Keywords: railway aerodynamics, freight-train wagon, aerodynamic drag, underbody geometry, wind-tunnel measurement, crosswind simulation facility.

The research presented focuses on reducing the aerodynamic drag of standard freight wagons by optimizing their geometry to improve energy-efficient operation and reduce the overall carbon footprint. Within the scope of this work, a variety of aerodynamic measures for an improved underbody geometry of conventional freight wagons have been investigated in a wind-tunnel experiment to provide a detailed overview of their effectiveness in drag reduction. The experiments were performed at a Reynolds number of 5.0×105 in the Crosswind Simulation Facility at DLR Göttingen with an optimized moving-ground condition simulated by a moving belt. The pivoted mounting system of the model enabled crosswind investigations with yaw angles of the model up to 10°, which corresponds to typical crosswind flow conditions during operation. The simplified geometry of a Lgs580 freight wagon was used as a generic baseline model in a scale of 1:10, to which aerodynamic improvements were added and compared. The aerodynamic drag was evaluated in terms of the aerodynamic forces on the full freight wagon model with container, which were measured with a 6-component strain-gauge balance between the mounting sting and the base plate of the freight wagon model. More than 50 different configurations were measured and further combinations are considered for future measurements in view of the benefits of single measures. Five selected measures are presented here based on the feasibility and the significant effect on the aerodynamic drag. The results have shown that simple, feasible measures like covering of roughness in the base frame design provide a significant decrease in the aerodynamic drag by 8-24%. A full fairing on the underbody was identified as the best aerodynamic measure with a decrease of 31%. The full parametric geometry investigation of the shape and size of aerodynamic fairings and side skirts offers train manufacturers recommendations for optimized wagon design for improvements in energy efficiency of next-generation freight trains.

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