for high-speed trains. The rationality of the experiment was assessed according to standards, based on which the accuracy of numerical simulations was validated. After the validation, further cases that were difficult to conduct in wind tunnel experiments were simulated to explore how the barrier length affects the train aerodynamics. Results show that the length of the wind barrier has an obvious influence on the head car other than the tail car. As the length of the wind barrier increases, the lift force of the head car decreases, while the lateral force increases, and the drag force approaches to 0. The lateral and drag forces of the head car do not change significantly when the wind barrier length was longer than 66.49H at a 20° yaw angle and 40.54H at a 30° yaw angle.
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To reduce the crosswind effect on high-speed trains, in this paper, by using the Improved Delayed Detached Eddy Simulation (IDDES) method and the SST (Formula presented.) turbulence model, a novel blowing measure is studied and compared by considering different positions of blowing slots on the train surface. The concerned blowing positions on the train surface include the top position (Top); windward side (WWS): the upper position (WU), middle position (WM), and lower position (WL); and leeward side (LWS): the upper position (LU), middle position (LM), and lower position (LL). The results show that in regard to the rolling moment coefficient around the leeward rail, CMxlee, the mitigation effect with LM for the head car is the largest, and the mitigation effect with WL for the middle car and tail car is superior to other cases. The corresponding drop percentages are 18.5%, 21.7%, and 30.8% for the head car, middle car, and tail car, respectively. The flow structures indicate that the blowing positions on the lower half of WWS and upper half of LWS would form a protective air gap to weaken the impact of coming flows and delay the vortex separation on LWS, and thus the train aerodynamic performance is improved. © 2022 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
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Chapter
The development of efficient weigh-in-motion and wheel defect detection methods with high accuracy estimation procedures from track measurements is one of the major subjects that draw the attention of both the railway industry and scientific researchers. This information triggers a warning in the administration system when a train is overloaded or operating under abnormal conditions. The main novel aspect of this study is to define a methodology to obtain weigh the train in motion and allows the identification of a wheel flat using a wayside monitoring system. To achieve this, two approaches were proposed to obtain an estimation of the wheel static load as well as distinguish the healthy wheel from the defective one in order to allow the system to activate the necessary alerts. A wide range of numerical simulations based on a train-track interaction model has been performed for different train speeds. From the obtained results, it is evident that the proposed approaches are capable tools and cost-effective methods to estimate the wheel static load as well as an abnormal condition of rolling stock.
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Chapter
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Chapter
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Wind tunnel tests have been widely applied in aerodynamic investigations owing to their unique advantages. However, it is difficult to theoretically establish a simplified symmetry or two-dimensional model because of the relative motion of the structures and proximity of the train to the ground/infrastructure. Additionally, railway-related aerodynamic problems tend to be more challenging than those encountered in other engineering structures. Moreover, transient and crosswind effects, as well as complex operation environments, need to be considered, thereby making aerodynamic analyses of train–bridge systems challenging. Advanced manufacturing methodologies can reproduce realistic scenarios of high-speed train (HST) operations in a wind tunnel. The development of a controllable and affordable experimental method presents considerable research opportunities and challenges. There exists a strong correlation between wind tunnel experimental methods and the understanding of aerodynamic mechanisms, and some wind tunnel tests are dedicated to identifying the aerodynamic behavior using specific test systems. This study mainly describes the types of tests typically performed in a wind tunnel to analyze the aerodynamic issues of train–bridge systems under wind action. To identify and understand the individual role of the above mentioned-correlated systems, trains and bridges in wind tunnel tests are described separately. High-speed trains on bridges must be made safe and environmentally friendly, and a few cases are presented as indications to reconsider our aerodynamic research priorities. Thus, advanced experimental activities have been proposed in the Central South University (CSU) wind tunnel, representing helpful practices in defining the real-world aerodynamic behavior of wind-vehicle-bridge systems.
