TSA - a Two Scale Approximation for Wind-Generated Ocean Surface Waves
2010
Perrie, William
(a) To provide an accurate, efficient, computational model (two-scale approximation, TSA) for the 4-wave interactions, in operational wave forecast models, suitable for global, basin and coastal scale applications, and able to transition seamlessly from deep to shallow water. (b) Fully test TSA with respect to exact codes for the full Boltzmann integral (FBI), for durationlimited, fetch-limited wave growth, turning winds, swell-windsea, interactions, etc. (c) Numerically investigate and clarify the basis for TSA, its limitations, errors, enhancements, improvements, self-similarity properties, and spectral flux properties. (d) Implement TSA in a variety of modern operational wave forecast models, e.g. WAVEWATCHTM (WW3) and SWAN for extensive tests on important, realistic wave conditions. (e) Derive, adapt and implement new formulations for source terms, Sin and Sds, from recent literature and the NOPP partnership, with TSA, in modern wave models, for tests, including veering or accelerating winds, sea and swell interactions, and real storm cases. For this reporting period: 1) To formulate a relatively extensive set of reference spectra with corresponding FBI results, in order to facilitate definitive comparisons with TSA, and to lead to better understanding of limitations and areas in need of improvement in the TSA formulation. 2) Results for TSA (in comparison with FBI) for directionally varying spectra, rapidly veering wind conditions and other difficult spectral cases where the formulation may fail. 3) Preliminary implementation of TSA in WW3, re-structuring of code as necessary.
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