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非结构波流耦合模型及近岸物质输运应用研究

发布时间:2017-12-30 19:37

  本文关键词:非结构波流耦合模型及近岸物质输运应用研究 出处:《大连理工大学》2014年博士论文 论文类型:学位论文


  更多相关文章: 大范围波浪模型 波生流 波流耦合模型 非结构网格 物质输运 粒子追踪


【摘要】:近岸物质输运涉及海洋环境和泥沙运动两大重要问题,其范围可达数十甚至数百公里。近岸物质输运的核心动力为近岸海水的流动,该流动包含了潮流、波浪引起的波生流和风生流等不同海洋动力要素的非等量贡献。构筑适应大范围近岸物质输运数值计算的水动力平台,成为近岸物质输运研究关注的热点。 已有研究中,风生流可通过在潮流模型中加入海面边界条件加以考虑,而考虑波生流的近岸流场模拟现有两种方法:一种是近岸波流统一模型,如基于Boussinesq方程的波生流统一模型[122],另一种是利用独立的近岸波浪模型计算波浪辐射应力等影响参量,再将其作为驱动因素添加到潮流场中,即为耦合模型。现波流统一模型在实际应用中仅适合于较小范围计算;而耦合模型可以考虑波浪一潮流的相互影响,又可适应于近岸大范围海水的流动模拟,是研究大范围波流耦合的现实途径。 大范围波浪模拟的控制方程主要为波谱平衡方程,而考虑波浪绕射则需要增加光程函数方程等进行联合求解。此外在数值计算中为实现波浪和潮流参数的直接交互,采用同一非结构化网格是便捷有效的方法;同时有限体积法能保证参量在非结构网格下离散时的通量守恒。目前尚缺乏将基于非结构化网格的有限体积法应用于上述波浪模型的相关研究。同样在考虑波生流的近岸流场模拟研究中,迄今也尚未见利用上述波浪模型与潮流进行耦合的相关研究。 本文在非结构网格下,构建了一个考虑波生流影响的大范围近岸海水流动的耦合模型;并在该水动力平台上结合物质输运方程及粒子追踪方法,构成保守物质输运模型,对实际海域的保守物质输运过程和特征粒子迁移规律进行了应用研究。 (1)基于修改后的波谱平衡方程和光程函数方程,建立了近岸大范围波浪模型。模型可考虑波浪绕射效应。波谱平衡方程采用算子分裂法分步数值求解,变量的空间离散则基于非结构网格采用有限体积法求解。波浪模型考虑了非均匀流场对其传播变形的影响,且波浪参量离散基于交错控制体,为后续与非结构流场模型的耦合提供了参量交互条件。通过多个实例验证了模型的精度和适应性。 (2)耦合三维流场模型与非结构波浪模型,得到近岸波流耦合模型。波浪、潮流及参量交互过程基于同一非结构化网格离散,计算效率较高。模型中流场考虑了波致辐射应力、波浪紊动及波流边界条件等因素,而波浪场则考虑流场的流速、流向及水位等条件影响。在波致辐射应力项中引入三维计算公式来研究波生流的垂向结构,同时模拟了理想和实际环境下的波生流场形态,以及波流耦合过程。结果表明波浪破碎会在近岸产生不同形态的波生流场,辐射应力的平面和垂向分布不均会引起平面及垂向环流。 (3)将近岸波流耦合模型与物质输运方程结合,得到近岸波流耦合下的保守物质输运模型。采用该模型,计算了纯浪、纯流以及浪流共同作用下保守污染物的迁移扩散问题,并进行了对比研究;模拟了不同条件下的污染物离散系数、迁移扩散过程,研究了波生流对近岸物质输运的影响。结果表明:波浪对污染物扩散的影响和流场在同一个数量级,近岸波浪破碎后产生的沿岸流场是污染物近岸输移的主要影响因素之一。 (4)结合粒子追踪法,将波流耦合下的近岸物质输运模型应用于大连湾及琥珀湾两个实际海域中,主要研究了近岸保守物质输运的规律。在大连湾海域,模拟计算的内容包括:耦合水动力场、余流场、特征粒子的迁移轨迹、保守污染物的输移特征和规律以及人工岛建设对湾内物质输运的影响。模拟得到:波生流对湾内流场影响较小,潮流是湾内污染物向外迁移的主要动力。保守污染物主要随潮致余流的方向迁移,湾南部及湾内各个子湾水域污染物易在湾内滞留。不同方案的人工岛对湾内不同区域的物质输运的影响不同,其尺度、形状和位置需进一步优化。 在旅顺琥珀湾海域,研究内容主要是琥珀湾现状条件下污染物的输移特征和规律,以及在湾底增加人工潮流通道后对湾内物质输运的影响。研究表明:波浪主要在琥珀湾口外近岸海域发生破碎,并形成波生流场,只会对近岸局部流场产生一定影响。琥珀湾口处的水动力较强,此处的粒子及保守污染物均会较快迁移出湾外,湾中和湾底处保守污染物及粒子迁移出湾外时间较长,且易在湾底滞留。湾底增加人工潮流通道后,可增加湾内的纳潮量,会明显促进湾内污染物的向外输移,对湾底及湾内西北部浅水区域的作用最为明显。
[Abstract]:Coastal transport relates to the marine environment and sediment movement are two important problems, which range up to tens or even hundreds of kilometers. The core power offshore material transport to the coastal water flow, the flow contains the trend of non equal contribution factors of wave induced currents and wind-driven current in different ocean wave induced dynamic force to construct. The water power calculation platform in large scale nearshore sediment transport and coastal sediment transport has become hot research focus.
In current study, wind-driven current may be added to the sea boundary condition in the flow model into consideration, and consider the existing two kinds of methods to simulate nearshore wave induced currents flow: a nearshore wave flow model, such as the Boussinesq equation based on the wave induced current unified model of [122], another is the use of nearshore wave model independent the calculation of wave radiation stress influence parameter, and then as the driving factors add to the trend in the field, which is now the wave current coupling model. The unified model for only in a small range of calculation in practical application; the influence of coupling model can be considered a wave tide, and can adapt to the wide range of coastal seawater flow simulation is a practical way to study a wide range of wave and current coupling.
The main control equation for large-scale simulation of wave spectrum balance equation, and consider the need for solving the wave diffraction combined with increased eikonal equations in numerical calculation. In addition to direct interaction of wave and tide parameters, using the same method of unstructured grid is convenient and effective; at the same time, the finite volume method can ensure the conservation of flux parameters in the unstructured grid of discrete time. There is still lack of study will be based on the application of unstructured grid finite volume method in the wave model. Also considering the nearshore current wave induced current research in simulation research using the coupled wave model and the trend has also not yet.
Based on the unstructured grid, construction of a large range of flow impact wave induced into coastal seawater flow coupling model; combined with the mass transport equation and particle tracking method in the hydrodynamic platform, a model of conservative substance transport, sea transport of conservative substance transport process and characteristics of particle migration law application study is carried out.
