Aerodynamic Analysis of the Opening Hood Structures at Exits of High-Speed Railway Tunnels

Abstract

As train operating speeds increase, the aerodynamic characteristics of the train within the tunnel become more pronounced, and effectively addressing the issue of micro-pressure wave (MPW) over-limits becomes especially crucial. This paper utilized the control volume method to investigate the key influencing parameters of tunnel exit hoods on the mitigation effectiveness of MPWs. Additionally, numerical simulation methods were used to validate these crucial parameters. The analysis considered various opening ratios, different opening forms, and the influence of hoods at tunnel entrances and exits on the amplitude and spatial distribution patterns of MPWs. A design methodology that comprehensively takes into account the advantages of tunnel entrance and exit hoods was proposed. The results showed that a higher opening ratio of tunnel exit hoods led to lower MPW amplitudes. Compared to without opening in the hood, when the opening ratio of the exit hood reached 90%, the maximum amplitude of MPWs at a distance of 20 m from the hood outlet decreased by 48.7%. Various opening forms of exit hoods resulted in distinct spatial distribution patterns of MPW amplitudes, with amplitudes near the openings notably higher than in other areas. There were differences in the mitigation mechanisms between entrance and exit hoods. In comparison to entrance hoods, exit hoods exhibited higher mitigation efficiency within a specific range of MPW amplitudes. Additionally, when both entrance and exit hoods were installed, they achieved the most effective mitigation of MPWs.