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The Lanzhou-Xinjiang High-speed Railway runs through a region of over 500[Formula: see text]km that is amenable to frequent winds. The strong wind and rainfall pose a great threat to the safe operation of high-speed trains. To tackle the aforementioned climate challenges, this paper investigates the dynamic response of the high-speed train-track-bridge coupling system under the simultaneous action of winds and rains for the safe operation of trains. Specifically, there are four main objectives: (1) to develop a finite element model to analyze the dynamic response of the train-track-bridge system in windy and raining conditions; (2) to investigate the aerodynamic loads posed to the train-track-bridge system by winds and rains; (3) to evaluate the effects of wind speed and rainfall intensity on the train-track-bridge system; and (4) to assess the safety of trains at different train speeds and under various wind-rain conditions. To this end, this paper first establishes a train-track-bridge model via ANSYS and SIMPACK co-simulation and the aerodynamics models of the high-speed train and bridge through FLUENT to form a safety analysis system for high-speed trains running on the bridge under the wind-rain conditions. Then, the response of the train-track-bridge system under different wind speeds and rainfall intensities is studied. The results show that the effects of winds and rains are coupled. The rule of variation for the train dynamic response with respect to various wind and rain conditions is established, with practical suggestions provided for control of the safe operation of high-speed trains.
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In this study, the influences of wind barriers on the aerodynamic characteristics of trains (e.g. a CRH2 train) on a highway-railway one-story bridge were investigated by using wind pressure measurement tests, and a reduction factor of overturning moment coefficients was analyzed for trains under wind barriers. Subsequently, based on a joint simulation employing SIMPACK and ANSYS, a wind–train–track–bridge system coupled vibration model was established, and the safety and comfort indexes of trains on the bridge were studied under different wind barrier parameters. The results show that the mean wind pressures and fluctuating wind pressures on the trains’ surface decrease generally if wind barriers are used. As a result, the dynamic responses of the trains also decrease in the whole process of crossing the bridge. Of particular note, the rate of the wheel load reductions and lateral wheel-axle forces can change from unsafe states to relative safe states due to the wind barriers. The influence of the porosity of the wind barriers on the mean wind pressures and fluctuating wind pressures on the windward sides and near the top corner surfaces of the trains are significantly greater than the influence from the height of the wind barriers. Within a certain range, decreasing the wind barrier porosities and increasing the wind barrier heights will significantly reduce the safety and comfort index values of trains on the bridge. It is found that when the porosity of the wind barrier is 40%, the optimal height of the wind barrier is determined as approximately 3.5[Formula: see text]m. At this height, the trains on the bridges are safer and run more smoothly and comfortably. Besides, through the dynamic response analysis of the wind–train–track–bridge system, it is found that the installation of wind barriers in cases with high wind speeds (30[Formula: see text]m/s) may have an adverse effect on the vertical vibration of the train–track–bridge system.
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Unsteady aerodynamic loads have a significant influence on the running safety of a train in crosswinds. Full-scale tests were carried out to measure the pressure on a fast streamlined train in crosswinds, and the unsteady aerodynamic loads were obtained by the discrete integration of the pressure to assess the influence of different crosswinds on the loads. The maximum wind speed was 34.0 m/s in the full-scale tests, and the maximum turbulence intensity was 0.202. The means and fluctuations of the side force coefficient, lift coefficient, and rolling moment coefficient around the lee rail at different yaw angles were studied. The means first increased and then decreased with the increase in the yaw angle, and the maximum values occurred in the range of 54.5◦–59.6◦. The coefficients of variation of the aerodynamic load coefficients were approximately twice the turbulence intensity, which indicated that the fluctuations of the aerodynamic load coefficients were due to the oscillations of the wind speed. For the frequency characteristics of the aerodynamic load coefficients, the most dominant frequencies were at Strouhal numbers of 0–0.4.
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The aim of the present study consists of evaluating the influence of the most relevant geometric, mechanical and aerodynamic vehicle properties in the risk of derailment caused by crosswinds. To achieve this objective, a vehicle-structure interaction model is used to carry out non-linear dynamic analyses to assess the train-track coupling behaviour in the presence of winds. By computing the wheel-rail contact forces, the derailment risk is evaluated based on the unloading criterion, as suggested by the European Norm EN 14067-6 (2016), for several scenarios with different train and wind speeds. The wind is simulated with a stochastic model that allows the generation of turbulent wind time-histories based on power spectral density functions. The reference vehicle adopted in this work corresponds to the European InterCity Express 3 (ICE-3) train, whose original properties were parameterized in order to evaluate their influence in the vehicle's stability. The parametric study focused on several properties of the vehicle, namely the carbody mass, height of the gravity centre, aerodynamic coefficients, and stiffness and damping of the suspensions. Apart from the suspensions' properties, which prove to have a negligible influence in the vehicle's stability, the remaining parameters have a significant impact in the running safety against crosswinds.