(1) equation and the eikonal equation of spectral balance based on the modified and established offshore large range wave model. The model can consider the effect of wave diffraction spectrum. Equilibrium equation using operator splitting method by numerical method, spatial discrete variables based on unstructured grid is solved by the finite volume method. The wave model considering the inhomogeneous flow of the influence of deformation propagation, and interleaving control based on discrete wave parameters, the coupling model for subsequent and non flow structure provides interactive parameter conditions. Through a number of examples to verify the model's accuracy and adaptability.
(2) the coupled three-dimensional flow model and the non structure wave model, get wave coupling model. The wave, tide and parametric interaction based on the same unstructured mesh, high computational efficiency. The model considers the flow wave radiation stress, wave wave and turbulent flow boundary conditions and other factors, and the wave field considering the flow velocity, flow and water level conditions. Influence to structure of wave induced radiation should be to study the wave induced current is introduced into 3D force formula in the vertical, while the simulation of wave induced flow field form ideal and actual environment, and the wave current coupling process. The results show that the flow field induced wave breaking will produce different in the coastal morphology, radiation stress and vertical plane will cause uneven distribution of planar and vertical circulation.
(3) the nearshore wave coupling model and mass transport equation combined with the model, get shipped conservative material transport under the wave current coupling. Using this model, pure wave calculation, pure flow and wave flow interaction under the migration of conservative pollutants diffusion problems, and make a comparative study of simulated pollutants in different conditions; the dispersion coefficient, diffusion process, studied the effects of wave induced currents on the coastal transport of substances. The results show that the effect of wave on pollutant diffusion and flow in the same order of magnitude along the flow field generated after the nearshore wave breaking is one of the main influencing factors of coastal pollutant transport.
(4) combined with particle tracking method, the material flow under the coupled wave nearshore transport model applied in Dalian Bay and amber bay two actual waters, mainly on coastal conservative mass transport law. In the waters of the Gulf of Dalian, including the simulation of coupled hydrodynamic field, residual flow field, migration trajectory the characteristics of particle transport, characteristics and laws of conservative pollutants and the influence of artificial island construction on the transport of substances. Simulation results: the wave induced current has little effect on the flow field, the tide is the main power in the outward migration. The direction of migration of pollutants with the main pollutants conservative tide induced residual current, and in the south of the Bay sub Bay pollutants easily in the Bay detention. Effects of different schemes on the artificial island in different regions of the transport of substances of different scale, the need to further optimize the shape and position.
In Lushun amber Bay, the main research content is the transport characteristics and rules of pollutants under the current conditions and the influence of amber Bay, increasing artificial tidal channel in the Bay after the end of the mass transport. The results show that the wave mainly in the coastal waters of amber Bay estuary is broken and the formation of a small flow, will only have a certain impact on the coastal local flow field. The water power strong amber bay at the mouth, the particles will move faster and conservative pollutants removed outside the Bay, bay and at the bottom of the Bay and conservative pollutants particle migration out of the bay outside a long time, and easy to remain in the bottom of the bay. The Bay bottom increased artificial tidal channel, tidal volume can increase the that will significantly promote the outward transport of pollutants, the shallow water area in the northwest region of the bottom of the Bay and the most obvious effect.

【学位授予单位】:大连理工大学
【学位级别】:博士
【学位授予年份】:2014
【分类号】:P731.2;X55

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