【作者】 王钊宁；

【导师】 罗兴锜； 郭鹏程；

【作者基本信息】 西安理工大学 ， 水利水电工程， 2006， 硕士

【摘要】 本文采用CFX5.5商用软件,基于雷诺时均N-S方程与标准κ?ε湍流模型,以某水电站混流式水轮机机组模型尾水管为算例,进行了定常和非定常三维湍流数值计算,获得了尾水管内部流场结构特征、涡带的空间状态、压力脉动的频率和幅值等。主要研究成果有:通过分析尾水管进口的流动状态,提出了尾水管进口边界条件的给定方法,建立了尾水管进口周期性旋进非定常速度模型,并采用User Fortran实现之。计算结果后处理清晰再现了小流量工况尾水管涡带的运动形式和三种工况下尾水管内部的流场和压力分布,情况和实际符合较好,验证了所建立的进口速度模型的逼近真实性。对无支墩尾水管和单支墩尾水管计算结果比较认为,小流量工况下支墩对改善流道流态环境,抑制涡的发生发展没有显著作用,但能有效降低压力脉动幅值;最优工况下,从流线的顺畅程度来看,支墩的作用还是显著的。同时,数值计算过程中在尾水管出口加尾水箱对计算的收敛作用较大。再者,将支墩尾部矩形断面改为圆柱形,能够改善尾水管出口边界条件,有助于加速收敛。小流量工况下尾水管内三维非定常计算结果表明,此工况下尾水管涡带压力脉动最大发生在直锥段下面靠近弯肘段,并且脉动频率符合实际的倍频规律。更多还原

【Abstract】 Commercial softerware-CFX5.5 was used in this paper. Based on Reynolds equations closed by k-εturbulence model,the numerical simulation of three-dimensional unsteady and steady turbulent flow was conducted under different operating conditions,achieving flow filed in the draft,vortex rope and frequency with fluctuation range,which was carried out in the model draft of a power station. The main research findings were as follows.The flow state at the draft tube inlet was specially discussed,suggesting the method of giving inlet boundary of draft, and then periodicity circumvolve inlet was modeled,achieved by User Fortran. The result clearly reappearances vortex movement at the part load condition and flow field and pressure distribution in the draft tube under different conditions,which were much more rational and similar to practical experiment results,and which assure that the inlet velocity model is very close to the authenticity.By comparing two simulation results with pier and without pier,it was assured that pier have no obvious effect to improve flow state and restrain vortex rope under condition of part load,but which can sharply decrease pressure value of fluctuation.It is obvious for the pier action from the extent to smooth flow line as sets runs optimum working condition.Also, outlet tank have a good effect to convergence in the process of calculation. And also, the rectangle at the tail of pier was remodeled to cylinder face before CFX-solver working, which can obviously improve the boundary conditions at the draft tube outlet and contribute to increase convergence.By simulation of three-dimensional unsteady turbulent flow at part load condition,the results show that the max compressive stress occur at the underside of cone part closed by bend.At the same time,the fluctuation frequency accorded with times frequency rule very well.更多还原