水温控制幕分层取水湍浮力流运动特性及取水效果研究

Selective withdrawal by water-blocking curtain on reservoir has advantage of taking into account the relationship between the ecological restoration and the power generation compared with the conventional methods of selective withdrawal, so it has great significance on the management of eco-friendly reservoir. But it is necessary to make clear the phenomenon of complicated buoyant turbulence caused by the discharge of water control project and the disturbance of the water-blocking curtain to control the temperature of released water efficiently. However, its mechanism and application are relatively uncommon in domestic. In this study, the data research, experimental research, numerical simulation and mechanism analysis methods are adopted to carry out the work. At first, it is important to develop the quantitative relationships between vertical thermal diffusion coefficient and parameters such as stratified mixing intensity, density and Froude number to illustrate the stratified mixing characteristics with the disturbance of water-blocking curtain. After that, the jet flow pattern on surface of water-blocking curtain, thermal stratified flow partition and law of its interface motion are analyzed to obtain the steady conditions of the jet flow with the influence of water-blocking curtain, and the complicated motion law of buoyant turbulence is revealed. And then, an inner relationship is developed between the released water temperature and the experimental parameters including the water-blocking position, height and so on. The key factors, which can influence the selective withdrawal effect, are identified and their coupled final quantitative relationships are revealed. Finally, the coupled mechanism between the effect of thermal selective withdrawal and the style of water-blocking curtain is clarified. This research would have important theoretical value and broad application prospects.

水温控制幕分层取水可同时兼顾生态恢复与发电量间的关系，较传统分层取水方式优越，对我国生态友好型水工程建设具有重要的借鉴意义。水温控制幕分层取水的关键是要弄清分层水体在孔口泄流、水温控制幕扰动等多重因素叠加作用下的复杂湍浮力流现象，以有效控制下泄水温。但国内外对其机理研究、规律认识还很不足，影响了实际应用。本研究拟采用资料调研、试验研究、数值模拟和机理分析等方法，提出水温控制幕分层取水水体垂向热扩散系数与掺混强度、密度弗劳德数等参数的定量关系，阐明控制幕扰动作用下的分层掺混特性；分析控制幕浮力射流流态、流动分区特征及分层界面运动轨迹，探讨控制幕表层浮力射流稳定性条件，揭示控制幕分层取水湍浮力流复杂运动规律；研究水温控制幕分层取水方式与出流水温的内在关系，识别影响分层取水效果的关键参数，建立耦合定量关系式，探明分层取水效果影响机制。研究成果具有重要的理论价值和广阔的应用前景。

水温控制幕分层取水可同时兼顾生态恢复与发电量间的关系，较传统分层取水方式优越，对我国生态友好型水工程建设具有重要的借鉴意义。水温控制幕分层取水的关键是要弄清分层水体在孔口泄流、水温控制幕扰动等多重因素叠加作用下的复杂湍浮力流现象，以有效控制下泄水温。但国内对其机理研究、规律认识还很不足，国外相关技术应用还存在诸多技术不确定性和风险，这与当前国内巨大的生态工程需求不相适应。本研究采用资料调研、试验研究、数值模拟和机理分析等方法，取得系列重要成果，具有重要的理论价值和广阔的应用前景。主要成果：1）阐明了分层取水效果与分层取水方式内在关系：开展了水温控制幕分层取水试验，结果表明控制幕运行高度越高，下泄水温温度越高；下泄水温随下泄流量的增加而增加；出水孔高度越高下泄水温亦越高；控制幕布置距离对下泄水温影响较小。建立了下泄水温与控制幕运行高度等参数的预测经验公式。2）揭示了控制幕作用下流动分区特性：将控制幕前后流动状态分为渐变区、急变区、回流区，渐变区幕前流速缓慢增加，来流流速越大，增速越快；急变区幕顶流速急剧增大，紊动能较大，最大流速出现在幕后一定距离处；回流区幕后顶部流速仍维持较强的紊动，下游形成回流，有利于能量传递和水气热交换，改善下泄水温。3）明晰了控制幕作用下水温分层运动规律：水幕运行后，幕布上方水体流速增大，紊动能显著增加，水温垂向逐步扩散并向下游发展，重新形成主流带，下泄水温显著提高。随着水幕持续阻水作用，出口水温垂向分布发生变化，表层水域最先升高，随后发展至底层，水库稳定分层被显著削弱直至消失，水温垂向均化。4）构建了水温分层取水数学模型：建立了含浮力效应的雷诺应力代数简化表达式和主动标量通量代数表达式，提出了三维非结构网格下的SIMPLE数值算法。对模型参数进行了敏感性分析，结果表明雷诺应力与温度梯度乘积项、浮力项对热通量有较大程度贡献，其他参数相对敏感度较低。