• International Journal of Railway
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• 제5권2호
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• pp.93-101
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• 2012

Owing to the lightening of railway vehicles and increased operation speeds, the reduction of running safety in the presence of crosswind is becoming an important problem. In particular, the running safety tends to decrease when vehicles run on curved track. When a crosswind acts on a vehicle negotiating a curve from the outer side, flange climbing can occur. In this study, a full-vehicle model was constructed using the multi-body simulation software SIMPACK, and a simulation of a bogie vehicle with two-axle trucks negotiating a curve was carried out to examine the running safety under the condition where a crosswind acts on the vehicle from the outer side of the curve. As a result, it was verified that the derailment coefficient of the first wheelset becomes large in the exit transition curve and the coefficient of the third wheelset does in the entrance transition curve, and this trend becomes pronounced at low operation speeds in the presence of a stronger crosswind. It was also shown that the critical derailment coefficients obtained by modified Nadal's formula considering the effect of attack angle become close to the actual derailment coefficients at the timing that flange climbing occurs.

• Structural Engineering and Mechanics
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• 제76권2호
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• pp.207-222
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• 2020

Due to the rugged terrain, metro lines in mountain city across numerous wide rivers and deep valleys, resulting in instability of high-pier bridge and insecurity of metro train subjected to fluctuating crosswind. To ensure the safe operation in metro lines in mountain cities, running safety of the metro train over the high-pier bridge under crosswind is analyzed in this paper. Firstly, the dynamic model of the wind-train-bridge (WTB) system is built, in which the speed-up effect of crosswind is fully considered. On the basis of time domain analysis, the basic characteristics of the WTB system with high-pier are analyzed. Afterwards, the dynamic responses varies with train speed and wind speed are calculated, and the safety zone of metro train over a high-pier bridge subjected to fluctuating crosswind in mountain city is determined. The results indicate that, fluctuating crosswind triggers drastic vibration to the metro train and high-pier bridges, which in turn causes running instability of the train. For this reason, the corresponding safety zone for metro train running on the high-pier is proposed, and the metro traffic on the high-pier bridge should be closed as the mean wind speed of standard height reaches 9 m/s (15.6 m/s for the train).

• Wind and Structures
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• 제21권1호
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• pp.63-84
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• 2015

The shape of a tall building has significant impact on wind force generation and wind-induced dynamic response. To study the effect of recessed cavities, wind excitations on a wind-tunnel model of an H-section tall building were compared with those on a square-section building model. Characteristics of the fluctuating wind pressures on the side faces of the two tall buildings and their role in the generation of crosswind forces on the buildings were investigated with the space-time statistical tool of proper orthogonal decomposition (POD). This paper also compares the use of different pressure data sets for POD analysis in situations where pressures on two different surfaces are responsible for the generation of a wind force. The first POD mode is found to dominate the generation of crosswind excitation on the buildings.

• Wind and Structures
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• 제20권4호
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• pp.509-525
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• 2015

A three-dimensional aerodynamic model and a vehicle dynamics model are established to investigate the effect of noise barrier on the dynamic performance of a high-speed train running on an embankment in crosswind in this paper. Based on the developed model, flow structures around the train with and without noise barrier are compared. Effect of the noise barrier height on the train dynamic performance is studied. Then, comparisons between the dynamic performance indexes of the train running on the windward track and on the leeward track are made. The calculated results show that the noise barrier has significant effects on the structure of the flow field around the train in crosswind and thus on the dynamic performance of the high-speed train. The dynamic performance of the train on the windward track is better than that on the leeward track. In addition, various heights of the noise barrier will have different effects on the train dynamic performance. The dynamic performance indexes keep decreasing with the increase of the noise barrier height before the height reaches a certain value, while these indexes have an inverse trend when the height is above this value. These results suggest that optimization on the noise barrier height is possible and demonstrate that the designed noise barrier height of the existing China Railway High-speed line analysed in this article is reasonable from the view point of the flow field structure and train dynamic performance although the noise barrier is always designed based on the noise-related standard.

• Wind and Structures
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• 제20권4호
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• pp.549-564
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• 2015

The three-dimensional unsteady incompressible Reynolds-averaged Navier-Stokes equations and k-${\varepsilon}$ double equations turbulent model were used to investigate the effect on the measurements of anemometers due to a passing high-speed train. Sliding mesh technology in Fluent was utilized to treat the moving boundary problem. The high-speed train considered in this paper was with bogies and inter-carriage gaps. Combined with the results of the wind tunnel test in a published paper, the accuracy of the present numerical method was validated to be used for further study. In addition, the difference of slipstream between three-car and eight-car grouping models was analyzed, and a series of numerical simulations were carried out to study the influences of the anemometer heights, the train speeds, the crosswind speeds and the directions of the induced slipstream on the measurements of the anemometers. The results show that the influence factors of the train-induced slipstream are the passing head car and tail car. Using the three-car grouping model to analyze the train-induced flow is reasonable. The maxima of horizontal slipstream velocity tend to reduce as the height of the anemometer increases. With the train speed increasing, the relationship between $V_{train}$ and $V_{induced\;slipstream}$ can be expressed with linear increment. In the absence of natural wind conditions, from the head car arriving to the tail car leaving, the induced wind direction changes about $330^{\circ}$, while under the crosswind condition the wind direction fluctuates around $-90^{\circ}$. With the crosswind speed increasing, the peaks of $V_X,{\mid}V_{XY}-V_{wind}{\mid}$ of the head car and that of $V_X$ of the tail car tend to enlarge. Thus, when anemometers are installed along high-speed railways, it is important to study the effect on the measurements of anemometers due to the train-induced slipstream.

