【作者】 张婷婷；

【导师】 董国海； 马小舟；

【作者基本信息】 大连理工大学 ， 港口、海岸及近海工程， 2011， 硕士

【摘要】 当波浪由外海传播至近海时,由于地形和建筑物的影响将发生浅水变形、折射、绕射、反射、破碎、再生等一系列变形,加之水流的影响,使得近岸波浪场变得异常复杂。潜堤是一种常用的海岸防护工程建筑物,泛指淹没在水中的防护堤,主要用来保护海岸线、促滩促淤、围海造田和放浪导流。研究波浪在潜堤上的传播变形及波流在潜堤上的相互作用有着重要的理论意义和使用价值。本文首先概述了Boussinesq方程的最新研究进展。Boussinesq方程是一种在一定水面和海底边界条件下,通过保留更高阶的项及选取不同代表速度项对Euler方程进行垂向简化而成的。此外,通过添加其他一些作用项,如破碎、底部摩擦阻力、Subgrid紊动混合项、数值海绵层等,扩展了对Boussinesq方程的应用范围。在详细的推导了Nwogu改进的Boussinesq方程基础上,应用有限差分格式对方程进行了离散求解。为了能在较大的频率和方向范围内衰减波浪的能量并增加数值模型的稳定性,采用计算域内造波的方法,并且在两端设置海绵层来吸收波浪能量。域内造波法通常用来在模型中产生线性波浪信号,本文采用该方法产生椭圆余弦波。应用所建立的模型,将模拟的结果与解析解进行了比对,验证了该方法也可以用来产生非线性波浪信号。随后利用本模型模拟了波浪在潜堤上的传播演化,并将波面和各阶谐波的计算值与文献的实验结果进行了比较,二者吻合良好,说明本文建立的模型是可靠的。并用在大连理工大学所做的物理实验模拟的规则波的数据与本模型计算值进行比对,吻合的也较好。分析了双色波群在不同的调谐率,平均频率和差频下,对主频、超谐波和次谐波的影响,并且与解析解相比较,其差别主要体现在次谐波中,也就是波群频率。加入水流后,顺流和逆流对于波浪组成部分的成长及发展影响较大。不仅对双色短波群产生的低频波浪做了较详细的分析,还利用本模型模拟了自由长波在潜堤上的传播变化,给出了长波幅值以及内部结构的变化规律。研究表明自由的低频波浪本身就是含有高阶谐波的。最后模拟了长短波相结合的双色波在常水深下的传播,并与解析解进行了对比,吻合的较好。显示了Boussinesq方程同时模拟长波和短波的优势。更多还原

【Abstract】 As the wave propagating to the offshore, wave will become deformed because of the influence of the topography and the buildings which case the shoaling, refraction, diffraction, inflection or breaking etc. Besides, the current is relatively strong in the entrance of title inlet and estuaries, which makes the nearshore wave field more complex. The submerged breakwaters are the buildings which are commonly used on the coastal protection engineering, whose functions including beach protection, accretion promotion, enclosing tideland for cultivation, diversion, and so on.By keeping the higher order term, using different velocity term and adding some "deep water terms", the resulting set of equations have significantly improved linear dispersion properties in the water of intermediate depth and extended the range of its applicability. Based on Nwogu’s extended Boussinesq equations, the finite difference scheme is applied. In order to increase the numerical stability and decrease the wave energy in larger frequency and in more direction, internal generation of wave is applied, and the sponge layers are set for absorbing the wave energy. The cnoidal wave is made by this way of which numerical results agree well with the analytical solutions so this model can be used to make nonlinear wave. Then the evolution of the wave propagation over the submerged sill is imitated using this model, which results agree well with the experimental data in the aspect of wave surface and the harmonic. Considering a range of modulation rates, group frequencies, and difference frequencies, the primary frequencies, super harmonics and the sub-harmonics induced by bichromatic wave groups are examined in DULT’s laboratory. It is also found that the following current and the opposing current have evidently impact on wave evolution. Not only the low frequency waves induced by bichromatic waves are analyzed, but also the evolution of free long waves over the submerged sill is simulated. The results show that they have super harmonics in its own internal structure. At last the free long waves combined the short waves are simulated in the constant depth water, and compared with theoretical values which have a good agreement. So the Boussinesq equations have great advantages in modulation of long wave and short wave.更多还原