Conference Paper
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This paper describes a new methodology to perform the cross wind risk analysis on railway lines. This study consists in the evaluation of the probability of rail vehicle's overturning when it is running on a railway line under the action of cross wind. According to the new methodology described in this paper, the cross wind risk analysis is based on a meteo study and on a stochastic approach. The former provides the probability of occurrence of wind gusts on the specific site on the line while the latter leads to the evaluation of the Characteristics Wind Curve (CWC) probability distribution. The probability of vehicle's overturning is calculated as the combined probability of the wind gust velocity occurrence and of the overcoming of the safety limit adopted for the definition of the CWC. Some preliminary results of the application of this new methodology to the Rome-Naples high speed railway line are also reported.
Article
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Abstract In order to address the issue of train overturning due to cross winds, the study proposes a robust,method,for the integration of turbulent cross,wind,forces,into train dynamic calculations. The unsteady,forces are determined,through,the concept,of aerodynamic weighting function from experimental,data of aerodynamic,admittance. For constant and sudden winds, the risk of overturning is investigated for a matrix of three mean cross wind and vehicle speeds, and two values of track twist. Limitations on large time scales cause the weighting function to filter out the turbulent fluctuations, making the derailment ratios to be dominated,by the transient behaviour of the steady cross wind forces. It is found that a track with cant deficiency presents a higher risk of overturning than one with cant excess. Higher mean,wind and vehicle speeds,generally increase therisk of overturning. For the derailment mechanism, roll over is more likely to occur than flange climbing, and is also more sensitive to the mean,wind speed. The effects of sudden cross winds on derailment are more,significant compared,with constant cross winds.
Article
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This paper describes the numerical investigations carried out by LSTM within the TRANSAERO project [1] to estimate side wind effects on a typical high-speed train. Air flow around a detailed geometry of the German InterRegio train was simulated by solving numerically the Reynolds-averaged Navier-Stokes equations, combined with the k — e turbulence model in three dimensions. Finite volume discretization was used to obtain the flow field around the train under different wind conditions and Reynolds numbers up to 1.063 x 108. The investigation was extended beyond the study of the flow characteristics to examine new concepts for protecting the trains from side wind. For this purpose, numerical simulation of the flow around a train travelling on an embankment behind a solid noise barrier was carried out. Detailed analysis of the results showed that noise barriers are effective means in reducing side wind induced forces and moments.
Conference Paper
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The development of a new concept of wind alarm systems for road and rail transportation is presented. The alarm is funded on a risk assessment approach, taking into account wind modelling and prediction, aerodynamic forces, vehicle dynamics.
Conference Paper
Incidents with heavy vehicles have brought the issue of directional stability of buses under the influence of crosswind gusts into focus. In this work the directional stability of buses when expose ...
Article
Experience in various parts of the world has shown that trains may overturn in very high winds. The aerodynamic forces on trains in cross-winds and other factors affecting overturning are discussed. A procedure for estimating the probability of overturning per year for fleet operation of trains over a particular route is described. Most of the probability is predicted to come from a small length of track on embankments in coastal locations or in hilly country. The computation is very sensitive to errors in the parameters that describe the exposure of the sites, so the value of the total probability is only approximate.
Article
JR East has in place a strong wind operation rule to prevent the occurrence of derailment or rollover of trains by strong wind. The rule mandates the Issuance of a 30-minute operation restriction order when strong wind Is observed. The uniform 30-minute operation restriction order continues to be In effect even when the strong wind Is no longer observed. In this respect, the operation rule is not necessarily rational. To tackle the issue, we are developing a strong wind warning system for issuing operation restriction orders. The system uses statistical deduction to predict future wine velocity from time series data of the wind velocity observed.
