Large-eddy simulation of turbulent boundary layer separation from a rounded step
Large-eddy simulation of turbulent boundary layer separation from a rounded step
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DOI：
10.1080/14685248.2011.637923
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发表时间：
2012-01-01
影响因子：
1.9
通讯作者：
Leschziner, Michael A.
中科院分区：
文献类型：
--
作者：
Bentaleb, Yacine;Lardeau, Sylvain;Leschziner, Michael A.
采用高分辨率大涡模拟（LES）来研究在高度为台阶8.5倍的通道中，标准边界层从弯曲台阶分离的特性。该流动被视为在展向上统计均匀，这与在一项配套研究计划中，在大宽高比通道内开展的相关实验研究条件相符。主要关注点在于分离过程的细节以及分离区域（包括再附着）的特性。从流动物理角度，针对多种特性（包括壁面压力和表面摩擦力、平均速度、雷诺应力及相关各向异性图、两点相关函数、非定常指标、雷诺应力收支以及表征湍流的长度尺度，还有平均应变场），报告并分析了结果。该研究突出了从缓曲面分离的一系列独特特征：分离过程在时间和空间上高度不稳定；湍流具有高度非局部特性；平均逆流区域薄且延伸很长；没有任何一部分流动始终处于逆流状态；分离后生成水平极高，导致与湍流能量平衡出现巨大偏离，各向异性程度极高，且在分离剪切层中有向单分量湍流发展的趋势。该结果除了有助于深入理解分离的物理机制外，还构成了一个有价值的数据集，可用于对模型解进行基准测试以及研究统计湍流闭合方案。
Highly resolved large-eddy simulation (LES) is used to investigate the characteristics of a canonical boundary layer separating from a curved step in a channel of height 8.5 times that of the step. The flow is treated as statistically spanwise homogeneous, in line with the conditions of a related experimental study in a large aspect ratio channel, undertaken within a companion research programme. Primary attention focuses on the details of the separation process and the properties of the separated region, including reattachment. Results are reported and analysed, from a flow physical perspective, for a wide variety of properties, including wall pressure and skin friction, mean velocity, Reynolds stresses and related anisotropy maps, two-point-correlation functions, unsteadiness indicators, budgets of the Reynolds stresses and length scales characterising the turbulence, and mean strain fields. The study highlights a range of distinctive features of separation from gently curved surfaces: the separation process is highly unsteady in time and space; turbulence is highly non-local in character; the mean reverse-flow region is thin and highly elongated; no part of the flow is reversed at all times; the level of production is extremely high following separation, resulting in massive departures from turbulence energy equilibrium, very high anisotropy and a trend towards one-component turbulence in the separated shear layer. The result, apart from offering insight into the physics of separation, constitutes a valuable data set for benchmarking model solutions and investigating statistical turbulence-closure proposals.