SHOALING SURFACE GRAVITY WAVES: A BISPECTRAL ANALYSIS

J.C. Doering, A.J. Bowen

Abstract


Nonlinearities (wave-wave interactions) play a vital role in many aspects of nearshore dynamics, such as wave shoaling and breaking, wave forces, wave-current interactions, radiation stress effects, and sediment transport. The importance of nonlinearities in the nearshore region cannot be overemphasized. At present, however, there is no wave theory that adequately accounts for these interactions, and field observations are sparse. Herein, the bispectrum is used to investigate the temporal and spatial variation of wave-wave interactions in cross-shore velocity for shoaling surface gravity waves in several nearshore environments. The implications for sediment movement of the sign of the observed wavewave interactions for both the real part of the velocity bispectrum (which is related to the skewness of the horizontal asymmetry) and the imaginary part of the velocity bispectrum (which is related to the skewness of the temporal derivative) are discussed. A parameterization is given for the amplitude and phase evolution of the self-self sum interactions within the wind-wave peak for both planar and barred nearshore topography. The results of this paper underline the potential importance of infragravity wave energy in determining nearshore morphology.

Keywords


shoaling; surface waved; gravity waves; bispectral analysis; spectral analysis

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