Chapter
Full scale tests with sidewind were performed on a German High Speed track using an unpowered InterRegio end car. The vehicle was equipped with load measuring wheelsets which allowed to measure the rolling moment of the car in different wind scenarios. The wind data was collected with an on board wind measuring device and the results were cross checked using anemometers mounted near the track. The track lies on an 8 m high embankment and is partly equipped with solid noise barriers and wind fences. Very high wind speeds beyond 15 m/s are extremely rare, in this sense the underlying tests were very “lucky”, because one was able to collect several data points of high quality up to approximately 13 m/s. The results are expressed as aerodynamic coefficients and could be compared both with wind tunnel data and results from numerical calculation. Although the scatter of the data coming from full scale tests naturally show a larger degree of scatter, the agreement between experiment and simulation is very good.The presence of solid walls and porous wind fences located near the track reduces the wind loads on the vehicle significantly.
Article
The problem of deriving approximations for multinormal integrals is examined using results of asymptotic analysis. The boundary of the integration domain given by g(x) = 0 is simplified by replacing g(x) by its Taylor expansion at the points on the boundary with minimal distance to the origin. Two approximations which are obtained by using a linear or quadratic Taylor expansion are compared. It is shown that, applying a quadratic Taylor expansion, an asymptotic approximation for multinormal integrals can be obtained, whereas using linear approximations large relative errors may occur.
Article
A computational model is a representation of some physical or other system of interest, first expressed mathematically and then implemented in the form of a computer program; it may be viewed as a function of inputs that, when evaluated, produces outputs. Motivation for this article comes from computational models that are deterministic, complicated enough to make classical mathematical analysis impractical and that have a moderate-to-large number of inputs. The problem of designing computational experiments to determine which inputs have important effects on an output is considered. The proposed experimental plans are composed of individually randomized one-factor-at-a-time designs, and data analysis is based on the resulting random sample of observed elementary effects, those changes in an output due solely to changes in a particular input. Advantages of this approach include a lack of reliance on assumptions of relative sparsity of important inputs, monotonicity of outputs with respect to inputs, or ad...
Article
when the power spectra and the cross spectra of wind fluctuations at many points are specified, the simulations of wind fluctuations are carried out by Lie method presented by Akeikc (1972). The method k makes ase of the multldimensiolal auteregregressive processes, Typical examples con-sidered here are the simulation of simear flow in the vertical direction in the almospheric boundary layer and tile simulation of two-dunensional homeogencons flow atamany points along the horizonial straight line perpendicular to the mean wind direction. The experimertal euuarions given by Davenport (1961), Hine (1971), Shirotani and Iwaiani (1971, 1979) and Iwatoni (1977) are adopted as the present medels of the shenn flow and the homogenecus flow. It is confirmed that both the power spectra and the crese spectra (coherence and phase) of the simu ated wind fluctuations are in very good agreement with the specitied ones as the models and that the frequency distributions of the similated wind fluclaations oecome the Caussiar. It is possible to make use of the simulated ones for practical applic atens. The programs for the above sinulations are listed to FORTRAN language.
Article
Aerodynamic loads on railway vehicles under cross winds are governed both by the shapes of the vehicles and of the surroundings. Apart from the inertial loads due to accelerations acting on the vehicle, aerodynamic loads due to cross winds are of paramount importance in the lateral equilibrium of the vehicle, in such a way that if the lateral wind speed becomes larger than a threshold value, overturning of the vehicle can take place. The degree of danger of overturning increases when the train is on a bridge, the reason being that the velocity in the atmospheric boundary layer grows as the height increases, leaving aside the fact that at ground level there may be other elements acting as windbreaks (mainly vegetation). The effects of different types of solid parapets on the side force and rolling moment acting on a 1/70 scale two-dimensional model of a typical high-speed train vehicle have been measured by wind-tunnel tests, both when the vehicle is placed on a bridge and when it is on ground. Experimental results show that, as one could expect, aerodynamic loads decrease as the height of the windbreak increases, and that solid parapets seem to be more effective on bridges than on ground.