• Wind and Structures
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• 제36권2호
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• pp.105-120
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• 2023

The present study is performed to find the effect of corner recession on a square plan-shaped tall building. A series of numerical simulations have been carried out to find the two orthogonal wind force coefficients on various model configurations using Computational Fluid Dynamics (CFD). Numerical analyses are performed by using ANSYS-CFX (k-ℇ turbulence model) considering the length scale of 1:300. The study is performed for 0° to 360° wind angle of attack. The CFD data thus generated is utilised to fit parametric equations to predict alongwind and crosswind force coefficients, C_fx and C_fy. The precision of the parametric equations is validated by employing a wind tunnel study for the 40% corner recession model, and an excellent match is observed. Upon satisfactory validation, the parametric equations are further used to carry out multiobjective optimization considering two orthogonal force coefficients. Pareto optimal design results are presented to propose suitable percentages of corner recession for the study building. The optimization is based on reducing the alongwind and crosswind forces simultaneously to enhance the aerodynamic performance of the building.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 춘계학술대회 논문집
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• pp.138-143
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• 2005

In this study, the cross-wind stability of the G7 train and TTX running under the high speed was investigated by using 2-dimensional Reynolds Averaged Navier-Stokes equations. It is very important to analysis the aerodynamic characteristic of bluff body located near a ground at the field of the aeronautical, wind engineering, ground vehicle system. To the point of running stability, it is meaningful to analysis the cross-wind effect to the G7 train and TTX developed by domestic technology. The aerodynamic characteristics of the G7 train equipped by bogie-cover is more superior to the case without bogie-cover. Also 2nd model of TTX has stream-shape body has the more good performance than 1st model of TTX.

• Wind and Structures
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• 제37권5호
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• pp.361-373
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• 2023

Suspended monorail trains (SMTs) are sensitive to crosswinds, and instantaneous aerodynamic characteristics of two SMTs passing each other under crosswinds are particularly complicated. In this study, a pressure measurement test is carried out on stationary train-bridge models arranged in several critical positions. In addition, a validated moving CFD model is developed with the dynamic and sliding mesh method to explore the realistic train movement effects. The time-varying aerodynamic forces and surface pressure distribution on, as well as the flow field around running trains and bridges during trains passing each other, are computed in detail to illustrate the shielding effect of the upstream train. The results reveal that when two trains begin to pass each other, the side force coefficient of the downstream train reduces significantly to negative values due to the wind shielding effect of the upstream train. The moving model successfully captures that airflow is separated on the middle line of the head car for the suspended monorail train, and the surrounding bluff double-beams can significantly affect the flow structures around the train. The wind shielding effect of the upstream train on the downstream train will weaken as the relative yaw angle decreases.

• Wind and Structures
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• 제32권5호
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• pp.487-499
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• 2021

The wind-blown sand effect on the high-speed train is investigated. Unsteady RANS equation and the SST k-ω turbulent model coupled with the discrete phase model (DPM) are utilized to simulate the two-phase of air-sand. Sand impact force is calculated based on the Hertzian impact theory. The different cases, including various wind velocity, train speed, sand particle diameter, were simulated. The train's flow field characteristics and the sand impact force were analyzed. The results show that the sand environment makes the pressure increase under different wind velocity and train speed situations. Sand impact force increases with the increasing train speed and sand particle diameter under the same particle mass flow rate. The train aerodynamic force connected with sand impact force when the train running in the wind-sand environment were compared with the aerodynamic force when the train running in the pure wind environment. The results show that the head car longitudinal force increase with wind speed increasing. When the crosswind speed is larger than 35m/s, the effect of the wind- sand environment on the train increases obviously. The longitudinal force of head car increases 23% and lateral force of tail increases 12% comparing to the pure wind environment. The sand concentration in air is the most important factor which influences the sand impact force on the train.

• Wind and Structures
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• 제20권1호
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• pp.75-93
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• 2015

This work is focused on a parametric numerical study of the barrier's bar inclination shelter effect in crosswind scenario. The parametric study combines mesh morphing and design of experiments in automated manner. Radial Basis Functions (RBF) method is used for mesh morphing and Ansys Workbench is used as an automation platform. Wind barrier consists of five bars where each bar angle is parameterized. Design points are defined using the design of experiments (DOE) technique to accurately represent the entire design space. Three-dimensional RANS numerical simulation was utilized with commercial software Ansys Fluent 14.5. In addition to the numerical study, experimental measurement of the aerodynamic forces acting on a vehicle is performed in order to define the critical wind disturbance scenario. The wind barrier optimization method combines morphing, an advanced CFD solver, high performance computing, and process automaters. The goal is to present a parametric aerodynamic simulation methodology for the wind barrier shelter that integrates accuracy and an extended design space in an automated manner. In addition, goal driven optimization is conducted for the most influential parameters for the wind barrier shelter.