A novel asymptotic linear method for micro-pressure wave mitigation at high-speed maglev tunnel exit: A case study with various open ratios on tunnel hoods
Authors: ZHANG Jie, ZHANG Mo-lin, HAN Shuai, LIU Tang-hong, GAO Guang-jun
A high-speed train travelling from the open air into a narrow tunnel will cause the “sonic boom” at tunnel exit. When the maglev train’s speed reaches 600 km/h, the train-tunnel aerodynamic effect is intensified, so a new mitigation method is urgently expected to be explored. This study proposed a novel asymptotic linear method (ALM) for micro-pressure wave (MPW) mitigation to achieve a constant gradient of initial compression waves (ICWs), via a study with various open ratios on hoods. The properties of ICWs and MPWs under various open ratios of hoods were analyzed. The results show that as the open ratio increases, the MPW amplitude at the tunnel exit initially decreases before rising. At the open ratio of 2.28%, the slope of the ICW curve is linearly coincident with a supposed straight line in the ALM, which further reduces the MPW amplitude by 26.9% at 20 m and 20.0% at 50 m from the exit, as compared to the unvented hood. Therefore, the proposed method effectively mitigates MPW and quickly determines the upper limit of alleviation for the MPW amplitude at a fixed train-tunnel operation condition. All achievements provide a new potential measure for the adaptive design of tunnel hoods.
