Effect of Surface Roughness on the aerodynamics of a High-Speed Train Subjected to Crosswinds
Most trains have irregular surfaces or parts attached to their bodies that can be represented as roughness in general. However, irregularities, which may exist on train surfaces have normally been ignored in previous studies concerned with train aerodynamics. Therefore, for the first time, this work investigates the effects of roughness on the overall pressure distribution on a train body subjected to crosswinds. This research was aimed onto providing an understanding of the aerodynamics of a 1:25 model-scale passenger train subjected to crosswinds, both with and without surface roughness. Roughness was applied to the roof of the train surface in the form of longitudinal strips, where the height and width of these strips was 1 mm and 2 mm, respectively. The research findings revealed that the roughness on the roof surface was able to reduce the surface pressure on the roof and leeside of the train. It was also observed that the roughness with a 0.7% relative size (the height of roughness/the height of train) was able to change the surface pressures on the roof up to a maximum of 59%. Overall, it was concluded that the rough roof surface could agitate the wind flow in a complex manner.
Keywords- Crosswinds, Pressure coefficients, Rough Surface, Smooth surface, Wind Tunnel tests, Train Aerodynamics.