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Study on the Motion Characteristics of Reverse Density Currents in Xiangxi Bay of the Three-gorge Reservoir

Author: CaoQiaoLi
Tutor: LiuDeFu
School: Three Gorges University
Course: Hydraulic Structure Engineering
Keywords: Xiangxi Bay Temperature difference Intrusion density flow Hydrodynamic characteristics Experimental study
CLC: TV145.2
Type: Master's thesis
Year: 2010
Downloads: 100
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Abstract

Three Gorges Reservoir, the reservoir level rises, slowing water flow, the residence time of the Bay and tributaries pollutants waters environmental conditions change significantly, has aroused extensive concern in the community. More and more scholars began to realize that the water flow slows Tributaries Bay of Three Gorges Reservoir eutrophication incentives. The one hand, the reservoir was filled Tributaries Bay flow rate slows conducive to bloom; the other hand, the water level of the reservoir regulation, and the reservoir Ganzhi water physical and chemical properties different reservoirs dry tributary water bodies in the frequent exchange of state, this exchange in turn further changes to the Bay, physical and chemical characteristics of the water body, which continue to affect the tributaries of the Bay, the occurrence of blooms. Therefore, the study clearly Tributaries Bay hydrodynamic characteristics and their characteristics by the reservoir main stream impact in the Three Gorges Reservoir, the Bay water environmental conditions and to solve the problem of water eutrophication foundation. To Three Gorges Reservoir Xiangxihe, Bay, site monitoring data analysis library Bay hydrodynamic characteristics as the basis for establishing intrusion density current indoor physical model to simulate the typical scheduling operating conditions in the Three Gorges Reservoir Hong River Gallery Bay intrusion gravity flow phenomenon further reveal the gravity flow of water dynamics and provide a theoretical basis for the study of other tributaries of the Bay hydrodynamic characteristics. The main work and understanding as follows: the Xiangxi Bay site monitoring data for 2008, the water flow rate, water temperature, density, water level, temperature, flow, and other factors were analyzed, the results show that the Xiangxi Bay has a long-term depth complex layering of different flow characteristics, the bottom of the Bay, there is always the undercurrent of flow to the estuary, at the mouth of the reservoir dry most of the time the water body the intrusion density flow in the form into the Bay of February and March to the bottom of the density current, 4 - September mainly for the middle density flow, water in Xunhou first stage mainly surface density flow, the second phase of water storage for the middle-density flow, 11 and 12 months, respectively, for the bottom and middle density current. The Xiangxi River intrusion density current formation of the root causes of poor reservoir main stream and tributaries of the Bay, water temperature difference and sediment concentration caused by the density difference, the difference in temperature is the dominant factor. 2, the initial water level, inflow, the temperature difference between the basic variables, a series indoor bottom in Table temperature difference intrusion density current experiment, by analyzing the density current head movement speed, thickness, height of the interface, sneak into the point of change of speed and other factors, to get the recognition that: (1) head movement speed along the density flow decreases linearly; same section at gravity flow head speed with the inflow, the initial water level and temperature difference increases. (2) different the heavy stream running process, at the end, the surface density the stream head the interface and middle density current head under the interface are increased linearly along with the inflow of the same cross-section at the height of the interface initial water level increased; interface height along middle density current head turned over almost unchanged, while at the same section height increases with the initial level. (3) the end of the surface density current head thickness decreases linearly along the way, the head is most sensitive to the thickness of the initial water level changes, with the initial water level rises and increased almost no effect on temperature changes its . (1) the same density current density current stable operation after the striker's interface morphology, density flow at the bottom of the environmental water interface of the bottom of the slope and the sink opposite the tendency of the surface density flow interface consistent with the bottom of the tank, the middle The density flow turned over to the the interface tendency sink at the bottom the opposite the following interface tendency is consistent with the bottom of the tank, and at the same time all the interface than the drop was less than the sink bottom slope. (2) heavy flow of indoor temperature difference compared with centralized sneak into the point Fr0 2 value distribution, with an average of about 0.54; sneak into the thickness is about 0.5 times the water depth, the the stable thickness is about 0.4 times the water depth. (3) within a certain range, gravity flow to sneak into the speed and into traffic, the initial water level and temperature difference were positively correlated; sneak into the the point thickness inflow and initial water level was positively correlated with the temperature difference was negatively correlated; (4) density current head speed and water density difference and the drag coefficient was significantly positively related; thickness of the heads, with the initial water level and inflow showed a significant positive correlation. (5) experimental density flow sneak into the distance characteristics of the site get basically the same, with the water level, the incoming traffic was a significant positive correlation was significantly negatively correlated with the density difference between the invasion of the body of water and environmental water. Indoor wild temperature difference intrusion density current motion characteristics were analyzed to obtain the following law:

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