The interest in underfloor aerodynamics of high-speed trains has increased in the last years due to the occurrence of several ballast projection incidents (flying ballast stones). Ballast projection has been considered as a problem in train aerodynamics since the 1980´s. Back then it was correlated with snow and ice accumulation on the trains underframe and its dropping during travel. This problem could be minimized e.g. by lowering the ballast. Since the beginning of the 21st century ballast projection incidents were reported also in the absence of winter conditions. This indicates that the aerodynamic loads induced by high-speed trains are high enough to move the ballasts on the track bed. To gain more information about the flow field underneath high-speed trains Particle Image Velocimetry (PIV) measurements are conducted in the water towing tank. Shown in the figure are PIV results obtained for the head car of a generic high-speed train in the water towing tank.
In the water towing tank obtained PIV results showing the ensemble averaged dimensionless field of the velocity component in traveling direction underneath the head car of a generic high-speed train model