Interactions of large-scale free-stream turbulence with turbulent boundary layers
Interactions of large-scale free-stream turbulence with turbulent boundary layers
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DOI：
10.1017/jfm.2016.435
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发表时间：
2016-08
影响因子：
3.7
通讯作者：
E. Doğan;R. Hanson;B. Ganapathisubramani
中科院分区：
文献类型：
--
作者：
E. Doğan;R. Hanson;B. Ganapathisubramani
本文研究了自由流湍流存在时湍流边界层内的尺度相互作用。自由流湍流由主动网格产生。自由流由单组分热线探针监测，而第二个探针在同一流向位置穿过边界层的高度。大规模的结构发生在自由流中示出穿透边界层，并增加整个流向的速度波动。据推测，根据渗透的程度，即基于自由流湍流的水平，近壁湍流产生峰值在不同的壁法线位置，而不是典型湍流边界层的预期位置$y^{+}\约15$。结果表明，对数区域的大尺度对近壁区域的小尺度有调制作用，随着自由流中湍流度的增加，即Re_{\unicode[STIX]{x1 D 706}_{0}}$的增加，这种调制作用更加显著。这种调制相互作用及其雷诺数趋势与高雷诺数下的典型湍流边界层相似，其中大尺度和小尺度包络之间的相互作用表现出纯振幅调制（Hutchins & Marusic，Phil.横河Soc. Lond. A，vol. 365（1852），2007，pp. 647-664;马西斯等人，流体力学杂志，第628卷，2009年，pp. 311-337）。这种相似性具有令人鼓舞的意义，对推广尺度相互作用的湍流边界层。
The scale interactions occurring within a turbulent boundary layer are investigated in the presence of free-stream turbulence. The free-stream turbulence is generated by an active grid. The free stream is monitored by a single-component hot-wire probe, while a second probe is roved across the height of the boundary layer at the same streamwise location. Large-scale structures occurring in the free stream are shown to penetrate the boundary layer and increase the streamwise velocity fluctuations throughout. It is speculated that, depending on the extent of the penetration, i.e. based on the level of free-stream turbulence, the near-wall turbulence production peaks at different wall-normal locations than the expected location of $y^{+}\approx 15$ for a canonical turbulent boundary layer. It is shown that the large scales dominating the log region have a modulating effect on the small scales in the near-wall region; this effect becomes more significant with increasing turbulence in the free stream, i.e. similarly increasing $Re_{\unicode[STIX]{x1D706}_{0}}$ . This modulating interaction and its Reynolds-number trend have similarities with canonical turbulent boundary layers at high Reynolds numbers where the interaction between the large scales and the envelope of the small scales exhibits a pure amplitude modulation (Hutchins & Marusic, Phil. Trans. R. Soc. Lond. A, vol. 365 (1852), 2007, pp. 647–664; Mathis et al., J. Fluid Mech., vol. 628, 2009, pp. 311–337). This similarity has encouraging implications towards generalising scale interactions in turbulent boundary layers.