Zou Ming-Song, Wu You-Sheng, Liu Jian-De, Liu Shu-Xiao «A Mixed Analytical-Numerical Method for the Vibro-Acoustic Analysis of an Underwater Ring-Stiffened Cylindrical Shell Containing Substructures» Акустический журнал, 64, № 5, с. pp. 596-604 (2018)

A new sono-elastic substructure method is proposed in this paper to improve the computational efficiency of the hull-substructure coupled and fluid-structure interacted vibration and acoustic radiation of a submerged cylindrical-shell-type vehicle. The typical part of the vehicle structure is divided into the main hull and the internal substructures. The fluid-structure interaction problem of the main hull is solved by an analytical method based on the simplified model of a single-hull ring-stiffened cylindrical shell simply supported at both ends. Meanwhile, the substructures are numerically modeled through the Finite Element Method, with the condensed dynamic stiffness matrices of them obtained via the Superelement Method of Modal Synthesis. The main hull and the internal substructures are then integrated according to the boundary compatibility conditions at the connecting parts. Thus, a Mixed Analytical-Numerical Substructure (MANS) method is formulated. The applicability of this method is validated by two numerical examples as well as the test results of a large-scale submerged structural model. It is shown that the MANS method is suitable for the prediction of vibration and acoustic radiation of typical cylindrical-shell-type submerged structures in the medium frequency region.

Zhou Fulin, Wang Bin, Fan Jun, Peng Zilong «Theoretical and Numerical Studies on in vacuo Structural Admittance of an Infinite, Coated Cylindrical Shell» Акустический журнал, 65, № 1, с. pp. 14-22 (2019)

Studying the interaction of sound with a coated cylindrical shell immersed in water is essential for improving existing underwater target detection and classification algorithms. According to the impedance theory of sound scattering, in vacuo structural admittance describes the relationship between the sonar-induced forces and the resulting vibration on the surface, which can be used to solve the problem of the acoustic scattering and radiation. In this work, we investigate numerically and theoretically the structural admittance of a coated cylindrical shell. Analytical expressions of the structural admittance are derived for different external forces: a plane acoustic wave, a normal point force, and a random noise field. The structural admittance is also numerically evaluated. The results show that the structural admittance is independent of exterior medium and fluid loading. According to the impedance theory of sound scattering, the scattered field of a coated cylindrical shell is calculated by combining the structural-, acoustic-, and internal-admittance matrices. Because of the non-local property of structural surface admittance, we build an algebraic model of a coated object by nonlinear curve fitting and study a local approximation of the structural admittance. We also find that simplifying the large matrices is useful for research on structural vibrations. Thus, this work presents a systematic study of the acoustic scattering characteristics of structural admittance of an infinite, coated cylindrical shell.