oil transportation;  oil storage tanks;  fluid-structure interaction system;  natural frequency;  Mode shape

Taking the railway horizontal circular oil storage tank (horizontal tank), the main tool in oil transportation, the principle of liquid-solid coupling and the finite element analysis software ANSYS as the tool were used to analyze and calculate the modal mode of the horizontal tank loaded with free liquid at different depths, and the natural frequency of the tank at different liquid depths and the osmogram of the natural frequency of the first four orders were obtained. The analysis results show that the natural frequency value of the horizontal tank gradually decreases with the increase of liquid depth, and the calculation results are quite different when the natural frequency of the system is solved by the coupling method and the average density method.