Abstract: A computational method is proposed based on the Rayleigh-Ritz method for the dynamic characteristics of a baffled completely free circular plate with a side crack and in contact with an infinite water domain on one side, in which the crack could be with arbitrary angle and depth. The functions corresponding to symmetric and antisymmtric modes are included in the displacement trial functions to describe the vibration of the circular plate with an arbitrary side crack. Based on the hypothesis that the water is incompressible, inviscid and irrotational, the added mass density of water is calculated by utilizing Green function method, and the natural frequencies and mode shapes for the wet mode of the cracked circular plate are obtained through Ritz procedure. After the validity and the accuracy of the proposed method are proofed basing on the comparison with the results gained by ANSYS, the influences of water on the dynamic characteristics of the completely free circular plates with side cracks are investigated, in which the cracks with various depths and angles are considered. It is found that the reduction ratios of natural frequencies increase with increasing mode order on the whole due to the influence of water, and the influences of crack depth and angle on the reduction ratios are not evident. The appearance of the crack increases the differences between the dry and wet modes, and the differences are evident for some higher modes.

Key words: Completely free circular plate, Crack, Dynamic characteristics, Fluid-structure interaction, Rayleigh-Ritz