A Study of Two-dimensional Unsteady Breaking Waves in Finite-depth Water
نویسندگان
چکیده
An experimental and numerical study is presented to investigate the breaking criterion of Song and Banner [J. Phys. Oceanogr. 32, 2541 (2002)] who suggested a threshold range of 3 (1.4 0.1) 10 for a predictive wave breaking parameter, measuring the rate of change of the local energy maximum and the local wave number, to differentiate between wave trains that lead to breaking and those that do not. To examine the breaking criterion experimentally, four separate wave groups of progressive surface gravity waves with slowly decreasing frequency are generated mechanically in a two-dimensional wave tank. Surface elevations as a function of time are measured using capacitance wave probes; surface elevations as a function of space prior to and during breaking are obtained by recording sub-regions with an imaging system, and combining the measurements from repeated experiments. In addition, nonlinear numerical solutions for the surface elevation profiles for the four wave groups are obtained by solving a set of nonlinear evolution equations using a pseudo-spectral method, and are compared with experiments and linear predictions. It is found that the breaking criterion of Song and Banner is sensitive to the choice of the local wave number, but that a particular local wave number based on local
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