Optimisation of focused wave group runup on a plane beach
Optimisation of focused wave group runup on a plane beach
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DOI：
10.1016/j.coastaleng.2016.12.001
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发表时间：
2017-03
影响因子：
4.4
通讯作者：
C. Whittaker;C. J. Fitzgerald;A. Raby;P. Taylor;J. Orszaghova;A. Borthwick
中科院分区：
文献类型：
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作者：
C. Whittaker;C. J. Fitzgerald;A. Raby;P. Taylor;J. Orszaghova;A. Borthwick
通过室内波浪水槽试验和数值模拟，研究了聚焦波群在平面海滩上的爬高。一个集中的波群作为一种替代的经验描述的波浪条件导致极端爬高。实验室造波机生成信号的二阶校正被观察到去除约60%的分谐波误差波，否则会污染海岸响应实验。波浪爬高时间历程的实验室测量是使用倾斜的电阻型导线和铜带连接到海滩表面。数值波浪爬高模型是基于混合Boussinesq-非线性浅水方程，经验参数的波浪破碎和床摩擦，和一个润湿和干燥的算法。对实验助跑数据校准后，数值模型再现令人满意的传播，变浅和助跑的聚焦波群在整个长度的波水槽。从一个全面的参数研究的结果表明，测量和预测的最大助跑海拔表现出强烈的依赖性的波群的线性焦点振幅（与其发生的概率），焦点位置，和波群在焦点的相位。结果还表明，极端的爬高事件，由于聚焦波入射不能单独使用光谱参数的特点。随着入射波组线性聚焦振幅的增大，聚焦位置的最佳波段向岸上移动。相位和焦点位置的优化导致在每个线性振幅处的最大助跑升高，并且当使用二阶校正桨信号生成时，最大助跑似乎在非常大的聚焦波振幅处接近饱和。因此，这项研究超越了简单的波聚焦，并提出了一个聚焦波组作为一种工具，用于调查极端的入射波场和极端波爬高之间的关系。
Insight is provided into focused wave group runup on a plane beach by means of laboratory wave flume experiments and numerical simulations. A focused wave group is presented as an alternative to an empirical description of the wave conditions leading to extreme runup. Second-order correction to the laboratory wavemaker generation signal is observed to remove about 60% of the sub-harmonic error wave that would otherwise contaminate coastal response experiments. Laboratory measurements of the wave runup time history are obtained using inclined resistance-type wires and copper strips attached to the beach surface. The numerical wave runup model is based on hybrid Boussinesq-Nonlinear Shallow Water equations, empirical parameters for wave breaking and bed friction, and a wetting and drying algorithm. After calibration against experimental runup data, the numerical model reproduces satisfactorily the propagation, shoaling and runup of focused wave groups over the entire length of the wave flume. Results from a comprehensive parametric study show that both measured and predicted maximum runup elevations exhibit strong dependence on the linear focus amplitude of the wave group (linked to its probability of occurrence), the focus location, and the phase of the wave group at focus. The results also demonstrate that extreme runup events owing to focused wave incidence cannot be characterised using spectral parameters alone. The optimal band of focus locations shifts onshore as linear focus amplitude of the incident wave group increases. Optimisation of phase and focus location leads to a maximum runup elevation at each linear amplitude, and, when generated using second-order corrected paddle signals, the maximum runup appears to approach saturation at very large focused wave amplitudes. This study therefore moves beyond simple wave focusing, and presents a focused wave group as a tool for investigating the relationship between extremes within an incident wave field and extreme wave runup.