Numerical investigation of the evolution of aerodynamic behaviour when a high-speed train accelerates under crosswind conditions

Abstract

Crosswind degrades the aerodynamic behaviour of trains, especially during train acceleration, and an understanding of the flow field and train safety details requires more research attention. In the present study, the improved delayed detached eddy simulation (IDDES) method is applied to investigate the aerodynamic behaviour when a high-speed train accelerates under crosswind conditions. The spatial–temporal evolution of eddies and pressure distributions on the train surface based on eight discrete moments are explored. Moreover, the effects of three acceleration values on the aerodynamic force/moment coefficients and safety indicators are evaluated. The results show that the distance between the eddy shedding from the head car and the train body becomes smaller and the negative pressure of the eddy core increases in the process of acceleration. The pressure on the windward side of the train is stable, while the pressure on the leeward side shows an increasing trend with increasing train speed. An increase in the acceleration value increases the maximum side force and rolling moment coefficients, most prominently for the head car. In addition, a larger acceleration value may cause stronger pulsation of the train. Although the acceleration values do not increase the maximum values of the safety indicators, they have a slight effect on the local maximum values.