For the deterministic decomposition and prediction of nonlinear short-crested irregular ocean waves, a Directional Hybrid Wave Model (DHWM), accurate up to second-order in wave steepness, has been developed. The Extended Maximum Likelihood Method is employed to determine the directional spreading of wave energy, and the initial phases of directional free-wave components are calculated using a least-square fitting scheme. The effects of nonlinear wave-wave interactions among the free-wave components are computed using a hybrid second-order wave-wave interaction model which is a combination of conventional and phase modulation approaches. The free-wave components are obtained by decoupling the nonlinear effects from the measurements. The wave decomposition is carried out through an iterative process of computing the free-wave components and their nonlinear interactions. Given an ocean wave field defined by multiple fixed-point measurements, the DHWM is capable of decomposing the wave field into a set of directional free-wave components. Based on the derived free-wave components, the wave characteristics of the wave field can be predicted deterministically and accurately by the DHWM in the vicinity of the measurements. The present method has been verified numerically and applied to both laboratory and field measurements in various scenarios. Satisfactory agreement between the predictions based on the decomposed free-wave components and the corresponding measurements indicates that the proposed method is reliable, flexible and robust. It is expected that the DHWM will have a variety of applications to ocean science and engineering.
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