Search

• The overset mesh technology is used to simulate the train running in the tube. • The flow topology considering the ground effect has been visualized numerically. • The influence of the nose length on the wave systems is reported. • Two distinct mechanisms for the formation of flow separation are identified. • The relationship between the aerodynamic loads and flow structures is described. The flow structure and aerodynamic loads in evacuated tube transportation with three nose lengths (5, 10 and 15 m) at 1500 km/h are investigated by overset mesh technology. The governing equations of the IDDES model for 3-D, unsteady compressible flow are employed. The numerical algorithm is validated via moving model and wind tunnel experimental data. The flow topology considering the ground effect is revealed and compared. The wake is highly complex, characterized mainly by wave systems and trailing vortices. Additionally, the influence of the nose length on the generation of wave systems is discussed in detail. The largest shock intensity is identified at 5 m case, followed by 15 m case, and the smallest case at 10 m. Differences in wave systems also caused the two distinct mechanisms for the formation of flow separation and the evolution pattern of the wake vortex to be identified for three nose configurations. By comparison, the nose length increase is helpful to reduce the length of the disturbed region of the leading shock wave, the aerodynamic loads on the train surface and aerodynamic drag. A qualitative description is also presented of the relationship between the fluctuations of aerodynamic loads and flow structures. [ABSTRACT FROM AUTHOR]