Study of acoustic radiation from the finite double cylindrical shells with rigid rib underwater

摘要

Finite cylindrical shells were widely used in many under water structures, whose acoustic radiation had been researched for 30 years. Most of the published investigators assumed the ribs as acoustic transparent, in which the acoustic influence of the ribs was not considered. In this presentation, a general approach is suggested to evaluate the acoustic radiation from the underwater finite double cylindrical shells with rings and ribs based on the assumption of acoustic rigid ribs. The vibration of the shell is obtained using the classical Donnell operator. Based on the assumption of acoustic rigid ribs, the interaction equations of fluid and structure consider the dominant forces between cylindrical shells and rings and ribs, such as radial forces, tangential and vertical forces, moments in circumferential direction. The influence of the blocking effect of the ribs in the acoustic field between shells is studied in this presentation. Referencing the solution of commercial software of finite element analysis, the numerical simulation under the acoustic rigid assumptions is better than the results under the acoustic transparent assumption in some frequency bands such as 140Hz-190Hz and 210Hz-230Hz, which corresponds to the natural frequencies of rib vibration in axial direction of cylindrical shells. It can be understood that the acoustic transparent assumption of ribs is available in the frequency band below 140Hz, while the acoustic rigid assumption of ribs can obtain more accurate results in the higher frequency band.