Abstract
Abstract The study of Reynolds number (Re) effects is crucial for optimizing train aerodynamics, enhancing safety and reducing energy consumption of high-speed trains. In this paper, a wind tunnel test was carried out to investigate the influence of Re on the train aerodynamic performance considering the shift of the air compressibility, which has not yet been explored to date. The test was conducted in a low-speed and large-scale tunnel with a stationary floor and the vehicle model was based on a 1/8th scaled train with three units. The Re ranges from 0.75 × 106∼3.12 × 106 by accelerating the uniform wind speed from U = 27.8 m/s to U = 115 m/s with zero-yaw. The Mach number (Ma) of the maximum speed scenario has exceeded 0.3, indicating that the airflow can be considered as being in the compressible range. The results show that the aerodynamic characteristics of high-speed trains exhibit a self-similarity region of Re, which is dependent on the flow velocity. The aerodynamic loads change little when Re ≥ 1.51 × 106, which corresponds to U ≥ 55.6 m/s. Therefore, the compressibility of the airflow within the range up to U = 115 m/s has a negligible effect on aerodynamic loads, and can thus be disregarded. However, the surface pressure significantly decreases when the incoming flow surpasses 0.3 Ma and transitions into a compressible state. While the compressibility has a relatively minor impact on macroscopic aerodynamics, it cannot be overlooked when considering detailed flow field, such as surface pressure.
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