畸形波生成的一种非线性机理分析

根据畸形波的非线性特点，采用控制深水波列演化的四阶修正非线性薛定谔方程，基于波列演化的边带不稳定性，研究了边带扰动条件下畸形波的生成与复波包谱的变化，并进一步详细分析了满足边带不稳定条件时，扰动频带宽度、初始扰动振幅、波陡及非线性阶数对边带不稳定性的发展和畸形波生成的影响。结果表明，载波能量向与之频率较近的不稳定边带快速转移，可引起波列在局部迅速增长而生成畸形波，因此该能量转移特性是边带不稳定性导致畸形波生成的一个根本原因。

A nonlinear mechanism analysis of freak wave generation

Sideband instability exists in the evolution of slowly modulated periodic wave train, and can cause a local exponential grow of its amplitude, so generation of freak waves and variation of corresponding complex envelope under the condition of sideband disturbance are studied, and the modified four-order nonlinear Schroedinger equation, which describes the evolution of complex envelope in deep water waves, is employed on the basis of nonlinear characteristids of freak waves. With sideband instability satisfied, the influences of frequency bandwidth and initial amplitude of perturbation, wave steepness and nonlinearity are particularly analysed on the development of sideband instability and freak wave appearance. Results show that it is an essential cause of freak wave occurrence arising from sideband instability that energy of carrier rapidly shifts to the neighbourly unstable sidebands.