Numerical investigation on application of train body airflow diversion device to suppress pressure waves in railway high-speed train/tunnel system

The development of the high-speed maglev train (HSMT) is important for the future of high-speed rail transit. A pressure wave (PW) is a common aerodynamic effect in high-speed railway tunnels. For HSMTs with a speed of 600 km/h, the amplitude of PW in the tunnel can be very big, which maybe far exceed the current design strength standard of the train body structure and seriously threatens the safety of the railway train/tunnel structure and passenger ear comfort. Therefore, aerodynamic PWs caused by a two-dimensional axisymmetric model with an ellipsoidal nose passing through a tunnel was investigate, and the numerical method adopted in this study was validated by two scaled moving model tests. The PWs caused by trains in four cases and the effects of train speed and tunnel length were analysed and compared. Some results show that diversion device significantly reduces the amplitude of the PWs (∆Cp) on the train surface and tunnel wall. The diversion device on the train tail (C4) not only changes ∆Cp, but also changes the waveform. The diversion device on the train tail (C3) and diversion device on both train head and tail which are connecting each other (C2) mainly reduced the ∆Cp. When the decrease in both PWs on the train surface and tunnel wall is considered, C2 has the best effect. With an increase in the train speed, the effect of C2 on restraining the PW on the train surface and tunnel wall increases to a certain extent. However, the restraining effect on the micro-pressure wave (MPW) at the tunnel exit does not exceed 5%. The suppression effect of C2 on ∆Cp on the train surface and tunnel wall decreases with an increase in the tunnel length. However, it does not change the distribution law of ∆Cp along the train and tunnel. This study can provide a reference for the design of the body of HSMTs and the suppression of PW in tunnels.