Acoustic scattering from a fluid-loaded cylindrical shell with discontinuities: Double plate bulkhead

Abstract

The far-field acoustic scattered pressure from a fluid-loaded cylindrical shell with two internal plate bulkheads is determined from knowledge of the junction forces between the shell and the internal plate structures. Results are shown for the circumferential modes n equals 0 and 2. This paper follows a previous paper in which a single internal plate bulkhead was considered. The approach used to solve for the junction forces is the same as that used in the previous paper. However, the results for the far-field scattered pressure show interesting features that can be associated with the acoustic and structural interaction between the two bulkheads. The interaction is due to both acoustic coupling and structural coupling. The scattered pressure associated with the radial forces at the bulkheads show an interference pattern with high and low intensity regions. The high intensity regions correspond to locations with constructive interference between the components of the scattered pressure by each bulkhead, which have dipolelike radiation characteristics. The low intensity regions correspond to locations with destructive interference. The same type of interference pattern is obtained in the scattered pressure component associated with the radial bending moments. The components of the scattered pressure associated with the bending moment at each bulkhead have quadrupolelike radiation characteristics. However, the contributions of these components is small compared to the other contributions. The scattered pressure components associated with the supersonic, axial longitudinal, and tangential shear waves do not show much of an interference pattern and this is mainly attributed to the fact that the scattering from these supersonic waves has preferred directions of propagation. All components of the scattered pressure show areas of high intensity at very specific frequencies which can only be attributed to structural interaction through the shell between the two internal bulkheads. The far-field scattered pressure results are presented for both bistatic and monostatic scattering.