Influence of turbulent incoming flow on aerodynamic behaviors of train at 90° yaw angle

Abstract

Turbulent incoming flow conditions are closely matched to the crosswinds experienced by trains in windy areas. Therefore, it is important to investigate how the turbulent inflow affects the flow dynamics around a train. The aerodynamic characteristics of a 1:8-scaled high-speed train at a 90° yaw angle were studied based on the improved delayed detached eddy simulation (IDDES) turbulence model. Four incoming flow conditions were set using a synthetic eddy method (SEM) turbulent generator, including uniform, Lu = 0.5H, Lu = 1H, and Lu = 2H inflow (Lu is turbulence integral length scale and H is reference height). The aerodynamic loads, surface pressure, mean vorticity, vortex structure, velocity deficit, turbulence characteristics, Reynold stresses, turbulence production term, and anisotropy of turbulence were thoroughly analyzed. Turbulent inflow and increasing inflow Lu increased the standard deviation of the aerodynamic loads on the train. A crisis of inflow Lu appeared around 0.5H, meaning the rolling moment and overturning moment were largest under this crisis condition. Turbulent inflow caused vortices on the train's leeward side to come closer to the train, increasing the vorticity thickness and shortening the back flow region. The Reynolds stresses on the train's leeward side under turbulent inflow conditions were strengthened. The spectrum-proper orthogonal decomposition method was used to analyze the dominant mode within the train's leeward region and the corresponding energy distribution in the frequency domain. The aerodynamic admittance function was used to investigate the frequency characteristics of the aerodynamic loads on the train.