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首页> 外文期刊>International Journal of Heat and Fluid Flow >Intense Reynolds-stress events in turbulent ducts
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Intense Reynolds-stress events in turbulent ducts

机译：激烈的雷诺 - 压力事件在湍流管道中

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The aim of the present work is to investigate the role of intense Reynolds shear-stress events in the generation of the secondary flow in turbulent ducts. We consider the connected regions of flow where the product of the instantaneous fluctuations of two velocity components is higher than a threshold based on the long-time turbulence statistics, in the spirit of the three-dimensional quadrant analysis proposed by Lozano-Dur ' an et al. (J. Fluid Mech., vol. 694, 2012, pp. 100-130). We examine both the geometrical properties of these structures and their contribution to the mean in-plane velocity components, and we perfom a comparison with turbulent channel flow at similar Reynolds number. The contribution to a certain mean quantity is defined as the ensemble average over the detected coherent structures, weighted with their own occupied volume fraction. In the core region of the duct, the contribution of intense events to the wall-normal component of the mean velocity is in very good agreement with that in the channel, despite the presence of the secondary flow in the former. Additionally, the shapes of the three-dimensional objects do not differ significantly in both flows. In the corner region of the duct, the proximity of the walls affects both the geometrical properties of the coherent structures and the contribution to the mean component of the vertical velocity. However, such contribution is less relevant than that of the complementary portion of the flow not included in such objects. Our results show that strong Reynolds shear-stress events are affected by the presence of a corner but, despite the important role of these structures in the dynamics of wall-bounded turbulent flows, their contribution to the secondary flow is relatively low, both in the core and in the corner.
机译：本作本作的目的是研究激烈的雷诺剪切应力事件在湍流管道中产生二次流动中的作用。我们考虑的流量的连接区域，其中两个速度分量的瞬时波动的乘积高于基于长时间湍流统计的阈值，本着Lozano-Dur'At'ET的三维象限分析的精神al。 （J. Fluid Mech。，Vol.694,2012，PP。100-130）。我们检查这些结构的几何特性及其对平均内侧速度分量的贡献，以及与类似雷诺数的湍流通道流的比较。对某个平均数量的贡献被定义为检测到的相干结构上的集合平均值，加权其自身占用的体积分数。在管道的核心区域中，尽管前者中存在二次流动，但是在平均速度的壁正常成分对平均速度的壁正常组分的贡献非常良好。另外，三维物体的形状在两种流中没有显着差异。在管道的拐角区域中，壁的接近影响相干结构的几何特性以及对垂直速度的平均分量的贡献。然而，这种贡献比不包括在这些物体中的流的互补部分的贡献较小。我们的研究结果表明，强烈的雷诺斯剪切应力事件受到角落存在的影响，但是，尽管这些结构在墙面缠绕流动的动态中具有重要作用，但它们对二次流动的贡献相对较低，两者都相对较低核心和角落。

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