Study on Characteristics of Unsteady Aerodynamic Loads of a High-speed Train under Crosswinds by Large Eddy Simulation

In order to study the characteristics of unsteady aerodynamic loads of a high-speed train under crosswinds,the mathematical and physical models of the three dimension flow filed of a high-speed train were established by large eddy simulation.The characteristics of unsteady aerodynamic loads of a high-speed train were studied under different crosswind speeds and at different train speeds,which included the characteristics of the time domain,the frequency domain,the composition and the pulsation.The computational results show as follows: The aerodynamic loads of a high-speed train under crosswinds have strong unsteady characteristics;the choice of the reduction center affects the unsteady characteristics of aerodynamic moments.From the angle of the coefficient of variability(CV) of unsteady aerodynamic loads,the unsteady levels of the side force,roll moment and yaw moment arise with increasing of the yaw angle,the unsteady levels of the capsizing moment and pitch moment reduce with increasing of the yaw angle and the unsteady levels of the lift force first arise and then reduce with increasing of the yaw angle.The frequency analysis shows as follows:There is a good corresponding relation between the peak frequencies of unsteady aerodynamic loads of the head car and the peak frequencies of unsteady aerodynamic loads of the streamlined head and car body;the peak frequencies of a high-speed train lie mainly in the range of 0~5 Hz,which are close to the natural vibration frequency of a high-speed train and so possibly cause the train under crosswinds to be resonated and even overturned.