Acoustic scattering from submerged finite-length cylinders with end caps and internal ribs: A comparison of methods

Abstract

The various methods that could be used to model the monostatic scattering of sound waves from cylindrical bodies of finite length with end caps and a coaxial set of reinforcing ribs, immersed in fluids, are compared. The various approaches include the Kirchhoff method, the Keller theory of geometrical diffraction (GTD), or combinations of these methods applied to soft cylinders having alternating bands of rigid and soft composition spaced at selected intervals on the cylindrical surface. The resulting four cases are tackled by the physical optics method and by the GTD. Parts of the work are compared to earlier findings [D. Brill and G. C. Gaunaurd, Proceedings, First French Congress on Acoustics, Lyon, Vol. 1, pp. 320–324 (1990)]. Numerical evaluations are produced in the various instances, analyzed, and they are contrasted to one another. In all cases the predictions reveal a lobe structure that resembles that of a diffraction grating. Ways to enhance or destroy this peculiar pattern, and other (more complex) ways to model this problem by accounting for the structure's elasticity, while retaining the simplicity of the above findings, are discussed. [Work supported by NSWC.]