Head-sea diffraction by a slender raft with application to wave-power absorption

Abstract

The parabolic approximation which has recently been found to be useful in other physical contexts, is extended to head-sea diffraction of short waves by a slender raft on deep water. In particular, it is a much more direct way of getting the inner approximation of the outer solution in a scheme of matched asymptotics than the original method of Faltinsen (1971). The present results are compared with a more involved integral equation method and are found to be remarkably accurate even when the raft length is comparable to the wavelength. Finally, the asymptotic method is modified for a compliant raft which absorbs wave power by suitably controlled impedance. Optimum efficiency and other performance characteristics are predicted.