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.
One of the main countermeasures to the problem of crosswind in railway vehicles is the introduction of windbreaks in the windiest points of a railway line. However, in some cases due to the morphology of the terrain or because operational reasons, gaps can be found in the stretch of windbreaks with a consequently reduction of efficiency. The goal of this work is to develop a methodology for the evaluation of the effects on the safety to crosswind of high-speed trains running in a track where a gap is present in barriers. An innovative numerical-experimental procedure has been developed based on experimental full-scale tests, wind tunnel tests, CFD with moving mesh and multi-body simulations. An "amplification function", defined as a non-dimensional function which represents the amplification effect due to the gap was evaluated for different scenarios. This amplification function is then combined with the force, obtained with the stochastic methodology for the evaluation of the aerodynamic force in presence of turbulent wind. The new forces accounting for the gap presence in the windbreak barriers, are the input of the multi-body model used for the evaluation of the train stability by computing the CWC, it means, the critical wind speeds that leads the vehicle to overcome the overturning safety limit threshold. The results for a highspeed train and porous windbreaks with gap of different dimensions have shown a reduction in CWC values.
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