Flow dynamics of train under turbulent inflow at different crosswind yaw angles

When the ultra-high-speed elevator car-counterweight system runs opposite each other, significant piston effects are caused, seriously affecting the elevator operation's stability. In order to explore the aerodynamic characteristics of the whole operation process of a car-counterweight system under multi-parameters, this study first establishes a three-dimensional transient model of the car-counterweight system and a multi-region dynamic layering numerical simulation method based on this model is proposed. Then, the actual elevator experiment validates the correctness of the model and the method. Finally, the influence rules of key parameters on the car's aerodynamic characteristics and ventilation effect are analyzed, and the car's aerodynamic characteristics at intersection time are analyzed emphatically. The results show that with the increase in the blocking ratio, the pressure drag and viscous drag have similar change trends at each stage, but the influence of pressure drag is more significant. The air displacement ratio increases by 34.1%, 75.8%, and 117.3%, respectively. With the increase in the hoistway height, the air displacement ratio decreases by 0.9%, 2.4%, and 2.9%, respectively. The spacing significantly affects the car's aerodynamic characteristics at the intersection time. The drag peak increases by 6.8%, 13.6%, and 20.5% and the lift peak by 21.2%, 47.8%, and 82.5%, respectively.

Section: E Computational Domain and Boundary Conditionsmentioning

confidence: 99%

Study on the aerodynamic characteristics and ventilation effects of ultra-high-speed elevator car-counterweight system under the influence of multiple parameters

Zeng,

He,

Zhang

et al. 2024

Aerodynamic characteristics of the train under real wind gust

Xue,

Chen,

Xiong

2024

Research on aerodynamic loads and flow field characteristics of trains under real wind gust is limited. Most studies focus on train's dynamics under wind gust. By using numerical simulation methods to model the spatiotemporal evolution of the flow field around the train under real wind gust, the aerodynamic load and flow field characteristics of the train were studied. The one-minus-cosine wind gust model was adopted to achieve the real wind gust and the improved delayed detached eddy simulation based on shear stress transport k–ω turbulence model was used to perform numerical simulations of train operation under wind gust by applying the specified wind gust model function to the velocity inlet boundary. During the wind gust, the peak values for most of the aerodynamic loads of the train cannot reach the levels corresponding to those under constant crosswind, since the flow field around the train cannot fully develop into a stable flow field akin to that under constant crosswind. Compared to the wind gust without zero-crossing, the differences between unsteady and quasi-steady peaks are greater for side force, rolling moment, and yaw moment under wind gust with zero-crossing. This study addresses the gap in research on train aerodynamics under real wind gust conditions, providing essential data for train dynamics and a theoretical foundation for the safe operation of the train.

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

Zhang,

Zhou,

Feng

et al. 2024

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