Parameterizing the High Frequency Evolution of Nearshore Waves in a Nonlinear Wave Model
NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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Waves propagating through the shoaling and surf zones exhibit properties not characteristic of linear sinusoidal waves. Nonlinear wave-wave interactions act to transfer energy between the different harmonics of the peak frequency this transfer is most apparent from the peak frequency of the spectrum to higher harmonics of the peak. As a result of these nonlinear interactions, the shape of a wave is altered making it asymmetrical vertically skewness and horizontally asymmetry. The effects of nonlinear interactions are most easily seen in wave spectra, and the accuracy of a models frequency dispersion relation greatly affects nonlinear interactions. Therefore, the frequency domain version of a nonlinear mild slope equation gives a very good representation of the propagation of waves through the shoaling and surf zones. However, such models are computationally expensive. To reduce the computational cost of the nonlinear mild slope equation model, it is combined with the high-wave number Toba range parameterization of Smith and Vincent 2003 to form a hybrid model, thus constraining the high frequencies to a specified energy level. The hybrid model reduces the number of frequency components explicitly modeled by the nonlinear mild slope equation so that the one-dimensional model satisfactorily replicates chosen experiments in minutes, rather than hours. However, important wave parameters, like skewness and asymmetry disagree with observations and full model results. Further work is needed to improve the hybrid models energy level computation for the parameterized portions of spectra and the models ability to produce results capable of adequately replicating important wave parameters.
- Physical and Dynamic Oceanography
- Numerical Mathematics
- Fluid Mechanics