Urban electric multiple units (EMUs) is based on high-speed trains and metro vehicle technology. Their design speeds are generally from 160km/h to 200km/h, which mitigates the low operating speeds of metro vehicles. Traditional Crosswind calculations for the aerodynamic characteristics of trains often assume a 3-marshalling train. Urban trains are generally 4-marshalling and 6-marshalling. Evaluating the aerodynamic characteristics of urban EMUs of different marshalling lengths is instructive for system design. Based on CFD, aerodynamic models of urban trains are established. The train models include 3-marshalling, 4-marshalling and 6-marshalling. The aerodynamic characteristics of 200km/h urban trains subject to different Crosswind velocities are numerically simulated. The research display that the aerodynamic performance of the head-car and the first middle-car, under the same Crosswind velocity, of different marshalling lengths, are almost the same, whereas the aerodynamic characteristics of the tail-cars for different marshalling lengths are significantly different. The side forces of the 4 middle-cars of the 6-marshalling train decrease, sequentially. At a Crosswind velocity of 35m/s, 34% difference in Fs of the tail-car of a 6-marshalling train compared to a 3-marshalling, and the overturning moment differs by 22. 8%. Because of the significant difference in side force and overturning moment, the three-marshalling train model cannot represent the real train. Therefore, the real marshalling length should be used, as far as possible, when studying Crosswind effects on the train.

At stations, high-speed trains frequently pass through the platform without stopping, where a combination of two island platforms represents the most common layout. The interaction between the train and the platform leads to certain problems, such as reductions in the comfort of the waiting environment and the safety of people around the platform. However, in the literature, there are few studies on the aerodynamic response between the train and the platform and on the airflow field characteristics above the platform when the train passes through the platform under different Crosswind speeds. Therefore, we attempted to fill this gap using numerical methods to study the aerodynamic characteristics of the train passing through island platforms at 350 km/h under different Crosswind speeds (10, 15, 20, 25, and 30 m/s). The aerodynamic response of high-speed trains combined with the flow field distribution is discussed in depth. We studied the wind speed distribution at different longitudinal distances above the platform, and obtained the position of the maximum wind speed when the head and tail car passed through the platform. Based on this, the wind speed distribution at different lateral distances above the platform was studied, and the reasons for the airflow changes above the platform were analyzed. The research results show that when a train enters a platform at 350km/h under a Crosswind speed of 30 m/s, the reductions in the drag and lateral force of the whole vehicle reach their maximum, which are 50. 44% and 66. 51%, respectively. However, the change trend in the whole car lift force is opposite to that of the drag and lateral force, which increase when the train enters the platform and decrease when it leaves the platform. The largest growth in lift force is 102. 39%, which occurred at a wind speed of 30m/s. The airflow velocity above the platform will increase rapidly as the head and tail car pass through the platform. A higher Crosswind speed will result in the monitoring point of platform reaching its maximum airflow speed to an earlier time as the tail car passes through the platform. Meanwhile, we found that the lateral distance 1 – 2m above the platform is the area with the largest wind speed attenuation.

The purpose of this work is to investigate transient aerodynamic characteristics of the coach under the Crosswind in straight-line situations with different uniform speeds and uniform accelerations. The transient aerodynamics caused by different speed changes are analyzed using the real-time interaction between aerodynamic simulation and dynamic simulation. The target model is a simplified coach on a full scale. The SST (Menter) K-Omega Improved Delayed Detached Eddy Simulation and overset mesh technique are used to predict the transient aerodynamic loads. The accuracy of the turbulence model is verified by a wind tunnel experiment of the 1/7th scaled coach model. The present results show that the transient aerodynamic loads have different locations of maximum side force and the holding duration of yaw moment for different constant speeds. The speed becomes larger, and the position where the side force is maximum becomes farther away. The holding duration of the top yaw moment is larger simultaneously. Moreover, proper acceleration for low initial driving speed and Crosswind of small influence range could build up stability. High speed driving in gust wind is not suggested for unskilled drivers.

High-speed passenger car requires a lighter weight for improving power performance and reducing fuel consumption; a car with higher-speed and lighter weight will lead to the passenger car more sensitive to the Crosswind, which will affect the stability and drivability of the passenger car. This study employs the fully-coupled method to investigate a passenger car subjected “ 1-cos” Crosswind with consideration of the vehicle motion. Large eddy simulation (LES) and dynamic mesh is adopted to investigate the unsteady aerodynamic, and the vehicle is treated as a three-freedom-system and driver’ s control is considered to investigate the vehicle dynamic. The one-way simulation and quasi-steady simulation are also conducted to compare with the fully-coupled simulation. The results of the three simulation methods show large difference. The peak value of the lateral displacement in fully-coupled simulation is the smallest between the three simulation approaches. While the change of aerodynamic loads and vehicle motion in fully-coupled simulation is more complicated than in one-way and quasi-steady simulation. These results clearly indicate the significance of including of the unsteady aerodynamic loads in passenger car moving analysis.

