Improved delayed detached eddy simulation-based investigation of aerodynamic performance and flow field characteristics of high-speed trains with plate brakes

As a key component, the braking system is vital for ensuring safe and comfortable operation of trains moving at high speeds. Because the aerodynamic drag depends linearly on the square of the vehicle speed, plate braking has broad prospects for high-speed trains. The train body interface is altered by the plate opening, which causes a sudden change in the flow field around the train and deteriorates its aerodynamic performance. In this study, dynamic grid technology was used to realize plate opening, and an improved delayed detached eddy simulation (IDDES) was used to simulate the unsteady aerodynamic characteristics of trains during plate braking. The simulations and settings were verified using wind-tunnel test data. The effects of the plate motion on the aerodynamic performance of the train were clarified by analyzing the changes of the aerodynamic loads of the plate and the train body within 0.2 s for an opening plate and 1.8 s for an opened plate. The aerodynamic forces of the different cars were significantly different during the plate-opening process, especially near the maximal opening angle. In particular, for the middle car, the aerodynamic force depended on the number of plates. The plate opening caused lateral aerodynamic fluctuations in the car body, which caused the car body to shake laterally, especially the downstream car, and the degree of the fluctuation of the lateral force of the car body also depended on the number of plates. Owing to the airflow inertia, the aerodynamic drag of the plate at the end of the motion appeared as a pulse peak, and the peak value decreased downstream of the train. The opening of the plates caused the flow field above the roof to develop disordered downstream. Owing to the coupling and superposition of the downstream flow field, the aerodynamic drag of the first plate fluctuated slightly, whereas that of the downstream plate fluctuated significantly, likely affecting the normal operation of the equipment on the top of the train, such as air conditioning and pantograph.