Linear free vibrations of cylindrical shell is analyzed in this research by means of ABAQUS software acoustic option. Liquid is assumed nonviscose and incompressible. First, natural frequencies of vertical cylindrical shell are calculated for various filling ratio with clamped- free and clamped- clamped boundary condition. Numerical results are validated through comparison with results of experimental and semi analytical finite element methods. After validation, more natural frequencies are calculated for various filling ratio. Second the analysis of vertical cylindrical shell, natural frequencies and mode shapes of horizontal cylindrical shell are calculated and compared with results obtained by using Rayleigh-Ritz method. Then considering oscillation of free surface, natural frequencies of the same shell with the same wet angles are calculated. Third validation of the results for unaxisymmetric geometry, natural frequencies of horizontal tank which is obtained by adding two flexible plates to previous horizontal shell are calculated. Then a horizontal tank with elliptical section and area equal to the previous tank is analyzed as a model of fuel carrying tank of a truck. It is shown that mode shapes don’t change but natural frequencies decrease noticeably. Finally, behavior of partially liquid filled shell is analyzed under harmonic load, and the amplitude of a point at the middle of the shell versus the excitation frequency is plotted. It is shown that resonance occurs when excitation frequency is equal to the natural frequency.
