DIRECTIONAL CHARACTERISTICS OF THE NONLINEAR ENERGY TRANSFER OF GRAVITY WAVE SPECTRUM

Abstract

The nonlinear energy transfer plays a critical role in determining the energy distribution of directional spectrum. Numerous studies of the important role of the nonlinear energy transfer in the evolutions of wave spectrum have been clearly demonstrated in the frequency domain, however little is known about the characteristics of the nonlinear energy transfer in the directional domain. In this paper, we investigate the characteristics of spatial and temporal changes of the directional spectra in consideration of nonlinear energy transfer as a possible mechanism of the change of directional distribution in deep water depth. Numerical computations are performed by three different types of the third-generation wave model, WAM, where each of them is implemented with DIA (Hasselmann et. al., 1985), RIAM (Komatsu et. al., 1993) and SRIAM (Komatsu et. al., 1996), respectively, for the computation of the nonlinear energy transfer. The JONSWAP type spectrum and Mitsuyasu's directional function are applied to define the energy distribution of directional spectrum. The characteristics of bimodal directional wave spectra are also discussed.