Key Takeaways & Executive Findings
- •• A biomimetic fishtail effectively suppresses alternating vortex shedding in the wake of high-speed trains, aligning drag fluctuation with fishtail oscillation. • The optimal configuration (1850 mm Eel fishtail, λ=1, T=8 s) achieves drag reduction rates of 39.12% for the tail car and 26.00% for the entire train. • Fishtail length, oscillation mode, and frequency significantly influence wake flow and aerodynamic drag, highlighting the importance of parameter optimization. • These findings provide a theoretical basis for designing low-resistance railway trains, contributing to sustainable and energy-efficient rail transit.
Abstract
The increase in aerodynamic drag brings high energy consumption, which is a critical issue in the development of high-speed trains. Inspired by the excellent hydrodynamic characteristics of fish movement in nature, a two-dimensional numerical simulation method based on spring-smoothing model and adaptive mesh technology was utilized to explore the effects of different fishtail structures and two flexible motion modes (Eel mode and Lunate-tail mode) on the wake of high-speed trains, and to assess their potential for aerodynamic drag reduction. Results indicate that the biomimetic fishtail successfully suppresses the alternating shedding of vortices in the wake, and induces the aerodynamic drag fluctuation period to align with the fishtail oscillation period. The fishtail length, oscillation mode, and frequency have a significant impact on the wake flow and aerodynamic drag of the train. Among these, a 1850 mm Eel fishtail with parameters of λ=1 and T=8 s achieves the optimal drag reduction effect, with drag reduction rates of 39.12% and 26.00% for the tail car and the entire train, respectively. These findings provide a theoretical basis for the design of new low-resistance railway trains, promoting the sustainable development of rail transit towards goals of high-speed and energy-efficient.
1. Introduction
As of the end of 2023, China's high-speed railway network has reached a total length of 45000 km [1], solidifying its position as the global leader in both the scale and growth rate of its high-speed railway networks. Extensive research has demonstrated that the aerodynamic characteristics of high-speed trains are significantly influenced by operating environment [2−5], with the aerodynamic drag being proportional to the square of the running speed [6]. Consequently, the increase in train operation speeds inevitably leads to a sharp rise in aerodynamic drag, posing significant challenges in terms of energy consumption [7]. Therefore, studies on aerodynamic drag reduction are crucial for the sustainable development of high-speed trains.
Currently, the primary methods to reduce the aerodynamic drag of high-speed trains include shape optimization [8, 9], active blowing/sucking and plasma technologies [10, 11], vortex generator implementations [12 −14], surface micro-structure design [15, 16] and bionic deflectors [17−19]. In nature, fishes propel themselves through the reciprocating motion of their spinal muscles, fins, and tails in water. This unique biomechanical mechanism enables fishs to swim with remarkable energy efficiency. Meanwhile, it also provides inspiration for bio-inspired robotics, automated vehicles manufacturing, and efficient locomotion control [20]. According to records, most fishes utilize body and/or caudal fin propulsion (BCF) to move [21], and scholars categorized BCF into several main patterns. These modes primarily differ in the generation patterns and propulsion mechanisms of the hydrodynamic waves induced by their body and caudal fin movements. Eel-like fishes in the anguilliform family have flexible bodies that generate propulsion through undulating waves, while tuna, characterized by a spindle-shaped body, derive most of their thrust from their tails [22]. To clearly differentiate the impact of bio-inspired fishtail propulsion modes on the flow field of the tail car, both the Eel mode and Lunate-tail mode were investigated in this study.
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LI Zhi-wei, ZHAO Yan-jia, ZENG Guang-zhi, ZHU Hai-bin, LIU Ying, HUANG Sha (2025). Effect of dynamic flexible biomimetic fishtail on the wake characteristics and aerodynamic drag of high-speed trains. Journal of Central South University. https://doi.org/10.1007/s11771-025-6136-7
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Frequently Asked Questions
What is the main objective of this study?
The study aims to investigate the effects of a dynamic flexible biomimetic fishtail on the wake characteristics and aerodynamic drag of high-speed trains, with the goal of reducing aerodynamic drag and energy consumption.
What methods were used in the research?
A two-dimensional numerical simulation method based on spring-smoothing model and adaptive mesh technology was utilized to simulate the flow around a high-speed train with different fishtail structures and motion modes.
What are the key findings regarding drag reduction?
The optimal configuration (1850 mm Eel fishtail with λ=1 and T=8 s) achieved drag reduction rates of 39.12% for the tail car and 26.00% for the entire train, while also suppressing alternating vortex shedding.
How does the biomimetic fishtail affect the wake?
The biomimetic fishtail suppresses alternating vortex shedding in the wake and aligns the aerodynamic drag fluctuation period with the fishtail oscillation period, leading to improved aerodynamic performance.
What are the practical implications of this research?
The findings provide a theoretical basis for designing new low-resistance railway trains, contributing to the sustainable development of rail transit by achieving high-speed and energy-efficient operation.
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