This article aims to study the thermal performances of four different natural draft cooling towers under Crosswind condition. The windbreakers and the oblique exit plane have been simultaneously included in the structure of the new cooling tower. A finite volume method using SIMPLE algorithm was used to simulate the flow field around each cooling tower. The thermal performance of the new geometry has been compared with those of others for the generally investigated wind velocity profile for 10 m/s, and also two uniform wind velocities for 3 and 7 m/s. The cooling capacity of the cooling tower utilizing windbreakers and the oblique exit plane was predicted as 98.3% of the design value in the presence of generally studied wind velocity profile of 10 m/s, while that of the cooling tower utilizing windbreakers was predicted as 93.5%. Of course, the percentage of the thermal improvements of the different restoring strategies are sensitive to the profile of an approaching wind. The uniform wind velocity decreases the thermal efficiency of the cooling tower more than the distributed one, while the restoring strategies using windbreakers provide a higher percentage of thermal improvements in the presence of uniform wind velocity.

A Detached Eddy Simulation (DES) method based on the SST k-ω turbulence model was used to investigate the instantaneous and time-averaged flow characteristics around the train with a slender body and high Reynolds number subjected to strong Crosswinds. The evolution trends of multi-scale coherent vortex structures in the leeward side were studied. These pressure oscillation characteristics of monitoring points on the train surfaces were discussed. Time-averaged pressure and aerodynamic loads on each part of the train were analyzed inhere. Also, the overturning moment coefficients were compared with the experimental data. The results show that the flow fields around the train present significant unsteady characteristics. Lots of vortex structures with different intensities, spatial geometrical scales, accompanied by a time change, appear in the leeward side of the train, in the wake of the tail car and below the bottom of the train. The oscillation characteristics of the flow field around the train directly affect the pressure change on the train surfaces, thereby affecting the aerodynamic loads of the train. The loads of each car fluctuate around some certain mean values, while the positive peak values can be higher than the mean ones by up to 34%. The load contributions of different parts to the total of the train are also obtained. According to it, to improve the Crosswind stability of the high-speed train, much more attention should be paid on the aerodynamic shape design of the streamlined head and cross section. In addition, this work shows that the DES approach can give a better prediction of vortex structures in the wake compared with the RANS solution.

Numerical simulations of the airflow around a hatchback and a sedan vehicle without and with spoilers are carried out, besides, its effect on drag and lift coefficients are investigated with and without Crosswinds. The effects of Crosswind on aerodynamic forces are considered and its results are compared with the case without considering the effects of Crosswind. For this purpose, the steady-state three-dimensional Navier-Stokes equations are solved by the Simple Method. Moreover, for turbulence modeling, the Realizable k-e model is implemented. The spoiler angle and its length are changed for both car models; furthermore, the effects of two spoilers on drag and lift coefficients are investigated in detail. All cases are simulated with and without Crosswind. The results show that the impact of the spoiler for without Crosswind conditions to decrease the lift coefficient in both models is significant; in addition, the drag coefficients are reduced for some cares. It can be concluded that the increase of spoiler length for both sedan and hatchback vehicles can increase the downward force and vehicle stability.

Most of drivers have to compensate small directional deviations from the desired driving path when disturbances such as Crosswinds, overtakings, road irregularities and unintended driver inputs are imposed. These types of deviations have a tiring effect on driver and traffic‟ s safety and should be minimised. To increase the understanding the influence of vehicle‟ s properties in Crosswind and overtaking conditions, specially vans and buses, and improving their safety, the vehicle was modeled using parameters based on real vehicle data for simulation in CarSim program. These parameters were validated or edited by simulation programs such as SOLIDWORKS, ADAMS/CAR ADAMS/CHASSIS and Well-known Calculation Software. A method for estimating the lateral error of vehicle due to original path in Crosswind and overtaking conditions is also presented using Multi-Step Taguchi method in MINITAB. Dealing with limited but most effective factors of Vehicle‟ s Properties instead of large variety of them can be used for optimal vehicle‟ s design and propose ideal Crosswind Controllers.