【作者】 李凯；

【导师】 江春波；

【作者基本信息】 清华大学 ， 水利工程， 2005， 硕士

【摘要】 从不可压缩流动的 N-S 方程出发,建立了三维非恒定流的水流水温耦合数学模型,本文模型由连续方程和动量方程导出关于压力的泊桑方程来求解压力分布,根据动量方程求解三个流速分量;取消了静水压力假定,适合于对复杂流态及其有密度分层流动的数值模拟。本文数值离散采用正交网格的有限体积方法,模型具有计算速度快的特点,能够应用于实际工程问题;模型除了在动量方程中考虑浮力项外,还采用大涡模拟紊流模型,使得流动与水温耦合计算;模型考虑了水面散热及其太阳辐射的影响因素。应用美国陆军工程公司于 1980 年在水库试验水槽上进行的温差异重流试验来验证数学模型,计算结果与实验资料以及前人的计算结果符合较好,说明论文所采用的数学模型和数值计算方法能够预测温差异重流的特性。水面热交换是引起水库水温分层的主要原因之一。本文分析了水面热交换的几种方式,在计算水面热交换时考虑了太阳辐射、湿度、气温、云量、风速等气象条件。并采用了一个直观的矩形试验水池,分别计算了两种不同气象条件的工况。结果表明水体中热传递符合客观规律,验证了在气象条件的影响下温度场计算的正确性。应用所建立的数学模型对三峡近坝区从庙河至坝前约 18km 水域的三维流场及温度场进行了数值模拟。采用入口断面的流量水温等实测资料作为入流边界条件,大坝孔口为出流边界条件,计算了从 2003 年 6 月至 2004 年 6 月的实际工况。计算所得的流场与河道地形相比可以看出,水面狭窄的江段水流流速较大,江段突扩段附近有明显回水区,流速的横向分布受河道弯曲及水下地形和河道主槽影响。计算出的水温分布与坝前观测的水温分布符合良好,而且同一层水体温度相差不大,表层受气象条件影响较小,垂向没有温度分层现象的出现。由于在蓄水初期,最高水位为 139m,水深相对较浅,而且在汛期虽然气温较高,但流量很大,难以形成水温分层,这与计算的结果相符。更多还原

【Abstract】 A three-dimension model coupled with flow and temperature is developed basedon Navier-Stokes equations for incompressible flows. The continuum-derivedPoisson equations are used to solve the pressure distribution and the momentumequations are used to solve the velocity components. Because the assumption of staticpressure of water is canceled, the model is appropriate for complex flows and densitylayered flows. The Finite Volume Method is adopted as the numerical discretizationmethod, the model has a fast computing velocity and it is applicable to engineering.Besides the buoyancy components considered in the momentum equations,anisotropic turbulent model is adopted in the model, such as Smagorinsky-DeardorffLarge Eddy Simulation, which enables the coupled flow and temperature can becomputed. The influence of the weather conditions is also considered in the model.The channel experiment which was made in 1980 by U.S Army EngineeringCorporation is adopted to investigate the validity and the reliability of the model. Theresults show that the computational results agree well with the results of theexperiments. It illustrates that the numerical model and the numerical methods cancorrectly predict the characteristics of thermal temperature flows.Some modes of heat exchange at the surface are considered. The radiant heat,humidity, air temperature, cloudage and wind speed are considered when computingthe heat exchange at the surface. Two conditions with different weather workingconditions are computed in a rectangle pool. The results show that the transfer of heatin the water agrees well with rules.The numerical model is applied to simulate the 3D-flow and temperature fieldsnear the Dam Area of Three Gorges Reservoir. The measured data is used as theboundary conditions in the entrance. Many different working conditions aresimulated from June 2003 to June 2004. The results show that the velocity of the flowbecomes larger at the narrow areas, the breadthwise distribution of the velocity isinfluenced by the underwater landform and the riverway. The computational watertemperature near the dam agrees well with the measured data. The temperature of thesame layer has little difference and the weather conditions have little influence on thetop layer. The layered temperature of the vertical did not occured. During thereservoir impoundment period with a 139m water level, although the air temperatureis high, it is difficult to form the layered temperature. It agrees well with thecomputational results.更多还原