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    Numerical investigation of the impact of wall boundaries on aerodynamic noise in high-speed trains
    (2026-01-01)
    Ma, Zhi Yuan
    ;
    Feng, Qing Song
    ;
    Prapamonthon, Prasert
    ;
    Cheng, Gong
    ;
    Sun, Zhen Xu
    As the operating speed of high-speed trains continues to rise, aerodynamic noise has become a critical factor influencing train performance and passenger comfort, especially in confined environments like tunnels. In this study, a comprehensive simulation of the aerodynamic noise generated during the entire ‘open air-tunnel-open air’ transition at 450 km/h was performed using the improved delayed detached eddy simulation (IDDES) turbulence model and overset grid method, with results validated against field measurements. The findings reveal that, compared to open-air conditions, the tunnel environment induces higher-flow velocities around the train, stronger pressure fluctuations on the train surface, and more pronounced vortex shedding in the wake. Sound pressure levels (SPLs) at surface measurement points are typically about 10 dB(A) higher in the tunnel, with the primary differences observed in the 100–300 Hz frequency range, while both scenarios exhibit spectral peaks near 530 Hz. In the bogie region, tunnel noise is dominated by pressure-wave coupling and wall reflections, which amplify low- and mid-frequency components, whereas under open-air conditions, local vortex shedding and wake instabilities prevail, resulting in more high-frequency noise. The web structure contributes to the reduction of aerodynamic noise from the bogie area, with a particularly significant decrease observed in tunnel conditions. Along the tunnel wall, the SPL initially increases and then decreases, reaching a peak of 125.7 dB(A). After exiting the tunnel, the measurement points at Section L in the open air show a reduction of approximately 10 dB(A) compared to the corresponding tunnel-wall points. This study highlights the substantial amplification of low-frequency noise caused by wall confinement and demonstrates the noise-reduction potential of the web structure. The results provide valuable theoretical insights and numerical evidence for aerodynamic noise control in higher-speed train tunnels, offering significant engineering implications.
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    Structural Responses of a Tunnel Lining Due to an Adjacent Loaded Pile
    (2023-06-01)
    Lueprasert, Prateep
    ;
    Jongpradist, Pornkasem
    ;
    Jongpradist, Pattaramon
    ;
    Schweiger, Helmut F.
    The work reported in this article numerically investigates the structural forces in a tunnel lining after applying an adjacent loaded pile for varying pile tip positions considering the tunnel and soil stratum. Analysis reveals that the structural responses are strongly associated with the distorted elliptical shape of the deformed tunnel, which depends on the relative position of the pile tip with respect to the tunnel crown. The change in bending moment in the tunnel lining is of greater concern than the change in the axial force of the tunnel lining. Although the maximum change in structural forces can be up to 115% of the initial value, assessment in terms of maximum change in the structural forces is unsuitable. This is because the maximum change does not occur at the location that has large initial forces. The total combined bending moment and axial force in the lining at the tunnel spring line and in the tunnel invert zone are recommended for cases where the pile tip level is at the tunnel spring line and cases with the deepest possible pile tip elevation, respectively, for the assessment.
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    Three-dimensional air quality assessment simulations inside sky train platform with airflow obstacles on heavy traffic road
    (2018-07-01)
    Suebyat, Kewalee
    ;
    Pochai, Nopparat
    Air pollutant levels in Bangkok are generally high in street tunnels. They are particularly elevated in almost closed street tunnels such as an area the Bangkok sky train platform with high traffic volume where dispersion is limited. This area has no air quality measurement stations even though there is a high percentage of people living around this vicinity. We are interested to conduct a research the Bangkok sky train platform due to the traffic density and enormous polluted areas. Therefore, we proposed a numerical modeling of air pollution concentration in sky train platform with airflow obstacles on heavy traffic road as an approximated solution of the three-dimensional advection-diffusion equation by using the finite difference methods. Our research presentation is based on how air pollution model depends on the flow of air pollution and wind directions including the governing equation of the corresponding three-dimensional advection-diffusion equation is presented. This also includes the initial condition and boundary conditions of traffic and polluted areas. In order to illustrate the performance of the model, the numerical experiments are presented. The comparison between the two methods and the simulations of air pollution control are proposed. The three-dimensional advection-diffusion equation is solved by using the Forward Time, Centered Space (FTCS) and Forward Time, Backward Space (FTBS) schemes. The results obtained indicate that the FTCS method provides a better result than FTBS method. Furthermore, the proposed experimental variations of the boundary condition in the entrance gate do affect the air pollutant concentration of each floor.
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    A numerical simulation of a three-dimensional air quality model in an area under a Bangkok sky train platform using an explicit finite difference scheme
    (2017-11-01)
    Suebyat, Kewalee
    ;
    Pochai, Nopparat
    One of the air pollution problems in areas under Bangkok sky train platforms are caused by the pollutant coming from the entrance to the tunnel. It increases the concentration of pollutant. This affects the well-being of humans and the environment. In this research, the governing equation of the air quality model in a considered area is a three-dimensional advection-diffusion equation with time dependence. A finite difference technique is employed to approximate the solution of the governing equation. This model is solved by using an explicit forward difference in time and central difference in space (FTCS). We consider the wind inflow in two cases: there is wind inflow only in x-direction and there are wind inflow in x- direction and y-direction. In addition, we added obstacles such as the columns along the middle into the tunnel. The results of the model are satisfactory. It will be able to be implemented on a problem of air pollution control in a more complicated tunnel.