Vibration and sound radiation from submerged finite cylindrical shells reinforced with axially periodic stiffeners

摘要

Based on modal analysis, an approximate analytic method is developed to study sound radiation characteristics of a finite submerged axial periodically stiffened cylindrical shell excited by radial harmonic forces. Supposing axial stiffeners interact on the cylindrical shell only through normal forces, the formula for calculating the additional impedance of axial stiffeners is derived. So, the axial stiffeners reaction force on a shell can be expressed by additional impedance. The approximate solutions are derived for the vibration and sound radiation from an axially-stiffened finite cylindrical immersed in acoustic fluid, in the expression of which additional impedance due to the axial stiffeners will appear in the coupled vibration equation of the shell. As a result, the vibration and sound radiation of the shell are dependent on the mechanical impedance of the shell, the radiation sound impedance and the additional impedance of the axial stiffeners. Based on the numerical simulation, the characteristics of the acoustic radiation and radial quadratic velocity on the surface of the shell and the influence of different parameters on the results are investigated, respectively. It is found that the axial stiffener number has just a slight influence on radiated sound power, whereas structural damping has a great influence on radiated power and radial quadratic velocity on the surface of the shell. This study can give some guidelines for noise reduction of his kind of shell.