Study on the critical diameter of the subway tunnel based on the pressure variation

When the subway train operates at a speed higher than 100 km/h, the corresponding aerodynamic issue becomes severe. To meet the future requirement for the speedup of subway trains, a research on the critical diameters of the subway tunnel for trains operating at 120 and 140 km/h has been performed based on passengers' aural discomfort caused by rail tunnel pressure variation. A three-dimensional computational fluid dynamic approach has been adopted for analysis. Meanwhile, trains with different airtight indices are considered and the pressure variations inside and outside the trains are both under investigation. Based on the corresponding criteria for different airtight indices, critical tunnel diameters for trains running at different speeds have been determined. This study would aid in the tunnel section design for future high-speed subway trains.