Numerical study for the aerodynamic performance of double unit train under crosswind

The present work focused on the aerodynamic performance of double unit trains (DUT) and traditional single unit trains (SUT) under crosswinds. The aerodynamic coefficient as well as the characteristics of the time-averaged and instantaneous flow of the SUT and DUT were calculated using the improved delayed detached eddy simulation (IDDES) method for 1/8th scale models. The numerical results were verified by wind tunnel tests. The time-averaged flow pattern on different cross-sections and horizontal planes were compared for the SUT and DUT. The pressure coefficients on the loops of different cars were also analyzed quantitatively. The vortices around the SUT and DUT were visualized, and the frequency characteristics of each car of the SUT and DUT were computed. The coupling region changed the forces on the train and increased the overall drag of the train. Faster vortex development was found on the last three cars of the DUT. Furthermore, a higher velocity belt was generated by the gap of the coupling region. The coupling region gave a significant influence of the power spectrum densities (PSD) on the last four cars and a relatively slight impact on the first two cars.