A new integral equation formulation for an axisymmetric structure

A new method is developed to compute the acoustic field outside an axisymmetric structure from the normal velocity values on the surface. Surface pressure and normal velocity are expanded in a series of functions that are orthonormal on the surface of the structure and have a constant ratio of pressure to normal derivative of pressure at vanishing frequency. The Helmholtz integral equation is next used to compute the field everywhere outside the structure. The method is tested by applying it to scattering from a rigid cylinder with hemispherical endcaps. The series is shown to converge very rapidly.