表面水波包络短强孤子的模拟与实验
Simulations and experiments of short intense envelope solitons of surface water waves
摘要：
本文通过实验室和数值模拟的方法，对深水中重力波稳定非线性群的存在性问题进行了修正。在实验室实验中再现陡度高达$A_{cr} ω_m^2 /g \approx 0.30$的波群（$A_{cr}$是波峰振幅，$ω_m$是平均角频率，$g$是重力加速度）。我们表明，对于超过60个波长或约15-30个基团长度，这些基团保持稳定，既没有表现出明显的辐射，也没有表现出结构转变。这些孤立波图案不同于传统的包络孤子，因为只有少数个别波包含在组中。实验结果和强非线性数值模拟的潜在的欧拉方程之间得到很好的协议。非线性薛定谔方程的包络孤子解被证明是一个合理的第一近似指定的造波机驱动信号。短强包络孤子具有与规则Stokes波相似的垂直不对称性，具有相同的频率和振幅。与对Stokes波速度的非线性修正相比，非线性对包络孤子速度的影响更大。
英文摘要：
The problem of existence of stable nonlinear groups of gravity waves in deep water is revised by means of laboratory and numerical simulations with the focus on intense waves. Wave groups with steepness up to $A_{cr} ω_m^2 /g \approx 0.30$ are reproduced in laboratory experiments ($A_{cr}$ is the wave crest amplitude, $ω_m$ is the mean angular frequency and $g$ is the gravity acceleration). We show that the groups remain stable and exhibit neither noticeable radiation nor structural transformation for more than 60 wave lengths or about 15-30 group lengths. These solitary wave patterns differ from the conventional envelope solitons, as only a few individual waves are contained in the group. Very good agreement is obtained between the laboratory results and strongly nonlinear numerical simulations of the potential Euler equations. The envelope soliton solution of the nonlinear Schrödinger equation is shown to be a reasonable first approximation for specifying the wavemaker driving signal. The short intense envelope solitons possess vertical asymmetry similar to regular Stokes waves with the same frequency and crest amplitude. Nonlinearity is found to have remarkably stronger effect on the speed of envelope solitons in comparison to the nonlinear correction to the Stokes wave velocity.
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