Study On Numerical Model Of The Long-term Sea Bed Evolvement Under Combined Action Of Wave And Current And Its Engineering Application

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.