Article
One major drawback of the eddy viscosity subgrid‐scale stress models used in large‐eddy simulations is their inability to represent correctly with a single universal constant different turbulent fields in rotating or sheared flows, near solid walls, or in transitional regimes. In the present work a new eddy viscosity model is presented which alleviates many of these drawbacks. The model coefficient is computed dynamically as the calculation progresses rather than input a priori. The model is based on an algebraic identity between the subgrid‐scale stresses at two different filtered levels and the resolved turbulent stresses. The subgrid‐scale stresses obtained using the proposed model vanish in laminar flow and at a solid boundary, and have the correct asymptotic behavior in the near‐wall region of a turbulent boundary layer. The results of large‐eddy simulations of transitional and turbulent channel flow that use the proposed model are in good agreement with the direct simulation data.
Article
This paper presents a framework for simulating railway vehicle and track interaction in cross-wind. Each 4-axle vehicle in a train is modeled by a 27-degree-of-freedom dynamic system. Two parallel rails of a track are modeled as two continuous beams supported by a discrete-elastic foundation of three layers with sleepers and ballasts included. The vehicle subsystem and the track subsystem are coupled through contacts between wheels and rails based on contact theory. Vertical and lateral rail irregularities simulated using an inverse Fourier transform are also taken into consideration. The simulation of steady and unsteady aerodynamic forces on a moving railway vehicle in cross-wind is then discussed in the time domain. The Hilber–Hughes–Taylor α-method is employed to solve the nonlinear equations of motion of coupled vehicle and track systems in cross-wind. The proposed framework is finally applied to a railway vehicle running on a straight track substructure in cross-wind. The safety and comfort performance of the moving vehicle in cross-wind are discussed. The results demonstrate that the proposed framework and the associated computer program can be used to investigate interaction problems of railway vehicles with track in cross-wind.
Article
Since train vehicle accidents caused by strong winds sometimes occur in Japan, Japan railway companies requested the Railway Technical Research Institute to promote research and development of preventive measures. To respond to this request, we have investigated aerodynamic forces acting on train vehicles and characteristics of strong winds and proposed several software and hardware preventive measures. This report presents the results of our investigation and the measures adopted in Japan Railway lines.
Article
This work presents aerodynamic results of crosswind stability obtained numerically and experimentally for the leading control unit (class 808) of Deutsche Bahn AG's high-speed train Inter-CityExpress 2. The train model is on top of a 6m high embankment in accordance with the proposed European code for interoperable trains, the so-called technical specifications for interoperability. The purpose of the study is to convey the predictive accuracy that typical steady-state computational fluid dynamics-Reynolds average Navier-Stokes methods (industry standard) return and to contribute to the understanding of the aerodynamics for the current application. Attention is drawn to the aerodynamics around the train and embankment when subjected to a steady block profile crosswind of 30° yaw angle on the basis of the onset velocity far upstream the embankment. The Re (Reynolds number) of the embankment cases is 4.6 × 10 ⁶ . Calculated results are obtained with the commercial code STAR-CD, with exclusively hexahedral meshes with a total cell count of 13.5 × 10 ⁶ . Results are obtained when the train stands on the windward and leeward tracks on top of the embankment. These results are first compared with a flat ground case from a previous study. Then experimental data are obtained in a high-pressure wind tunnel with a model scale of 1:100. Re effects are compensated by raising the ambient pressure by a factor of 60, which increases the air density and thus the Re by a similar factor. Calculated results are in fair agreement with the experiments, where both the calculations and the experiments predict the leeward case to be the more critical one. In addition, the related consequences on the mechanical behaviour, i.e. the stability of the car, are briefly addressed by means of a quasi-static mechanical analysis. The results of the present study indicate that the 6m high embankment concerning the current train reduces the permissible crosswind speed with approximately 20 per cent.
Article
A new approach to modelling the stability of trains in high cross winds is suggested. A train journey is simulated along a length of track subject to the passing of a fictitious storm. Four distinct components of the model are developed to achieve this: 1. Spatially correlated time histories of wind velocities for a number of points along the track are simulated. 2. Wind velocity time histories are combined with data from full-scale aerodynamic measurements in order to obtain wind-induced forces and train displacements. 3. The predicted rolling moment is then compared with the restoring moment due to the weight of the train in order to assess train stability. 4. A Monte Carlo simulation is used to in order to establish the probability of trains overturning against various trains speeds for one particular type of storm. It is suggested that this new approach has the potential to provide an insight into the complex issue of train overturning in cross winds.
