Characteristics of a breaking wind-wave field in the light of the individual wind-wave concept |
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Authors: | Momoki Koga |
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Institution: | (1) Geophysical Institute, Faculty of Science, Tohoku University, 980 Sendai, Japan;(2) Present address: Department of Geophysics, Faculty of Science, Hokkaido University, 060 Sapporo, Japan |
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Abstract: | The relation between the intensity of breaking of individual wind-wave crests and parameters of wave size and wave form (e. g., height, period, steepness and skewness) is examined, and the process of change of these parameters is studied in a wind-wave
tank (reference wind speed 15 m sec−1, fetch 16 m). Distributions of the wave form parameters are different for breaking and nonbreaking waves. Fully breaking
waves seem to hold the relationH ∞T
2, whereH is the individual wave height andT is the period. The condition of breaking is not simply determined by the simple criterion of Stokes' limit. Wave height and
steepness of a breaking wave are not always larger than those of a nonbreaking wave. This suggests the existence of an overshooting
phenomenon in the breaking wave. The wave form parameters are found to change cyclically in a statistical sense during the
wave propagation. The period of the cycle in the present case is estimated to be longer than four wave periods. An intermittency
of wave breaking is associated with this cyclic process. Roughly speaking, two or three succeeding breaking-waves sporadically
exist among a series of nonbreaking waves along the fetch. |
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Keywords: | |
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