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首页> 外文期刊>Flow, turbulence and combustion >Numerical Study of Turbulent Channel Flow over Surfaces with Variable Spanwise Heterogeneities: Topographically-driven Secondary Flows Affect Outer-layer Similarity of Turbulent Length Scales
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Numerical Study of Turbulent Channel Flow over Surfaces with Variable Spanwise Heterogeneities: Topographically-driven Secondary Flows Affect Outer-layer Similarity of Turbulent Length Scales

机译：湍流通道流过血管血管间异质性的湍流通道流动的数值研究：拓扑驱动的二次流动影响湍流长度尺度的外层相似性

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摘要

Wall-bounded turbulent flows over surfaces with spanwise heterogeneous surface roughness - that is, spanwise-adjacent patches of relatively high and low roughness - exhibit mean flow phenomena entirely different to what would otherwise exist in the absence of spanwise heterogeneity. In the outer layer, mean counter-rotating rolls occupy the depth of the flow, and are positioned such that "upwelling" and "downwelling" occurs above the low and high roughness, respectively. It has been comprehensively shown that these secondary flows are Prandtl's secondary flow of the second kind (Anderson et al., J. Fluid Mech. 768, 316-347 2015). This behaviour indicates that spanwise spacing, s (y) , between adjacent patches of high and low roughness is, itself, a problem parameter; in this study, we have systematically assessed how s (y) affects turbulence structure in high Reynolds number channel flows via two-point correlations. "High roughness" is imposed with streamwise-aligned pyramid elements with height, h, selected to be ae 5% of the channel half height, H. For , we find that the aforementioned domain-scale mean circulations exist and the surface may be regarded as a topography. For s (y) /H ae(2) 0.2, turbulence statistics show characteristics very similar to a homogeneous roughness and thus the surface may be regarded as a roughness. For 0.2 ae(2) s (y) /H ae(2) 2, the spatial extent of the counter-rotating rolls is controlled by proximity to adjacent rows, and we define such surfaces as being intermediate. We refer to such surfaces as intermediate state.
机译：壁有限的湍流在具有翼肌异质表面粗糙度的表面上流动 - 即跨越相对高且低粗糙度的斑块 - 表现出完全不同于诸如在没有霉共异质性的情况下存在的平均流动现象。在外层中，平均旋转辊占据流动的深度，并且定位成使得“升值”和“贫困”分别在低粗糙度高于和高粗糙度之上。已经全面地表明，这些二次流量是普朗特的第二种二次流动（Anderson等，J. Fluid Mech。768,316-347 2015）。这种行为表示，在高低粗糙度的相邻斑块之间的跨度间距，s（y）是本身的问题参数;在本研究中，我们系统地评估了S（Y）如何影响高雷诺数信道中的湍流结构通过两点相关性。用高度，H的流动对准​​金字塔元素施加“高粗糙度”，选择为频道半高的5％，H.对于，我们发现存在上述域标度的平均循环和表面可以被视为作为地形。对于S（Y）/ H AE（2）0.2，湍流统计显示与均匀粗糙度非常相似的特性，因此表面可以被视为粗糙度。对于0.2 AE（2）S（Y）/ H AE（2）2，反向旋转辊的空间程度由与相邻行的接近控制，并且我们将这种表面定义为中间体。我们将这种表面作为中间状态指。

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