Article
The results of full-scale and wind tunnel experiments to measure the cross wind time averaged and unsteady forces and moments on trains are presented. The results demonstrate good agreement between the two sets of experiments but also illustrate the need for care in simulating local roughness effects in the wind tunnel simulation. It is also shown that quasi-steady effects need to be taken into account when calculating force and moment aerodynamic admittances. (C) 2004 Published by Elsevier Ltd.
Article
The paper presents some of the experimental result that have been obtained during an extensive investigation of the behaviour of urban trees in high winds. In particular, results are presented of tests to determine tree mechanical and aerodynamic parameters. The mechanical properties that were measured (stiffness, natural frequency, and damping) were obtained from tree winching ans quick release experiments. It was fouind that, for the small number of specimens tested, the stiffness of each specimen did not vary greatly through the year, but the magnitudes of natural frequencies and damping ratios were dependent upon whether or not the tree was in leaf. For a tree in leaf the natural frequency was lower and the damping higher than when not in leaf. Measurements of tree deflection in the wind (for a semi-mature plane tree) enabled further estimates of natural frequency and damping ratio to be made, and also enabled drag coefficient values to be measured. It was shown that these coefficients are substantially greater when the tree is leaf, than when it is not in leaf. These experiments did not lend support to the hypothesis that tree drag is proportional to velocity, rather than (velocity)2, as has been previously suggested.
Article
In periods of high wind three types of wind-induced vehicle accidents can be expected to occur: 1.(1) overtuning accidents,2.(2) sideslip accidents,3.(3) rotation accidents,This paper sets out a general analysis which throws some light on these types of accident and their interrelation. Simplifying assumptions have to be made for the problem to be tractable and these are discussed in some detail. For the Leyland Atlantean bus it is shown that overturning accidents are much more likely to occur than the other types of accident.
Article
Measures at present in use in the U.K. to control vehicle movement at exposed sites during windy periods are rather arbitrary and ill defined. This note presents rational methods for such traffic control based on an analytical model developed by the author. A “two level” system of control is proposed with high sided vehicle speed being restricted to 10 m s−1 at a wind gust speed of 17.5 m s−1 and vehicle movement being stopped completely at a windgust speed of 22.5 m s−1. The analytical model suggests that no account should be taken of wind direction, and also shows that the inter-relation between accident wind speed and vehicle speed and wind direction is far from being straightforward.
Article
A computational model is a representation of some physical or other system of interest, first expressed mathematically and then implemented in the form of a computer program; it may be viewed as a function of inputs that, when evaluated, produces outputs. Motivation for this article comes from computational models that are deterministic, complicated enough to make classical mathematical analysis impractical and that have a moderate-to-large number of inputs. The problem of designing computational experiments to determine which inputs have important effects on an output is considered. The proposed experimental plans are composed of individually randomized one-factor-at-a-time designs, and data analysis is based on the resulting random sample of observed elementary effects, those changes in an output due solely to changes in a particular input. Advantages of this approach include a lack of reliance on assumptions of relative sparsity of important inputs, monotonicity of outputs with respect to inputs, or adequacy of a low-order polynomial as an approximation to the computational model.
Article
This paper describes the methodology for safety assessment related to the risk of a train overturning in strong cross-winds. As an example, this methodology is applied on the high-speed line Botniabanan being built for a maximum speed of 250 km/h in the northeast coastal region of Sweden. The process starts with a systematic identification of locations along the line having a potential high risk of overturning due to cross-winds. This is followed by a cross-disciplinary study. The first step is to estimate the probabilities of wind velocity and wind directions. The next step is aerodynamic computation of overturning forces and moments acting on relevant types of train. Further, the critical overturning wind velocity is determined by a multi-body simulation technique. Finally, the overturning accident frequency is calculated. The calculated risk is compared with generally accepted risk levels in modern train operation.
Article
Increasing train speeds combined with the predicted reduction in the weight of new trains ensure that the effect of crosswinds on train stability is of continued interest to the rail industry. Changes in the approaching wind velocity can in turn lead to changes in both the lift and side force on a vehicle. Calculations of the wind induced force can either be undertaken in the frequency domain with knowledge of aerodynamic admittance characteristics or in the time domain using aerodynamic weighting functions. This paper investigates the applicability of developing a universal aerodynamic admittance function and a corresponding analytical weighting function for a variety of train types based on a range of experimental data. It is suggested that only two variables are required to parameterise both the admittance and weighting functions. It is also argued that for certain train types one of these variables can be considered as a constant across a wide range of yaw angles.
