多向随机波列中畸形波的概率分析

发布时间：2018-08-18 20:56

【摘要】：畸形波是海洋中一类特殊的灾害性波浪,随着人类海上活动的增加,畸形波对船舶以及海洋平台等结构物的破坏越来越多,逐渐引起了人们的重视,但由于畸形波本身的复杂性,并且真正完整的观测记录也相对较少,至今畸形波的生成机理和基本特性等,尤其是关于畸形波的发生概率仍然不是十分明确,虽然很多学者也进行了大量的研究,并取得了相应的成果,但大部分都是基于二维波浪,而实际的海浪是三维的,不仅有不同频率的组成波,还有不同方向的组成波。因此,本文对多向不规则随机波列中畸形波的发生概率及影响因素等开展了研究。本文考虑了不同方向分布和相对水深的影响,对多向不规则波列进行了长时间的物理模拟。对多向不规则波列的统计参数(如有效波高、偏度、峰度和频谱)以及波高、波峰和波谷的概率分布进行了分析,并研究了波陡、方向分布和相对水深等参数对波列统计参数和概率分布的影响。研究结果表明：1.波浪的方向分布和相对水深对波列的统计参数有明显的影响,当相对水深较大,方向分布较窄时,由于波浪的非线性不稳定性,峰度值随着波浪的传播,有逐渐增大的趋势,波列的频谱出现主频下移,高频能量减小等现象；当相对水深较浅时,波浪的不稳定性受到抑制,峰度值随波浪的传播变化不大,频谱的主频甚至出现上移。2.波浪的方向分布和水深也会影响到波高、波峰和波谷的概率分布,当相对水深较大,方向分布较窄时,由于波浪的非线性不稳定性,波高、波峰和波谷的概率分布末端越增大,并随着波浪的传播而明显增大；对于浅水情况,不稳定性受到抑制,二阶非线性起到主要作用,方向分布的变化对波高、波峰和波谷的概率分布影响不如深水时明显。3.从不同的方向分布生成的畸形波的实验过程中可以看出,当波浪越趋于单向的时候,则畸形波的生成更多的是基于波浪自身的不稳定性自聚焦而成,而当波浪的方向分布较大,特别是趋于均匀分布的时候,畸形波的生成则更多的是基于波浪之间的汇聚而成。本文通过对多向不规则波列中统计参数和概率分布的分析,可以得出,当相对水深较深,方向分布较窄时,由于波浪的不稳定性,大波高的出现概率增大,因此,畸形波更容易出现在这种海况下,海上结构物设计时,应充分考虑到海况对波高分布的影响。
[Abstract]:Deformed waves are a special kind of disastrous waves in the ocean. With the increase of human activities at sea, the damage of deformities to ships and structures such as offshore platforms is becoming more and more serious, and people pay more and more attention to them. However, due to the complexity of the deformity wave itself and the relatively few truly complete observation records, so far the formation mechanism and basic characteristics of the deformity wave, especially about the occurrence probability of the deformed wave, are still not very clear. Although many scholars have done a lot of research and obtained corresponding results, most of them are based on two-dimensional waves, but the actual waves are three-dimensional, not only have different frequencies of the component waves, but also in different directions. Therefore, in this paper, the occurrence probability and influencing factors of abnormal waves in multidirectional irregular random wave trains are studied. In this paper, the effects of different direction distribution and relative water depth are considered, and a long time physical simulation of multidirectional irregular wave train is carried out. The statistical parameters (such as effective wave height, deviation, kurtosis and spectrum) and the probability distribution of wave height, peak and trough of multidirectional irregular wave train are analyzed, and the wave steepness is studied. The influence of direction distribution and relative water depth on the statistical parameters and probability distribution of wave train. The results of the study show that 1: 1. The directional distribution of wave and the relative water depth have obvious influence on the statistical parameters of wave train. When the relative water depth is larger and the direction distribution is narrower, because of the nonlinear instability of the wave, the kurtosis value increases gradually with the wave propagation. When the relative water depth is shallow, the wave instability is restrained, the kurtosis value changes little with the wave propagation, and the main frequency of the frequency spectrum even moves up. 2. The directional distribution and water depth of wave also affect the probability distribution of wave height, wave peak and trough. When the relative water depth is larger and the direction distribution is narrower, the higher the wave height, the more the probability distribution end of wave peak and trough is due to the nonlinear instability of wave. For shallow water, the instability is restrained, the second order nonlinearity plays a major role, and the variation of directional distribution has less effect on the wave height, the probability distribution of wave peaks and troughs than that of deep water. It can be seen from the experimental process that the abnormal waves generated in different directions tend to be generated on the basis of the instability of the wave itself when the wave tends to be unidirectional, but when the direction distribution of the wave is larger, the formation of the deformable wave is mainly based on the instability of the wave itself. Especially when it tends to uniform distribution, the formation of abnormal waves is more based on the convergence of waves. Through the analysis of the statistical parameters and probability distribution in multidirectional irregular wave trains, it can be concluded that when the relative water depth is deeper and the direction distribution is narrower, the occurrence probability of large wave height increases due to wave instability. Deformed waves are more likely to occur in such sea conditions, and the influence of sea conditions on wave height distribution should be fully taken into account in the design of offshore structures.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P731.2

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