Ride comfort degradation triggered by jet flow as ultra-high-speed trains enter tunnels

Abstract

With the development of ultra-high-speed trains approaching 600 km/h, aerodynamic phenomena at tunnel entrances have become increasingly influential on ride comfort. This study investigates the flow field evolution and dynamic response of an eight-car CRH380B train model entering a tunnel at speeds ranging from 300 to 600 km/h. Using Improved Delayed Detached Eddy Simulation (IDDES) combined with a dynamic mesh validated against field pressure sensor data, the aerodynamic characteristics across this speed range are analyzed. Results reveal a pronounced nonlinear increase in horizontal jet velocity beyond 450 km/h, with coach 5 experiencing a sharp rise in aerodynamic loads near the tunnel entrance, identifying it as a critical region for ride comfort degradation. These findings provide insights for the aerodynamic design and operational safety of next-generation ultra-high-speed trains.