Modulation instability and extreme events beyond initial three wave systems
Modulation instability and extreme events beyond initial three wave systems
复制标题
调制不稳定性和超出初始三波系统的极端事件
DOI：
10.1115/omae2016-54916
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
A. Chabchoub and T. Waseda
中科院分区：
文献类型：
--
作者：
A. Chabchoub and R. H. J. Grimshaw;A. Chabchoub and T. Waseda
模拟海洋极端事件动力学的一个可能机制是调制不稳定性（MI）。后者是在20世纪60年代发现的，自那时以来，在理解调制不稳定深水波的物理学方面取得了重大进展。MI不稳定性从规则斯托克斯波的周期性扰动开始，该扰动的振幅增强，因此在特定的调制周期范围内产生周期性的大波。在谱域，同样的过程从幅值非常小的对称边带对开始，位于主载波频率峰值的不稳定范围内，然后开始增长，同时由它们自己产生一个边带级联。本文报道了一种新的周期调制不稳定斯托克斯波，其初始动力学始于多个唯一的不稳定边带对。在大型水波盆地中进行了室内实验，并采用改进的非线性Schrödinger方程和边界元法进行了数值模拟。实验结果与数值模拟结果基本吻合。此外，还将详细讨论这些模型的有效性、局限性和适用性。
One possible mechanism that models the dynamics of extreme events in the ocean is the modulation instability (MI). The latter has been discovered in the 60s and significant progress in understanding the physics of modulationally unstable deep-water waves has been achieved since then. The MI instability starts its dynamics from a minor periodic perturbation of a regular Stokes wave, which enhances in amplitude, generating therefore periodic large waves, within the specific range of modulation period. In the spectral domain the same process starts from in amplitude very small symmetric side-band pair, lying in the unstable range from the main carrier frequency peak, which then starts to grow while generating by their own a side-band cascade. We report a new type of periodically modulated and unstable Stokes waves which initial dynamics starts from more that one unique unstable side-band pair. Laboratory experiments have been conducted in a large water wave basin, while numerical simulations have been performed using the modified nonlinear Schrödinger equation and the boundary element method. Both, experiments and numerical simulations are in reasonable agreement. Furthermore, the validity, limitations and applicability of such models will be discussed in detail.