Non-Gaussian properties of second-order wave orbital velocity
Non-Gaussian properties of second-order wave orbital velocity
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DOI：
10.1016/j.coastaleng.2016.01.001
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发表时间：
2015-10
影响因子：
4.4
通讯作者：
A. Alberello;A. Chabchoub;O. Gramstad;A. Babanin;A. Toffoli
中科院分区：
文献类型：
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作者：
A. Alberello;A. Chabchoub;O. Gramstad;A. Babanin;A. Toffoli
应用随机二阶波浪模型来评估水面以下随机海况下波轨道速度的统计特性。通过蒙特卡罗方法研究了方向扩散效应以及水深的依赖性。与表面高程不同，次谐波对轨道速度的二阶贡献占主导地位。我们发现，最有活力和最陡峭的群体会出现显着的下降。这会在轨道速度的时间演化中产生负偏度。注意到概率密度函数的上尾和下尾与高斯分布有很大的偏差；与线性理论预测相比，波谷下方的速度较快，波峰下方的速度较慢。二阶非线性效应随着水深的减小而增强，随着波谱的拓宽而减弱。结果得到实验室数据的证实。考虑波场的方向性，在大型波浪池中进行了相应的实验。如图所示，实验室数据与数值预测非常吻合。
A stochastic second-order wave model is applied to assess the statistical properties of wave orbital velocity in random sea states below the water surface. Directional spreading effects as well as the dependency of the water depth are investigated by means of a Monte-Carlo approach. Unlike for the surface elevation, sub-harmonics dominate the second-order contribution to orbital velocity. We show that a notable set-down occurs for the most energetic and steepest groups. This engenders a negative skewness in the temporal evolution of the orbital velocity. A substantial deviation of the upper and lower tails of the probability density function from the Gaussian distribution is noticed; velocities are faster below the wave trough and slower below the wave crest when compared with linear theory predictions. Second-order nonlinearity effects strengthen with reducing the water depth, while weaken with the broadening of the wave spectrum. The results are confirmed by laboratory data. Corresponding experiments have been conducted in a large wave basin taking into account the directionality of the wave field. As shown, laboratory data are in very good agreement with the numerical prediction.