American Society of Civil Engineers


Laboratory Study of Unidirectional Focusing Waves in Intermediate Depth Water


by Yuxiang Ma, (corresponding author), (Ph.D. Candidate, State Key Laboratory of Coastal and Offshore Engineering, Dalian Univ. of Technology, Dalian 116023, People’s Republic of China E-mail: yuxma@student.dlut.edu.cn), Guohai Dong, (Professor, State Key Laboratory of Coastal and Offshore Engineering, Dalian Univ. of Technology, Dalian 116023, People’s Republic of China. E-mail: ghdong@dlut.edu.cn), Shuxue Liu, (Professor, State Key Laboratory of Coastal and Offshore Engineering, Dalian Univ. of Technology, Dalian 116023, People’s Republic of China.), Jun Zang, (Lecturer, Dept. of Architecture and Civil Engineering, Univ. of Bath, Bath BA2 7AY, U.K.), Jinxuan Li, (Lecturer, State Key Laboratory of Coastal and Offshore Engineering, Dalian Univ. of Technology, Dalian 116023, People’s Republic of China.), and Yiyan Sun, (Ph.D. Candidate, State Key Laboratory of Coastal and Offshore Engineering, Dalian Univ. of Technology, Dalian 116023, People’s Republic of China.)

Journal of Engineering Mechanics, Vol. 136, No. 1, January 2010, pp. 78-90, (doi:  http://dx.doi.org/10.1061/(ASCE)EM.1943-7889.0000076)

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Document type: Journal Paper
Abstract: The results of laboratory measurements of large focusing wave groups, which were generated using the New Wave theory, are presented. The influences of both the steepness and frequency bandwidth on focused wave characteristics were examined. The influence of frequency bandwidth on focused wave groups with small and moderate steepness was very small. However, for cases with the large steepness, the nonlinearity increased with increasing bandwidth frequency and widened free-wave regimes are identified for those cases with large steepness at the focal location. The underlying nonlinear phase coupling of focused waves was examined using wavelet-based bicoherence and biphase, which can detect nonlinear phase coupling in a short time series. For wave groups with large initial steepness, as wave groups approached the focal location, the values of bicoherence between primary waves and its higher harmonics progressively increased to 1 and the corresponding biphase was gradually close to zero, suggesting that an extreme wave event can be produced by considering Stokes-like nonlinearity to very high-order. Furthermore, the fast change of bicoherence of focused wave groups indicates that the nonlinear energy transfer within focusing waves is faster than that of nonfocusing wave trains.


ASCE Subject Headings:
Water waves
Laboratory tests
Wavelet
Spectral analysis
Methodology

Author Keywords:
Water waves
Nonlinearity
Wavelet
Spectra
Methodology