河口海岸泥沙输移的分组数学模型研究

Study on the Fractional Modeling of Sediment Transport in Estuarine and Coastal Waters

根据河口海岸水沙输移的特点,建立了一个新的二维分组数学模型,用来预测该区域的水沙输移过程。该模型耦合了水动力模块、泥沙输移模块和床面演变模块。其中水动力模块基于浅水方程组,综合考虑了柯氏力、床面切应力以及表面风应力的影响,引入干湿判断法处理动边界。泥沙输移模块首先将泥沙按照粒径分组,针对不同泥砂性质,对各组泥沙分别进行建模求解。床面演变模块基于质量守恒方程,实时更新床面高程以及床沙级配变化,并传递给水动力模块,更新底部边界。该模型被应用在了英国塞汶(Severn)河口,其预测的泥沙浓度和实测数据以及不分组的模型的预测结果进行了比较,结果显示,文中建立的分组模型预测的结果要明显好于不分组模型。

A new two-dimensional fractional numerical model is established in this paper to simulate the hydrodynamics and graded sediment transport process in estuarine and coastal waters. The model is coupled by the hydrodynamic module, sediment transport module and bed evolution module. The Corlioli effect, bed shear and wind shear are introduced in the hydrodynamic module and the wetting-drying method is adopted to deal with the moving boundary. The sediment mixture is divided into several fractions according to the grain size and each fraction is simulated separately in the sediment transport module. Based on the mass conservation equation, the processes of bed elevation change and sediment grain size sorting are simulated in a real-time way in the bed evolution module, and the data are transferred to the hydrodynamic module immediately to renew the bottom boundary. The model has been applied in the Bristol Channel and Severn estuary in the UK. The predictions by the present model are compared with the field data and those by the single-fraction model. The results show that the present model predictions have better compliance with the field data than the non-fractional model results.