Effect of RANS Model on the Aerodynamic Characteristics of a Train in Crosswinds Using DDES

Abstract

Detached eddy simulation has been widely applied to simulate the flow around trains in recent years. The Reynolds-averaged Navier-Stokes (RANS) model for delayed detached eddy simulation (DDES) is an essential user input. The effect of the RANS model for DDES on the aerodynamic characteristics of a train in crosswinds is investigated in this study. Three different DDES models are used, based on the Spalart-Allmaras model (SA), the realizable k-ε model (RKE), and the shear stress transport k-ω model (SST). Results show that all DDES models can give relatively accurate predictions of pressure coefficient on almost all surfaces. There are only some specific differences in the small vortices, while similar flow patterns around trains could be predicted. The SST based DDES model (SSTDDES) gives the most accurate numerical results among the three models for the surface pressure. The variations in pressure on the leeward face play a key role in the variation of the side force.