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

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-εmodel(RKE),and the shear stress transport k-ωmodel(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.

Numerical Study on Aerodynamic Performance of High-Speed Pantograph with Double Strips

Pantograph is a critical component of the high-speed train.It collects power through contact with catenary,which significantly affects the running safety of the train.Pantograph with double collector strips is one common type.The aerodynamic performance of the collector strips may affect the current collection of the pantograph.In this study,the aerodynamic performance of the pantograph with double strips is investigated.The numerical results are consistent with the experimental ones.The error in the aerodynamic drag force of the pantograph between numerical and experimental results is less than 5%.Three different conditions of the strips are studied,including the front strip,the rear strip,and the double strips.Results show that the presence of the front strip will affect the lift force of the rear strip,and reduce the resistance of the rear strip under the opening condition.Meanwhile,the rear strip has few effects on the front strip under the opening operation condition.The law of the resistance for the interaction between two strips under the closing condition is similar to the opening one.