Experimental Study On The Evolution Characteristics Of Wave Periods Of Breaking Waves

Wave height and wave period are the important environmental conditions for the ocean engineering design. Especially the significant wave height and significant wave period are crucial. At present, it's prevailing that numerical wave models are used to calculate the wave characteristics in ocean engineering design. The widely used numerical models, such as SWAN and WAVEWATCH, can output the significant wave height and spectral averaged periods by integrating the wave spectrum, but there is often a deviation between the simulation results and measured values of wave periods. This difference is mainly due to the uncertainty of the parameterization of various physical processes which affect the development of waves, and wave breaking is one of those. Wave breaking is common in the ocean waves. Energy loss during breaking process is the important physical mechanism of the source term of energy dissipation in the wave model. Due to wave breaking is very complicated physical process, the understanding about energy dissipation mechanism and period changing is still less. Considering those problems mentioned above, the evolution characteristics of the wave period of deep-water breaking waves and breaking waves due to the shallow water are experimentally studied in this paper.In chapter ?, the method of focusing wave generation is introduced, and deep-water focusing waves and breaking waves with different wave characteristics are generated in a 2-D flume in the laboratory. The wave periods related to the spectrum and the average period and significant period based on Zero-up crossing method are computed for surface elevations. The evolution characteristics of wave periods are discussed. In addition, the influence of wave energy spectrum distribution forms and frequency width on wave period evolution is also studied. In the third chapter, the sloping-bottom platform is firstly designed, and the evolution characteristics of the wave periods of breaking waves in shallow water are discussed. And the influence of incident wave period on the evolution of wave periods is also studied. In the fourth chapter, the parameters of wave nonlinearity and breaking strength are summed up. Based on lots of experimental data, the relationship between the spectral averaged periods and periods based on Zero-up crossing method, the relationship between the change rate of wave periods and wave parameters are studied, and corresponding relations are presented through the least square fitting method.In this article, through laboratory experiments, the evolution characteristics of wave periods of deep-water extreme breaking waves and breaking waves caused by water depth are studied, and the relationship between the change rate of wave periods and characteristic wave parameters indicating breaking intensity or nonlinear interaction are discussed. Research results are meaningful for ocean engineering design and improving the existing numerical wave models.