Research On Clean Water Diversion Numeric Simulation And Water Diversion Scheme In Urban Lake

In hydraulic engineering, clean water diversion is an important method to improve aquatic quality of urban lakes, the basic principle for this method is: inducting relatively clean water to the contaminated water and making use of the function of dilution and replacement.The aquatic qualities of Nanjing XuanWu Lake were chosen for this studying. In view of the impacts of substrate sludge and the wind, a 2D mathematical model for current flow coupled with water quality and substrate sludge pollution was established. Under the framework of Finite Volume Method, Osher scheme was adopted for approximation of Riemann problem. Using this method, the water volume and momentum along with the flux of pollutant transportation were predicted. The main work for this research is summarized as:For better adaptation to the complex characteristic of bridge and culvert existed in XuanWu Lake, a special method is used to treat the internal boundary, to this end, the process of clean water diversion was simulated based on the flux scale of current water diversion. And then, Gorge and disgorge flow under present primer scale, wind-drift current under different wind direction and mixed current under the coupled actions of wind field and water diversion were successfully stimulated, Furthermore, the hydrodynamic force characteristics of XuanWu Lake were also analyzed. After considering the impacts of the wind stress and the sediment dispersions, it is shown that wind field is one of important factors to the effect of clean water diversion. The impacts of the sediment dispersion of pollutants considered or not are both compared in the process of clean water diversion.An appraisal indicator system available for water diversion scheme was established based on the consideration of water quality improvement. A much better scheme for water diversion may have the following characteristics: a homogeneous flow field, small static or backwater area and low mean concentration of pollutant. Six different water diversion schemes were designed according to different diversion scales, different allocation models of water volume, different outlet positions and different drain modes, and then a scientific, reasonable, economical, relatively most optimized water volume and water diversion scheme is chosen along with the considerationof appraisal indicator system.