Arafat, Mohammad (2023) CFD analysis on the aerodynamic characteristics around a next-generation high-speed train subjected to crosswind. Masters thesis, Universiti Tun Hussein Onn Malaysia.

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Abstract

The development of Next-Generation High-Speed Trains (NG-HST) made of lightweight materials is a challenging task for the transport industry. With the increasing speed and decreasing structural mass of high-speed trains, it raises concerns about the effects of strong crosswinds on their aerodynamics and train stability. Understanding the aerodynamic characteristics is a requirement for train operational safety analysis of the high-speed train under sudden crosswind. Thus, the goal of this thesis is to investigate the aerodynamic loads and unsteady flow structure around a NG-HST subjected to crosswind using computational fluid dynamics (CFD) analysis. A hybrid Detached eddy simulation (DES) was used to resolve incompressible flow around the train. Based on the height of the train model and freestream velocity, the Reynolds number (Re) for the simulation was 1.3×106. The simulation was run in different conditions such as crosswind angles of 15°, 30°, 45° and 60°, no crosswind, six Re, and steady and transient crosswind. Later, the simulation was compared with the wind tunnel from the previous study for validation purposes. In the results, according to power spectral density (PSD) analysis, increasing the Re increased the turbulence intensity of the wake, which gradually dissipated as the distance from the train increased. In terms of transient responses, even low-velocity wind had a very high impact on the aerodynamic loads of the NG-HST. For example, Cs value changes were 166%, 183%, and 190% higher during transient loads for 15m/s, 25m/s, and 35m/s, respectively, compared to normal conditions. In addition, the Cl and Cs with Croll and Cpitch provide a strong justification for the running safety subjected to transient crosswind. On the other hand, the vortex structure formation is relatively complex and unsteady at 13° yaw angles for transient as compared to the vortex formation observed for the steady crosswind. The findings of the study may be used to better understand the flow characteristics in the wake of NG-HSTs for future development

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