Aerodynamic Optimization of Freight Trains. Part 2: Efficiency and safety recommendations from validated wind-tunnel experiments

In this work a method based on wind tunnel experiments is described to propose recommendations for aerodynamic optimized freight trains to improve energy efficiency and reliability. The sensitivity of a previous parameter drag study has been investigated against different upstream flow conditions using boundary layer argumentation. The wind tunnel measurements were compared to field test results gained by a real-world operational data acquisition system, the DLR's FR8-LAB. The results of this investigation are used to improve an incremental drag database, which is used to calculate the difference between the cumulative, aerodynamic drag of different loading schemes as well as estimate the energy and cost saving potential. The wind tunnel experiments were performed at a yaw angle of 0° and 5° to include crosswind effects and allow predictions for operational scenarios under realistic environmental conditions as well as safety related assessments. The experiments were performed in the Crosswind Simulation Facility at DLR Göttingen. The implementation of an iterative improvement of the drag database and validation with the use of the FR8-LAB's real-world data enables an evaluation for aerodynamic optimized rail freight transport with view on energy efficiency and safety in today's operation as well as forecasts and recommendations for future high-speed freight rail.