The aerodynamics of a high-speed train running adjacent to windbreak walls

Crosswind stability of high-speed trains has been a prominent research topic for several decades, primarily motivated by the stability problems faced under strong crosswinds in order to make transport safer. In this study, the influence of different windbreak walls on train aerodynamic properties whilst subjected to crosswinds was assessed. Windbreak walls are built along the railway line, at sections where strong crosswinds are expected, to enhance the stability of trains and improving passenger comfort. The experimental campaign measured surface pressures on a stationary 1:25 model-scale of Class 390 Pendolino train under varying wind incidence angles with different windbreak walls inside a wind tunnel. The purpose of the stationary wind tunnel tests was to achieve valuable understanding of the aerodynamic flow that exists around a train surface due to the presence of different shapes of windbreak walls. In addition, these tests provided useful experimental data that acted as a benchmark for validating the numerical work carried out in this study. For the first time, the work considers transition regions in windbreak walls, where transition regions refer to the specific design implementations in terms of the geometry of a windbreak wall to tackle different topographies. This includes the changes in the distance of the windbreak wall from the railway track and the relative angles of different wall panels to each other. The numerical aspect of this study comprised of using Computational Fluid Dynamics to explore and map how a crosswind flow develops around a passenger train running adjacent to a windbreak wall, consisting of a transition region. Differences in pressure distribution on the train surface with and without different windbreak walls were evident. At a wind incidence angle of 90° for the stationary case, the tallest windbreak wall usually provided the most negative mean pressure distribution on the surface of the model train due to the shielding effects; while the windbreak wall with a transition region consisting of a transition angle of 90° usually produced the lowest negative mean pressure distribution, comparatively. At a wind incidence angle of 30° for the stationary case, the results from windbreak walls with transition regions were relatively uniform indicating a smooth pressure distribution. Overall, the windbreak wall was able to significantly reduce the intensity of the pressures on the windward side of the train while also providing uniformity to the results on the leeward side of the train. This confirms the shielding effects provided by the windbreak wall to the train body from the oncoming crosswind flows. The transition region in a windbreak wall was observed to influence the flow in a significant manner. Different flow features were visible behind the transition region due to the non-uniformity of the transition region. Between the stationary and moving train cases, there were significant differences observed in the flow fields that develop around the trains with a windbreak wall