Research on aerodynamic characteristics of evacuated tube train in dynamic operation

The research on aerodynamic characteristics of the evacuated tube train provides a reference for the construction of ETT(Evacuated Tube Train) test platform. A 3-dimensional model was established, and the SST k–ω model was used to solve the flow field. The aerodynamic resistance, pressure distribution and flow field characteristics under constant speed and acceleration conditions were compared, and the influence mechanism of acceleration on the aerodynamic resistance was revealed. The results show that the aerodynamic drag of the head car and the tail car is mainly affected by the choked flow and the detach of the tail shock. In no-choked state, the drag of the tail car increases slowly while that of the head car is unchanged. Compared with the acceleration condition, the reflection of the oblique shock caused by the large starting speed leads to the pressure fluctuation on the train surface, and the amplitude of the fluctuation gradually decreaseswith time. As the head car compresses the front air slowly and the precursor shock wave is weak under the acceleration condition, the changes of the aerodynamic resistance and surrounding pressure of the head car lags behind that of the running speed, and the smaller the acceleration is, the more obvious the lagging effect is. In the stage of uniform speed, the length of the choked section and the tail shock is proportional to the operation time.