Abstract:

This work is devoted to the analytical and numerical modelling of acoustic scattering in a fluid layer by an elastic cylindrical shell,which is located near one of the layer boundaries.The recently proposed Multi-Modal Integral Method (MMIM)is used for solution of the boundary value problem.The method provides a quickly converging and highly accurate solution taking into account all evanecsent modes of the waveguide up to infinite order.Selected snapshots showing the total and the scattered pressure fields in the vicinity of the shell are presented and analysed.Pictures of both the total acoustic field and its scattered component are presented.It is shown that the acoustic waves near the shell take the form of surface pressure waves with the wavefronts normal to the shell surface.In the area between the shell and the boundary the acoustic field experiences multiple reflections from the shell and the boundary,forming a standing acoustic wave.The results show the importance of the near-field oscillations and the surface waves for correct prediction of the scattered signal in the far field.In waveguides the near-field oscillations are described in terms of the evanescent modes.