大型水库建成后由于库区水动力学特性、光混特性、热量特性等发生了改变,水库垂向水温将呈现出明显的分层现象,对库区及其下游河道的生态环境造成显著影响,常通过采用分层取水措施加以改善。针对控制幕分层取水方法,通过温分层水槽试验,研究了分层水体中设置水温控制幕后,控制幕前水温、流速分布特征以及下泄水温的变化情况。试验考虑了不同热冷水流量比、控制幕距取水口距离、取水口位置和控制幕遮挡率等因素的影响。试验结果表明:控制幕设置后,控制幕上游近幕布区域温跃层厚度减小,温跃层强度增大,水体掺混受到抑制;控制幕下游温跃层厚度增大明显,控制幕促进了控制幕下游水体的垂向扩散,破坏了原水体分层现象;控制幕上游近幕布区域,热冷水流量比越小取水口位置越低,控制幕遮挡率越小温跃层厚度越厚,温跃层强度越小。热冷水流量比增大,取水口位置提高以及控制幕遮挡率增加均会使下泄水温升高。
Abstract
Selective withdrawal is widely implemented to moderate the effect of thermal stratification in large reservoirs and to solve the problem caused by the changes of hydrodynamic and thermal characteristics after the construction of dam. An experimental study was conducted to investigate the temperature and flow fields in front of the temperature-control curtain (TCC) set in thermal structure for selective withdrawal. Impacts of hot-cold water flow ratio, distance from the curtain to water intake, water intake position and water retaining proportion were systematically investigated in the experiments. Outflow temperature was also measured. The results indicated that thermocline thickness upstream side of TCC decreased while thermocline intensified, thus inhibiting water mixing. The thermocline thickness increased obviously, and the vertical diffusion of water was promoted downstream of TCC. When hot-cold water flow ratio, height of water intake and water retaining proportion reduced, the thickness of thermocline increased while the intensity of thermocline attenuated. In addition, the outflow temperature climbed with the augments of hot-cold water flow ratio, position of water intake and water retaining proportion.
关键词
水温分层 /
水温控制幕 /
分层取水 /
温跃层 /
下泄水温
Key words
water temperature stratification /
temperature control curtain /
selective withdrawal /
thermocline /
outflow temperature
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