Volume 9 (2017) Issue 3 Pages 57-65
An integral equation method for wave problems in frequency domain has a bottleneck in solving a linear system of equation with completely dense and complex coefficient matrix by discretization. A fast multipole algorithm (FMA) is a fast computation method for wave radiation fields and is used as a ways of coping the bottleneck. In the FMA, multipole expansion coefficients for the wave radiation fields is computed by using an element integration. It needs to precisely evaluate the multipole expansion coefficients for wave analysis with high accuracy. This paper aims to realize an accurate evaluation of the multipole expansion coefficient with the lowest computational costs. The authors previously presented a method to reduce a square element integration (double integration) to a single one. The above idea is applied to the computation of the multipole expansion coefficients. Numerical experiments disclose a relationship between the number of abscissas for the Gauss-Legendre quadrature and the accuracy of the computation for the multipole expansion coefficient.