CFD analysis of flow patterns induced by high-speed and freight trains in tunnels and their impact on platform regions

This study investigates the aerodynamic slipstream generated by high-speed and freight trains inside tunnels, focusing on passenger exposure along platforms. CFD simulations validated against unique full-scale measurements collected in a real railway tunnel enable the first systematic comparison of slipstream aerodynamics for two different train types operating under identical infrastructure and operating conditions in a double-track tunnel with a passenger platform. The validated URANS simulations show good agreement with experiments in slipstream regions, with relative errors generally below 10% for key flow features. Results reveal distinct slipstream topologies driven by different separation mechanisms and their interaction with tunnel confinement: high-speed trains produce wake-dominated flows with localized velocity peaks in the near wake, whereas freight trains generate stronger front-loaded gusts caused by separation at the locomotive and inter-car gaps. Spatial distributions of velocity maxima highlight asymmetric exposure between near and far tracks and support CFD-based safety assessment in mixed-traffic railway tunnels.