Experimental Study Of The Flume System On The Mixing Characteristics Of Salt-fresh Water In The Estuary Area

Because the estuary area is in the joint zone between river and ocean, it has a special function connecting the river and ocean. But the density current of the estuary water area caused by the mixing of salt and fresh water does not only have an influence on characteristics of sediment motion in the estuary and the development of subaqueous delta, but also on the water quality and the optimal scheduling of the joint development of water resources. And then, it can affect the development of estuarine city. So we must grasp the characteristics of flow motion and the mixing characteristics of fresh-salt water in the estuary for achieving the estuarine sustainable development, solving estuarine resources utilization of freshwater and construction of port and waterway and estuary regulation and tideland reclamation, for example:estuarine ecological environment protection the contaminant net,the irrigation,water supplying and so on.The freshwater flows to the open sea via upper layer, and the salt water invades via the bottom layer lower, the freshwater and the saltwater must get mixed because of the action of turbulent motion of flow and molecular diffusion. The mixing process of the fresh and salt is an important part of the process of hydrodynamic action in the estuary.Because of the complex terrain in the estuary, the flow and the mixing of salt in the estuary are influenced by tidal range, geometric shape, upriver flow, the wind and waves. And it has cycle on tide and flood of dry. Normally, upriver flow, water depth and tidal strength have the most important influence. On the basis of a systematic physical model test made, this paper studies the mixing characteristics of fresh and salt waters in the estuary area, and analyzes the influence on the mixing by tidal range, upriver flow, the depth of water and salinity. Main contents and conclusions are:1.By searching large literatures, this paper describes the research methods of water flow motion of tidal waters and the mixing of salt-water and the research status on the characteristics of flowing movement and salt-water mixing home and abroad.2.In these tests, tidal cycle is forty minutes, volume of river runoff are 01/s,11/s,21/s, tide range are 2.7cm,3.6cm,4.5cm, depth of water are 10cm,13cm,16cm. Completing 8 group tests and measuring velocity of measuring point in model.3.According to velocity data of test, drawing the change maps of flow velocity with time of each measuring point in the circumstances of different river runoff,different tide range,different depths of water, and analyzing the influence on the water flow motion by the tidal range,the depths of water and upstream runoff in the estuary area.4.In these tests, tidal cycle is forty minutes, volume of river runoff are 0.51/s,11/s,21/s, tide range are 2.7cm,3.6cm,4.5cm, depth of water are 10cm,13cm,16cm, salinity are 4.5%,8%,12%,19%. Completing 13 group tests and measuring salinity of measuring point in model.5.According to the measured salinity data, this paper gives the salinity process curve of the point during the process of flooding and ebbing tide, the relation curves between average salinity and the upstream runoff,the tidal ranges,the depths of water underwater 1cm,3cm,5.5cm,8cm.6.Analyzing the longitudinal and horizontal distribution characteristics of salinity in the estuary area and the influence on the vertical distribution of salinity by upstream runoff,the tidal range,the depths of water and the salinity of open sea.