Simulation of unsteady aerodynamic loads on high-speed trains in fluctuating crosswinds

Abstract

To study the unsteady aerodynamic loads of high-speed trains in fluctuating crosswinds, the fluctuating winds of a moving point shifting with high-speed trains are calculated in this paper based on Cooper theory and harmonic superposition method. The computational fluid dynamics method is used to obtain the aerodynamic load coefficients at different mean yaw angles, and the aerodynamic admittance function is introduced to calculate unsteady aerodynamic loads of high-speed trains in fluctuating winds. Using this method, the standard deviation and maximum value of the aerodynamic force (moment) are simulated. The results show that when the train speed is fixed, the varying mean wind speeds have large impact on the fluctuating value of the wind speeds and aerodynamic loads; in contrast, when the wind speed is fixed, the varying train speeds have little impact on the fluctuating value of the wind speeds or aerodynamic loads. The ratio of standard deviation to 0.5\( \rho K\bar{u}^{2} \), or maximum value to 0.5\( \rho K\bar{u}^{2} \), can be expressed as the function of mean yaw angle. The peak factors of the side force and roll moment are the same (~3.28), the peak factor of the lift force is ~3.33, and the peak factors of the yaw moment and pitch moment are also the same (~3.77).