Sound scattering by a fluid-loaded finite cylindrical shell

Abstract

Let a thin-walled finite cylindrical shell with the hemispherical end caps be immersed in a fluid medium. The shell contains structural inhomogeneities like radial solders and internal ribs and is excited by an axisymmetric pressure load. The paper deals with the numerical and experimental investigation of the sound-pressure field scattered by the shell and its internals. The numerical solution of the problem is based on the finite element method (FEM) with the use of the thin shell theory elements. The Green’s function of the structure is obtained by the FEM and is further used in the boundary element solution scheme using both physical and modal coordinates. Flexural and membrane type eigenmodes of the fluid-loaded structure can be determined and identified. A time-domain solution to the problem obtained by the inverse Fourier transform gives echo-signals of the sound scattered by the structure. Individual pulses in the echo-signal help to localize structural inhomogeneities and to appreciate their importance in the scattered sound field. The membrane type vibrations are shown to be substantially modified by the internal solders and substructures. Experimental investigation is performed for a steel target immersed in a water tank and the numerical results correlate well with the experiment.