Aerodynamics of high-speed train entering a tunnel

Pao Yue-kong Library Electronic Theses Database

Aerodynamics of high-speed train entering a tunnel

 

Author: Zhang, Qi
Title: Aerodynamics of high-speed train entering a tunnel
Degree: M.Sc.
Year: 2015
Subject: High speed trains -- Aerodynamics.
Tunnels -- Aerodynamics.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Mechanical Engineering
Pages: xxvi , 166 pages : color illustrations
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2825406
URI: http://theses.lib.polyu.edu.hk/handle/200/8190
Abstract: The modern railway system requires faster transportation and more tunnel applications, where aerodynamic effects become increasingly severe. Among all the aerodynamic problems, the fierce pressure fluctuation induced by a train entering a tunnel is one of the most significant phenomenon which can result in passenger discomfort, the crush of the train windows, the fatigue failure of the train frame and the micro-pressure wave at the tunnel portal. Thus, the knowledge of the unsteady aerodynamics of a train entering a tunnel is essential to the modern railway system design. In this dissertation, a numerical computation of the train-tunnel system with scaled dimensions is carried out by using an axisymmetric, unsteady, turbulent, compressible flow model, where the flow field and corresponding pressure waves are investigated. This case is validated to the experiment data of a journal paper in order to verify the numerical methods and mesh design. To alleviate the fierce pressure fluctuation, two kinds of hood design and one branch solution are discussed. The results show that the presence of a blind hood aims to increase the time of first pressure rise induced by a train entering the tunnel, where the first pressure rise is split into several stages and the maximum pressure gradient is reduced by 45.8%. The introduction of uniformly distributed gaps onto the blind hood also extends the duration of the first pressure rise, while it remains its one-step character and the maximum pressure gradient can be reduced by 31.5%. By adding the branch, the pressure fluctuation pattern is changed critically, which results from the more reflections of pressure waves inside the tunnel. The results show that the maximum pressure magnitude and pressure gradient is attenuated by 14.0% and 13.6% respectively.

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