IDENTIFICATION OF THE RESONANCES OF A CYLINDRICAL-SHELL STIFFENED BY AN INTERNAL LENGTHWISE RIB

A theoretical and experimental study of the acoustic response of a sub merged stiffened cylindrical shell is presented. The internal rib is m odeled as a clamped-free plate mounted inside the shell perpendicular to the shell surface. The stiffened shell is excited by a normally inc ident acoustic pressure wave. Wave propagation around the circumferenc e of the shell and associated sound radiation are discussed. From the directivity of the monostatic scattering, the resonances in the scatte red sound pressure field can be separated into three different types. A mechanical admittance is used to help identify the different types o f resonances excited in the fluid-loaded stiffened shell. Each type of resonance is shown to be associated with a particular type of interac tion between the shell and the rib in terms of the components of the c oupling forces: i.e., the normal force, the transverse force, and the coupling moment. For kR ranging from 16 to 35, the normal coupling for ce is shown to control the symmetric flexural vibration held in the sh ell, while the coupling moment controls the antisymmetric vibration fi eld. The rib interacts with the membrane vibrations in the shell via t he transverse coupling forces. (C) 1996 Acoustical Society of America.