Tunnel ventilation, including aerodynamics

The paper outlines the development of the design of the Channel Tunnel, as influenced by aerodynamic and ventilation considerations. It also indicates the nature of the detailed simulation work, which was required to prepare simple but robust operational procedures, which could respond to the complete range of normal and abnormal operating conditions in the tunnel. The tunnel's ventilation and aerodynamic properties are dominated by the effects of large shuttles moving at high speed in the single-track running tunnels, where the blocking ratio of train-to-train cross-section is 50%. Even during abnormal operating conditions, for example where an evacuation is occurring, the powerful effects of even slow-moving shuttles on local air velocities and ventilation conditions must be assessed carefully. The paper discusses the design considerations, and describes: (1) the normal ventilation systems; (2) the supplementary ventilation system; (3) the piston relief ducts and dampers; (4) the crossover doors; and (5) the operation of the ventilation system. For the covering abstract see IRRD 877203.