论文标题
近壁条纹与湍流通道流中的大规模运动之间的相互作用
Interaction between near-wall streaks and large-scale motions in turbulent channel flows
论文作者
论文摘要
研究了壁挂式湍流外部区域的近壁条纹与大规模运动（LSM）之间的相互作用。从两个角度来看，Toh＆Itano（2005）的共同支持假设以低至中等雷诺数的全尺寸通道进行检查。为了研究外部结构对近壁条纹的跨度运动的自上而下的影响，使用粒子图像速度测定启发的方法用于跟踪条纹的跨度位置。发现它们的跨度对流速度受到对数层中大规模循环的层次结构的影响，但是它们的跨度条纹密度仅与LSMS无关。证据表明，正如Toh＆Itano（2005）所建议的那样，自上而下的影响是存在并驱动条纹向跨度方向漂移，但是假设的条纹积累很少发生。然后，进行了RE_TAU的数值实验约535，以阐明近壁条纹在外部LSM的生成和保存中的作用。结果表明，近壁条纹的合并仅与LSM的产生弱相关，并且去除LSMS的近壁根并不会影响其外部区域的演变。结论是，近壁条纹的自下而上影响对于LSM的生成和保存并不是必需的，也削弱了共同支持假设的证据。
The interactions between the near-wall streaks and the large-scale motions (LSMs) of the outer region of wall-bounded turbulent flows are investigated. The co-supporting hypothesis of Toh & Itano (2005) is checked in full-scale channels at low to moderate Reynolds numbers, from two points of view. To study the top-down influence of the outer structures on the spanwise motion of the near-wall streaks, a method inspired by particle-image velocimetry is used to track the spanwise position of the streaks. Their spanwise advection velocity is found to be affected by the hierarchy of large-scale circulations in the logarithmic layer, but their spanwise streak density is only weakly related to the LSMs. The evidence suggests that a top-down influence exists and drives the drift of the streaks in the spanwise direction, as suggested by Toh & Itano (2005), but that the hypothesized streak accumulation rarely occurs. Numerical experiments at Re_tau about 535 are then performed to clarify the role of the near-wall streaks in the generation and preservation of the outer LSMs. The results show that the merger of the near-wall streaks is only weakly correlated with the generation of the LSMs, and that removing the near-wall roots of the LSMs does not affect the evolution of their outer region. It is concluded that the bottom-up influence from the near-wall streaks is not essential for the LSM generation and preservation, also weakening the evidence for the co-supporting hypothesis.
