| Abstrakt: |
Strong gusts of crosswind have been found to pose serious safety risks to both road and rail vehicles worldwide. When wind conditions suddenly change, it can impact the aerodynamic forces acting on rail vehicles, potentially leading to instability and even overturning. Moreover, most prior works on aerodynamic performance primarily focused on constant or steady crosswind conditions. However, the unpredictability and variability of aerodynamic forces in transient crosswinds present a significant drawback for high-speed rail vehicles, highlighting the importance of investigating the influence of wind fluctuations on their performance and safety. This study aims to investigate the aerodynamic behavior of a next-generation high-speed train (NG-HST) subjected to transient crosswinds utilizing computational fluid dynamics (CFD) simulation. A stepwise wind model for two different wind loads of 25 and 35 m/s was selected to simulate transient wind conditions while the train operating condition was 400 km/h. A hybrid Reynolds-Averaged Navier–Stokes (RANS) and Large Eddy Simulation (LES) approach known as Delayed Detached Eddy Simulation (DDES) turbulent model was employed in this study. The results of the CFD simulation indicate that low-velocity winds have a significant influence on the aerodynamic forces of the train. For example, the pitching moments (Cpitch) at wind speeds of 25 and 35 m/s were found to be 192 and 194% higher, respectively, compared to conditions with the absence of crosswind. Additionally, changes in side force coefficient (Cs) during sudden wind conditions were 183 and 190% higher in comparison with no crosswind condition at 25 and 35 m/s, respectively. Furthermore, a variation of 10 m/s in wind load results in more than a 50% increase in the effects observed for all force and moment coefficients, with the rolling moment coefficient experiencing a particularly notable increase, reaching approximately 168%. For the vortex structure, it showed comparatively unsteady and complex behavior at a 25 m/s wind load under transient conditions compared to constant crosswind, as fluctuating wind speeds induce variations in vortex intensity and distribution, resulting in heightened turbulence levels within the airflow. |
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