Empirically, a parametrical description of the windsea spectrum could be motivated by the observation that the spectra of growing windseas appear to have approximately the same shape for a wide variety of generation conditions. The spectral distributions differ only with respect to the frequency and energy scales. Furthermore, the two scale parameters are found to be approximately interrelated when nondimensionalized in terms of g and the local wind speed U or friction velocity u *. Thus the spectrum of a growing windsea can be characterized to first order by a single nondimensional variable, for example the nondimensional energy E* = Eg 2 u * −4 . This determines all other nondimensional variables, such as the nondimensional peak frequency f p* = u * f p/g and Phillips’ “constant” α. The ratio of E* to its value E ∞* for a fully developed sea provides a unique measure of the “age” of the windsea.
KeywordsWind Direction Source Function Local Wind Speed Couple Hybrid Model HYPA Model
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