Comparison between train-tunnel pressure signatures single unit vs double unit

The aerodynamic effects that occur when a high-speed train enters and crosses a railway tunnel are different from those observed in open air. Their prediction is important as the pressure variations may be critical for the train structures and for the health and comfort of passengers. European regulations impose pressure thresholds limits which the trains must comply to be homologated for the circulation in tunnels. Nowadays, full-scale tests are required to demonstrate the respect of this constraints. The growing demand of the high-speed transport has pushed the rail network managers to explore new strategies to increase the railway capacity; one of these are the double unit trains, which consist of the coupling of two trains of the same type. In this work, through experimental analysis, the pressure variation produced by a double unit train passing through a tunnel are compared to the results of a single unit train. Furthermore, the possibility of obtaining the pressure curves of the double unit train starting from the single unit data is discussed. Finally, a possible explanation of the difference found between the measurements concerning the single and the double units is given.