浅水区域随机波浪的非线性特征研究

发布时间：2018-04-14 07:11

本文选题：Boussinesq模型 + 浅水　；参考：《大连理工大学》2015年硕士论文

【摘要】：波浪由深水传播到浅水的过程中,由于浅水变形及非线性的影响,波浪的形态会发生巨大变化,如波长变短,波幅、波陡变大及波浪破碎。Boussinesq方程对模拟波浪在浅水传播过程中的变化比较理想,本文利用改进的线性色散关系可以达到一阶Stokes波色散关系Pade[4,4]近似,精确到O(U2,ε3μ2)的完全非线性Boussinesq方程来模拟波浪在浅水区域传播过程。通过与理论靶谱、物理模型实验结果进行对比验证,证明了该模型模拟随机波浪在近岸传播的有效性。随后应用该数值模型研究了随机波浪在潜堤上传播的变形情况,波浪非线性特征参数(如不对称度,偏度)的变化。结果表明,随着水深的减小,波浪的不对称度和偏度逐渐增大,它们的最大值均出现在堤顶迎浪侧,然后逐渐减小,如果堤顶浅水区足够长,它们在堤顶浅水区会达到一个稳定的状态,之后在反变浅区水深增加的过程中偏度逐渐减小到零,而不对称度有一个略微的增长然后再逐渐减小到零。基于波面过程线的波形变化及其波浪谱变化分析了这些参数变化的原因,接下来基于小波二阶谱分析了小波二阶谱实部与偏度、虚部与不对称度变化的关系。然后分析了潜堤坡度、谱峰周期、波陡、堤顶浅水区水深、谱峰因子等因素对不对称度和偏度变化的影响。随后分析了变浅区、反变浅区、堤顶浅水区三个区域不对称度和偏度与当地Ursell数的关系,根据数值模拟结果拟合了各区域波浪的不对称度和偏度与Ursell数之间的经验公式,并与相关研究进行了对比。最后利用该模型研究了随机波浪在潜堤上传播时畸形波的发生情况及其影响因素。当随机波浪在潜堤上传播时,波浪的偏度和峰度均随着水深的减小而增大,畸形波发生的概率也随之增大,偏度和峰度的最大值以及畸形波发生概率最大的位置均出现在堤顶浅水区前端。并且发现入射波浪的谱峰周期、斜坡的坡度以及堤顶浅水区的水深均对畸形波产生的概率有影响,而代表波浪谱宽的谱峰因子对于随机波浪在浅水区域传播时畸形波产生的概率影响并不显著。偏度和峰度的变化与最大波高的变化呈现相关性,而坡度会影响偏度与峰度之间的关系。
[Abstract]:In the process of wave propagation from deep water to shallow water, due to the influence of shallow water deformation and nonlinearity, the shape of wave will change greatly, such as the wave length becomes shorter, the wave amplitude becomes shorter,The Boussinesq equation is ideal for simulating the wave propagation in shallow water. By using the improved linear dispersion relation, the first-order Stokes wave dispersion relation Pade [4 ~ 4] approximation can be obtained.The complete nonlinear Boussinesq equation is used to simulate the wave propagation in shallow water region with the accuracy of OFU _ 2, 蔚 _ 3 渭 _ 2).Compared with the theoretical target spectrum and the experimental results of the physical model, it is proved that the model is effective in simulating the propagation of random waves near the shore.Then the numerical model is used to study the deformation of random waves propagating on the submersible embankment and the variation of wave nonlinear characteristic parameters such as asymmetry degree and deviation degree.The results show that with the decrease of water depth, the asymmetry and deviation of the waves increase gradually, and their maximum values appear at the top of the embankment, and then gradually decrease, if the shallow water area of the top of the embankment is long enough,They will reach a stable state in the shallow water area of the top of the embankment, and then decrease to zero in the process of increasing the water depth in the reverse shallow area, while the asymmetry degree increases slightly and then decreases to zero gradually.The causes of these parameters are analyzed based on the waveform changes of the wavefront process line and the wave spectrum changes. Then, the relationship between the real part and the bias of the wavelet second order spectrum and the variation of the imaginary part and the asymmetry degree is analyzed based on the wavelet second order spectrum.Then, the effects of slope, peak period, wave steepness, shallow water depth and spectral peak factor on the variation of asymmetry and deviation are analyzed.Then, the relationship between the asymmetry degree and deviation degree and the local Ursell number of the three regions in the shallow area of the shallow area, the reverse shallow area and the top of the embankment are analyzed. According to the numerical simulation results, the empirical formulas between the asymmetry degree and the deviation degree and the Ursell number of the waves in each region are fitted.And compared with the related research.Finally, using the model, we study the occurrence and influence factors of the abnormal wave when the random wave propagates on the submersible embankment.When the random wave propagates on the submersible embankment, the deviation and kurtosis of the wave increase with the decrease of the water depth, and the probability of the abnormal wave also increases.The maximum values of skewness and kurtosis, as well as the largest occurrence probability of deformities, occur at the front of the shallow water area at the top of the embankment.It is also found that the frequency peak period of the incident wave, the slope of the slope and the water depth in the shallow water area of the top of the embankment have an effect on the probability of the abnormal wave.But the peak factor, which represents the wave spectrum width, has no significant effect on the probability of the abnormal wave when the random wave propagates in shallow water region.The variation of skewness and kurtosis is correlated with the change of maximum wave height, while the slope will influence the relationship between skewness and kurtosis.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TV139.2

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