Effect of Nonlinearity on Groupiness of Random Wave Fields |
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| Authors: | YU Dingyong XU Delun ZHENG Jianguo
Professor Engineering School Ocean University of Qingdao Qingdao P R China
Professor Physical Oceanology Laboratory Ocean University of Qingdao Qingdao P R China
Lecturer Engineering School Ocean University of Qingdao Qingdao P R China |
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| Institution: | YU Dingyong XU Delun ZHENG Jianguo
Professor,Engineering School,Ocean University of Qingdao,Qingdao 266071,P. R. China
Professor,Physical Oceanology Laboratory,Ocean University of Qingdao,Qingdao 266071,P. R. China
Lecturer,Engineering School,Ocean University of Qingdao,Qingdao 266071,P. R. China |
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| Abstract: | Theoretical studies so far on random wave groups have all been in linear ways. Methods to simulate random wave groups, an important subject in ocean engineering, also employ relationship resulting from a Gaussian process. Many filed measurements have shown that the real sea surface displacement deviates somewhat from Gaussian distribution. Tayfun et al. have further depicted in theory that the envelope spectral peak frequency is constantly zero for a Gaussian process which means that the groupiness factors will be constants, too. In this paper, the effect of nonlinearity on groupiness of a random wave field is examined via the theoretical results derived by Tayfun et al. from an expression of amplitude-modulated Stokes waves. When the surface displacement is treated as a non-Gaussian process, it is found that the group height factors GF1 and GF2 proposed by Zhao et al. and Yu et al. , respectively, depend on a nonlinearity factor as well as a spectrum-bandwidth factor, deferring from the case of a Gaussion process. Comparison between the theoretical results and the field data shows a favorable agreement in consideration of errors from instrumentation and measuring means. The significance of the results is also discussed. |
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| Keywords: | groupiness factor wave envelope nonlinearity |
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