Abstract: An unsteady aerodynamic characteristics caused by steady crosswind affect the safety and comfort of viaduct operation train. The wind tunnel test of viaduct operation electric multiple units(EMU) under steady cross wind is carried out. The time-history curve of the surface pressure of the car body is tested and recorded to analyze its unsteady aerodynamic characteristics and vibration characteristics. The test results show that:under the same sideslip angle and the same wind speed, the average value of the time course pressure at the same side of car body is not much different, and is basically equal. When the sideslip angle remains unchanged at 90°, the average, maximum and minimum values of the aerodynamic pressure at the measuring point are proportional to the square of the synthetic wind speed; as the wind speed increases, the unsteady pressure fluctuations at the measuring point increase and the fluctuation amplitude is significant increase. When the synthetic wind speed is maintained at 60 m/s, the average, maximum and minimum values of the aerodynamic pressure at the measuring point are proportional to the 1.27 th power of the sideslip angle; as the sideslip angle increases, the peak-to-peak value at the measuring point appears parabolic change law, the amplitude of unsteady fluctuation first decreases and then increases. The main vibration frequency band of viaduct operation EMU coach remains unchanged with the increase of the crosswind wind speed and the same with the increase of the sideslip angle; the vibration frequency of two sides are both in the range of 0-18 Hz, and there are obviously several main vibrations frequency bands are 8-10 Hz, 0-2 Hz, 14-16 Hz and 16-18 Hz respectively.

Key words: unsteady aerodynamic characteristics, viaduct, EMU, vibration characteristics, experimental research