The Study Of Estuary Hydrodynamics With OpenFOAM

Estuary, which is a transition zone from land to sea and freshwater to saltwater, is always the communication of the river and the broad sea. Generally speaking, the estuary is formed by the sand and mud brought with river-flows, and it is influenced by natural factors such as tide. Nowadays, estuaries have become one of the most productive natural habitat in the world, as well as the most densely inhabited places for humans. Hence, studies on the hydrodynamic of river estuary have become one of the most attentional researches.Due to the unique environment of estuaries, where river and sea meats together and the silt on seabed will affect wave propagation, it is important to study the shoreline water-silt intersection. Moreover, the free surface hydrodynamic of the estuary is of great importance to ship running and controlling, which is significant in port and waterway engineering. As far as we know, such problems can be solved to a certain extent by numerical simulations of the free surface, which can be helpful for a better understanding in water movements. During the river-flowing, the silt is carried along from upstream to downstream until reaching into the sea, where the water-speed suddenly drops and the silt will be deposited in the vicinity of the estuary delta.OpenFOAM is an open-source computational fluid dynamics (CFD) software package, and like most other commercial soft-wares, it is divided into three modules, which is the pre-processing, the solver and the post-procession. By using the finite volume method in solving partial differential equations and using overloading function of C++operator, it is greatly simplified in description of the calculus equations and the corresponding physical problems. OpenFOAM also supports three-dimensional polyhedron grids, which can be useful in hierarchical description of the simulating objects as well as dealing with the complex geometry. As an open-source software package, OpenFOAM itself has compiled a number of pre-solvers, application tools and models, which greatly improves the efficiency of users and the continuity of programs. Therefor, in this paper, OpenFOAM is used to solve estuary hydrodynamics.The two-phase free-surface flow in a three-dimensional river bed is investigated numerically using interFoam solver of the open-source Computational Fluid Dynamics (CFD) code OpenFoam. The turbulence is modeled by large-eddy simulation (LES) model and the free surface is treated by the volume of fluid (VOF) method. The objective of this paper is to study the flow pattern near the mouth of the river which is important to predict the silt deposition. The effect of flow quantity and slope of river bed are investigated. At the same flow quantity, with increasing the slope, the free surface fluctuates significantly, and rate of aeration increases as well. At the same slope, with increasing flow quantity, the free surface fluctuates greatly and the aeration increases significantly.A multiphase flow model was constructed based on the solver interMixingfoam within OpenFOAM. The water propagation as well as the silt-spreading over the silty seabed were numerically studied and analyzed. The influence of the different silt on the water over shoreline was investigated with different silt parameters such as the silt viscosity, the silt density and the inlet-water velocity. The numerical model built was applicable to the general water-silt interaction problems over seabed, with focuses on the water-silt interaction and the corresponding water-silt interface. The results showed that the attenuation increased first and reduced later with the silt from soft to hard, and a maximum attenuation was got with silt 3 (some-hard). Furthermore, with higher the inlet-water and inlet-silt speed, the water and silt mixed more, and thus leading to the silt being uplifted.