The flow field produced by a pitched blade turbine : characterization of the turbulence and estimation of the dissipation rate
The flow field produced by a pitched blade turbine : characterization of the turbulence and estimation of the dissipation rate
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DOI：
10.1016/0009-2509(93)80346-r
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发表时间：
1993
影响因子：
4.7
通讯作者：
S. Kresta;P. Wood
中科院分区：
文献类型：
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作者：
S. Kresta;P. Wood
本文比较了用于估计搅拌槽内湍流长度尺度和/或湍流动能耗散率（ε）的各种方法。测试的系统是一个四叶片45°倾斜叶片涡轮，在圆柱形全挡板水箱中旋转，用激光多普勒风速仪测量速度。选择四种方法进行实验应用。所采用的方法及其原理可概括为：梯度假设法采用ek-ε模型的本构方程；将时间导数转换为空间导数的泰勒假设；维度上的争论导致ε的估计使用定长尺度；最后，利用自相关系数函数计算欧拉积分时间尺度，再结合k函数估计ε。对每一种方法都提出了各种修正建议，其中许多方法在本工作中进行了测试和比较。虽然所有这些方法以前都应用于搅拌槽，但潜在的假设和近似往往是隐含的。这些假设对最终结果的影响，特别是尾涡的重要性，在本文中已经在定量意义上进行了评估。
This paper compares various methods which have been used for the estimation of turbulent length scales, and/or the rate of dissipation of turbulence kinetic energy (ε) in stirred tanks. The system examined was a four-blade, 45° pitched blade turbine rotating in a cylindrical, fully baffled tank with velocity measurement by laser Doppler anemometry. Four methods were chosen for experimental application. The methods used, and the principles upon which they rest, can be summarized as follows: thegradient hypothesismethod uses the constitutive equation from thek-ε model;Taylor's hypothesisis used to convert time derivatives to spatial derivatives;dimensionalarguments lead to the estimation of ε fromkusing a constant length scale; finally, theautocorrelationcoefficient function is used to calculate the Eulerian integral time scale, which is then combined withkto estimate ε. Various corrections have been suggested for each of these methods, many of which were tested and compared in this work. Although all these methods have previously been applied in stirred tanks, the underlying assumptions and approximations have often been implicit. The impact of these assumptions on the final result, in particular, the importance of the trailing vortices, has been evaluated in a quantitative sense in this paper.