Pressure and spanwise velocity fluctuations in turbulent channel flows: Logarithmic behavior of moments and coherent structures
Pressure and spanwise velocity fluctuations in turbulent channel flows: Logarithmic behavior of moments and coherent structures
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DOI：
10.1103/physrevfluids.4.044601
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发表时间：
2019-04
影响因子：
2.7
通讯作者：
A. Mehrez;J. Philip;Yoshinobu Yamamoto;Y. Tsuji
中科院分区：
文献类型：
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作者：
A. Mehrez;J. Philip;Yoshinobu Yamamoto;Y. Tsuji
我们根据摩擦雷诺数 Reτ 高达 4000 的湍流通道流直接数值模拟获得的数据集，研究了压力方差 (p+2) 的对数行为。发现 p 的高阶矩在距壁相同距离处遵循对数行为，其中 (p+2) 显示其对数剖面。对于相同雷诺数下的展向速度波动 w 也得到了相同的结果，其中 p 和 w 都遵循超高斯行为。 (p+2) 和 (w+2) 测井剖面出现的最小雷诺数为 Reτ≈500，其中发现流动结构 O(h) 或更少对这些剖面有显着贡献。从不同壁法线位置的条件采样获得的发夹涡流结构的配置显示了 p 和 w 波动之间的紧密联系。正压波动位于发夹涡的腿部之间，而负压波动则与发夹涡的头部一致。正向和负向展向速度波动强烈地定位于发夹涡腿，与涡腿产生的反向旋转运动一致。还发现这些结构在几何上是自相似的，其长度和宽度随着距墙壁的距离线性增加。
We study the logarithmic behavior of the pressure variance (p+2) from the datasets obtained from direct numerical simulations of turbulent channel flow for friction Reynolds number Reτ up to 4000. The higher-order moments of p were found to follow logarithmic behaviors at the same distances from the wall where (p+2) shows its log profile. The same results have been confirmed for the spanwise velocity fluctuations w at the same Reynolds numbers, with both p and w following a super-Gaussian behavior. The minimum Reynolds number for (p+2) and (w+2) log profiles to appear is Reτ≈500, where flow structures O(h) or less were found to significantly contribute to these profiles. The configuration of the hairpin eddy structures obtained from the conditional sampling at different wall-normal locations showed a strong link between p and w fluctuations. Positive pressure fluctuations are located between the legs of the hairpin eddy, while the negative pressure fluctuations are consistent with the head part of the hairpin eddy. Positive and negative spanwise velocity fluctuations are strongly positioned with the legs of the hairpin eddy, consistent with the counter-rotating motion resulting from the eddy legs. The structures were also found to be geometrically self-similar such that their length and their width increase linearly with the distance from the wall.