PIV Investigation of the Flow Field Underneath a Generic High-Speed Train Configuration

In this paper a 2C PIV measurement of the flow field underneath a 1:50 generic high-speed train configuration (front car, 2 coaches and tail car) and a smooth generic high-speed train configuration (the same model but without bogies and the bogie cut outs and inter car gaps filled) hauled through a water towing tank at a speed of 4 m/s is presented. The 2C PIV set-up was installed so that the vertical plane (XZ) between the ground and the train, in the centre line of the train, could be measured. The PIV system that was used could measure with an acquisition rate of 10 Hz, at this frequency 6 PIV images of the instantaneous flow field with a distance of 0.4 m from each other were made per run. The total field of view was 0.065 m x 0.025 m (WxH), to cover the entire flow field underneath the train model the position had to be shifted 8 times this was realized with the help of a trigger system. At every position 10 runs were made from which the ensemble average was calculated and reconstructed with the known shift, leading to the average flow field underneath the generic high-speed train configuration. All the presented results in this paper are from the calculated ensemble aver-age. The PIV measurement technique was applicable to measure the flow field underneath a down scaled train model in a water towing tank. The generic high-speed train configuration was compared to a full scale measurement. The same structure of the flow field was found for the flow around the head and the tail of the train. The flow field was fully developed at the begin-ning of the 2nd coach for both configurations. This also agrees with the full scale measure-ment. To achieve more realistic results in the future the simplified bogies that were used should be replaced with bogies with a higher degree of details. For the comparison between the two measured configurations a clear difference was found, the generic high-speed train configuration had a higher induced velocity underneath the train due to the protruding bogies