Niebling Michael J, Tallakstad Ken Tore, Toussaint Renaud, Måløy Knut Jørgen
Department of Physics, University of Oslo, P. O. Box 1048, 0316 Oslo, Norway.
Institut de Physique du Globe de Strasbourg, EOST/Université de Strasbourg, CNRS, 5 rue Descartes, F-67000 Strasbourg, France.
Phys Rev E Stat Nonlin Soft Matter Phys. 2014 Jan;89(1):013026. doi: 10.1103/PhysRevE.89.013026. Epub 2014 Jan 31.
In a plane Couette cell a thin fluid layer consisting of water is sheared between the sides of a transparent band at Reynolds numbers ranging from 300 to 1400. The length of the cell's flow channel is large compared to the film separation. To extract the flow velocity in the experiments, a correlation image velocimetry method is used on pictures recorded with a high-speed camera. The flow is recorded at a resolution that allows us to analyze flow patterns similar in size to the film separation. The fluid flow is then studied by calculating flow velocity autocorrelation functions. The turbulent patterns that arise on this scale above a critical Reynolds number of Re=360 display characteristic patterns that are proven by use of the calculated velocity autocorrelation functions. The patterns are metastable and reappear at different positions and times throughout the experiments. Typically these patterns are turbulent rolls which are elongated in the stream direction, which is the direction in which the band is moving. Although the flow states are metastable they possess similarities to the steady Taylor vortices known to appear in circular Taylor Couette cells.
在平面库埃特流槽中，一层由水组成的薄流体层在一个透明带的两侧之间被剪切，雷诺数范围为300至1400。流槽的流动通道长度与薄膜间距相比很大。为了在实验中提取流速，在高速摄像机记录的图片上使用相关图像测速法。以允许我们分析与薄膜间距大小相似的流动模式的分辨率记录流动。然后通过计算流速自相关函数来研究流体流动。在临界雷诺数Re = 360以上这个尺度上出现的湍流模式显示出特征模式，这通过使用计算出的速度自相关函数得到了证实。这些模式是亚稳的，并且在整个实验过程中会在不同位置和时间重新出现。通常这些模式是湍流涡旋，它们在流带移动的方向（即流向）上拉长。尽管流动状态是亚稳的，但它们与已知出现在圆形泰勒库埃特流槽中的稳态泰勒涡旋有相似之处。
