Experimental Study of the Pressure Waves inside a Railway Tunnel during a Passage of a High-Speed Train

During the entry of a high-speed train into a tunnel, pressure waves are generated, which increases the loads on the structure of the train and the tunnel and on the equipment inside the tunnel. Furthermore, the instantaneous pressure changes can cause discomfort of the train's passengers. Further, if the tunnel walls are smooth and there is no ballast bed, the compression wave generated due to the train's nose entry can steepen and results in the so-called tunnel-boom at the opposite end of the tunnel. To ensure a safe and comfortable tunnel passage modern high-speed trains are sealed, which involves extra weight and therefore a higher energy consumption of the train. Furthermore, the train velocity is reduced during the tunnel passage. In the near future, trains are meant to be faster and have double-deck waggons with a large cross-sectional area. Additionally, tunnels will be single-track and double-tube tunnels and will have a small cross-sectional area for each tube. Because of these developments, this pressure-wave issues must be solved by developing a system to damp these pressure waves. To study the pressure waves in model scale, experiments were done in the tunnel-simulation facility Göttingen (TSG), which is a moving-model rig and was built in 2010. The train used is a model of the German high-speed train ICE3 in the scale 1:25 and the tunnel has a length of 10m. It can be equipped with an extended portal, which is meant to have an influence on the first compression wave. The train velocity varied from 37m/s to 46m/s and the pressure inside the tunnel was measured with piezoresistive pressure transducers. Additionally, high-speed particle image velocimetry (high-speed PIV) was used to study the flow field around the train's nose and inside the tunnel portal. The results of the tests with and without tunnel hood show, that the shape of the hood has a big influence on the slope of the pressure. By adjusting number and size of the vents of the hood, the pressure gradient, which is the important factor for the pressure-depending problems, can be reduced by about 45%. The results achieved with the new facility show a high repeatability and reproducibility. The investigation of train-tunnel interaction is more realistic than in conventional wind tunnels. Additional to the pressure changes inside a tunnel, forces on trackside objects induced by a passing train can be studied