Aerodynamic study of high-speed railway tunnels with variable cross section utilizing equivalent excavation volume.

The article focuses on the aerodynamic effects of high-speed trains (HSTs) passing through tunnels with variable cross sections, analyzed using numerical simulations based on equivalent excavation volume. It investigates how different change ratios of tunnel cross section (CR) influence transient pressures on trains and tunnel walls, slipstreams, aerodynamic loads, and micro-pressure waves (MPWs). Results indicate that increasing CR significantly reduces negative pressure peaks on train surfaces and pressure peaks within tunnels, with a maximum pressure relief of about 17.7%, and attenuates MPWs outside tunnel exits by up to 16.4%. However, variable cross section tunnels can intensify slipstreams and lateral aerodynamic loads at tunnel junctions, potentially affecting operational safety and comfort, suggesting the need for design optimizations such as gradual transitions. The study validates its numerical approach through experimental tests and highlights the potential of variable cross section tunnel designs to improve aerodynamic performance while noting limitations related to single-train scenarios.