Investigating the Effect of Clearance Distance between the Floor of a High-speed Train and Ground on Aerodynamic Forces in Presence of Side Wind

Abstract

The main objective of this paper was to propose the real model of the high speed train regarding the side wind disturbance. In the first part of this article, the turbulent air flow around a simplified design of a high-speed vehicle was numerically analyzed using finite volume method and four RANS turbulence models, including k-ω SST, k-ε RNG, Spalart-Almaras, and Launder and Sharma. The results of numerical simulations regarding the wall function were validated by experimental works and it was shown that in the area near the wall, the SST k-ω model had the best simulation for the horizontal component of the velocity (21% error). The results of the lift coefficients showed that at short distances from the train floor to the ground due to relatively strong wind with angles less than 0.2 radians, the lift coefficient was negative and as a result, the forces acting on the train were downward. Finally it was shown that by increasing the wind angle, this coefficient gradually becomes positive, which can disrupt the stability of the train. It can be concluded that in trains whose floor to ground distance is more than 0.136 of the train height, the balance is maintained only in the absence of side wind.