The slipstream and wake of a high-speed train

This paper describes the results of experimental work to determine the stru cture of the slipstream and wake of a high speed train. The experiments wer e carried out using a 1/25th scale model of a four-coach train on a moving model rig (MMR). Flow velocities were measured using a rake of single hot f ilms positioned close to the model side or roof. Tests were carried out at different model speeds, with and without the simulation of a crosswind. Vel ocity time histories for each configuration were obtained from ensemble ave rages of the results of a number of runs. A small number of particle imagin g velocimetry (PIV) experiments were also carried out, and a wavelet analys is revealed details of the unsteady flow structure around the vehicle. It w as shown that the flowfield around the vehicle could be divided into a numb er of different regions of distinct flow characteristics: an upstream regio n, a nose region, a boundary layer region, a near wake region and a far wak e region. If the results were suitably normalized, the effect of model spee d was small. The effect of crosswinds was to add an increment to the slipst ream and wake velocities, and this resulted in very high slipstream velocit ies in the nose region.