Xiao Xiangkai, Song Baofang
Center for Applied Mathematics, Tianjin University, Tianjin 300072, China.
Entropy (Basel). 2020 Oct 16;22(10):1167. doi: 10.3390/e22101167.
Channel flow turbulence exhibits interesting spatiotemporal complexities at transitional Reynolds numbers. In this paper, we investigated some aspects of the kinematics and dynamics of fully localized turbulent bands in large flow domains. We discussed the recent advancement in the understanding of the wave-generation at the downstream end of fully localized bands. Based on the discussion, we proposed a possible mechanism for the tilt direction selection. We measured the propagation speed of the downstream end and the advection speed of the low-speed streaks in the bulk of turbulent bands at various Reynolds numbers. Instead of measuring the tilt angle by treating an entire band as a tilted object as in prior studies, we proposed that, from the point of view of the formation and growth of turbulent bands, the tilt angle should be determined by the relative speed between the downstream end and the streaks in the bulk. We obtained a good agreement between our calculation of the tilt angle and the reported results in the literature at relatively low Reynolds numbers.
在过渡雷诺数下，通道流湍流呈现出有趣的时空复杂性。在本文中，我们研究了大流动区域中完全局域化湍流带的运动学和动力学的一些方面。我们讨论了在完全局域化带下游端波产生理解方面的最新进展。基于该讨论，我们提出了一种倾斜方向选择的可能机制。我们测量了不同雷诺数下湍流带主体中完全局域化带下游端的传播速度和低速条纹的平流速度。与之前研究中将整个带视为倾斜物体来测量倾斜角不同，我们提出，从湍流带的形成和生长角度来看，倾斜角应由下游端与主体中条纹之间的相对速度决定。在相对较低的雷诺数下，我们对倾斜角的计算与文献中报道的结果取得了良好的一致性。
