Research Of The Human Activity Impact On Hydrodynamic Environment In Pearl River Delta

The variation of river situation in Pearl River Delta, ascribe to the high frequent human activity in short-term mainly, the extensive and large range intervention changed the natural development characteristic of the river strongly, which cause the situation and hydrodynamic environment of river take place violent variety. And domestic scholars have reached common understanding basically to this. The form that the river network demonstrates in delta is that various and complicated human activities are intervened and acted on the synthesis under together, but not the independent influence result of a certain activity (or project). This paper separates the pestering various kinds of complicated factors together out that hide behind river surface characteristic, carrying on independent research respectively, which make the problem clear and understanding. The achievement of the paper has the signification for guiding the river management and scheme of plan in the future.This paper generally according to three "clue" and three "direction" go on, namely from microcosmic to the macroscopic, from simple project to the group of projects, from single river to the river network or the basin; Different effects influenced to river refers to: On the "abscissa" contract the width of river (or dwindle the crossing area), on the "ordinate" extend the length of river, on the "vertical" cut river deeply, etc. Embody the effect of superposing of the human activity (the group of projects) and the process of the effect accumulates from "quantitative change" to "qualitative change". And the paper shows that mankind's activity contribution to the impact on hydrodynamic environment of river in different "direction ".This dissertation includes 7 chapters: one Introduction and six formal chapters. In Introduction, summarizes the hydrodynamics study status in Pearl River delta river-netdistrict, explains the significance and necessary to study the selected topic. Briefly introduce the research approach and existing problem at present, expound the research contents, method and characteristic of this paper.In chapter 1, simulate the interference to the fluid from the project, set up the high-resolution finite element model, combine with subgrid model (large eddy simulation) and unstructured grid successfully simulate the horseshoe vortex and Karmen eddy street around of square pier, study the mechanism that the simplest project influences to the flow structure.In Chapter 2: On the basis of that deal with approximately to natural riverway, using 1-d flow model research the superposing impact of water level lifting on single river from project and project colony, simulate the course that the effect superposed accumulates from "quantitative change" to "qualitative change", or the process of making the situation or question "upgrade". Establish conversion relation of roughness"n" and local loss coefficient "ζ", lay the foundation for choosing suitable value ofroughness "n" in model.Chapter 3: Fully investigate and analyze that the degree of human activity on "abscissa" contracting the river narrowly in Pearl River Delta. According to the quantity, distribution of the project colony and situation of blocking flow obtained from the field investigation, deal with approximately to river network (riverway) in delta. Set up the one-dimensional river network mathematics model based on three-step-solving technique, simulate the trend of impact that the different distributed density of project colony and differently blocked section area on hydrodynamic environment in delta. Point out the Proportion of blocked section area and distribution density of project colonies are two decisive factors of influencing hydrodynamic environment (consider "abscissa" influence only) in delta, whichever increase too much can transform the influence of the projects from "qualitative change" into "quantitative change".Chapter 4: Analyzing the degree of riverbed descending on "vertical" caused by quarrying riversand on a large scale in Pearl River Delta. Analyze its impact on riverbed development, using mathematic model simulate the variation tendency of hydrodynamicenvironment (consider "vertical" influence only) in delta 5 years later.In Chapter 5, analyse the speed and extent of natural extension (include innings) in Pearl River Delta estuary on the "ordinate" or "longitudinal" direction. Set up two-dimensional mathematics model of river estuary under orthogonal curvilinear coordinates system. Using finite volume method disperses unified form of every equation. Utilize "half coupling" ways link one-dimensional model of the upper river network and two-dimensional model of the river estuary, make it become a systematic model include the river network and the river estuary of the whole delta. On the basis of verifying the model fully, simulate the influence of hydrodynamic-environment in delta after river mouth extends 5 years and 10 years in dry season and flood period.Chapter 6 is the conclusion and prospect. In this chapter, it sum up the whole paper, explain the reason of the water level variation last few years in Pearl River delta, and prospects further study in future.