Two-dimensional Morphological Model Research Articles

NUMERICAL MODELLING OF MORPHODYNAMICS AROUND A TIDAL INLET

A two-dimensional morphological model is used to study sediment transport and morphdynamics around a tidal inlet. The model includes the processes of erosion on side slope for the avalanching effects. The model has been tested against a laboratory study of an idealised tidal inlet configuration over 68 tidal cycles. The results show a reasonable agreement between the model and experiment measurements with a typical pattern of accretion at up-drift of the inlet and erosion at the down-drift. This study also reveals the importance of surface waves and cross-shore sediment transport to the evolution and migration of the tidal inlet.

A two-dimensional morphological model based on next generation circulation solver II: Application to Caofeidian, Bohai Bay, China

This paper is a companion of a two-part papers on the development of a two-dimensional morphological model—CurWaC2D-Sed, based on next generation circulation solver. In this paper, the model developed in paper I is applied to the large-scale construction of near-harbor industrial zone with deep water harbor by reclamation in Caofeidian, Bohai Bay, which is a typical sandbar–lagoon bay-type tidal inlet system. Characteristics of tides, currents, waves and sediments in Caofeidian are firstly analyzed with field data from comprehensive field observations carried out in 2008. These data are then used for model calibration and validation, showing a good agreement between simulated results and field measurements for tides, currents and suspended sediments. The verified model is applied to study the effects of the construction of Caofeidian embankment and the on-going engineering scheme on hydrodynamics and sediment transports as compared with no constructions under three representative tide conditions and their combinations with normal and strong waves as well as on morphology evolution. The simulated results indicate that the present scheme leads to morphological changes in Caofeidian with acceptable rates of erosion and sedimentation. However, some attentions should be paid to erosion at offshore wharf in front of Caofedian foreland which may lead to potentially increasing landslide risks due to steep slope and sedimentation in Laogonggou creek.

A two-dimensional morphological model based on a next generation circulation solver I: Formulation and validation

This paper presents an effective morphological modeling system with new module designs. A two dimensional (2D) morphological model which contains grid generation module, circulation module, wave module, transport module and bed evolution module has been developed and validated. The grid generation module is based on unstructured triangular grid with second order accuracy achieved through cell reconstruction using multiple least square methods. The circulation module is based on semi-implicit Eulerian–Lagrangian method, which is stable and free from Courant–Friedrichs–Lewy (CFL) constraint. Using the cell reconstruction, the circulation module relaxes the grid orthogonality requirement of previous similar circulation solvers. In the wave module, unstructured SWAN model was incorporated to simulate the effects of current–wave interaction simultaneously. The transport module is developed with finite-volume method with high-order resolution. The modeling of suspended sediment transport and updating of morphological evolution is contained in the sediment-morphology module. The morphological modeling system is referred as CurWaC2D-Sed. Following the detailed description of each module, a number of theoretical and laboratory validation studies were conducted. The CurWaC2D-Sed model has shown to perform well in all those validation tests. The applications of this model to the field cases are presented in a companion paper.

Numerical Model for Sediment Transport and Bed Degradation in the Yangtze River Channel Downstream of Three Gorges Reservoir

This paper presents a two-dimensional morphological model for unsteady flow and both suspended-load and bed-load transport of multiple grain size to simulate transport of graded sediments downstream from the Three Gorges Reservoir. The model system includes a hydrodynamic module and a sediment module. The hydrodynamic module is based on the depth-averaged shallow water equations in orthogonal curvilinear coordinates. The sediment module describing nonuniform sediment transport is developed to include nonequilibrium transport processes, bed deformation, and bed material sorting. The model was calibrated using field observations through application to a 63-km-long alluvial river channel on the middle Yangtze River in China. A total of 16 size groups and a loose layer method of three sublayers were considered for the transport of the nonuniform bed materials in a long-term simulation. Predictions are compared with preliminary results of field observations and factors affecting the reliability of the simulated results are discussed. The results may be helpful to the development of more accurate simulation models in the future.