Train slipstream assessment in open air and confined spaces through full-scale experimental tests

The train slipstream, referring to the air velocity induced by the train, significantly impacts the safety of passengers and track workers. While extensive research examined slipstream effects in open air, fewer studies address their behavior in tunnels. This study bridges the gap through a full-scale experimental campaign analyzing slipstream effects for high-speed, conventional, and freight trains in both open air and tunnel environments. The results reveal substantial differences in slipstream behavior. In open air, airspeed increases steadily around the train, creating smoother airflow transitions. Conversely, tunnels amplify slipstream effects due to confinement, with stronger wind peaks near the train nose caused by piston and blockage effects. High-speed and conventional trains generate notable backflow between tunnel walls and the train, absent in open air, whereas freight trains exhibit limited backflow due to their highly turbulent flow. A statistical analysis of maximum airspeed peaks shows velocity fluctuations 10%–30% higher in tunnels for passenger trains on specific sides, causing potential risks for platform users, while freight trains display variable trends influenced by tunnel geometry. This study underscores the amplified slipstream effects in tunnels and the need for enhanced safety measures, and highlights the need to develop future research based on numerical methods to expand the understanding of slipstream effects in tunnels.