On the Growth of the Spectrum of a Wind Generated Sea According to a Modified Miles-Phillips Mechanism and Its Application to Wave Forecasting

摘要

It is necessary to develop detailed numerical forecasting techniques that accurately specify the process of wave generation because the need for accurate wave forecasts is increasing. The growth of the wave spectrum can be approximated by the combined effect of two mechanisms to a point where the crest of the wave breaks on a nonlinear effect becomes dominant. One mechanism is the Phillips resonance mechanism for wave generation, and the other is the exponential growth mechanism, originally proposed by Miles. Recently, this second growth mechanism was revised by Phillips in terms of the wave-induced atmospheric perturbations. Calculations suggest that this new mechanism explains the available observations, which had previously been unexplainable from the original instability growth mechanism. To verify the theory, various spectra estimated from wave observations are used, along with measurements provided by fetch limited field experiments made by Snyder and Cox. After some assumptions about energy dissipation are applied, the spectral-growth equation, which is a function of frequency, wind speed, and duration (or fetch), is obtained.