Experimental study on the effect of Reynolds number on aerodynamic performance of high-speed train with and without yaw angle

Author(s):  
Jiqiang Niu ◽  
Xifeng Liang ◽  
Dan Zhou
2019 ◽  
Vol 58 (6) ◽  
pp. 890-910 ◽  
Author(s):  
Jiabin Wang ◽  
Guangjun Gao ◽  
Xiaobai Li ◽  
Xifeng Liang ◽  
Jie Zhang

Complexity ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-17
Author(s):  
He-xuan Hu ◽  
Wan-xin Lei ◽  
Ye Zhang

With the world development of high-speed railways and increasing speeds, aerodynamic forces and moments acting on trains have been increased further, making trains stay at a “floated” state. Under a strong crosswind, the aerodynamic performance of a train on the embankment is greatly deteriorated; lift force and horizontal force borne by trains will be increased quickly; trains may suffer derailing or overturning more easily compared with the flat ground; train derailing will take place when the case is serious. All of these phenomena have brought risks to people’s life and properties. Hence, the paper establishes an aerodynamic model about a high-speed train passing an air barrier, computes aerodynamic forces and moments, and analyzes pulsating pressures on the train surface as well as those of unsteady flow fields around the train. Computational results indicate that when the train passed the embankment air barrier, the head wave of air pressure full wave is more than the tail wave; the absolute value of negative wave is more than that of the positive wave, which is more obvious in the head train. When the train is passing the air barrier, pressure pulsation values at head train points are more than those at other points, while pressure changes most violently at the train bottom, and pressure values close to the air barrier are more than those points far from the air barrier. Pressure values at the cross section 1 were larger than those of other points. Pressure values at measurement points of the tail train ranked the second place, with the maximum negative pressure of 1253 Pa. Pressure change amplitudes and maximum negative pressure on the train surface are increased quickly, while pressure peak values on the high-speed train surface are in direct ratio to the running speed. With the increased speed of the high-speed train, when it is running in the embankment air barrier, the aerodynamic force and moment borne by each train body are increased sharply, while the head train suffers the most obvious influences of aerodynamic effects.


2017 ◽  
Vol 55 (5) ◽  
pp. 681-703 ◽  
Author(s):  
Ji-qiang Niu ◽  
Dan Zhou ◽  
Tang-hong Liu ◽  
Xi-feng Liang

1997 ◽  
Vol 119 (3) ◽  
pp. 416-421 ◽  
Author(s):  
Jim Bonvouloir

Several different configurations of single-stage ferrofluidic seals were tested on a spindle which was capable of operating at very high rotational speeds (up to 55 KRPM). A dimensionless number based on the ratio of magnetic force to centrifugal force was defined. It was discovered that this ratio is not a good predictor of high speed seal failure. Reynolds number was found to be a better predictor of seal failure; therefore an empirically derived model for predicting seal failure based on Reynolds number is proposed. The data herein may provide a basis for developing new theoretical models for ferrofluidic seal failures at high speed.


2021 ◽  
Author(s):  
Mengying Wang ◽  
Zhenxu Sun ◽  
Shengjun Ju ◽  
Guowei Yang

Abstract Conventional studies usually assume that the train surface is smooth, so as to simplify the numerical calculation. In fact, the surface of the train is irregular, which will change the flow characteristics in the boundary layer and further affect the aerodynamic performance of a train. In this work, roughness is applied to the roof of a 1:25 scaled train model in the form of longitudinal strips. Firstly, the improved delayed detached eddy simulation (IDDES) method is adopted to simulate the aerodynamic performance of the train model with both smooth and rough surface, which are subjected to crosswind. Results show that the side force coefficient and the roll moment coefficient subjected to rough model decreased by 3.71% and 10.56% compared with the smooth model. Then, the width, height and length of the strips are selected as variables to design different numerical simulation schemes based on the orthogonal experimental design method. Through variance analysis, it can be found that four design parameters have no significant effect on the side force coefficient. Meanwhile, for the roll moment coefficient, the length of the strips in the straight region of the train has a significant effect and the width of the strips has a highly significant effect on it. These conclusions can provide a theoretical basis to improve the aerodynamic performance of the high-speed train subjected to crosswind.


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