Keywords: slipstream, flow structures, double-deck train model, roughness elements, wake turbulence, conditional sampling, high-speed piv, tsg, tsi.

Trackside induced airflow velocities are an important criterion for the design of highspeed trains. Due to the limited model size and different Reynolds numbers in moving model experiments, the induced flow may not be comparable to real trains. The idea is to control the thickness of the boundary layer using roughness elements. High- Speed PIV is used to measure the induced flow velocities. The boundary layer analysis yields to an increase of the displacement thickness along the train model and a slightly decrease near the rear end. As expected, the use of roughness elements leads to an artificial increase of the flow velocities in the head section and a thicker boundary layer for both measurement heights. According to the equalizing form factor along the end car, it can be assumed, that the model length is sufficient to gain an increased boundary layer without artificial flow structures. Conditional sampling is used to analyse the size and dynamics of the flow structures at the time of maximum velocity in the near wake. The results show, that the roughness elements effect mainly the flow structure at a lower measurement height by increasing the average and maximum velocity.

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