Article
The current UK standard for the determination of wind loads on temporary road signs is generally perceived by the industry to be unrealistic. To enable a rational revision of the standard to take place full scale data have been collected on the wind induced force acting on a representative range of 750mm road signs, 1500mm road signs and a pedestrian barrier. These have been expressed as non-dimensional coefficients of force based on sign area and wind speed. Sign shape appears to have no significant effect on the magnitude of the wind force coefficient but the inclusion of a mounting frame around a sign does increase its susceptibility to wind induced forces. Nominal sign size (750 or 1500mm) appears to have some effect on the overall force coefficient, with larger signs experiencing more severe wind forces. This effect may be partly due to the proximity of the 750mm signs to the ground. Spectral analysis of the sign response shows a general agreement with wind tunnel data for flat plates with, however, increased response in the reduced frequencies range 0.1–1. This is perhaps due to the asymmetry of full scale turbulent eddies near to the ground. The results presented form part of a wider study, which included the wind and vehicle induced effects on flat plates in the atmospheric boundary layer.
Article
This paper presents an extension of an earlier theory developed by the author to describe the behaviour of vehicles in high cross winds, and applied it to the investigation of the behaviour of high-sided road vehicles. A parametric investigation of accident risk is carried out which identifies those parameters which most affect the likelihood of wind-induced accidents, and which thus suggests areas in which research effort should be concentrated. In addition, the complex problem of driver-vehicle interaction in high cross winds is considered.
Article
This paper examines the wind induced forces and moments experienced by a high sided lorry. Full-scale measurements are combined with wind tunnel and CFD simulations in order to gain an insight into the flow field around the vehicle. Differences and similarities between the three techniques are noted. It is shown that the rolling moment coefficient obtained from full-scale measurements and CFD simulations agree consistently across a wide range of yaw angles. With respect to the side force coefficient, good agreement between the wind tunnel and full-scale data are achieved. Pressure distributions over selected sections of the lorry reveal that despite good agreement with the overall forces, the localised pressure field can be significantly different.
Article
Aerodynamic properties of high-sided coaches with various body shapes were investigated in order to improve directional stability. The idea was to find out whether it would be possible, from an aerodynamic point of view, to suggest an optimal coach body design. The subject has previously been paid little attention in the scientific literature. The fact that during the last few years at least 10 wind-related coach crashes have occurred in Sweden indicates that here a serious problem exists and that cross-wind effects should be carefully considered by coach designers. The observations made in the present study suggest that it should be possible to find an ideal coach body shape. The ideal shape of the coach includes a rounded front face, rounded top sides and sharp rear corners.
Article
The cross wind risk analysis is today, within the European railway operators, one of the most important items related to the safety problem. In order to define the risk associated with the cross wind along a railway line, the effect of the infrastructure scenario on the aerodynamic loads acting on a vehicle have to be investigated. A typical railway line is mainly characterized by two main types of scenario: viaduct and embankment. In this work, the aerodynamic coefficients of the ETR500 train, measured through wind tunnel tests, for the standard TSI infrastructure scenarios (flat ground with and without ballast and rail and 6 m-high embankment) and for a typical Italian viaduct are presented. Moreover, each infrastructure is characterized in terms of flow modification with and without train. A comparison between the experimental results obtained with the different scenarios allows to point out the effects of the infrastructure on the aerodynamic loads.
Article
The aerodynamic characteristics of train/vehicles under cross winds depend on not only the shapes of the vehicles but also those of infrastructures. Accordingly three kinds of wind tunnel tests were made to evaluate the aerodynamic characteristics of typical configurations of the vehicles on typical configurations of infrastructures such as bridges and embankments.The main results obtained from the wind tunnel tests are summarized below.1.The aerodynamic side force coefficient of the vehicle increases more as the thickness of the bridge girder becomes larger. It also increases more as the roof of the vehicle becomes edgier.2.The aerodynamic characteristics of the vehicle on the embankment depend on the distribution of the boundary layer on the ground. The aerodynamic side force coefficient of the vehicle on a high embankment is larger than that on a low embankment.
