Study On Selective Withdrawal With Temperature Control Curtain

The construction of the reservoir has great economic and social benefits,but after the completion of the reservoir dams to store water bodies,the flow of water in the reservoir area slow or even tend to static,coupled with the influence of solar radiation and many other reasons,the water in the reservoir perpendicularly presents the phenomenon of seasonal temperature stratification.Water temperature stratification can directly lead to water quality and ecological stratification within the reservoir,which in turn affects the quality of the water discharged,leading to a range of ecological degradation and social problems.For the water temperature stratification problem,the use of stratified water intake measures,there are stratified water intake measures such as stacked beam door,pipe type intake,multi-layer intake and so on need to be considered in the reservoir design.(1)The observations of the upstream and downstream flow patterns of the curtain were carried out under different influencing factors,mainly analyzing the hot water flow(distribution of different water temperatures),the control screen height H,the influence of the control screen form on the morphology of the cold and hot water interface and its inclination,and the distribution of the mainstream area.The study shows that the hot water flow Q and the control screen height H will affect the size of the angle between the cold and hot water interface and the horizontal surface upstream of the control screen,the larger the Q,the larger the H,the larger the angle.Downstream of the control curtain near the curtain area there is a mixing zone,in the mixing zone of cold and hot water interface fluctuation is obvious,and with the larger Q value,the more severe the interface fluctuation,and at the same time there is vortex mixing zone.When using the bottom form of control screen mainstream area is located in the hot water layer,a small amount of cold water leakage;when using the top form of control screen mainstream area is located in the cold water layer,a small amount of hot water leakage;when using the central form of control screen cold water layer is divided into two parts,respectively,from the control screen through the upper and lower,the upstream cold and hot water interface was concave.(2)The observations of the temperature and velocity distribution of water in a typical cross-section were carried out,and the temperature and velocity distribution of water in a typical cross-section were measured simultaneously to analyze the velocity distribution law and the change law of the thermocline.The test conditions were set up for different hot water flow(different water temperature distribution),control screen height,control screen form and the distance between the control screen and the water intake.The results show that the control curtain has the effect of inhibiting the mixing of water upstream of the curtain and promoting the mixing of water downstream of the curtain.The flow rate increases along the water depth from the bottom of the sink to the surface,and is logarithmically distributed in the hysteresis layer,gradually increases to a maximum value in the thermocline layer,then gradually decreases,and again conforms to the logarithmic distribution in the surface thermosphere.As the Q value increases the thickness of the thermocline layer increases,the depth of the thermocline layer appears,as the curtain height H increases and rise.(3)A three-dimensional model of water temperature was established,and numerical simulations were performed by the VOF model,and the reliability of the model was verified by comparing the simulated water temperature distribution with the actual reservoir water temperature distribution.Based on the calculations,the factors influencing the temperature of the downspout and the changes in the distribution of the temperature field of the flow velocity field in the reservoir were analyzed.Calculation results show that the arrangement of the bottom form of control curtain,hot water leakage gradually replace the downstream water body,so that the downstream water stratification phenomenon is reduced or even disappeared,the higher the curtain the more obvious the effect.Reservoir drainage water temperature and control curtain height,control curtain form and the water body itself,water temperature structure.The higher the height of the control curtain,the higher the temperature of the drainage water.When the stratification of the reservoir is more pronounced,i.e.,the temperature gradient of the thermojump layer is greater,the lower the temperature of the downspout is.The bottom form of the control curtain has the most obvious effect on raising the temperature of the downpour.Central and top forms of the control curtain,can play a role in reducing the temperature of the drainage water.Temperature control curtain in the improvement of reservoir drainage water temperature has a broad application prospects.