Spectra of energy transport in turbulent channel flows for moderate Reynolds numbers
Spectra of energy transport in turbulent channel flows for moderate Reynolds numbers
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DOI：
10.1017/jfm.2016.564
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发表时间：
2016-09
影响因子：
3.7
通讯作者：
Y. Mizuno
中科院分区：
文献类型：
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作者：
Y. Mizuno
为了揭示槽道流中湍流动能输运的尺度依赖性，采用直接数值模拟对谱能量收支方程的组成部分进行了评估。在缓冲层和重叠层的每一个高度，向上的湍流输送提供能量的波动在小尺度上，但从那些在大尺度上删除。从重叠层中的大尺度中移除的能量被向上携带到通道的中心，并且还向下携带到壁的附近。大尺度下的向下能量通量导致了近壁湍流强度和收支方程的分量的显著异常。在重叠层中，空间湍流输运的共谱被混合长度很好地标度。结果表明，湍流输运中的涨落结构在这一层是自相似的，支持了经典假设。还评价了压力-应变相关性的共谱。它们不是由近壁的壁单元缩放的，但是在共谱中没有观察到大尺度结构的影响的症状，至少对于目前的雷诺数范围。在缓冲层以上，压力-应变相关的共谱几乎是各向同性的，它们的相关长度尺度由重叠层中的混合长度给出。因此，压力-应变相关性是相当局部的量。
To reveal the scale dependence of the transport of turbulent kinetic energy in a channel flow, the constituents of a spectral energy budget equation are evaluated using direct numerical simulations. At each height in the buffer and overlap layers, the upward turbulent transport provides energy to the fluctuations at small scales, but removes it from those at large scales. Energy removed from the large scales in the overlap layer is carried upward to the centre of the channel and also downward to the vicinity of the wall. The downward energy fluxes at the large scales result in the well-known anomaly of turbulence intensity and the constituents of the budget equation near the wall. In the overlap layer the cospectrum of the spatial turbulent transport is scaled well by the mixing length. It shows that the structure of fluctuations involved in turbulent transport is self-similar in this layer, supporting the classical assumption. The cospectra of pressure–strain correlations are also evaluated. They are not scaled by the wall unit near the wall, but no symptom of the influence of large-scale structures is observed in the cospectra, at least for the present range of Reynolds numbers. Above the buffer layer the cospectra of the pressure–strain correlations are almost isotropic, and their relevant length scale is given by the mixing length in the overlap layer. The pressure–strain correlations are therefore rather local quantities.