近岸斜向波浪不对称特征参数化

Parameterization of asymmetries for obliquely incident waves in coastal region

近岸波浪的不对称特征对浅水区泥沙输运以及海岸结构物受波浪冲刷影响而引起的破坏都起着关键作用,而目前关于波浪不对称特征的研究多集中在正向传播方式上,没有考虑斜向传播的影响,因此,对斜向波浪在近岸传播过程中的波形不对称特征展开研究具有重要的意义。基于高阶Boussinesq水波方程建立了斜向入射波浪沿斜坡传播的数值模型,并利用该模型进行数值试验,模拟了入射波浪沿0°~75°不同方向的传播过程。通过对不同角度入射得到的结果进行比较,讨论了入射角度对波浪不对称特征的影响。结果表明:入射角度越大的波浪,其在变浅过程中的二阶谱以及波浪的偏度和不对称度参数也越小。说明随着波浪入射角度增大,其非线性相互作用程度会发生减弱,导致波浪的非线性特征增长趋势逐渐变缓。最后,给出了考虑斜向角度影响的波浪不对称特征参数经验公式。

In the coastal region,the characteristics of wave asymmetry are closely related to the sediment transport. It plays a crucial role in determining the structure failure of a coastal defense due to the toe scour. However,most of the researches related to the wave asymmetry focus on the normal incident waves,there have not been sufficient researches on the evolution of wave asymmetry for obliquely incident waves. Therefore,it is necessary to investigate the evolutions of wave asymmetries for obliquely incident waves in the coastal region. In this study,a numerical model is developed to conduct the numerical experiments,which is based on the fully nonlinear Boussinesq equations. Irregular waves with incident angles ranging from 0° to 75°are simulated. The effect of incident angle on the wave asymmetries is analyzed by comparing the numerical results obtained with different incident angels. The results showed that the parameters of wave skewness and asymmetry,as well as bispectrum in the shoaling process,are moderated with an increase in the incident angle. This indicates that the degree of the triad wave interactions could be weakened by increasing the incident angle,which leads to a decrease in the nonlinear wave characteristics. In conclusion,the empirical formulae for wave skewness and wave asymmetry by combining the influence of incident angles are recommended.