MOVING MODEL ANALYSIS OF THE SLIPSTREAM OF A LONG GROUPING HIGH-SPEED TRAIN

The slipstream is the air flow induced by the high speed train passing by, which continues to be an important aspect of aerodynamic performance and a critical factor of safe operation. In this paper, a 1:8 scaled eight-group type model of a high-speed train was measured on the moving model rig, and the characteristic of the flow around high-speed train can be observed. The long group type model can break through the limitation of the reduced length to wide ratio in the moving model experiment. The slipstream of a high-speed train has a stable local peak in the nose and a remarkable unsteady characteristic in the area of body and wake of the high speed train which indicated by the ensemble average profile and the ensemble standard deviation profile of the slipstream. The slipstream profile indicated that fluctuation of the flow around the eight-group high-speed train appeared at the second coach, the velocity rose vibrationally and reach the local maximum at the seventh coach. But the perturbation caused by bogie cabins and inter carriage gaps did not appear in the slipstream profile. The experimental results in the wake of slipstream were decomposed by Proportional Orthogonal Decomposition (POD). It is found that the fluctuating energy intensively appeared in the near-wake region, and appeared in the trailing area of body secondly. Conditional averaging was applied to analyzing the experimental results of slipstream in the moving model experiment. The condition of the conditional averaging was the distance between the peak location of slipstream profile and the tail of the high speed train model. The result of conditional averaging of slipstream indicated that the relative position between the slipstream measurement probes and the wake vortices may impact the peak of slipstream profile in the wake of the train when the vortices generated.