Research On Water-sediment Transportaion And Its Controlling Mathematical Model Of Middle And Lower Reaches Of Yangtse River

Based on the features of middle and lower reaches of Yangtse River system, such as: river system is complex, basin area is large, regional difference is distinct, spatial scale varies greatly, regional composition is complex, coupling effect, interrelationship and interaction are strong, and so on, a water-sediment transportation mathematical model is built in the dissertation, which explores laws of water-sediment transportation in reach and lake of middle and lower reaches of Yangtse River system. This model is constructed derived on deep research on one dimensional unsteady flow , nonuniform river network water-sediment transportation model and bed development model; two dimensional lake water-sediment transportation model adopting finite volume method; numerical calculation modes of hydraulic units, which include water-sediment calculation mode specialized on distributary point and confluence point, calculation mode of varied river network boundary, calculation mode of sediment discharge rate in lake, calculation mode of river bed resistance, calculation mode of channel cross section distortion. The results meet the actual measurements well, which is generated by long durative simulations on water-sediment transportation and river bed distortion in middle and lower reaches of Yangtse River. Based upon above researches, argumentation and calculation of several flood control plans of middle and lower reaches of Yangtse River are carried out, and the results are applied in the flood control plan of middle and lower reaches of Yangtse River. In addition, the mathematical model built in the dissertation extends to the real time flood forecast and simulation of regulation, which is the inner core in real time flood forecast and regulation system of middle and lower reaches of Yangtse River. The system has been tested in the flood prevention of middle and lower reaches of Yangtse River, which obtains good effect.There are six chapters in the dissertation. The first chapter is preface, which addresses the background, scientific significance and present situation of subject. The second chapter discusses the features of water-sediment of middle and lower reaches of Yangtse River, which focuses the complexity of water-sediment features and the difficulty of model construction. The third chapter shows the core algorithm of numerical simulation on one dimensional river network water-sediment transportation, in which water-sediment transportation calculation mode of complex river system is constructed and scientific processing of key points is discussed aiming at problems of simulation on water-sediment transportation in complex river system. The fourth chapter covers the core algorithm of numerical simulation on horizontal two dimensional water-sediment transportation, in which finite volume mehod of simulation on two dimensional water-sediment transportation is built by utilizing the present high-powered flow calculation approach; furthermore, calculation mode of sediment accumulation in lake is introduced according to the laws and features of two dimensional sediment accumulation in lake. The fifth chapter is the calibration and verification of model, which are implemented by using actual measurements of water-sediment in middle and lower reaches of Yangtse River. The sixth chapter considers the model application, which highlights actual application of research results.