This works focuses on a series of experimental tests carried out to investigate overpressures in tunnels due to train crossings. Although the above-mentioned topic is well known and also defined in European standards, in the literature full-scale data are lacking, which are useful to validate the numerical codes required in the certification process and are used in train structural dimensioning. In this respect, an extensive full-scale experimental campaign was planned for observing as many test conditions as possible, such as single passages of different trains, two train crossing, different tests speed, and different tunnel characteristics. In detail, the understanding of the pressure wave generation and transmission is deeply enhanced by studying the pressure evolution both on board and at trackside, considering both single train passages or two trains crossings and having the possibility to compare aerodynamic loads on sealed and unsealed trains. Furthermore, the position of sensors, the speed of the train, and the initial conditions within the tunnel have been proven to be fundamental parameters for properly estimating the pressure loads on trains.

The advent of high-speed trains led to new issues and constraints for railway network manufacturers and operators. This is the case of crosswind effect, that occurs when train is running in strong wind conditions. The combination of train speed and wind speed generates a relative flow that affects the train stability. Wind tunnel tests on still railway vehicles (relative wind-train velocity in coincidence with absolute wind velocity) are mandatory according to Technical Specification for Interoperability (TSI) to ensure high-speed train safety. However, issues related to the correct evaluation of the full-scale aerodynamic behaviour of the trains can arise. In the present work, aerodynamic force and pressure coefficients measured in wind tunnel tests on a scaled model of ETR1000 high-speed train on single track ballast and rails are presented. The tests were performed in the GVPM wind tunnel of Politecnico di Milano. Results show that different flow behaviours can occur at high yaw angles when the train behaves like a bluff body depending on wind speed used during the test.

Large overpressures can be produced when a high-speed train enters and crosses a railway tunnel. Predicting them is important since, in critical conditions, pressure variations may be dangerous for train structures and for passengers’ health and comfort. European regulations impose pressure thresholds which trains must comply with in order to be homologated for travelling through tunnels. Currently, full-scale tests are required to demonstrate respect of these prescriptions. In this work, a procedure for calculating the pressure variations inside the tunnel based on 3 D steady CFD simulations and a 1 D compressible fluid-dynamics model is proposed, to be used both as a design tool and for virtual homologation of new rolling stock. Results of a large experimental campaign performed on the Italian high-speed line are used to set-up the proposed methodology and to validate it. Different train geometries, tunnel crossing speeds and tunnel initial air conditions are considered.