The influence of bandwidth on the energetics of intermediate to deep water laboratory breaking waves
The influence of bandwidth on the energetics of intermediate to deep water laboratory breaking waves
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DOI：
10.1017/jfm.2023.645
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发表时间：
2023-09
影响因子：
3.7
通讯作者：
Rui Cao;E.M. Padilla;A. H. Callaghan
中科院分区：
文献类型：
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作者：
Rui Cao;E.M. Padilla;A. H. Callaghan
摘要介绍了二维色散聚焦实验室破碎波的实验研究。我们描述了带宽对破碎波能量的影响，包括光谱能量演化、特征群速度、能量耗散率和能量耗散率，以及破碎强度参数。为了评估带宽的作用，采用了三种波群陡度的定义，其中$S_S$和$S_n$与带宽有关，而$S_p$在带宽变化时保持不变。我们的数据显示了破碎波群的两个谱能量演化区域，这两个区域都与带宽有关：能量耗散和增益分别出现在$f>；0.95f_p$($f_p$是峰值频率)和$f<；0.95f_p$。用于能量耗散计算的特征群速度在破碎后最多增加7%，对于带宽较大的破碎波来说，增加的幅度更大。S_p与分数波能量耗散和绝对波能量耗散之间存在明确的带宽依赖关系。带宽较大的波群在较低的$S_p$处破裂，因此损失的能量相对较多。能量耗散率取决于断裂持续时间，而断裂持续时间本身与带宽有关。因此，无论是S还是S，在耗能率上都没有观察到明显的带宽效应。然而，当参数化为$S_p$时，$b$的变化具有系统性的带宽依赖性，并且它们之间的关系随着带宽的增加而变得越来越非线性。当参数化为$S_S$时，$b$对带宽的依赖性显著降低。最后，从实验上验证了《流体力学》(《流体力学》2016年第790卷，第553-581页)数值研究中的$b$和$S_S$的数值破缺起始及其关系。
Abstract An experimental investigation of two-dimensional dispersively focused laboratory breaking waves is presented. We describe the bandwidth effect on breaking wave energetics, including spectral energy evolution, characteristic group velocity, energy dissipation and its rate, and breaking strength parameter, $b$. To evaluate the role of bandwidth, three definitions of wave group steepness are adopted where $S_s$ and $S_n$ are bandwidth-dependent and $S_p$ remains constant when bandwidth is changed. Our data show two regimes of spectral energy evolution in breaking wave groups, with both regimes bandwidth-dependent: energy dissipation and gain occur at $f > 0.95f_p$ ($f_p$ is the peak frequency) and $f < 0.95f_p$, respectively. The characteristic group velocity, which is used in energy dissipation calculations, increases by up to 7 % after wave breaking, being larger for higher bandwidth breaking waves. An unambiguous bandwidth dependence is found between $S_p$ and both the fractional and absolute wave energy dissipation. Wave groups of larger bandwidth break at a lower value of $S_p$ and consequently lose relatively more energy. The energy dissipation rate depends on the breaking duration which itself is bandwidth dependent. Consequently, no clear bandwidth effect is observed in energy dissipation rate when compared with either $S_p$ or $S_s$. However, there is a systematic bandwidth dependence in the variation of $b$ when parameterised in terms of $S_p$, with their relationship becoming increasingly nonlinear as bandwidth increases. When parameterised with $S_s$, $b$ shows a markedly reduced bandwidth dependence. Finally, the numerical breaking onset and relationship between $b$ and $S_s$ in the numerical study of Derakhti & Kirby (J. Fluid Mech., vol. 790, 2016, pp. 553–581) is validated experimentally.