Characteristics of the velocity field in slipstream induced by a CR 400 high-speed train lead-carriage

This paper experimentally investigates the characteristics of the velocity field induced by the slipstream from the leading carriage model of a CR 400 high-speed train. The tests were carried out using a 1:16.8 scale model on a moving model rig developed at the Central South University, PRC. The slipstream velocity field was measured at a point cloud involving 25 locations on a plane orthogonal to the track orientation. Aiming at understanding the slipstream ensemble characteristics, especially those unique to the CR400 train, observations were analyzed to evaluate the ensemble-averaged profiles, spatial variations, gusts and time-frequency characteristics of velocity fluctuations in the slipstream. The results suggest that the moving train model and testing rig used in this study capture the unsteady and time-variant features of the slipstream. The spatiotemporal profile of the slipstream usually includes a primary and a secondary peak at the nose tip and the region immediately next to it, respectively. Among the collection of locations studied, the primary peak reaches its maximum at a lateral location close to the train side at the nose height. Finally, the time-frequency portraits of the spatiotemporal variations of the slipstream were obtained using wavelet scalograms of the velocity field, which offered an insightful understanding of the various scales of velocity fluctuations around the nose and their locale.