Laminar mixing and chaotic mixing in several cavity flows
Laminar mixing and chaotic mixing in several cavity flows
复制标题
多腔流中的层流混合和混沌混合
DOI：
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发表时间：
1986
影响因子：
3.7
通讯作者：
J. Ottino
中科院分区：
文献类型：
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作者：
W.;H. Rising;J. Ottino
本文在一个新的实验系统中，利用材料线和液滴变形，对几种二维空腔流的层流混合进行了实验研究。该装置可以调节以产生一系列的纵横比（0.067-10）、雷诺数（0.1-100）和具有一个或两个移动边界的各种流场。流动可视化是通过在流动的自由表面下用低扩散性的示踪剂溶液进行标记来进行的，示踪剂溶液的密度和粘度与流动的流体大致相同。实验研究了材料团块的初始位置、两个带的相对运动以及流动区域的几何形状的微小变化的影响。空腔流中两个带的交替周期性运动是可能导致混沌混合的层流的一个例子。控制参数是壁f的无量纲振动频率，在适当的条件下，该频率能够产生各种类型的马蹄函数。斑点的变形是理解混合的核心，可以通过研究来识别马蹄函数。结果表明，混合效率强烈依赖于f的值，存在一个最佳的f值，在给定的时间内产生最佳的混合。
The objective of this work is an experimental study of laminar mixing in several kinds of two-dimensional cavity flows by means of material line and blob deformation in a new experimental system consisting of two sets of roller pairs connected by belts. The apparatus can be adjusted to produce a range of aspect ratios (0.067–10), Reynolds numbers (0.1–100), and various kinds of flow fields with one or two moving boundaries. Flow visualization is conducted by marking underneath the free surface of the flow with a tracer solution of low diffusivity and of approximately the same density and viscosity as the flowing fluid. The effects of the initial location of the material blob, relative motion of the two bands, and minor changes in the geometry of the flow region are investigated experimentally. The alternate periodic motion of two bands in a cavity flow is an example of a laminar flow which might lead to chaotic mixing. The governing parameter is the dimensionless frequency of oscillation of the walls f which, under the proper conditions, is able to produce horseshoe functions of various types. The deformation of blobs is central to the understanding of mixing and can be studied to identify horseshoe functions. It is found that the efficiency of mixing depends strongly on the value of f and that there exists an optimal value of f that produces the best mixing in a given time.