Abstract: The environment in regions with high altitudes is relatively harsh, and the greater the altitude, the lower the air pressure, temperature and density. Therefore, the study on the aerodynamic performance of the high-speed train running in high-altitude regions is of great significance to the running safety of the train and the construction of the high-altitude railway. Taking a high-speed train as the research object, the aerodynamics of the single train, trains passing each other in the open air and the train passing through a tunnel are carried out to study the aerodynamic loads and transient pressure characteristics of the train at different altitudes. The results show that the aerodynamic drag and lift force of the high-speed train decrease with the increase of altitude when the train is running in the open air. However, the aerodynamic drag and lift force coefficients do not change basically with the altitude increase. The pressure drag force coefficient of the aerodynamic resistance coefficient decreases with the altitude increase, whereas the viscous drag force coefficient increases. The pressure waves of trains passing each other and passing through the tunnel for different altitudes have the same changing law, respectively. However, the amplitude decreases with the increase in altitude. Meanwhile, the peak values of the pressure wave generated by trains passing each other have a direct correlation with altitudes, and so are the pressure waves, the micro-pressure waves at the tunnel exit generated by the train passing through the tunnel. Moreover, the temperature change caused by the increase in altitude reduces the speed of sound, thereby reducing the propagation speed of the pressure wave. As a result, the pressure wave in the tunnel and the micro-pressure waves at the tunnel exit appear hysteresis at different altitudes.

Key words: high-speed train, plateau, altitude, aerodynamic performance, numerical simulation