Key Takeaways & Executive Findings
- •• Speed reduction from 280 km/h to 200 km/h significantly mitigates tunnel aerodynamic effects, with a 49.8% decrease in peak-to-peak pressure and a 50.7% decrease in transient pressure instability on inner walls. • Entrance buffer structures effectively reduce maximum positive pressure by up to 25.7% and transient pressure instability by 29.0%, while also increasing pressure decay rate by 32.2%. • Both speed reduction and buffer structures are proven to reduce micro-pressure wave levels with a simpler monotonic relationship, despite complex wave propagation in tunnels. • The study provides practical insights for designing maglev tunnel systems to enhance passenger comfort and reduce aerodynamic noise and drag.
Abstract
Maglev trains experience significant aerodynamic effects when passing through tunnels. A moving model test was conducted to explore the practical effects of speed reduction and entrance buffer structures on mitigating tunnel/maglev aerodynamic effects. It is found that both have an overall positive effect on mitigating the aerodynamic environment inside and outside the tunnel. Trains operating at 200 km/h show a 49.8% decrease in peak-to-peak pressure and a 50.7% decrease in transient pressure instability on inner walls compared to those at 280 km/h. Lower speeds resulted in a 65.6% decrease in amplitude and a 24.5% decrease in decay rate, both of which are parameters for exponential fittings of pressure peaks that decay naturally after the train leaves. The buffer structures result in a reduction of up to 25.7% in the maximum positive pressure and a 29.0% decrease in transient pressure instability. Additionally, a reduction in amplitude of up to 21.2% and a 32.2% increase in decay rate were observed with the use of buffer structures. Nevertheless, it is difficult to conclude direct correlations between the maximum pressure, peak-to-peak values, etc., and the speeds or buffer structures due to the complex wave propagation in tunnels. However, speed reduction and buffer structures are proven to be effective in reducing the micro-pressure wave levels with a simpler monotonic relationship.
1. Introduction
Maglev trains represent a cutting-edge mode of rail transportation, showcasing significant promise for the future of public transportation [1, 2]. Characterized by their advantages such as remarkable speeds, a smooth ride, and low noise, maglev trains have garnered significant attention and investment worldwide [3 – 5]. As countries such as Japan, South Korea, and China have several maglev lines currently in service, the operational success of these trains is evident; therefore, these countries, along with others, are planning to construct additional maglev train lines [6, 7].
However, despite their promise, maglev trains face several major challenges, especially when it comes to the complex aerodynamics associated with train-tunnel interactions [8 −11]. In many regions, railway lines are frequently built through tunnels or underground spaces due to geographical and spatial constraints. This is especially common for urban maglev systems, where available land is limited, and largely occupied by existing infrastructure [12]. Issues arise when trains, especially high-speed trains like maglev, travel through tunnels, confined spaces, as complex airflow patterns develop. The air in front of the train is compressed, creating a high-pressure region, while the surrounding air rapidly fills the space left behind, resulting in a strong low-pressure area [13 −15]. Meanwhile, the sudden formation of these initial high-pressure and low-pressure regions significantly disturbs the air in the tunnel, which then spreads and generates the initial compression and expansion waves, characterized by high pressure and low pressure, respectively. Then, the initial compression and expansion waves reflect and generate secondary waves when they encounter other disturbances, such as changes in space caused by geometric discontinuities or the uneven surfaces of trains and tunnels [16 −18]. Additionally, the strong initial compression wave with high pressure releases suddenly upon reaching the tunnel exit, forming a sonic explosion known as a micro-pressure wave [19, 20]. All the above factors contribute to the complex aerodynamics in train-tunnel coupling, leading to adverse effects, including increased drag, noise, and reduced passenger comfort [21, 22]. These phenomena become even more pronounced at higher speeds of maglev trains, which can reach speeds of up to 600 km/h or more [23, 24].
In light of these aerodynamic challenges, various measures and strategies have been implemented worldwide [25]. One of the earliest approaches involved designing streamlined train shapes to minimize the disturbances created as trains enter tunnels [26 −28]. In Japan, engineers implemented speed reduction protocols as trains approach tunnel entrances.
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GUO Zi-jian, CHEN Zheng-wei, GUO Zhan-hao, ZENG Guang-zhi, PENG Cheng (2025). A moving model test of a maglev train passing through tunnels: Effect of train speed and buffer structure on aerodynamic environment. Journal of Central South University. https://doi.org/10.1007/s11771-025-6135-8
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Frequently Asked Questions
What is the main objective of the study on maglev trains passing through tunnels?
The study aims to investigate the effects of train speed reduction and entrance buffer structures on mitigating the aerodynamic environment inside and outside tunnels for maglev trains, using a moving model test.
How does reducing train speed affect tunnel aerodynamics?
Reducing train speed from 280 km/h to 200 km/h results in a 49.8% decrease in peak-to-peak pressure and a 50.7% decrease in transient pressure instability on inner walls, along with a 65.6% decrease in amplitude and a 24.5% decrease in decay rate of pressure peaks.
What is the effect of buffer structures on aerodynamic pressure?
Buffer structures reduce maximum positive pressure by up to 25.7% and transient pressure instability by 29.0%, while also decreasing amplitude by up to 21.2% and increasing decay rate by 32.2%.
Are speed reduction and buffer structures effective in reducing micro-pressure waves?
Yes, both speed reduction and buffer structures are proven to be effective in reducing micro-pressure wave levels, with a simpler monotonic relationship compared to other aerodynamic parameters.
What are the practical implications of this research for maglev tunnel design?
The findings provide quantitative data that can guide the design of maglev tunnel systems, including optimal speed limits and the implementation of buffer structures to enhance passenger comfort, reduce noise, and improve overall aerodynamic performance.
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