Turbulent fluctuations above the buffer layer of wall-bounded flows
Turbulent fluctuations above the buffer layer of wall-bounded flows
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DOI：
10.1017/s0022112008002747
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发表时间：
2008-09
影响因子：
3.7
通讯作者：
J. Jiménez;S. Hoyas
中科院分区：
文献类型：
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作者：
J. Jiménez;S. Hoyas
本文利用雷诺数τ≤2000时通道模拟的谱信息和概率密度函数，分析了湍流对数层和外层的速度和压力脉动特性。在较高的雷诺数与实验数据进行比较。它被发现，在协议与以前的调查，流向和展向速度分量的强度分布的对数范围内被追踪到扩大的光谱范围的规模接近壁。压力在理论上和观测上都是如此，但法向速度和切向应力共谱却不是这样，尽管这两个量也有长度为壁距几百倍的结构。因为对数范围随着雷诺数的增加而变长，所以在这个意义上“附着”的变量在缓冲层中以混合单位缩放。这些结果有力地支持了汤森（1976）提出的附着涡方案，但它们与任何特定的涡模式无关。外模式的缩放也检查。在固定y/h时，流向速度的强度随雷诺数的增加而增加。这是追溯到大规模的模式，并增加强度的喷射，但不是扫描。不同流动的外部结构之间存在一些差异。边界层中展向和壁面法向速度的外模比内流中的外模强，并且它们的流向速度更靠近壁面穿透。因此，它们的对数层较薄，并且它们的一些对数斜率不同。渠道统计数据可在http://torroja.dmt.upm.es/ftp/channels/上以电子方式查阅。
The behaviour of the velocity and pressure fluctuations in the logarithmic and outer layers of turbulent flows is analysed using spectral information and probability density functions from channel simulations at Reτ≤2000. Comparisons are made with experimental data at higher Reynolds numbers. It is found, in agreement with previous investigations, that the intensity profiles of the streamwise and spanwise velocity components have logarithmic ranges that are traced to the widening spectral range of scales as the wall is approached. The same is true for the pressure, both theoretically and observationally, but not for the normal velocity or for the tangential stress cospectrum, although even those two quantities have structures with lengths of the order of several hundred times the wall distance. Because the logarithmic range grows longer as the Reynolds number increases, variables which are ‘attached’ in this sense scale in the buffer layer in mixed units. These results give strong support to the attached-eddy scenario proposed by Townsend (1976), but they are not linked to any particular eddy model. The scaling of the outer modes is also examined. The intensity of the streamwise velocity at fixed y/h increases with the Reynolds number. This is traced to the large-scale modes, and to an increased intensity of the ejections but not of the sweeps. Several differences are found between the outer structures of different flows. The outer modes of the spanwise and wall-normal velocities in boundary layers are stronger than in internal flows, and their streamwise velocities penetrate closer to the wall. As a consequence, their logarithmic layers are thinner, and some of their logarithmic slopes are different. The channel statistics are available electronically at http://torroja.dmt.upm.es/ftp/channels/.