Author(s): Yanjing Yang

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Keywords: Water-temperature structure; Control curtain; Flow pattern;

Abstract: Water temperatures stratification in large deep reservoirs can significantly influence the water-temperature process and environmental system in downstream. Layered intake is an effective measurement to control water temperature in downstream. Temperature control curtain before the intake can block off the unsuitable temperature water and pass through the fit temperature water. In addition, it is a comparatively achievable method for environmental restoration of running projects. Current research on control curtain focuses on the change of water-temperature structure close to intake. However, there is a lack of clear recognition of the relationship between water-temperature structure and hydraulic conditions like pressure and velocity. A large reservoir is taken as an example. Compared with nature temperature before operation, the water temperature discharged from reservoir declined from 18.4°C to 15.1°C from March to June which is spawning period. In order to mitigate the adverse effects of low-temperature water on fish breeding, a control curtain across section before the intake is designed. Basing on the measured data, a 2-D water-temperature model is adopted to analyze the flow field and the temperature field influenced by the control curtain. The result demonstrates that the curtain barrier significantly changed the flow characteristics near the dam area and lead to a considerable alteration in the water-temperature structure in whole reservoir. Under the effect of pumping action by discharging from reservoir, the water passed through the curtain from the surface and the bottom to the intake. At the same time, the vertical mixing with the upper temperature water body and the low temperature water body at the bottom of the reservoir are accelerated to the front of the dam, and the gradual discharge of the low temperature water body also causes the bottom of the reservoir to gradually heat up. The use of the curtain makes the influence of low temperature water during the heating period and the high temperature water during the cooling period weakened, and the improvement effect is obvious. Different drowning depths of curtains have different effects on the water temperature structure and the discharge temperature process in the reservoir area. The submerged depth becomes shallower, the thickness of the high-temperature water body in the surface layer is compressed, and the effect of improving the low-temperature water is more obvious, which will mitigate the effect of low temperature water on spawning of fish at downstream.

DOI: https://doi.org/10.3850/38WC092019-1247

Year: 2019