Deterministic wave model for short-crested ocean waves: Part I. Theory andnumerical scheme

A directional hybrid wave model (DHWM) has been developed for deterministic prediction of short-crested irregular ocean waves. In using the DHWM, a me asured wave field is first decomposed into its free-wave components based o n as few as three point measurements. Then the wave properties are predicte d in the vicinity of the measurements based on the decomposed free-wave com ponents. Effects of nonlinear interactions among the free-wave components u p to second order in wave steepness are considered in both decomposition an d prediction. While the prediction scheme is straightforward, the decomposi tion scheme is innovative and accomplished through an iterative process inv olving three major steps. The extended maximum likelihood method is employe d to determine the directional wave spreading; the initial phases of direct ional free-wave components are determined using a least-square fitting sche me; and nonlinear effects are computed using both conventional and phase mo dulation methods to achieve fast convergence. The free-wave components are obtained after the nonlinear effects being decoupled from the measurements. Variety of numerical tests have been conducted, indicating that the DHWM i s convergent and reliable. (C) 1999 Elsevier Science Ltd. All rights reserv ed.