改进的相位调制法模拟畸形波:Ⅱ-畸形波特征参数和模拟效率的影响因素探讨

The generation of freak waves based on the modified phase modulation method:Ⅱ-discussion

在改进的相位调制法模拟畸形波的理论基础上,探讨了调制方向、调制波浪的数目、组成波数、谱的宽度以及谱峰周期等模拟参数对聚焦处畸形波特征参数和模拟效率的影响。结果发现,调制方向、调制波浪的数目、组成波数和谱的宽度是影响畸形波的特征参数和模拟效率的主要因素,谱峰周期(在模拟范围8s-16s内)的影响可以不计。高频向低频调制优于低频向高频调制。高频波浪对畸形波的形成具有极其重要的作用。在高频向低频调制方式下,组成波数一定时,畸形波波高、波峰高、畸形波波高与有效波高的比以及畸形波波峰高与畸形波波高的比随调制波数的增加而增大;波浪全部调制时,畸形波波高、波峰高和畸形波波高与有效波高的比随组成波数的增加而增大。畸形波波高、波峰高、畸形波波高与有效波高的比、畸形波波峰高与其前一波高和后一波高的比以及畸形波波峰高与畸形波波高的比均随谱宽度的增加而增大。在本文所采用的组成波数范围内(50-100),畸形波的模拟效率随调制波数和谱宽度的增加而提高。通过模拟试验推荐给出了改进的相位调制法模拟畸形波时截断频率、组成波数和调制波数的取值范围。

Based on the modified phase modulation method for simulating freak waves,this paper analyzed the influences of modulation ways,number of modulated waves,number of wave components,width of the target wave spectrum and spectral peak periods on freak wave characteristics and generation efficiency.The results show that freak wave characteristics and generation efficiency are influenced by the modulation ways,number of modulated waves,number of wave components and the width of the target wave spectrum,however,the influence of spectral peak period（8s-16s in simulations） can be neglected.The modulation way of high frequency to low frequency is superior to the way of low frequency to high frequency.Waves with high frequency are important factor in formation of freak waves.In the modulation way of high frequency to low frequency,with a certain number of wave components,freak wave height and its crest height,the ratio of the freak wave height to the significant wave height and the ratio of the crest height to the freak wave height are increased as the number of modulated waves increased.While all waves modulated,the heights of freak wave and its crest,and the ratio of the freak wave height to the significant wave height are increased as the number of wave components increased.Freak wave height and its crest height,the ratio of the freak wave height to the significant wave height,the ratio of the freak wave height to the fore-going and the following wave heights and the ratio of the crest height to the freak wave height are increased with the increase of spectrum band width.Within the range of 50 to 100 wave components adopted in the paper,the generation efficiency of freak waves is increased as the number of modulated waves and spectrum band width increased.Through numerical simulation,this paper makes recommendation values of truncation frequency,number of wave components and number of wave components to be modulated for simulating freak waves with the modified phase modulation method.