EN 14067-5: Aerodynamic Requirements for Trains in Tunnels

What is EN 14067-5?

EN 14067-5 is a specialized part of the European Standard series titled “Railway applications – Aerodynamics – Part 5: Requirements and test procedures for aerodynamics in tunnels.” As trains enter tunnels at high speeds, they generate complex piston effects and pressure waves that can affect the structural integrity of the train and the tunnel infrastructure.

This standard provides the methodology to calculate and measure these pressure fluctuations. It is essential for ensuring that train windows do not shatter, doors remain sealed, and trackside equipment within the tunnel is not dislodged by the rapid change in air pressure.

Key Technical Phenomena Addressed

When a train enters a tunnel, it acts like a piston in a cylinder, compressing the air ahead and creating a vacuum behind. EN 14067-5 focuses on managing the following:

• Maximum Pressure Changes: Limits are set on the peak-to-peak pressure variations to protect the health of passengers’ eardrums and the train’s airtightness.
• Airtightness Requirements: Specifications for the “pressure sealing” of the vehicle body. If a train is not sufficiently airtight, the rapid pressure changes can cause physical discomfort or injury to passengers.
• Micro-Pressure Waves (Sonic Boom): Guidelines for managing the wave that exits the far end of the tunnel, which can cause environmental noise complaints and structural vibrations in nearby buildings.
• Aerodynamic Loads on Tunnel Equipment: Ensuring that signals, cables, and walkways can withstand the cyclic pressure pulses.

Testing and Simulation Methods

EN 14067-5 mandates specific validation techniques to prove compliance before a new train or tunnel is commissioned:

• Numerical Simulations (CFD): Advanced Computational Fluid Dynamics are used to predict pressure signatures based on the tunnel’s cross-sectional area and the train’s nose shape.
• Moving Model Tests: Small-scale models are launched into scaled tunnels to observe wave behavior.
• Full-Scale Tests: Measuring actual pressure variations using sensors mounted on the train and tunnel walls during high-speed runs.

Comparison: Open Air vs. Tunnel Aerodynamics

Importance for High-Speed Rail

As train speeds exceed 200 km/h, the aerodynamic power required increases with the cube of the speed. EN 14067-5 is the guiding document for engineers to optimize the “blockage ratio” (the ratio of train cross-section to tunnel cross-section). Proper application of this standard allows for higher speeds in existing tunnels and helps determine the minimum diameter for new tunnel construction projects.