ABSTRACT To reduce the crosswind effect on high-speed trains, in this paper, by using the Improved Delayed Detached Eddy Simulation (IDDES) method and the SST turbulence model, a novel blowing measure is studied and compared by considering different positions of blowing slots on the train surface. The concerned blowing positions on the train surface include the top position (Top); windward side (WWS): the upper position (WU), middle position (WM), and lower position (WL); and leeward side (LWS): the upper position (LU), middle position (LM), and lower position (LL). The results show that in regard to the rolling moment coefficient around the leeward rail, CMx lee, the mitigation effect with LM for the head car is the largest, and the mitigation effect with WL for the middle car and tail car is superior to other cases. The corresponding drop percentages are 18.5%, 21.7%, and 30.8% for the head car, middle car, and tail car, respectively. The flow structures indicate that the blowing positions on the lower half of WWS and upper half of LWS would form a protective air gap to weaken the impact of coming flows and delay the vortex separation on LWS, and thus the train aerodynamic performance is improved.

https://doi.org/10.1080/19942060.2022.2064921

Mitigating crosswind effect on high-speed trains by active blowing method: a comparative study

As train speeds continuously increase, the crosswind stability of high-speed trains (HSTs) has been a prominent research topic. Benefiting from advances in railway technology, the coupled operation of different HSTs has been proven to be permissible, but the crosswind performance of double-connected train groups composed of different kinds of HSTs has rarely been studied. This paper therefore studied the differences in the aerodynamic performance of double-connected train groups composed of same and different train units under crosswinds. We employed an improved delayed detached-eddy simulation (IDDES) method to investigate the flow features around different groups of double-connected train. Two one-eighth-scale standard HSTs—Train 1 (T 1) and Train 2 (T 2)—currently operating in China were selected to form different group configurations for double-connected trains: T 1-T 1 (Case 1–1), T 1-T 2 (Case 1–2), T 2-T 1 (Case 2–1), and T 2-T 2 (Case 2–2). First, the reliability of the numerical algorithm and mesh independence were verified to ensure the accuracy of the numerical results. Second, the aerodynamic force coefficients, time-averaged, and instantaneous flow structures of different double-connected train group types were compared and analyzed. 

Aerodynamic characteristics of double-connected train groups composed of different kinds of high-speed trains under crosswinds: A comparison study

Under strong winds, the effect of sudden windbreak transition (WT) on high-speed trains is severe, leading to a deterioration of train aerodynamics and sudden yawing motion of the car body. To address these problems, based on a high-speed train and the specific geometric conditions derived from Xinjiang railway, first, the impact of a WT on the train and reasons for sudden changes in aerodynamic forces were determined by flow structural analysis. Furthermore, based on a multibody system dynamic model, the dynamic responses to WT were analysed. The results show that the impacts of WT were the strongest on the head car. WT had a strong effect on the train due to the unreasonable structural shape and the insufficient height of the windbreak in the transition region. This led to a strong push effect on the train; subsequently, the train’s dynamic characteristics deteriorated.

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Unsteady Aerodynamic Characteristics of a High-Speed Train Induced by the Sudden Change of Windbreak Wall Structure: A Case Study of the Xinjiang Railway

Lei Wang

Papers

Study on the pressure pipe length in train aerodynamic tests and its applications in crosswinds