Experimental research on unsteady aerodynamic characteristics of EMU in crosswind environment

Under the influence of the steady cross wind environment, the stability, comfort and safety of the EMU running in flat ground conditions will deteriorate. In order to reveal the mechanism of its deterioration, a wind tunnel test was carried out for the EMU to run under the condition of flat ground with steady cross wind. Obtaining the curve of the train surface pressure changing with time, the time-domain and frequency-domain characteristics of the unsteady aerodynamic load on the train are analyzed. The test results of wind tunnel are shown as follows. Under the same wind speed and the same wind direction angle, measuring points No. 1～8 are on the windward side, and No. 9～16 are on the leeward side of the surface of EMU running on level ground. The average pressure of each measuring point on the same side fluctuates within a certain range, and the overall difference is not big. When the wind angle is 90°, the amplitude and maximum value of the pressure at the measuring point increase with the increase of the wind speed, and the average value is proportional to the square of the wind speed of the wind tunnel. That is, unsteady aerodynamic pressure vibrates violently, and the fluctuation range increases significantly. When the synthetic wind speed is 60 m/s, the average, minimum and maximum aerodynamic pressure of the measuring point increases first and then decreases with the increase of the wind angle, showing a sinusoidal function change law. When the wind angle increases to 75°, the inflection point appears, that is, the maximum point. The amplitude of the measurement points on both sides of the vehicle body surface increases with the increase of wind speed, that is, the unsteady aerodynamic pressure vibrates violently, and the vibration amplitude increases significantly. However, the crosswind wind speed and wind angle have little effect on the main vibration frequency band of the unsteady aerodynamic load. The frequency peaks of the measuring points on both sides of middle car body are concentrated in the range of 0～18 Hz. The main vibration frequency is concentrated in the range of 0～4 Hz, and there are obviously three frequency bands of 4～6 Hz, 6～ 8 Hz and 10～14 Hz. The research conclusions provide theoretical basis and data reference for the body design of high-speed EMUs and intercity EMUs. © 2023, Central South University Press. All rights reserved.