Experimental-Numerical Analysis of High-Speed Train Slipstream in Open Air and Confined Spaces

The study addresses the aerodynamic impact of train slipstreams, crucial for passenger and worker safety. While previous research has extensively examined openfield scenarios, limited attention was given to slipstream development in confined spaces. In literature the differences between slipstream in open fields and tunnels were observed, highlighting the role of infrastructure parameters in airflow restriction during train passage, mainly through numerical simulations; however, the computational fluid dynamics analysis with only few experimental data available remains challenging. To bridge this gap and fully understand the slipstream differences in open air and tunnels, the results from a full-scale experimental campaign on an Italian railway line for analyzing airflow in different environments were considered. This paper presents findings exploiting data from the campaign, comparing slipstream features in tunnels and open spaces, thanks to air speed measurements collected in both environments simultaneously, considering geometrical effects given by asymmetrical tunnel shapes. In the second part of the work a computational fluid dynamics model is employed for a deeper analysis of the velocity field in tunnels, providing insights into the complex interaction between train and tunnel geometry and give the basis to further work exploiting the capability of the computational fluid dynamics model to reproduce the slipstream stochastic nature.