Numerical Simulation On River Sand Extraction Effect

As the economic construction is developing rapidly in the Yangtze River Basin in recent years, architectural demands of sands and stones increase greatly with the sand price going up. Driven by the considerable economic interest, miscellaneous sand dredgers poured in across the middle and lower reach of the Yangtze River, and an over-exploitation situation came into being. To exploit such resources as sand material in the Yangtze River etc. in a scientific and reasonable way, the research of the impact of sand excavation is in urgent need. What's dealt with in the article is as follows:(1)Substantive relevant literature at home and abroad in recent years are summarized on rivers and the impact of sea sand excavation. The impact research of sand excavation is suggested to extend from traditional river dynamics to more aspects, for instance, its impact on ecological environment, water quality and diffusion pollution of heavy metal etc. The shortcomings of domestic research of sand excavation in river channels at present are analyzed.(2)By the finite volume method, a plane two-dimensional numerical model of flow and sediment is developed and applied to the simulation of a typical channel. Calculation shows that the numerical model is reliable. Considering complexity of sand excavation and high requirements of experiment conditions by the physical model, to conduct simulation research by applying numerical model is also feasible.(3)Preliminary analyses of the impacts and consequences of sand excavation in river courses are given. The application of foreign research achievements of sand excavation to river sand excavation featuring suspended load proves inapplicable and shows some guidance for future research.(4)Calculation for natural river channels and sandpit-channels with different conditions of incoming water and sediment and geometrical boundary is carried out. The interference effect of sandpit on channel local flow field, riverbed topographical evolution and sediment concentration distribution of suspended load in surrounding water flow under various conditions are contrasted and analyzed. With many factors playing a decisive role in the impact of sand excavation, a quantitative index for reasonable control of sand excavation is called for.(5)Preliminary analyses of the feasibility of applying FLUENT CFD software to river dynamics for calculation are done. By using FLUENT, numerical simulation of Vertical Two-dimensional water and sediment in partial sandpit is carried out. It shows that sandpit changes flow field and sediment distribution structure in vertical directions, too.In the respects of terms that calculation of sand extraction effect under different flow-sand conditions and sand-pit's forms and the sand extraction research fruits abroad applied to the river circumstances at home, there are some creative conclusions.