Double-averaged velocity and stress distributions for hydraulically-smooth and transitionally-rough turbulent flows
Double-averaged velocity and stress distributions for hydraulically-smooth and transitionally-rough turbulent flows
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水力平滑和过渡粗糙湍流的双平均速度和应力分布
DOI：
10.2478/s11600-008-0028-8
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发表时间：
2008
期刊：
影响因子：
2.3
通讯作者：
S. Coleman
中科院分区：
文献类型：
--
作者：
S. Cameron;V. Nikora;S. Coleman
我们分析了水力光滑和过渡粗糙床湍流明渠流的实验测量使用双平均方法。使用粘度为15×10−6 m2/s的油代替水，这样可以用大的（11.1 mm）粗糙度元素获得过渡范围的粗糙度雷诺数，从而更容易测量平均速度场的空间变化。双平均速度，湍流强度，形式诱导强度，粘性，雷诺数，形式诱导和总剪应力的分布进行了研究与水力光滑，过渡粗糙，完全粗糙的边界之间的分布进行比较。当使用对数速度分布的零平面位移d调整高程标度时，所有实验测得的流向湍流强度在距床恒定距离（z++d+ = 15）处达到峰值。这种崩溃表明，湍流强度分布可能是有用的，在评估适当的值d过渡粗糙和完全粗糙的边界。形成诱导的正常和剪切应力以上的粗糙度顶部被发现崩溃对一个共同的曲线独立的粗糙度雷诺数。
We analyse experimental measurements of turbulent open-channel flow over hydraulically-smooth and transitionally-rough beds using the double-averaging methodology. Oil with a viscosity of 15×10−6 m2/s is used instead of water so that transitional-range roughness Reynolds numbers can be achieved with large (11.1 mm) roughness elements, allowing spatial variations in the mean velocity field to more easily be measured. Distributions of double-averaged velocities, turbulence intensities, form-induced intensities, and viscous, Reynolds, form-induced and total shear stresses are studied with comparisons made between distributions for hydraulically-smooth, transitionally-rough, and fully-rough boundaries. Measured streamwise turbulence intensities for all experiments peaked at a constant distance from the bed (z++d+ = 15) when elevation scale is adjusted using the zero-plane displacement d for the logarithmic velocity distribution. This collapse suggests that turbulence intensity distributions may be useful in assessing appropriate values of d for transitionally-rough and fully-rough boundaries. Form-induced normal and shear stresses above the roughness tops were found to collapse towards a common curve independent of roughness Reynolds number.