Inner and outer scalings in rough surface zero pressure gradient turbulent boundary layers
Inner and outer scalings in rough surface zero pressure gradient turbulent boundary layers
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DOI：
10.1063/1.2732439
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发表时间：
2007-06-01
影响因子：
4.6
通讯作者：
Castillo, Luciano
中科院分区：
文献类型：
--
作者：
Brzek, Brian;Cal, Raul Bayoan;Castillo, Luciano
为了研究表面粗糙度和雷诺数对零压力梯度湍流边界层的影响，进行了一系列新的实验。为了正确地捕捉单点统计的x依赖关系，进行了11个流向位置的连续测量，这使得能够使用完整的边界层方程来计算表面摩擦。对于光滑和粗糙的表面，这个量的精度分别在3%和5%以内。对于所使用的沙粒型粗糙度，只有Zagarola和Smitts标度，U-无穷大增量(*)/增量，能够从外部变量的速度分布中消除粗糙度和雷诺数的影响。然而，对于固定的实验条件，每一次用于速度亏缺分布的标度都会导致自相似解。当考察内部区域的雷诺应力时，0分量对粗糙度的影响最大，对于完全粗糙的区域轮廓，壁面附近的高峰值减小，并且变得接近平坦。此外，在固定的实验条件下，外部变量的雷诺应力具有自相似性。然而，随着粗糙度参数k(+)的增加，所有雷诺应力分布在形状上变得相似，表明壁面附近的各向同性增加。此外，由于粗糙度的影响，边界层参数也有较大幅度的增加。(C)2007年美国物理研究所。
A new set of experiments have been performed in order to study the effects of surface roughness and Reynolds number on a zero pressure gradient turbulent boundary layer. In order to properly capture the x dependence of the single point statistics, consecutive measurements of 11 streamwise locations were performed which enabled the use of the full boundary layer equations to calculate the skin friction. This quantity was obtained within 3% and 5% accuracy for smooth and rough surfaces, respectively. For the sand grain type roughnesses used, only the Zagarola and Smits scaling, U-infinity delta(*)/delta, was able to remove the effects of roughness and Reynolds number from the velocity profiles in outer variables. However, each scaling used for the velocity deficit profiles resulted in self-similar solutions for fixed experimental conditions. When examining the Reynolds stresses in the inner region [i.e., 0 component showed the largest influence of roughness, where the high peak near the wall was decreased and became nearly flat for the fully rough regime profiles. In addition, the Reynolds stresses in outer variables showed self-similarity for fixed experimental conditions. However, as the roughness parameter, k(+) increases, all Reynolds stress profiles became similar in shape indicating increased isotropy near the wall. Furthermore, the boundary layer parameters also showed a considerable increase due to roughness. (c) 2007 American Institute of Physics.