Large eddy simulation of the flow around a train passing a stationary freight wagon

In this paper, the effect of track spacing on the aerodynamic performance of a stationary double-stacked freight wagon passed by a high-speed passenger train is investigated using large eddy simulation (LES). The passenger train is a 1/20th scale model of an ICE2-shaped high-speed train and consists of nose, two coaches, inter-carriage gap and tail. Based on the speed and height of the passenger train, a flow Reynolds number of 2 × 10⁵ is used in the simulation studies. To isolate the effect of the mesh resolution computations are performed using three different meshes: coarse, medium and fine, consisting of 3.2 × 10⁶, 6.9 × 10⁶ and 9.0 × 10⁶ nodes, respectively. The results are also validated with available experimental data and a good agreement is demonstrated. The aerodynamic loads on the freight containers and passenger train are obtained during a passing process. High side force values are generated on the freight containers when the passenger train approaches followed by a sudden reduction when the nose of the passenger train passes the freight wagons. There is also a reduction in the side force when the tail of the passenger train passes the freight wagon followed by a significant increase when the wake flow hits the freight wagon. Similar behavior is observed for the lift and drag coefficients. The effect of track spacing is investigated by performing simulations at three different track spacing values: 3.5, 4 and 4.5 m. The results show that a reduction in track spacing generally increases the aerodynamic forces on both the freight wagon and passenger train.