Method of superposition applied to axisymmetric structures

The method of superposition is applied to axisymmetric structures to solve for the scattered field produced by a general, non-axisymmetric incident field. The scattered field is written as a sum over the fields produced by rings of source distributions placed on a surface inside the scatterer. The source distribution on each ring is next expanded in circumferencial modes. Similarly, the field produced by the source distribution is expanded in circumferential modes. The source distribution is solved for by requiring the scattered field to satisfy the proper boundary conditions on the structure surface. This reduces the computational load of the method previously applied of placing point sources on a surface inside the structure since it reduces the size of the matrices to be inverted, thus extending the applicability of the method to higher frequencies. Results are shown for a finite cylindrical structure with hemispherical end-caps satisfying soft boundary conditions. [Work supported by ONR.]