ACOUSTIC RADIATION FROM CYLINDERS WITH A PLANE OF SYMMETRY USING INTERNAL MULTIPOLE LINE SOURCE DISTRIBUTIONS .1.

A new method is proposed to address the two-dimensional exterior acoustic radiation problem from infinite cylinders with a plane of symmetry. This approach, which has its roots in fluid mechanics, is based on the use of internal monopole and dipole line source distributions within the surface. The monopole and dipole line source distributions are determined by prescribed normal velocity conditions over the surface of the shell and are subsequently used to determine the associated surface pressure. The exterior acoustic field is then simply calculated using the surface velocity and pressure via the usual surface Helmholtz integral equation. In contrast to earlier integral equation formulations of the problem the present method does not suffer from either nonuniqueness or result in hypersingular integral equations. Numerical results are presented to illustrate the accuracy of the new internal source density method for the case of a circular cylinder subjected to various specified normal velocity boundary conditions and frequencies. Additional numerical results are also presented for the exterior acoustic radiation problem for a strip on an elliptical cylinder. These results show the characteristics of the surface pressure as a function of the surface velocity and strip width.