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Calculation method for safety boundary of high-speed train derailment during aerodynamic braking operation under dynamic gust load
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DOI：10.1016/j.jweia.2026.106592.png)
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Abstract
En 中文
HSTs equipped with ABS derive their effective braking force from the train's airflow. As operating speeds increase, the train interacts with the stationary ground, surrounding infrastructure, and other trains on the track, generating complex fluid-structure interaction effects. This brings about a complex turbulent flow field around the train, which features boundary layer separation, large side slip angles, and strong wake effects. Under complex wind conditions characterized by gusts, both the flow field around the train and the aerodynamic forces exhibit non-steady, non-linear spatiotemporal variations, resulting in exceptionally complex dynamic interactions between the train and the track. This significantly increases the risk of derailment or overturning attributed to aerodynamic braking, posing safety hazards for HST operations. Hence, concerning HSTs equipped with ABS, therefore, it is urgent to establish the derailment safety boundaries and operational safety speed limits for aerodynamic braking operations in gusty environments to ensure train operational safety. • A function of the aerodynamic drag and torque loads of trains in strong wind environments with respect to time was established based on the results of wind tunnel tests or numerical simulations of the aerodynamic drag and torque coefficients of high-speed vehicles equipped with wind-resistant braking devices under different side deflection angles and wind loads. This function can be applied to solve for the aerodynamic loads of trains at any given time and space state (time, wind speed, train speed, and wind direction angles) through interpolation methods. This method is reliable and efficient in calculating the dynamic characteristics of HSTs equipped with ABD under dynamic wind conditions and applies to the calculation of wind load characteristics for any type of rail transit vehicle. • Under gust load conditions, the vertical force between the wheels and rails on the leeward side of HSTs equipped with ABD increases, while the windward side exhibits a symmetrical reduction in load. The train derailment safety evaluation indicators P, Q, H, Q/P, ΔP/P, and D all present an approximate linear increase trend with increasing train speed and gust wind speed. Under the same operating conditions, D and ΔP/P are the first to exceed the operational safety limits, while P, Q, H, and Q/P have significant safety margins. Hence, in this study, D and ΔP/P are selected as the derailment safety criteria for HST operational safety under gusty wind conditions, serving as critical evaluation indicators for train aerodynamic braking operational safety in high-wind environments. • Compared to the prototype train, the derailment safety evaluation indicators for the head car of HSTs equipped with ABD increase to varying degrees during operation, with P, ΔP/P and D revealing more significant increases. The largest range of changes occurs during the increase and decay phases of the cap-type gust index. Moreover, the most dangerous moments for train aerodynamic braking operation occur when the gust speed linearly increases to the average value and at the moment corresponding to the maximum gust speed. The lateral displacement and lateral acceleration of the train body's center of gravity under aerodynamic braking demonstrate significant fluctuations when gusts are applied, particularly during the stages of gust wind speed index changes. Under lateral gust conditions with a train speed of 200 km/h and a maximum wind speed of 20 m/s, the maximum body displacement during aerodynamic braking operation is 0.264m, which increases by 13.0% compared to the prototype train, and the maximum instantaneous acceleration increases by over 50%. • Under different operating speed conditions, the maximum values of ΔP/P and D for the most dangerous wheelset of the train first increase and then slow down with the growing wind direction angle. Within 0°-60°, they increase linearly at a relatively high rate; within 60°-90°, the increasing rate gradually decreases until it reaches a maximum at 90°. Therefore, the system's dynamic response and derailment safety criteria under lateral gust loads corresponding to the most unfavorable wind direction angle of 90° should be considered for safety assessments of train operations under high wind loads. At a speed of 400 km/h, the D under lateral gust conditions with aerodynamic braking is 0.927, representing an increase of 84.27% compared to the operating conditions at a wind direction angle of 10°. • Upon the critical limits for train operational safety and derailment safety, the following aerodynamic braking safety critical speeds were calculated for HSTs equipped with ABD operating in lateral gust environments with maximum wind speeds of 22 m/s, 18 m/s, and 14 m/s: 165.3 km/h, 246.1 km/h, and 369.4 km/h, respectively.
Keywords:
High-speed train
Aerodynamics
Aerodynamic braking
Aerodynamic braking device
Operational safety
Gust
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