Abstract
Type of wave breaking - plunging or spilling - depends on symmetry of waves. The spilling waves are asymmetric against horizontal axis and are practically symmetric against vertical axis so the phase shift between first and second nonlinear harmonics (or biphase) is close to zero. The plunging breaking waves have larger asymmetry against vertical axis, (biphase is close to -pi/2), and near symmetric on horizontal axis (close to saw-toothed form). Non-linear wave transformation influences on depth-induced wave breaking. Breaking index depends on relation of wave energy in frequency range of second nonlinear harmonics to wave energy in frequency range of main harmonic and on biphase. The dissipation rate of spilling breaking waves energy quadratically depends on frequency, while in plunging breaking, this dependency is practically linear for all frequencies.
Highlights
Many features of processes of wave energy dissipation in the surf zone, important for sediments transport and changing of bottom relief, are remain studied non-sufficient
As we seen from the laboratory and field experiments the wave breaking type, breaking criteria and frequency selectivity of energy dissipation due to breaking depend strongly on amplitude-phase frequency structure of waves and cannot be predicted correctly on the base input wave parameters and average bottom slope of coastal zone
To predict correctly the breaking type and position of breaking it is need to analyze the scenario of nonlinear wave transformation in the coastal zone
Summary
Many features of processes of wave energy dissipation in the surf zone, important for sediments transport and changing of bottom relief, are remain studied non-sufficient. With adjustable constant or breaking index γ=0.8 (for heights of individual waves (Battjes and Janssen 1978) or γ=0.6 (for significant wave height (Thornton and Guza 1983)) is suitable for most wave breaking cases, but many experimental data, including our, testify the wide range of γ: from 0.4 up to 1.2 (Saprykina et al 2017). We suppose that the variations of γ and type of wave breaking can be explained by the distinctions of the amplitudephase frequency (spectral) structure of waves before breaking due to nonlinear wave transformation. The frequency selectivity of wave energy dissipation depends on nonlinear process of wave transformation and organized in the manner to compensate the results of it (Kuznetsov and Saprykina 2004). The main goal of this work is to testify the influence the nonlinear structure of coastal zone waves on their breaking and energy dissipation features
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