The Research On Underwater Acoustic Radiation Characteristics Of Stiffened Cylindrical Shell By Airborne Sound

Submerged stiffened cylindrical shell and double cylindrical shell are the main structures of the pressure hull of submarine. In practice, machines in hull arouse hull's vibration and underwater sound radiation in three ways: the vibrational machines inspiriting hull through bases; the vibrational machines inspiriting hull through pipelines; the machines radiating sound as sound sources, and the sound pressure inspirits the hull. The sound radiation by mechanical force has been investigated properly by many investigators. This thesis mainly study acoustic radiation mechanisms of double cylindrical shell by sound source, the comparisons of underwater sound radiation properties of single cylindrical shell and double cylindrical shell by mechanical force and sound source are carried out.In this thesis, a' cavity-inner cylindrical shell-ring flow field-out cylindrical shell-out radiated sound field' coupling equation based on Flügge thin shell theory and Helmholtz equation is presented for evaluating the vibration and sound radiation characteristics of a submerged stiffened double cylindrical shell which excited by harmonious forces and airborne sound pressure. To solve this coupling equation, the shell's displacement is expanded in a series of its in-vacuo eigenmodes. The cavity's displacement is expressed by acoustic modes. The inside and outside sound pressure are treated as reaction forces which act on the shell are applied into the general controlling shell equation. Lastly, the acoustic-fluid-structure coupling vibration equation expressed by shell's displacements is gotten. The focus of the numerical calculation are the analysis of the inside and outside pressure level, inside radial quadratic pressure level, radial quadratic velocity level, outside acoustic radiated power level and translate function of a finite stiffened double cylindrical shell. The effects of structure geometrical parameters, physical parameters on the vibration and sound radiation of double cylindrical shell are discussed in detail. And the comparisons of underwater sound radiation properties of single cylindrical shell and double cylindrical shell by exciting force and sound source are carried out. Some meaningful conclusions are obtained.