Study On Diversion Aerated Flow And River Reoxygenation

Environmental deterioration and pollution river ecosystems has become one of the world recognized problem,So it made a number of technical methods on river restoration,there are physical, chemical and biological repair processes and so on.Water pollution effective long-term approach is to restore the body’s own water purification capacity,dissolved oxygen(DO) content directly affect the degradation of aquatic plants and animals grow and self-purification capacity of rivers,high DO content, the normal growth of aquatic organisms, active group of aerobic bacteria, like water quality;DO content is low, the water was a serious threat to aquatic organisms or even on the verge of extinction,and rivers of aerobic bacteria species decreased, serious deterioration of water quality.Among them, the water turbulence intensity have a huge impact on the extent of reoxygenation,water point between the layers of turbulent water flow collide with each other and blended to produce the phenomenon,this makes the energy loss of a body of water larger, while allowing momentum between water bodies and water points between the layers, heat and mass transfer exchange increases.Theoretical Study oxygen flux surface reoxygenation indicates that surface water body oxygen complex surface REOXYGENATION transfer speed and turbulence intensity down the rate of diffusion of water was proportional,therefore, the water turbulence intensity, the greater the concentration of dissolved oxygen.In recent years, it has been studied by the construction of hydraulic structures and optimized the shape of the building and other measures of water,making full use of the vibrant flow through hydraulic structures when formed when, tumbling, turbulence and other flow phenomena to increase the concentration of dissolved oxygen in water, which can increase the capacity and self-purification ability reoxygenation river, so as to achieve the purpose of improving water quality.Based on previous studies, through three simple common roughness of the smooth surface of dam body were roughened by model tests of different roughness body of water reoxygenation capacity, the main contents of the following aspects :1. reoxygenation model tests: respectively, dam surface smooth and roughened surface of dam(flat cylinder roughness and roughness) on downstream water DO concentrations were measured simultaneously, and the two were compared.While the smooth surface of the dam, a cylinder and a flat surface roughness dam dam surface roughness DO concentration at different flow rates and different temperatures were measured.2. For each dam surface roughness flow pattern is analyzed.3. For each surface roughness dam downstream DO concentrations were measured analysis results:each Roughness were to some extent on downstream water bodies have increased DO concentration effect, but the effect is different, each dam type reoxygenation capacity decreasing order:large stones close> pebbles close> pebbles dilute> Flat 3> large stones dilute> flat 2.1> 2.1 Cylindrical> Cylindrical 1.5> smooth surface of dam.4. In the winter and summer, respectively, two seasons dam surface smooth, cylindrical 2.1, 2.1, and flat plate 3 roughness dam on three dissolved oxygen test,founding that, while the temperature of the upstream and downstream oxygen deficit recovery rate was less affected in the coming phase flow conditions, indicating that the same type at the dam, the main factors affecting the dam downstream oxygen deficit is the water recovery rate turbulence caused by the dam type, and temperature changes not so much.5. dam surface smooth, cylindrical 2.1, 2.1, and flat plate 3 three roughness dam at three different flow test measurement, analysis results of various roughness dam should exist on a recovery rate of oxygen deficit limit, when it reaches its upper limit, the flow rate increases, the oxygen deficit recovery rate is not changed on this point requires further research to confirm.The above test results show that, by laying the dam surface roughness different body shapes can increase the oxygen content of the water to some extent, different roughness shape and arrangement of each dam REOXYGENATION roughness different abilities.Although the model test scale effect due to the presence reduced, leading to the test results will be slightly different from the actual project, the actual project results are often larger than the model test.At the same time due to the dissolved oxygen content is an ever-changing dynamic process, measuring process will inevitably there are some errors, but the test results by the model is still the ability to qualitatively describe REOXYGENATION differences between dam type for the follow-up research work for reference.