Effect of internal inhomogeneities on acoustic scattering from finite cylindrical shell bounded by hemispherical endcaps

Abstract

The acoustic scattering from an air-filled finite cylindrical shell with hemispherical endcaps is considered. In axial incidence, experimental studies have shown formation of compressional wave S0 resonances. These resonances are predicted and identified by applying the phase-matching condition over the meridian circumference. However, frequency irregularities observed experimentally on spectra have suggested that the assemblage quality during the manufacturing of the object may be not negligible. Indeed, internal nonuniformities of the shell at the junctions of cylindrical and hemispherical shells are present and modify certain wave propagation phenomena. The aim of this study is to discover these experimental conditions of the studied object through a numerical model with internal annular inhomogeneities localized at the junctions of the substructures and for two different b/a ratios (internal to external radius ratio) equal to 0.97 and 0.99. In the studied frequency range (50–300 kHz), in addition to the S0 wave, another peripheral wave A can be generated for the ratio b/a=0.97. The numerical approach is based on the discretization of the shell and determination of its eigenmodes (FEM). Acoustical pressure field is found by the boundary integral equation procedure (BEM). The comparison of numerical and experimental results is presented in frequency and time domains.