ACOUSTIC SCATTERING FROM CYLINDERS WITH A PLANE OF SYMMETRY USING INTERNAL MULTIPOLE LINE SOURCE DISTRIBUTIONS .2.

A general internal source density approach to evaluate the acoustic scattered field from rigid infinite cylinders that are symmetric about a plane is presented. The approach is based on the use of internal source density line distributions that are either monopoles or dipoles along the plane of symmetry of the surface. A least-mean-square error method is used to match the normal velocity field from the internal sources at the surface of interest with the normal surface velocity due to an incident wave field. The resultant procedure leads to sets of linear algebraic equations that can be easily solved for the monopole and dipole source strengths. The source strengths are subsequently used to obtain the scattered pressure on the surface. The pressure in the exterior field can then be simply determined by evaluating the surface Helmholtz integral formula via usual quadrature methods. Typical numerical results for the surface and far-field pressures are presented for plane wave scattering by a circular cylinder and compared with closed form solutions. To illustrate the general applicability of the approach, plane wave scattering by elliptic cylinders of various aspect ratios is also addressed. These results indicate the characteristics of the scattered pressure as a function of frequency and aspect ratio.