渠系分流口区域三维流场特征的研究

发布时间：2018-10-08 15:49

【摘要】：渠系分流口区域作为渠系水道的咽喉要道,对分流分沙具有重要的作用,受边界控制,水流结构复杂。在前人研究的基础上,本文基于南亚某待建泵站取水工程,采用理论分析,模型试验和数值模拟相结合的方法,对不同运行工况时,渠系分流口区域的水流要素及流场特征等相关问题开展了研究,主要成果如下:1.提出研究分流口区域流场特征的意义,指出分汊流运动的复杂性,回顾了分汊流相关研究历史和现状以及分汊河道水流运动的规律,论述了数值模型研究进展及在分汊流计算应用现状。2.结合多组试验工况,对分流口区域上下游干渠段、掺混区和支渠段的三维流场特征进行研究,得出了如下规律:对于上下游干渠段水流,横向自右岸至其与口门近区交界线,流速不断递减,右岸为河道的主流速带,上下游干渠段沿纵向受渠道取水的影响不大;掺混区存在很明显的水流混掺现象,口门交界面处流速梯度较大,流场三维特征明显;水流进入引水支渠后,在支渠左岸形成一定范围的平面回流,支渠内断面收缩,水动力轴线集中在明渠前进方向右岸一侧,形成较为明显的螺旋流。经过引水支渠前端复杂掺混流动区域,水流形态逐步过渡为一维特征较为明显的常规明渠流动。3.根据室内模型试验水流运动现象的观测,利用RNGk-ε紊流模型并借助FLOW-3D软件,建立了分流角为73°时渠系分流口区域的水力特性分析的计算模型。通过数值模拟结果与试验结果的对比分析,验证了该分析计算模型的准确性和可靠性。以所建立的数学模型为分析计算平台,对于渠系分流口近区以及口门断面不同工况多个水力要素进行了分析。重点探究三维流速沿水深的变化规律:在引水明渠前端形成的平面回流随水深加大有减小趋势。口门断面处存在明显的三维特征,流速分布也较常规明渠水流特征有所不同。4.引入单宽流量比的概念,重点介绍了不同单宽流量比的情况下,渠系分流口区域回流区的长度与宽度及引水支渠进水断面收缩系数的变化规律,并推出拟合公式。分析结果表明:随单宽流量比的增大,分流口区域回流区范围增大,支渠渠道进水断面收缩系数减小。
[Abstract]:As the main throat of canal system channel, the diversion area of canal system plays an important role in the separation of sediment and is controlled by the boundary, and the structure of water flow is complex. On the basis of previous studies, this paper, based on the water intake project of a pump station to be built in South Asia, adopts the method of combining theoretical analysis, model test and numerical simulation. The main results are as follows: 1. The significance of the study on the characteristics of the flow field in the diversion channel is presented, and the complexity of the branching flow is pointed out. The history and present situation of the research on the bifurcation flow and the law of the flow movement in the branching channel are reviewed. The research progress of numerical model and its application in bifurcation flow calculation are discussed. Combined with multiple test conditions, the three-dimensional flow field characteristics of upstream and downstream main canal, mixing area and branch channel in the diversion channel region are studied. The following laws are obtained: for the upstream and downstream main canal section, the flow is transversely from the right bank to the junction line between the upper and lower main channel and the adjacent area of the mouth gate. The flow velocity is decreasing, the right bank is the mainstream velocity zone of the river, the upstream and downstream main channel section is not affected by the channel water intake along the longitudinal, the mixing area has obvious mixing phenomenon, the velocity gradient at the interface of the mouth door is larger, and the three-dimensional characteristics of the flow field are obvious. After the flow enters the branch canal, a certain range of plane return is formed on the left bank of the branch canal, the cross section of the branch canal shrinks, and the hydrodynamic axis is concentrated on the right bank of the forward direction of the open channel, forming a more obvious spiral flow. Through the complex mixing flow area at the front end of the diversion branch canal, the flow pattern is gradually transformed into the conventional open channel flow with obvious one-dimensional characteristics. According to the observation of flow motion in indoor model test, using RNGk- 蔚 turbulence model and FLOW-3D software, a calculation model of hydraulic characteristic analysis of diversion outlet region of canal system is established when the diversion angle is 73 掳. The accuracy and reliability of the model are verified by comparing the numerical simulation results with the experimental results. Based on the established mathematical model, several hydraulic factors are analyzed in the near region of the diversion port of canal system and the section of the portal under different working conditions. The change rule of 3D velocity along the water depth: the plane reflux formed in the front end of the diversion channel has a decreasing trend with the increase of the water depth. There are obvious three-dimensional characteristics at the entrance section, and the velocity distribution is different from that of the conventional open channel. In this paper, the concept of single width flow ratio is introduced, and the variation law of the length and width of the reflux region in the diversion channel and the shrinkage coefficient of the inlet section of the diversion branch canal under different single width flow ratio are introduced, and the fitting formula is deduced. The results show that with the increase of the ratio of single width to flow, the range of reflux area increases and the shrinkage coefficient of inlet section decreases.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV133

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