Abstract
There are numerous analytical approaches for the calculation of sound scattering from cylinderlike structures. However, limitations exist in the complexity of objects, which can be handed that way. In this case numerical methods are necessary to compute the acoustical response of the model. The investigated structure consists of two cylinders of different radii connected by a conical section. The ends are covered by hemispherical caps. An axisymmetric finite-element code (SARA2d) has been used to calculate the response of the target, due to an incident plane wave. Semi-infinite elements are implemented at the boundary of the acoustic fluid to take care of the Sommerfeld radiation condition. In the covered frequency range, which comprised Helmholtz numbers up to ka∼13, specular and elastic properties of the target contribute to the scattered signal. The calculations were performed during a one year research stay at the Naval Undersea Warfare Center (NUWC) in Newport, Rhode Island, USA. Additionally an attempt has been made to compare parts of the results with boundary element methods (SYSNOISE) and coupled FEM/BEM (ANSYS/SYSNOISE). For the coupled calculations only three-dimensional methods have been available, hence those results are restricted to relatively low Helmholtz numbers.
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