A STUDY OF BISPECTRA IN RELATION TO THE ADEQUACY OF WAVE SPECTRAL MODEL

In this paper, the characteristics of laboratory wind waves under vari ous wind speeds and water depths are studied. It is found that either the real or the imaginary part of the bispectrum can be related to the asymmetry of the wave profile, and the bicoherence is related to the ratio of nonlinear to linear wave component. Occasionally, these two c ategories of nonlinear index lead to opposite inferences, because each of them has its own significance and functions. The applicability of linear wave spectral model in ocean waves becomes questionable only wh en strong nonlinearity is indicated by both of these two indexes, The linear spectral representation of wave fields does not necessarily bec ome inadequate as water depth decreases, and its appropriateness can b e examined through the characteristics of the bispectrum.