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弯管内三维流场水力特性数值模拟

Numerical Simulation of Hydraulic Characteristics of Three Dimensional Flow Field in Elbow

  • 摘要: 为研究弯管三维流场的流态、压强分布及局部水流空化等水力特性,采用Realizable k–ε紊流模型对弯管流场进行三维数值模拟,研究分析雷诺数、渐变段形状、曲率半径比及转角对弯管流场的影响。结果表明:随着雷诺数增大,弯管内侧压强逐渐减小,甚至出现负压,此时水流易产生空化现象;在雷诺数相同的情况下,弯管入口上游设置渐变段更易使水流脱离弯管内侧,从而造成弯管内侧出现负压,渐变段到弯管入口的距离对弯管流场影响不大;弯管曲率半径比越小,弯管内侧压强越小;减小转弯角度能使水流在弯管分布更均匀,从而显著减小弯管负压区的分布范围,甚至能避免空化现象的产生。

     

    Abstract: To study the hydraulic characteristics such as flow pattern,pressure distribution and local flow cavitation in the elbow,the Realizable k-ε turbulence model is used to simulate three dimensional flow field characteristics. The influence of Reynolds number,shape of transition section,curvature radius ratio and turning angle on the flow field in elbow are studied and analyzed. The results show that with the increase in the Reynolds number,the pressure on the inner side of the elbow decreases gradually and even negative pressure appears,which is prone to cavitation. In the case of the same Reynolds number,it is easier to separate the water flow from the inner side of the elbow by setting a transition section upstream of the elbow inlet,which results in negative pressure on the inner side of the elbow. And the distance from the transition section to the elbow inlet has little effect on the flow field in the elbow. With the decrease in curvature radius ratio,the pressure on the inner side of the elbow decreases. Reducing the turning angle can make the water distribution more uniform in the elbow,which can significantly reduce the negative pressure area in the elbow,and even avoid cavitation phenomenon.

     

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