CFD ANALYSIS OF PRESSURE WAVES AND LOADS ON NON-TIGHT TRAINS PASSING TUNNELS

Computing the loads for a train passing a tunnel requires to predict both the external and the internal pressure variations in time, both of which are strong and quick for a non-pressure tight train. The key achievement of this work has been the development of 3D CFD Star-CCM+ overset mesh simulations capable of simulating the single train tunnel entry and tunnel passage as well as the two trains crossing inside the tunnel. Unfortunately it is not affordable to execute a 3D CFD study for the tunnel passage of each new train model, so 1D CFD codes have been employed, simplified predictive models have been developed and both have been compared to the 3D CFD results. An important result has been identifying the influence of several parameters on the loads caused both by the travelling pressure waves generated when the train enters the tunnel and by the pressure disturbances due to train crossing inside the tunnel, using Star-CCM+ parameters sweeps simulations over train speed and train and tunnel geometrical parameters. The main conclusion is that the internal pressure variation is particularly important to compute the loads, especially for non-tight trains. For this reason it is necessary to take into account both the carriage free length and the position along the carriage on which the loads are needed