Latheef M, Swan C, Spinneken J
Department of Civil and Environmental Engineering, Imperial College London, London SW7 2AZ, UK.
Proc Math Phys Eng Sci. 2017 Mar;473(2199):20160290. doi: 10.1098/rspa.2016.0290. Epub 2017 Mar 8.
This paper concerns the description of surface water waves, specifically nonlinear changes in the directionality. Supporting calculations are provided to establish the best method of directional wave generation, the preferred method of directional analysis and the inputs on which such a method should be based. These calculations show that a random directional method, in which the phasing, amplitude and direction of propagation of individual wave components are chosen randomly, has benefits in achieving the required ergodicity. In terms of analysis procedures, the extended maximum entropy principle, with inputs based upon vector quantities, produces the best description of directionality. With laboratory data describing the water surface elevation and the two horizontal velocity components at a single point, several steep sea states are considered. The results confirm that, as the steepness of a sea state increases, the overall directionality of the sea state reduces. More importantly, it is also shown that the largest waves become less spread or more unidirectional than the sea state as a whole. This provides an important link to earlier descriptions of deterministic wave groups produced by frequency focusing, helps to explain recent field observations and has important practical implications for the design of marine structures and vessels.
本文关注地表水波的描述，特别是方向性的非线性变化。提供了辅助计算，以确定定向波生成的最佳方法、定向分析的首选方法以及该方法应基于的输入参数。这些计算表明，一种随机定向方法，即单个波分量的相位、振幅和传播方向是随机选择的，在实现所需的遍历性方面具有优势。在分析程序方面，基于矢量量输入的扩展最大熵原理能对方向性给出最佳描述。利用描述单点水面高程和两个水平速度分量的实验室数据，考虑了几种陡浪状态。结果证实，随着海况陡度的增加，海况的整体方向性降低。更重要的是，还表明最大的波浪比整个海况的传播范围更小或更单向。这为早期对频率聚焦产生的确定性波群的描述提供了重要联系，有助于解释最近的现场观测结果，并且对海洋结构物和船舶的设计具有重要的实际意义。
