Particle image velocimetry of the undercarriage flow of downscaled train models in a water-towing tank for the assessment of ballast flight

In this thesis the issue of ballast flight for high-speed trains is closely examined using (a) two-component high-speed particle image velocimetry of the undercarriage flow beneath 1:50 high-speed train models in a water-towing tank and (b) simplified momentum calculations regarding the path of motion of a dislodged trackbed ballast particle. The horizontal and vertical velocity components in the vertical plane extending between the trackbed and the train undercarriage in the trackbed line of symmetry were measured for three different train and three different ground configurations. The measured undercarriage flow fields were applied to an exposed, simplified and virtual ballast particle in the trackbed to simulate its dislodgement, its transport over the trackbed and its flight path.