The spatial inhomogeneity of turbulence above a fully rough, packed bed in open channel flow
The spatial inhomogeneity of turbulence above a fully rough, packed bed in open channel flow
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明渠流中完全粗糙的填充床上方湍流的空间不均匀性
DOI：
10.1007/s003489900107
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发表时间：
2000
影响因子：
2.4
通讯作者：
A. Papanicolaou
中科院分区：
文献类型：
--
作者：
C. Dancey;M. Balakrishnan;P. Diplas;A. Papanicolaou
报告了在完全发展的、完全粗糙的、湍流的明渠流动中，直接在壁面上方和靠近壁面测量的单点湍流统计。为了研究湍流的空间不均匀性，测量是在平行于粗糙度床面的平面上的测量点矩阵上获得的。测量采用三分量激光多普勒测速仪(3D-LDV)。重点介绍了与垂直速度分量相关的湍流统计特性，包括条件平均垂直速度、均方根分布和平均垂直动量通量。对于与本研究相关的雷诺数和弗劳德数，以及本研究中所采用的特定粗糙度几何形状(直径均匀的球体填充床)，发现局部平均垂直速度的分布对粗糙度分布具有非零贡献，并且这有助于平均垂直动量通量进入粗糙度床。然而，由于湍流起伏引起的垂直动量净通量在床外为正值，这与光滑壁面的行为一致。这些结果与泥沙夹带和悬浮/沉积以及沟道芯流和粗糙床内流体之间的化学物质交换和输运的研究有关。
Single point turbulence statistics measured directly above and in close proximity to the wall in a fully developed, fully rough, turbulent open channel flow are reported. In order to investigate the spatial inhomogeneity of the turbulence, the measurements were obtained over a matrix of measurement points in a plane parallel to the roughness-bed surface. The measurements were obtained with a three-component laser Doppler velocimeter (3D-LDV) system. The turbulence statistics associated with the vertical velocity component, including conditioned mean vertical velocities, rms distributions, and mean vertical momentum fluxes are emphasized. For the Reynolds and Froude numbers associated with this investigation, and with the specific roughness geometry employed in this study (a packed bed of uniform-diameter spheres), it is found that the distribution of the local mean vertical velocity, <w>, has non-zero contributions over the roughness pattern and that this contributes to a mean net vertical momentum flux into the roughness bed. However, the net vertical momentum flux due to turbulent fluctuations is positive out of the bed, consistent with smooth-wall behavior. These results are relevant to the study of sediment entrainment and suspension/deposition as well as the exchange and transport of chemical species between the channel core flow and the fluid within the roughness bed.