Integral equation methods such as the boundary element method are becoming increasingly popular as methods for the numerical solution of linear elliptic partial differential equations such as the Helmholtz equation. The application of (discrete) collocation to the integral equation formulation of the Helmholtz equation requires the computation of the discrete operators. In this paper Fortran subroutines for the evaluation of the discrete Helmholtz integral operators resulting from the use of constant elements and the most simple boundary approximation to two-dimensional, three-dimensional and axisymmetric problems have been described and demonstrated.
The subroutines have been designed to be easy-to-use, flexible, reliable and efficient. It is the intention that the subroutines are to be used as a `black box' which can be utilised either for further analysis of integral equation methods or in software for the solution of practical physical problems which are governed by the Helmholtz or Laplace equations. The subroutines have already been applied to various problems in references [15], [19], [22], [24]. A full description of the application of the subroutines to interior, exterior and modal analysis problems is given in Kirkup [25].