Nonlinear infragravity–wave interactions on a gently sloping laboratory beach
Nonlinear infragravity–wave interactions on a gently sloping laboratory beach
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DOI：
10.1175/jpo-d-14-0186.1
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发表时间：
2015-02
影响因子：
3.5
通讯作者：
A. D. de Bakker;T. Herbers;P. Smit;M. Tissier;B. Ruessink
中科院分区：
文献类型：
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作者：
A. D. de Bakker;T. Herbers;P. Smit;M. Tissier;B. Ruessink
分析了在缓坡海滩上收集的三种不规则波情况的高分辨率数据集，以研究涉及亚重力频率的非线性能量传输。这项研究使用双谱分析来识别主要的非线性相互作用，并估计能量转移来研究光谱内的能量流动。能量流通过将传输划分为四种类型的三和弦相互作用来识别，其中三和弦包括一个、两个或三个亚重力频率分量，以及仅在短波频率之间的三个三和弦相互作用。在浅水区，能量转移一般是从谱峰向其高次谐波和亚重力频率的转移。在接收净能量的同时，亚重力波参与相互作用，将短波峰值的能量传播到相邻的频率，从而产生更广泛的能谱。在短波冲浪区，超重力-亚重力相互作用发展，在海岸附近，它们主导相互作用。将非线性能量通量与总能量通量的梯度进行了比较，并观察到它们几乎完全平衡。总体而言，亚重力频率和短波频率的能量损失在很大程度上可以用一系列向高频(比如f。1.5赫兹)，在那里能量可能被耗散。超重力-超重力相互作用似乎引起更高的谐波，从而使超重力波的形状转变为对称的。超重力波高的最大降幅出现在近岸，在那里超重力-超重力相互作用占主导地位，并且超重力波是不对称的，这表明波浪破碎是超重力波消散的主要机制。
A high-resolution dataset of three irregular wave conditions collected on a gently sloping laboratory beach is analyzed to study nonlinear energy transfers involving infragravity frequencies. This study uses bispectral analysis to identify the dominant, nonlinear interactions and estimate energy transfers to investigate energy flows within the spectra. Energy flows are identified by dividing transfers into four types of triad interactions, with triads including one, two, or three infragravity–frequency components, and triad interactions solely between short-wave frequencies. In the shoaling zone, the energy transfers are generally from the spectral peak to its higher harmonics and to infragravity frequencies. While receiving net energy, infragravity waves participate in interactions that spread energy of the short-wave peaks to adjacent frequencies, thereby cre- ating a broader energy spectrum. In the short-wave surf zone, infragravity–infragravity interactions develop, and close to shore, they dominate the interactions. Nonlinear energy fluxes are compared to gradients in total energy flux and are observed to balance nearly completely. Overall, energy losses at both infragravity and short-wave frequencies can largely be explained by a cascade of nonlinear energy transfers to high frequencies (say, f . 1.5 Hz) where the energy is presumably dissipated. Infragravity–infragravity interactions seem to induce higher harmonics that allow for shape transformation of the infragravity wave to symmetric. The largest decrease in infragravity wave height occurs close to the shore, where infragravity–infragravity in- teractions dominate and where the infragravity wave is asymmetric, suggesting wave breaking to be the dominant mechanism of infragravity wave dissipation.