Study On Temperature Of Water Released By Selective Withdrawal From Thermal Stratified Reservoirs

Most reservoirs are typically temperature stratified as a result of the radiation ofthe sunlight and some other physical and chemical effect. Low-temperature waterwithdrawn in a traditional manner from deep reservoir is unsuitable for irrigation andmay easily cause a hazard to aquatic organisms living downstream. Thus, watershould be released from different depths, which is the core concept of selectivewithdrawal. Selective withdrawal was a valid method to reduce the negative effect oflow temperature water, and the selective withdrawal facilities were widely used insome high dam projects.This paper mainly contained three parts. In the first part, we went through theexisting similarity theory of withdrawn water temperature and made some extensionto it; we also proposed a primary theory of temperature distribution conversion. Thesecond part focused on the experiment study of the withdrawn water temperatureusing side type orifice intake and floating point intake. In the third part, the PIVsystem was brought into the research, we conducted some experiments to study theflow filed nearby the intake. The contents and conclusions were as followed:(1) A brief introduction was made on the thermal stratified formation mechanism;the effects of low temperature water and the selective withdrawal facilities. Someconclusions of the temperature distribution defining, predicting and simulating wereconducted. The summary of research output both with the model test and numericalsimulation was also presented.(2) Based on the previous similarity theory of withdrawn water temperature, weextended the similar condition. To solve the problem accounted in the model test, weproposed the theory of temperature distribution conversion, and the new conversionrelation between the withdrawn water temperature of model and prototype was alsopresented.(3) A model was built according to the similarity theory of withdrawn watertemperature, some experiments were conducted around the withdrawn watertemperature using side type orifice intake and floating point intake. We selected threetypical kinds of temperature distribution, four different submersing depth intakes andthree kinds of flow rates. With the analysis of the experiment results, we studied theinfluence of temperature distribution, intake submersing depth and flow rates. And acomparison of withdrawal characteristics between the side type orifice intake and floating point intake was conducted. Meanwhile we proposed a predication equationof withdrawn water temperature using side type orifice intake.(4) For the side type orifice intake, we used the PIV system to study the flowfield near the intake, results shows that temperature distribution in the reservoir surlylead to the change of velocity field, and the range of withdrawal measured in the testconfirms the pervious conclusion of flow characteristics of side type orifice intake.