Flow characteristics induced by a multiform windbreak in complex terrains with and without a train: A simplified method for calculating aerodynamic loads

This study aims to investigate common multiform windbreaks, aligned parallel to railway tracks and perpendicular to incoming wind, in complex terrains. Using unsteady simulations, the study analyzes airflow downstream of these windbreaks and the aerodynamic characteristics during train passage. It evaluates the wind-protection performance of various windbreak types and transitions and identifies factors that influence performance. Results indicate that the vertical surface walls offer stronger wind protection compared to slope walls or viaduct barriers. Flow patterns near transitions reveal that upstream airflow shifts longitudinally from high-performance windbreaks to lower-performance ones, reentering the railway line space from the latter. This suggests a design approach in which neighboring windbreaks exhibit similar performance to optimize protection. On aerodynamic characteristics of the train, the maximum side force on the leading vehicle is found proportional to wind speed and train speed to the powers of 1.6 and 0.5, respectively; train speed affects the pressure on the streamlined head and the vortices around the leeward side. A simplified calculation for aerodynamic loads on a vehicle is proposed and explored with a consideration of wind speed above the railway line. An error margin of the maximum side force by this simplified method is 8.4%, and the saving is at least 88.2% of the computational resources when assessing the crosswind stability of a vehicle. The proposed design for the multiform windbreak, along with the simplified calculation method, can improve the performance of a multiform windbreak and increase the efficiency of assessing crosswind safety for railway operations downstream of the windbreak.