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Based on the wave propagation method and improved Fourier series, the coupled vibration model of double-sided immersion (DI) cylindrical shell under arbitrary boundary conditions is established, and its coupled vibration characteristics are solved. The coupling vibration characteristic experiment of a cylindrical shell under the DI condition is carried out for the first time. The calculated natural frequency and vibration acceleration are compared with the model experimental results, which not only verifies the reliability of the theoretical method but also proves the effectiveness of the experimental results. Finally, the coupled vibration characteristics of DI cylindrical shells with arbitrary boundary conditions are analyzed. The results show that the natural frequency and acceleration of underwater immersed cylindrical shells are consistent with those of liquid filling cylindrical shells. The natural frequency and peak acceleration of the single-sided submerged cylindrical shell are greater than that of the DI cylindrical shell. The spring stiffness at both ends of the DI cylindrical shell can be divided into three sections: free boundary, elastic boundary, and rigid boundary. [ABSTRACT FROM AUTHOR]

In order to study the vibration isolation characteristics in water, based on the Flügge theory, a double-walled cylindrical shell model with spring connection is established using the wave propagation method. The fluid inside the inner shell is considered in the model. The reliability of the theoretical method is verified by comparing the calculation results of the mean square velocity with those of the finite element method. The effects of spring stiffness, spring number, fluid load, and inter-shell fluid thickness on vibration transmission of inner and outer shells are studied. The results show that the fluid loading effect of the water medium inside the inner shell can act on the inner shell and the outer shell simultaneously, while the fluid loading effect of the outboard fluid only acts on the outer shell. Under the condition of keeping the total spring stiffness unchanged, increasing the number of springs can reduce the vibration transmission from the inner shell to the outer shell, especially the vibration transmission from the inner shell to the outer shell at low frequencies. The "vibration short circuit" effect easily occurs in the inter-shell water, which is independent of the thickness of inter-shell water. When the elastic connection stiffness is small, the inter-shell water plays a leading role in vibration transmission in the whole frequency range. When the stiffness of elastic connection is large, the inter-shell water plays a leading role in vibration transmission at low frequencies, while the elastic connection plays a leading role in vibration transmission at high frequencies. [ABSTRACT FROM AUTHOR]