What is it about?

This study develops a scaled wavefront generator (WFG) using instantaneous high-pressure air release to simulate initial compression waves (ICW) and micro-pressure waves (MPW) induced by high-speed trains entering tunnels. The device’s reliability is verified via airtightness checks, transducer calibration, and repeatability tests (accuracy within ±2%). Key findings include: device parameters map to engineering values—chamber initial pressure (P0) to train speed , solenoid valve opening voltage (U0) to streamline length , and valve number (N0) to blockage ratio. ICW propagates with slight attenuation due to wall friction and steepens at higher pressure amplitudes. Tunnel pressure fluctuates periodically (T=4×tunnel length/wave velocity) with exponentially decaying amplitude. MPW amplitude correlates positively with P0, U0, N0, and experimental results match theoretical values within 15%. Acoustically, MPW sound pressure level exceeds 100 phon in most cases, surpassing the human hearing threshold. This low-cost WFG provides a practical tool for studying train-tunnel aerodynamics and MPW mitigation.

Featured Image

Why is it important?

This study is significant for addressing the critical need to mitigate aerodynamic issues (ICW and MPW) in high-speed train-tunnel interactions, offering a low-cost, efficient alternative to costly full-scale measurements and mesh-sensitive numerical simulations. Its uniqueness lies in developing a multi-solenoid-valve-based WFG that simplifies train entry via instantaneous high-pressure air release, with well-established mapping relationships between device parameters (chamber pressure P0, valve voltage U0, valve number N0) and key engineering variables (train speed, streamline length, blockage ratio). Unlike existing wavefront generators, it systematically investigates the complete aerodynamic process—ICW generation/propagation, tunnel pressure fluctuations (period T=4×tunnel length/wave velocity with exponential amplitude decay), and MPW radiation—validated through rigorous reliability tests (airtightness, transducer calibration, ±2% repeatability) and showing good agreement with theoretical predictions (<15% deviation). Additionally, its acoustic evaluation of MPW (exceeding 100 phon in most cases) provides direct insights for noise control, filling gaps in comprehensive aerodynamic simulation and practical engineering application of scaled devices.

Perspectives

This study’s development of a multi-solenoid-valve wavefront generator (WFG) marks a pragmatic and impactful contribution to high-speed rail aerodynamics research, addressing long-standing limitations of traditional methods—such as the high cost of full-scale tests and mesh sensitivity of CFD simulations—with a low-cost, reproducible alternative. What stands out most is the clear, engineering-relevant mapping between device parameters (chamber pressure, valve voltage, valve number) and critical train-tunnel variables (speed, streamline length, blockage ratio), which transforms a lab-scale setup into a directly applicable tool for engineers designing tunnel structures or mitigating micro-pressure wave (MPW) hazards. The systematic acoustic evaluation of MPW, revealing its consistent exceedance of 100 phon, also adds actionable insights for noise control, aligning experimental results with real-world human auditory impacts. While the device’s valve voltage range and scaling effects present room for refinement, its ability to replicate the full cycle of initial compression wave (ICW) generation, propagation, and MPW radiation—with <15% deviation from theoretical predictions—fills a crucial gap in accessible, reliable aerodynamic testing, making it a valuable asset for advancing high-speed rail safety and environmental compatibility.

Feng Liu
Taiyuan University of Technology

Read the Original

This page is a summary of: Characterizing a device for easy simulation of compression waves induced by trains passing through tunnels, Physics of Fluids, November 2024, American Institute of Physics,
DOI: 10.1063/5.0237738.
You can read the full text:

Read

Contributors

The following have contributed to this page