Treatment of an infinitely extended free surface for indirect formulation of the boundary element method

A new approach which uses the full-space Green's function is proposed to eliminate the influence of the finitude of the segmented free surface in the indirect formulation of the Boundary Element Method. The absence of a contribution from the far parts of the free surface that are neglected in the computation is compensated for, assuming that the wave field along flat parts of the surface far from the localized irregularity can be substituted by the reference solution, i.e., the wave field in the half space with a completely flat free surface which is given analytically. The nonphysical waves radiated at the two ends of the segmented model of the free surface are eliminated efficiently by this approach. This reduces the amount of computer main memory required and the CPU time consumed for calculation. Moreover, physical consideration of the relation to existing approaches shows clearly that our approach gives a more precise approximation, in particular for high frequency problems. The capacity of the indirect formulation of the Boundary Element Method therefore is bettered by this approach.