Abstract: This paper describes the implementation of a Fast Multipole Algorithm (FMA) into Aquaplus, a in-house diffraction/ radiation code, to make possible the simulation of
large hydrodynamic problems (104 ? 106 unknowns using Boundary Element Methods).
The FMA permits to solve large and dense linear systems by accelerating matrixvector products into an iterative solver. This algorithm is based on the multipole expansion of the free-surface Green’s function in the frequency domain. The accuracy of the modified software is assessed by comparing the fluid potential and the hydrodynamic coefficients on a heaving and surging hemisphere to analytical results.