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To better understand the aerodynamic characteristics of a train-bridge system under crosswind, an in-house experimental apparatus was developed in a wind tunnel at Central South University (CSU). The new facility consists of trains, a bridge, U-shaped slide rails, and positioning systems with winches. A wireless data acquisition system for pressure measurements was mounted within the train carriage to avoid any potential aerodynamic interference. A 1:25 scaled model of CRH2 running over a simply supported girder bridge was tested in a wind tunnel. The aerodynamic characteristics of the train-bridge system under various combinations of crosswind speed, train speed, and vehicle location on the bridge were identified. The experimental results reveal that the cosine law for surface wind pressure on a train under crosswind is no longer valid when the train runs on the bridge. The moving model method can better capture the more practical aerodynamic characteristics and the impact of train movement on the bridge. The present study indicates that the wind tunnel experiments using the stationary model cannot fully reveal the aerodynamic characteristics of both the train and bridge during crossing. The results captured using this unique approach provide insight into the aerodynamic characteristics of trains and bridges. [ABSTRACT FROM AUTHOR]

A running train induces a slipstream around it, which is closely related to its aerodynamic features and crucial for the safety of people and structures near the track. However, the effect of crosswinds is almost inevitable when the train runs on a bridge. In this work, an experimental study using moving model testing technology was conducted to investigate the effects of wind speeds, train speeds, and yaw angles on the aerodynamic performance of a Fuxing Hao high-speed train running on a bridge under the influence of crosswind. The results show that, for the crosswind cases, the slipstream velocities on the leeward side of the train are generally higher than those in the no-crosswind cases. Moreover, the results were compared for the cases with the same effective yaw angle of 21.8° but different wind speeds (6 m/s, 8 m/s) and train speeds (15 m/s, 20 m/s), which suggests the method of the resultant wind's yaw angle is no longer valid when the train runs on a bridge due to the aerodynamic interactions. [ABSTRACT FROM AUTHOR]

High-speed trains (HSTs) are being buffeted by accelerating running speed, and with that comes the aerodynamic issues. The slipstream is related to the train aerodynamic characteristics and of importance to the safety of surrounding people and structures. In this study, the ensemble-averaged and instantaneous characteristics of the slipstream of a simplistic high-speed train model with a square-back were experimentally investigated using a novel moving model rig. The present investigation indicates that the double-line substructure causes obvious asymmetry in the slipstream even at locations apart from the bridge surface with a large distance. The square-back of the HST attenuates its slipstream significantly relative to that with a streamlined tail. Besides, the decaying rate of the slipstream is higher in the wake of a square-back HST. The presents results suggest that the trailing vortices downstream of the square-back HST are substantially suppressed. [ABSTRACT FROM AUTHOR]

With the increase of the running speed of the high-speed train (HST), aerodynamic interference between the HST and surrounding structures becomes more and more important. Traditional wind tunnel experiments using the stationary model can not fully reveal the pulsing behavior of the aerodynamic forces on both the HST and surrounding structures. This paper numerically investigates the aerodynamic characteristics of an HST running on a bridge in cross-wind. The simulation results reveal that when there is no wind barrier, the stationary model case with the yaw angle identical to the moving model case can roughly reproduce the main flow structures around the train. However, once the train runs downstream a wind barrier, the stationary model cannot reveal its aerodynamic characteristics regardless of the yaw angle adopted. The moving model scenario successfully captures the pulsing behavior of the forces on both the train and wind barrier, which is concealed in the cases with a stationary model. The present results indicate that only the moving model method can fully reveal the aerodynamic characteristics and interactions between the train and surrounding structures, especially in evaluating their dynamic response. [ABSTRACT FROM AUTHOR]

• The slipstream of the CR400 high-speed train is experimentally investigated by a moving train rig. • Measured by a point cloud of 25-locations, the ensemble-averaged profiles, spatial variations, gusts, and time–frequency characteristics of the slipstream were analyzed. • The spatial–temporal variation in the properties of flow around the head car has been explained regarding the shape of the train. 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. [ABSTRACT FROM AUTHOR]