The wave parameters (the wave height and period) are important environmental factors in the ocean engineering design. General numerical wave models, such as SWAN and WAVEWATCH, are widely employed to simulate the wave conditions. However, significant differences were observed between the measurement and the simulation for both the wave height and period, which asks for wave model improvements. The differences are mainly due to the uncertainty of parameterizing various physical processes, including the wave breaking. The energy transfer and loss during the wave breaking involves an important physical mechanism, and the energy dissipation and the period changes are not well studied. This paper studies the deep and shallow water wave breaking using the wave focusing and the slope platform random wave experiments. The characteristics of the wave periods under different conditions are studied in detail, including the period variation. The results show that the periods change during the wave propagation and breaking processes. The energy transfer caused by the strongly nonlinear interaction between the wave components, as well as the energy loss caused by the wave breaking, are the primary causes. The corresponding relationships are established by fitting the data. For the deep water breaking waves induced by the wave focusing, the spectrally averaged period (SAP) increases, and a positive correlation between the rate of change and the wave steepness is found. In the shallow water, the nonlinear interactions are stronger than in the deep water, the wave periods are significantly reduced, and a negative correlation between the rate of change and a nonlinear parameter is found. The inherent mechanism of the period variation is analyzed based on the energy spectrum distribution variations. The contributions of the nonlinear interactions and the wave breaking to the SAP evolution are discussed.

中文翻译：

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破波波周期变化的演化特征及量化

波浪参数（波浪高度和周期）是海洋工程设计中的重要环境因素。通用的数值波浪模型，例如SWAN和WAVEWATCH，被广泛用来模拟波浪条件。但是，在波高和周期方面，在测量和仿真之间观察到了显着差异，这需要改进波模型。差异主要是由于参数化各种物理过程（包括波浪破碎）的不确定性。破波过程中的能量传递和损失涉及一个重要的物理机制，对能量的耗散和周期的变化还没有很好的研究。本文利用波浪聚焦和斜坡平台随机波实验研究了深水和浅水波的破裂。详细研究了不同条件下的波浪周期特征，包括周期变化。结果表明，周期在波传播和破坏过程中会发生变化。主要原因是由波成分之间强烈的非线性相互作用引起的能量转移以及由波破坏引起的能量损失。通过拟合数据来建立对应的关系。对于由波聚焦引起的深水破碎波，频谱平均周期（SAP）增加，并且发现变化率与波陡度之间呈正相关。在浅水中，非线性相互作用比在深水中要强，波浪周期明显减少，发现变化率与非线性参数之间呈负相关。基于能谱分布变化分析了周期变化的内在机理。讨论了非线性相互作用和波浪破裂对SAP演化的贡献。