Aerodynamic transients at high-speed railway tunnel exits and their effects on passenger ride comfort: a mechanistic study

The frequent exit of high-speed trains from tunnels induces significant aerodynamic load changes, critically impacting vehicle stability and passenger comfort. This study investigates passenger vibration comfort during tunnel exits at 300–400 km/h by integrating an aerodynamic model with a coupled train-track-seat-human body dynamics model. Results reveal that tunnel exit exposes the train to compression/expansion waves and airflow deflection, causing persistent lateral sway (especially in the tail car) and greatly reduced comfort. Carriage vibration is predominantly vertical and more intense in the tail car. While the car body and floor vibrate below 10 Hz, resonance with aerodynamic loads and structural modes occurs near 25 Hz. The 23–28 Hz vibration in calves and thighs stems from floor-transmitted roll/pitch and minimal lateral restraint. Other body parts vibrate below 10 Hz, with the undamped head showing intense vertical resonance. Human vibration during high-speed train tunnel exit exhibits a pronounced speed-dependent deterioration, with lateral vibration being significantly more severe and persistent than vertical vibration. When the train speed reaches 400 km/h, the vibration dose value (VDV) at the front of both the head and tail cars exceeds 0.95, indicating a potential health risk associated with the transient aerodynamic impact.