Study On The Permeable Factors And Mechanical Characteristics Of Temperature Control Curtain For Selective Withdrawal In Hydropower Stations

Since water temperature stratification is easy to form in deep water reservoir,the deeper layer is kept in a lower temperature state all year round.The temperature of the deeper layer discharged through outlets is low,resulting the production reduction of downstream farmers and fisheries and the reduction of regional biodiversity.As a selective withdrawal facility,the temperature-control curtain can effectively alleviate the influence of low-temperature water drainage.In the early stage,the main factors such as the submerged depth of the curtain and the location of the layout were studied on the effect of water temperature improvement.At present,there are few studies on the influence of water permeability factors on the discharge water temperature Therefore,in this paper,a three-dimensional hydrodynamic water temperature numerical model was established by means of numerical simulation method for stratified deep water reservoir,and the influence of water permeability factors on the improvement of the water temperature of drainage water curtain was studied.At the same time,the fluid-structure interaction three-dimensional numerical model of flexible temperature-control curtain structure is established to study the mechanical characteristics of the curtain.The main research contents and results are as follows:(1)A three-dimensional hydrodynamic water temperature numerical simulation model was established for the water area in front of the dam of a large reservoir,and the influence of different water permeability,single side and both sides water passing forms of temperature-control curtain was analyzed.The simulation results show that the permeability of temperature-control curtain has an obvious effect on the improvement of water temperature,and the improvement of water temperature decreases with the increase of the permeability.In the distribution of water temperature in May,2% material permeable rate conditions make the drainage of water temperature increased by 0.89 ℃.For curtain edge over water condition,The smaller the surface area,the higher the discharge temperature.Under the condition of unilateral edge water passage,The water temperature can be increased by 2.28 ℃ at most.In all the working conditions of edge water passage,the working conditions in which both sides of the edge water passage simultaneously and the water passage area is the largest do not meet the downstream demand,and the remaining working conditions can meet the demand.It can be seen that the effect of water passing through the edge of the curtain is more obvious than that of the permeable factor.(2)Three kinds of ropes layout schemes were proposed for the water-proof temperature-control curtain.Shape finding analysis was carried out by establishing a numerical model of the water-proof curtain membrane structure.Results show that the various forms of temperature-control curtain both the maximum displacement in the top of the screen near the midpoint of the curtain shows that the maximum stress produced in the curtain side,rope on both sides of maximum stress produced in angular point,considering the rope dosage and the arrangement of the difficulty,the maximum displacement of the curtain,structural stability and engineering economy factors,such as selecting the cords a better form of vertical arrangement structure,provide support for the fluid-structure interaction model.(3)A generalized three-dimensional fluid-solid coupling numerical model of the watertight curtain was established,and the influence of different constraints,different flow rates and different structural material parameters on the structure of the curtain was compared and analyzed.The results show that: with the increase of the flow rate,the deformation and stress of the curtain and the rope increase.The total simulated reaction force under the check condition is 4728.62 k N,the maximum stress of the curtain is 136 k Pa,and the maximum stress of the rope is 289 k N.The maximum deformation of the curtain is located in the middle of the top of the curtain and is offset to the left bank.The rope is the main stress component.The research results of this paper provide technical support for the popularization of temperature-control curtain structure and have guiding significance for the engineering application of temperaturecontrol curtain.