What is it about?
This study extends the TWS method to double-track tunnels for pressure wave simulation, based on characteristic wave superposition. Validated via field measurements and 3D simulations (peak-to-peak errors <10%), the method is computationally efficient (5 seconds for a 1000m tunnel). It reveals that tunnel wall pressure (max, min, peak-to-peak values) fluctuates periodically with train crossing positions, more notably in shorter tunnels. Simultaneous train entry causes the highest max and peak-to-peak pressures at the tunnel center, while peak min pressure occurs under non-simultaneous entry. Importantly, optimizing train entry time difference can reduce peak-to-peak pressures by 50%, providing theoretical support for train scheduling and tunnel design optimization.
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Why is it important?
This study holds significant theoretical and practical value: theoretically, it fills the technical gap in rapid simulation of pressure waves during train crossings in double-track tunnels by extending the single-track TWS method to double-track scenarios, establishing a dual-track TWS model based on characteristic wave superposition that balances high accuracy (peak-to-peak errors <10%) and ultra-high computational efficiency (simulating a 1000-meter tunnel in only 5 seconds), addressing the shortcomings of traditional 1D models’ inaccuracy and 3D models’ time-consuming nature; it also reveals the periodic fluctuation law of pressure waves in double-track tunnels, clarifies the influence mechanisms of tunnel length, train crossing position, and entry time difference on pressure amplitude, and discovers key phenomena such as the "most unfavorable tunnel length" and "pressure cancellation effect," deepening the theoretical understanding of tunnel aerodynamic effects in high-speed railways. Practically, it enables a 50% reduction in peak-to-peak pressure on tunnel walls by simply adjusting the train entry time difference without additional hardware investment, effectively reducing fatigue damage to tunnel linings and alleviating passengers’ ear pressure discomfort to enhance operational safety and comfort; it provides theoretical basis for optimizing tunnel parameters such as length and cross-sectional size, helping to avoid the "most unfavorable tunnel length," reduce structural reinforcement costs, and extend tunnel service life, with targeted control effects especially for short tunnels (100-1000 meters); the high efficiency of the TWS method supports rapid multi-parameter iterative calculations, greatly shortening the design cycle for optimizing tunnel aerodynamic effects and reducing engineering R&D costs, adapting to the construction needs of high-density and high-speed railway networks; additionally, it provides quantitative indicators and practical schemes for pressure wave control in double-track tunnels, supplementing the gaps in existing railway aerodynamic safety standards and facilitating the standardized construction of high-speed and ultra-high-speed (e.g., 600 km/h maglev) railway tunnels.
Perspectives
As the authors of this study, we hold that it makes meaningful contributions to both railway aerodynamics theory and engineering practice. Extending the TWS method to double-track scenarios fills a key gap—previous tools either lacked accuracy (1D models) or were computationally prohibitive (3D simulations), while our model achieves <10% peak-to-peak error and simulates a 1000m tunnel in 5 seconds. We are particularly encouraged by the core finding: optimizing train entry timing can cut tunnel wall peak-to-peak pressure by 50% without extra hardware, offering a cost-effective solution to structural fatigue and passenger discomfort. The discovery of periodic pressure fluctuations, especially pronounced in short tunnels, deepens understanding of wave superposition mechanisms. While the study neglects wave mutual interference and auxiliary structures, it lays a solid foundation for future refinements. We believe this work not only advances theoretical insights into train-tunnel interactions but also provides actionable guidance for scheduling and tunnel design, supporting the safe development of high-speed and maglev rail networks.
Feng Liu
Taiyuan University of Technology
Read the Original
This page is a summary of: Optimizing train entry timing to mitigate pressure waves in high-speed double-track tunnels: A train wave signature-based study, Physics of Fluids, November 2025, American Institute of Physics,
DOI: 10.1063/5.0298668.
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