Comparison of dynamics characteristics of empty and full load gondola cars subjected to crosswind

An aerodynamics model of freight train with one locomotive and four gondola cars was developed. The pressure distributions on the surfaces of empty and full load gondola cars at different wind speeds were studied. The aerodynamic loads on gondola cars were calculated and applied to the aerodynamics model. The dynamics characteristics of empty and full load gondola cars under crosswinds with different speeds were analyzed from the perspectives of vehicle posture and operation safety. Research results show that the first gondola car behind the locomotive suffers the largest side force, lift force and rolling moment under crosswind. At a wind speed of 10 m·s^-1, the maximum values are -7.17 kN, 4.59 kN, and 1.89 kN·m, respectively. For the first gondola car, when wind speed is 10 m·s^-1, the side force, pitch moment, and yaw moment at full load state decrease by 15.8%, 79.0%, and 12.2% compared to no load state, respectively. Conversely, the lift force and side rolling moment increase by 39.9% and 56.6%, respectively. Thus, the loading state significantly affects the aerodynamic loads on gondola cars under crosswind. Empty gondola car is more susceptible to the aerodynamic loads. At the wind speeds of 25 and 30 m·s^-1, the lateral displacements of the first empty gondola car are -12.66 and -14.82 mm, respectively, while those of the first full load gondola car are -12.01 and -13.68 mm, respectively. The side rolling angles of the first empty gondola car are -0.69° and -0.83°, respectively, compared to -0.64° and -0.73° for the first full load gondola car. Therefore, the lateral displacement and side rolling angle of empty gondola car are greater than those of full load gondola car. At a wind speed of 25 m·s^-1, the wheel load reduction rate of empty gondola car reaches 0.68, exceeding the limit of 0.65, while that of full load gondola car is 0.24, below the limit. At a wind speed of 30 m·s^-1, the overturning coefficient of empty gondola car reaches 0.75, approaching the limit of 0.80, while that of full load gondola car is only 0.23. Thus, there is a safety risk for empty gondola cars under high-speed crosswind.