Aerodynamic design of HS2 tunnels

The aerodynamic design of HS2 tunnels has been achieved through balancing the civils design with the specification of the required aerodynamic characteristics of the rolling stock, resulting in smaller, more economic tunnel cross-sectional areas than would be provided in other countries for the same line speeds. Issues considered include aural comfort and safety for passengers and crew, increased drag on the trains, fatigue effects from aerodynamic pressure loading on structures and equipment in the tunnels, and the potential for sonic booms caused by micro-pressure waves emitted from tunnels into the environment. The paper includes a summary of the numerical modelling methods and their validation against scale model testing undertaken specifically for HS2.

The aerodynamic solutions developed for the HS2 tunnels provide a reference for future HSR projects faced with the challenge of combining high line speeds with relatively small tunnel cross-sections. The risk of sonic booms poses a particular challenge due to a cube law relation with train speed, meaning that the tunnel entrance hood designs used in other countries to mitigate these would be insufficient. HS2’s novel tapered form of tunnel entrance hoods will be of particular interest to future high-speed rail projects with similarly high line speeds.