Numerical and experimental study on the aerodynamic force coefficients of railway vehicles on an embankment in crosswind

It is necessary to obtain the aerodynamic force coefficients of the train on the embankment for the assessment of the running safety in a crosswind. In general, wind tunnel tests are conducted using the static train model on the embankment model. In this paper, the influence of the airflow condition and the distance from the upstream end of the embankment model to the train model on the aerodynamic force coefficients is investigated. In the wind tunnel tests, the side force coefficients (C-S) reached their maximum values at a yaw angle of 50 degrees in smooth flow while they reached their maximum values at a yaw angle of 90 degrees in atmospheric boundary layer (ABL) flow. Largeeddy simulation (LES) was made on the flow around the train model on the embankment, and it was found that C-S became larger as the upstream embankment length became smaller owing to the vortex generated near the upstream end of the embankment at the yaw angle of 50 degrees. LES on the flow around the embankment model showed that the distance over which the flow field was affected by this vortex was 16 times the height of the embankment model in smooth flow, and it was 12 times in ABL flow at the yaw angle of 50 degrees.