本文關(guān)鍵詞： 畸形波 非線性薛定諤方程 Benjamin-Feir不穩(wěn)定性 Jonswap譜　出處：《大連理工大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

【摘要】：畸形波是一種在沒有預(yù)警的情況下突然發(fā)生,并迅速消失的災(zāi)害性事件。由于畸形波會給海洋建筑物和船只帶來巨大威脅,畸形波受到人們越來越多的重視。以往的研究主要集中在畸形波的生成機制,而在工程中我們更加關(guān)心的是畸形波的發(fā)生概率和如何預(yù)報。 本文采用四階非線性薛定諤方程模擬了二維JONSWAP譜情況下畸形波的生成。為了探討波浪參數(shù)對畸形波的影響,模擬實驗分成了多組初始波浪參數(shù)不同的工況。首先分析了深水不穩(wěn)定波列的演化過程�；尾◤男纬傻较У难莼^程即調(diào)制一反調(diào)制的過程：調(diào)制過程中,畸形波位置處能量發(fā)生匯聚,波高升高,其附近的波高減��；反調(diào)制過程中,畸形波位置處波幅減小,直至畸形波的特征消失,其他位置處波高增大。 然后本文探討了峰度、有效波高、偏度值和波浪譜的演化過程以及JONSWAP譜參數(shù)對它們的影響。結(jié)果表明：Benjamin-Feir指數(shù)(BFI)是判斷波列不穩(wěn)定調(diào)制是否發(fā)生的重要參數(shù)；峰度值的空間演化曲線和畸形波生成概率曲線趨勢一致,峰度值可以預(yù)測畸形波生成概率的大小。在隨機波浪場中,譜寬較窄和有效波高較小時,畸形波較容易發(fā)生。有效波高和偏度值在波浪傳播過程中基本無變化,偏度的大小與初始波陡有關(guān)。波浪之間的非線性作用導(dǎo)致主頻處的能量向高頻和低頻部分傳遞,因此在波浪傳播過程中譜峰高度下降,頻譜變寬。在討論了前面一系列問題的基礎(chǔ)上,我們分析了Benjamin-Feir不穩(wěn)定性與深水畸形波的內(nèi)在聯(lián)系和畸形波的發(fā)生機制�；尾ǖ纳膳c波浪二階非線性和束縛波關(guān)系很小,畸形波的生成主要是四波共振造成的,也就是Benjamin-Feir不穩(wěn)定性。 最后對模擬實驗波高進行了統(tǒng)計分析。結(jié)果表明：對于BFI1.0的情況,模擬波高分布與瑞利分布基本一致；而對于BFI1.0的情況,由于發(fā)生了不穩(wěn)定調(diào)制,瑞利分布只在演化初期與模擬波高分布相吻合,在其他位置處瑞利分布會低估大波發(fā)生的概率,畸形波發(fā)生概率比瑞利分布預(yù)測的大一個數(shù)量級以上。初始有效波高較小,譜峰升高因子較大時,波高分布與瑞利分布的差異較大。Forri stall分布和瑞利分布均不能很好的預(yù)測波峰分布。在非線性成長后,MER分布與模擬波高分布吻合較好,能夠準確預(yù)報畸形波的發(fā)生概率。
[Abstract]:Freak wave is a sudden occurrence without warning, and rapidly disappearing disaster events. Because of the freak wave will bring a huge threat to the marine structures and ships, freak waves have attracted more and more attention. Previous studies focused on the generation mechanism of freak waves, and in the project we are more concerned about the occurrence probability and how to forecast the freak wave.
This paper uses four order nonlinear Schrodinger equation to simulate the two-dimensional JONSWAP spectrum under the freak wave generation. In order to investigate the influence of freak wave wave parameters, simulation experiment is divided into several groups of different parameters of the initial wave conditions. Firstly, analyzing the evolution of deepwater instability. The freak wave wave from the formation to the evolution of the process of disappearing a modulation counter modulation: modulation process, the position of the freak wave energy aggregation, wave height increased, in the vicinity of the wave height decreases; the anti modulation process, the position of the freak wave amplitude decreases, until the disappearance of freak wave characteristics, the other position of the wave height increases.
Then this paper discusses the effective wave height, kurtosis, skewness and evolution of the wave spectrum and JONSWAP spectrum parameters influence on them. The results showed that the Benjamin-Feir index (BFI) is an important parameter in evaluating whether modulation instability wave train; curve and abnormal wave generation probability curve consistent evolution of kurtosis value space, kurtosis can predict the probability of freak wave generation. In random wave field, narrow spectral width and wave height is small, the freak wave is easy to occur. The effective wave height and skewness in the wave propagation process basically no change, and the size of the initial wave steepness of the partial nonlinear interaction between waves. The frequency of lead energy transfer to high frequency and low frequency, therefore in the process of wave propagation in the peak height decreased, the spectrum becomes wider. Discusses a series of problems on the front, we analyzed Benjamin-Feir The relationship between instability and deep-water freak waves and the mechanism of freak waves occur. The generation of freak waves is very limited to the two order nonlinear and bound waves. The generation of freak waves is mainly caused by four wave resonance, that is, Benjamin-Feir instability.
At the end of the simulation wave were analyzed. The results show that: for BFI1.0, simulation of wave height distribution and Rayleigh distribution are basically the same; and in the case of BFI1.0, due to the instability of modulation, the Rayleigh distribution only in the early stage of evolution and Simulation of wave height distribution match in other locations will underestimate the probability distribution of Rayleigh wave the freak wave occurrence prediction biruili distribution probability of a large number of above. The initial effective wave height is smaller, peak elevation factor is higher, the difference with the Rayleigh distribution of wave height distribution of larger.Forri stall distribution and Rayleigh distribution is not a good predictor of peak distribution. In the non-linear growth, MER distribution and wave height the distribution agreement can accurately forecast the occurrence probability of freak wave.

【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：P731.22

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本文編號：1463509