Experimental and numerical study of the propagation of focused wave groups in the nearshore zone

Abstract

The propagation of focused wave groups in intermediate water depth and the shoaling zone is experimentally and numerically considered in this paper. The experiments are carried out in a two-dimensional wave flume and wave trains derived from Pierson-Moskowitz and JONSWAP spectrum are generated. The peak frequency does not change during the wave train propagation for Pierson-Moskowitz waves; however, a downshift of this peak is observed for JONSWAP waves. An energy partitioning is performed in order to track the spatial evolution of energy. Four energy regions are defined for each spectrum type. A nonlinear energy transfer between different spectral regions as the wave train propagates is demonstrated and quantified. Numerical simulations are conducted using a modified Boussinesq model for long waves in shallow waters of varying depth. Experimental results are in satisfactory agreement with numerical predictions, especially in the case of wave trains derived from JONSWAP spectrum.

Frequency Downshifting in Wave Spectra in Coastal Zone and Its Influence on Mudbank Formation

“…However, as was shown experimentally and numerically for experimentally and numerically for the spatial evolution of frequency spectra of unidirectional narrow-banded waves (breaking and non-breaking) in deep water, frequency downshifting is explained by nonlinear energy transfer and the breaking processes are not necessarily responsible for it [4]. Laboratory and numerical experiments with waves in shallow water have shown the importance of the shape of the initial spectrum for the frequency downshifting that is also an indirect confirmation of the main role of nonlinear processes [6].…”

“…Wave transformation leads to changes in the shape of the wave spectrum. Sometimes, the major peak frequency shifts to the low-frequency region-where so-called "frequency downshifting" is observed [4][5][6][7]. It is not completely understood in detail how the frequency downshift occurs.…”

Laboratory study of non-linear wave-wave interactions of extreme focused waves in the nearshore zone

“…The following is a brief consideration of present wave trains generation; more details of the experiments can be found in Abroug et al, 2020. The experiments were conducted in a two-dimensional wave flume of the Morphodynamique Continentale et Côtière laboratory at Caen University, France.…”

“…The data used in this work are issued from Abroug et al, 2020. The present study relates to seven wave trains derived from the averaged JONSWAP spectra (i.e.…”

“…However, we do not distinguish which wave components are involved in the wave-wave interactions and the wave modes that undergo the strongest non-linear interactions. Consequently, the wavelet bicoherence tool is used herein to provide information about the non-linear wave interactions that are not easily obtained from the Fourier analysis which was used in Abroug et al, 2020. https://doi.org/10.5194/nhess-2020-209 Preprint. Discussion started: 20 July 2020 c Author(s) 2020.…”