Aerodynamic Characteristics Around a Generic Train Moving on Different Embankments under the Influence of Crosswind
Keywords:generic train, grid convergence index, crosswind, flow regime, flow structure
In this article, simulations of crosswinds over a generic train model that are moving on different embankment configurations are discussed. The different configurations of embankment cases were studied using various slope inclinations (i.e. 150°, 160° and 170°). The result is also compared with the base case i.e. train running on a flat ground (FGC). The incident flow angle is varied from 0? to 90?. The flow around the train has been considered incompressible and is obtained by solving the incompressible form of the Reynolds Navier-Stokes (RANS) equations combined with the SST ???? ? ???? turbulence model. A grid convergence study is presented in order to examine the reliance of the flow solution on spatial discretization. The Reynolds number used, based on the height of the train and the freestream velocity, is 3.7 × 105. In the result, it is established that variations of incident flow angle resulted in the development of different flow behaviors. Two unique flow regimes appear which represent a slender body behavior at a smaller range of incident flow angles (below 45°) and bluff body behavior at a much higher range of incident flow angles (above 45°). Due to the existence of embankment structure underneath, flow rising over the top accelerated considerably at the windward area. The wake size especially in the bluff body flow regime (above 45°) was much larger since the changes of the altitude with the flat ground allowed the wake to rotate and move more freely in the leeward region. Subsequently, changing in flow patterns has its impact on the important aerodynamic loads such as the coefficients of side force, lift force, and rolling moment in which there were also worsen for the train running on the embankment as compare to FGC.