【作者】 胡克林；

【导师】 丁平兴；

【作者基本信息】 华东师范大学 ， 自然地理学， 2003， 博士

【摘要】 本文建立了一个用于波—流共同作用下长江口平面二维悬沙计算的数值模型系统，主要由四部分组成，即考虑风、浪、潮、径流的二维复合流场模型、SWAN海浪模型、波—流相互作用的底边界层模型以及二维悬沙输运模型。采用三个不同大小的区域进行嵌套计算，三个计算区域分别为东中国海区域、长江口杭州湾区域和长江口区域。 模型系统采用广义曲线坐标系下的形式，使用高精度的自适应网格拟合复杂岸界。复合流场学模型中考虑了波浪辐射应力的作用，底摩擦由波—流相互作用边界层模型提供。为了较高精度的模拟天文潮，在开边界加上了七个主要分潮。台风天气下，在东中国海区域计算由风产生的水位变化，插值到长江口杭州湾区域的外海开边界上作为余水位，这样就同时考虑了局地风和非局地风的影响。 悬沙输运模型利用切应力方法来确定对流扩散方程中的泥沙源函数，其中的临界起动速度利用经典的泥沙起动流速公式前面增加一个局地系数得到，这个系数能反映河床底质结构及固结程度，通过系列数值试验和实测资料的统计分析确定。计算中的底部剪切应力由波流边界层模型给出波—流共同作用下的形式。泥沙颗粒絮凝沉降速度考虑了流速、盐度、含沙浓度的影响。 将模型系统应用到长江口区域，经过了大量的实测资料的验证。其中复合流场模型中的天文潮利用众多测站的实测调和常数进行验证；波浪模型首先进行了水槽实验的检验，然后在台风过程中，进行了测站有效波高过程线的比较。复合流场模型的水位过程、流速过程，以及悬沙模型的含沙量过程则经过了洪、枯季及大、中、小潮的多个站点的实测过程验证。分析流场、波浪场以及正常和台风天气下的悬沙场的计算结果，表明该模型系统能合理地反映长江河口区域的水动力场和泥沙场的分布。更多还原

【Abstract】 In order to calculate depth-averaged two-dimensional (2-D) suspended sediment transport under waves and currents in the Yangtze Estuary, a numerical model system is developed. Four models, a 2-D compound fluid model including wind, waves, tides and river runoff, a SWAN wave model, a wave-current bottom boundary layer model and a 2-D suspended sediment transport model are integrated. Three different calculating regions, East China Sea region, Yangtze Estuary and Hangzhou Bay region and Yangtze Estuary region, are defined for nesting computation.The model system is in the generalized curvilinear coordinates, using high precision self-adaptive grids to fit the complicated topographies and coastal shapes. The effect of wave radiation stress is considered in the compound fluid model. The value of bottom friction is offered by the wave-current bottom boundary layer model. Seven main constituents are added to the open boundaries for perfectly simulating astronomical tides. Under the typhoon weather, residual elevations at the open boundaries of the Yangtze Estuary and Hangzhou Bay region can be obtained by interpolating from the elevation varieties induced by wind in the East China Sea region. In this way, the local wind and the non-local wind can be taken into account simultaneously.In the suspended sediment transport model, the method of shear stress is adopted to determine the source function in the suspended sediment diffusion equation. Through a series numerical experiments and statistical analyses of observed field data, a local coefficient, which can reflect the bottom material and consolidation, is introduced into the classic critical erosion velocity of the sediment. In calculation, the bottom shear stress under the effect of waves and currents is supplied by the wave-current bottom boundary layer model. The floe settling velocity of sediment particles is taken as the function of current velocity, salinity and suspended sediment concentration.The model system is verified by lots of observed data when applied to the Yangtze Estuary. Observed tidal harmonic constants in many stations are used to verify the astronomical tides in the compound fluid model. The wave model is testedby a set of wave flume data at first. Then the results are compared by the actual processes of significant wave height in gauging stations. The processes of surface elevation, current velocity in the compound fluid model and suspended sediment concentration in the suspended sediment transport model are verified by observed data of many stations in flood/dry season and in spring/middle/neap tide. The analyses of the calculated current fields, wave fields and suspended sediment distributions under normal or typhoon weather show that the model system can preferably reflect hydrodynamic fields and sediment distributions in the Yangtze Estuary.更多还原