Article
Sensitivity analysis (SA) is an important procedure in engineering design to obtain valuable information about the model behavior to guide a design process. For design under uncertainty, probabilistic sensitivity analysis (PSA) methods have been developed to provide insight into the probabilistic behavior of a model. In this paper, the goals of PSA at different design stages are investigated. In the prior-design stage, PSA can be utilized to identify those probabilistically non-significant variables and reduce the dimension of a random design space. It can reduce the computational cost associated with uncertainty assessment without much sacrifice on the optimum solution. For post-design analysis, probabilistic sensitivity analysis can be used to identify where to spend design resources for the largest potential improvement of a performance. Based on the interested distribution range of a random response, the PSA methods can be categorized into two types: the global response probabilistic sensitivity analysis (GRPSA) and the regional response probabilistic sensitivity analysis (RRPSA). Four widely-used PSA methods: Sobol' indices, Wu's sensitivity coefficients, the MPP based sensitivity coefficients, and the Kullback-Leibler entropy based method are selected for comparison. The merits behind each method are reviewed in details. Their advantages, limitations, and applicability are investigated. Their effectiveness and applicability under different design scenarios are compared in two numerical examples and two engineering design problems.
Book
T his book is currently in its Second Edition, released March 2001, and comes with a customized software package on CD-ROM; Xtremes 3.0. The version included with the book is the Academic Edition, which does not allow for as many rows of data as the professional version, and does not provide the server, which exports estimators, data generation routines and plotting facilities for use by other packages. The professional version of the software must be purchased separately. The book is in paperback, and runs to 462 pages. It is currently available for £39. The textbook itself constitutes a compendium of Extreme Value Analysis as an area of Applied Statistics. It is divided into five sections, dealing with: I Modelling; II Inference for Parametric Models; III Multivariate Analysis; IV Topics in Hydrology, Insurance and Finance; and V a section comprised of five case studies. Sections I to IV contain a total of 14 chapters. There is also a substantial Appendix which provides an introduction to Xtremes. The book is comprehensive in scope. In the Preface to the First Edition (also included in the Second Edition), the authors emphasise that practitioners in many fields of modern science, engineering or insurance may profitably employ the textbook and the software. I believe this to be true, and I feel that this is the book's strength. I am less convinced, however, of its value for teaching purposes. A stated aim of the second edition is to reinforce a characteristic of the first edition, in providing a broad statistical background to enhance the material on extremes. However the authors state in the Preface to the First Edition that for large parts of the book it is assumed the reader has some knowledge of basic statistics, and that "yet more and more statistical prerequisites are needed in the course of reading this book." This remains true of the second edition. The approach taken is to integrate the exposition of relevant ideas on extreme value analysis with bits of general statistical theory and methodology which are deemed relevant at the time. However, as the material becomes more sophisticated, it becomes less practicable to fill in the likely gaps in statistical knowledge of a less experienced reader, hence the need for more background knowledge. Thus the diversions into general statistical issues are more prevalent near the beginning of the book. As an example, in Chapter 1, in addition to the expected ideas on the limiting distributions for maxima, on return levels, and so on, we find sections on the Poisson Approximation of Binomial Distributions; on Kurtosis and a Concept of Fat-Tailedness; and even a rather philosophical comparison of viewpoints on robust statistics. In my view, this has the effect of making the organisation of material rather incoherent. In particular, issues of modelling and theory become confused.
Article
Vehicle sensitivity to the influence of side winds is a relatively well-know phenomenon. Indeed this question had already been investigated as part of research connected with the introduction of TGV systems, findings of the study had confirmed the compatibility of TGV runs with this phenomenon on existing TGV lines given their layout and meteorological situation. The presentation reviews studies and methodology to ensure safety, that had been undertaken for the TGV-MED line (« LN5 »), which holds a very specific risk. The TGV MED line (« LN5 ») is located in a zone characterised by strong gusts. The existence of tall engineering structures and high embankments increases the velocity of winds blowing hard by reference to the line axis. The operation on this line of TGV-Duplex trainsets whose main cross-sectional area – at least for the trailing coaches – presents a higher wind-take the that of other TGV trains.