Abstract Two-point concentration measurements are obtained in a meandering passive-scalar plume released at five different heights within the fully-turbulent region of a high-Reynolds number turbulent boundary layer (TBL). Mean statistics of two-point concentration measurements are found to agree very well with the single-point measurements previously reported in Talluru et al. (2017a). The two-point correlation results of concentration indicate strong coherence in the scalar field similar to the large-scale coherence observed in the streamwise velocity fluctuations in a TBL (Marusic and Heuer, 2007). Particularly, the isocontours in the two-dimensional correlation map of concentration fluctuations illustrate that the scalar structures are inclined at 30∘ to the direction of the flow; such a trend is consistently observed for all the elevated plumes below z/δ ≤ 0.33. This observation of steeper inclination angle of scalar structures relative to the inclination angle of large-scale velocity fluctuations in a TBL is explained using the physical model put forth by Talluru et al. (2018). Most importantly, these results provide insights on the differences in the structural organisation of a passive scalar plume in the near- and the far-field regions.

中文翻译：

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湍流边界层中近场标量涨落的结构倾角

摘要 在高雷诺数湍流边界层 (TBL) 的完全湍流区域内的五个不同高度释放的蜿蜒被动标量羽流中获得了两点浓度测量值。发现两点浓度测量的平均统计数据与 Talluru 等人先前报道的单点测量非常吻合。(2017a)。浓度的两点相关结果表明标量场中的强相干性类似于在 TBL 中的流向速度波动中观察到的大尺度相干性（Marusic 和 Heuer，2007 年）。特别是浓度波动二维相关图中的等值线表明，标量结构与流动方向呈30∘倾斜；对于低于 z/δ ≤ 0.33 的所有升高的羽流，始终观察到这种趋势。使用 Talluru 等人提出的物理模型解释了这种观察到的标量结构相对于 TBL 中大规模速度波动的倾角更陡峭的倾角。(2018)。最重要的是，这些结果提供了关于近场和远场区域被动标量羽流结构组织差异的见解。