【作者】 张宏伟；

【导师】 康海贵； 陈兵；

【作者基本信息】 大连理工大学 ， 港口、海岸及近海工程， 2009， 博士

【摘要】 海岸带泥沙输移问题以及海床长期演变是海岸工程研究的重要组成内容。我国海岸多为粉砂淤泥覆盖,在风浪掀沙和水流输沙的作用下,有较多泥沙悬浮和输移。泥沙输移问题涉及到港口选址规划布置、航道的疏浚、抛泥区的选择、海岸线侵蚀、区域性填海设计、海洋结构物基础的安全等。而且随着经济的发展,污染物排放处置、滩涂促淤围垦和海洋环境保护等方面的问题日益突出,这些问题不仅与泥沙输移密切相关而且还属于多因素影响下的海床长期行为。因此对海床长期演变的趋势研究,尤其是针对淤泥粉砂质海床长期演变数学模型的研究,在工程界更为关注,也是泥沙数值模拟中迫切需要解决的问题之一。由于B.Latteux海床长期演变概化模式,不仅能够有效地克服“岸线模型”的小波浪入射角假定以及只考虑岸线平移、不考虑海滩剖面变形等缺点,而且还具有计算精度高,计算耗时少等优点,是比较先进的概化模式。但是,该模式存在主要“以推移质运动为主”的不足。因此,本文对该概化模式作了进一步的完善与推导,在已有的对悬移质运动特性研究的众多成果的基础上,将悬移质输移作为海床运动的主要影响因素,加入到B.Latteux海床长期演变概化模式中。从而,将该概化模式进一步推广到以悬移质运输移动为主的淤泥粉砂质海床的长期演变计算中,并建立了二维波浪、潮流共同作用下全沙(悬移质、推移质)海床长期演变数值模型。在数值计算方面,基于无结构网格对复杂边界的较好适应性以及FVM(FiniteVolume Method)格式对对流项通量的良好守恒性,利用三角网格上的FVM的Roe型二阶迎风型格式分别对二维浅水方程、悬沙输移方程进行数值离散求解。并成功地引入了国际上较为成熟的第三代海浪模型SWAN(40.41),利用改进后的矩形网格向三角形网格插值技术,配合三角网格下FVM格式的复合流场模型和全沙模型的计算。其中,在复杂地形条件下,为避免模拟底部地形多变的静止水体时水体发生虚假流动,对通量梯度项和源项采用Rogers方法进行了平衡处理;在对流项通量Roe型二阶迎风格式重构的基础上,加入Sweby限制器来保证重构的单调性和抑止其振荡。在数值求解方法方面,本文采用Ambrosi提出的分步求解方法对二维浅水控制方程以及悬移质运动方程进行求解,该方法能够很好地避免由于源项而引起的计算不稳定。分别利用K.ANSTASIOU二维溃坝的数值计算结果、波浪在圆形浅滩上变形和在双突堤中传播变形的实验数据以及在黄河三角洲桩西海域所实测的悬沙浓度数据,分别对水动力模型(潮流、波浪模型)以及泥沙运动模型进行了验证,取得了较为理想的结果。探讨了黄河三角洲桩西海域的特征波、代表潮的选取方法,并以其代入本计算模型,对黄河三角洲周围海域的水动力特征以及桩西海域海床长期演变规律分别进行了验证和解析。其中,选取特征波时,将该海域的波况分为强浪以及常见浪两种波况,再分别进行加权平均概化处理的方法。该海域的潮流条件采用三个代表潮(分别接近大潮、中潮以及小潮)来进行构建。由数值模拟结果,总结了该海域的海床长期演变规律。本数学模型能够较好地模拟出以“悬移质运动为主”的海床长期演变的特征,可以应用于淤泥粉砂质海床的长期演变计算。更多还原

【Abstract】 Sediment transport is an important factor which influences the evolution of the estuarine and coastal. In china, many estuarine and coastal areas are covered by fine silts and mud, and there are a lot of sediments to be suspended and transported under the action of tidal current and waves. Sediment transport problem have an influence on location selection of port, layout of port, waterway dredging, seashore erosion, design of reclamation project, safety of ocean engineering construction and so on. As the economy develops, emission of pollutant and environmental protection become more and more important, these are also closely related to sediment transportation. Whereas, these issues are mostly belong to the long-term behavior influenced by many factors. So, the trend of long-term evolution of the seabed, attracts more and more attentions in practical engineering as well as in scientific researching, and is also the question need to be sloved urgently.In this paper, the generalized model of B. Latteux seabed long-term evolution, which do not only overcome the shoreline model’s disadvantages of beach profile invariability translation, as well as the assumption of small wave incident angle, but also has the advantages of higher calculational accuracy and less time consuming, was further improved to include the suspended load movement. Base on the reserach work of large number of experts, we take the suspended load movement as a major factor, and add it into B. Latteux’s seabed long-term evolvement generalization model. As a result, the B. Latteux’s model was further promoted into the computing of silty mud seabed long-term evolution, and we established a two-dimensional numerical model of the seabed long-term evolution under the combained action of wave and tidal, which could includes the suspended load and bed load movement.In the numerical modelling, based on adaptability of the unstructured grid for the complex border, as well as better conservation character of the FVM (Finite Volume Method), we use the triangular grid FVM and the second-order Roe-type upwind format to slove the two-dimensional shallow water equations and suspended sediment transport equation respectively. And the SWAN (40.41) was successfully introduced into the flow and sand model, using the improved interpolating technology of rectangular grid to the triangular grid. The Ropers method is applied to deal with the bed slope source term in the equation, so that the flux can be balanced. The Ambrosi’s substep solver is used to calculate the friction source terms and enhance the stability of calculation. The numerical resluts of K.Anstasiou, the experiment data of wave distortion in round shoal and in single breakwater and the suspend sediment concentration data in Zhuangxi waters of Yellow River delta were used to verify the hydrodynamic model (tidal current ,wave model) and the sediment transport model, respectively, and got better results.In this paper, the method of properly selecting the representative wave and tide are discussed, which are used to simulate the tidal current and sediment transport in Yellow River delta and to analyse the long-term evolvement characters in Zhuangxi waters of Yellow River delta.This model could scucessfully simulate the characteristics of seabed long-term evolution with the suspended load as a major factor, and could be applied to compute the silty mud sea-bed long-term evolution.更多还原