Laboratory Study of the Nonlinear Transformation of Irregular Waves over A Mild Slope  

作　　者：于博 马玉祥 马小舟 董国海 

机构地区：[1]State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology

出　　处：《China Ocean Engineering》2014年第4期489-500,共12页中国海洋工程（英文版）

基　　金：financially supported by the National Nature Science Foundation of China(Grant Nos.51109032 and 11172058);A Foundation for the Author of National Excellent Doctoral Dissertation of PR China(FANEDD,Grant No.201347)

摘　　要：This paper considers the nonlinear transformation of irregular waves propagating over a mild slope （1：40）. Two cases of irregular waves, which are mechanically generated based on JONSWAP spectra, are used for this purpose. The results indicate that the wave heights obey the Rayleigh distribution at the offshore location; however, in the shoaling region, the heights of the largest waves are underestimated by the theoretical distributions. In the surf zone, the wave heights can be approximated by the composite Weibull distribution. In addition, the nonlinear phase coupling within the irregular waves is investigated by the wavelet-based bicoherence. The bicoherence spectra reflect that the number of frequency modes participating in the phase coupling increases with the decreasing water depth, as does the degree of phase coupling. After the incipient breaking, even though the degree of phase coupling decreases, a great number of higher harmonic wave modes are also involved in nonlinear interactions. Moreover, the summed bicoherence indicates that the frequency mode related to the strongest local nonlinear interactions shifts to higher harmonics with the decreasing water depth.This paper considers the nonlinear transformation of irregular waves propagating over a mild slope （1：40）. Two cases of irregular waves, which are mechanically generated based on JONSWAP spectra, are used for this purpose. The results indicate that the wave heights obey the Rayleigh distribution at the offshore location; however, in the shoaling region, the heights of the largest waves are underestimated by the theoretical distributions. In the surf zone, the wave heights can be approximated by the composite Weibull distribution. In addition, the nonlinear phase coupling within the irregular waves is investigated by the wavelet-based bicoherence. The bicoherence spectra reflect that the number of frequency modes participating in the phase coupling increases with the decreasing water depth, as does the degree of phase coupling. After the incipient breaking, even though the degree of phase coupling decreases, a great number of higher harmonic wave modes are also involved in nonlinear interactions. Moreover, the summed bicoherence indicates that the frequency mode related to the strongest local nonlinear interactions shifts to higher harmonics with the decreasing water depth.

关 键 词：irregular waves shallow water nonlinear interactions wave height distribution wavelet bicoherence 

分 类 号：P751[交通运输工程—港口、海岸及近海工程] P731.2[天文地球—海洋科学]