Long-wavelength Approximation of Wave Force on Two-body Axisymmetric System

The well-known long-wavelength (or small-body) approximation for the wave excitation force on a single immersed body is generalised to a group of bodies, all of which have linear extension very small compared to the wavelength. An axisymmetric system, w hich consists of a floating buoy and a submerged plate-like body, is studied, in particular. In order to investigate how far the validity of the approximation may be reasonably well acceptable, the approximation is compared with results from numerical c omputations. The range of validity seems to be wider than anticipated.