Effects of weak elasticity on the stability of high Reynolds number co- and counter-rotating Taylor-Couette flows
Effects of weak elasticity on the stability of high Reynolds number co- and counter-rotating Taylor-Couette flows
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弱弹性对高雷诺数同向和反向旋转 Taylor-Couette 流稳定性的影响
DOI：
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
S. Muller
中科院分区：
文献类型：
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作者：
C. Dutcher;S. Muller
本研究探讨了聚合物稀溶液对同心旋转圆柱体之间独特的孤立二次流，即泰勒-库埃特（TC）流的影响。我们使用牛顿和稀聚环氧乙烷（PEO）溶液在雷诺数范围为− 100 < Reo < 500和0 < Rei < O（103）的情况下绘制了流动状态的稳定性图，其中下标“o”和“i”分别表示外圆柱体和内圆柱体。PEO流体的弹性数（El）定义为弹性力与惯性力的比值，范围为O（10− 4）至O（10− 2）。这项工作扩大了以前的研究（a）显着扩大范围的Rei，Reo，和El检查，（B）使用一致的，保守的协议，达到流动状态，和（c）流变特性的解决方案，通过剪切和毛细管破裂拉伸流变仪。通过对r-z或z-θ平面流动显示的谱分析，我们发现El对层流和混沌轴对称和非轴对称流态的临界条件的影响是非单调的和依赖于模式的，对涉及小尺度特征的高阶转变的影响更大。虽然临界条件被修改为低El的所有过渡，流动状态不同的牛顿流体在较高的Rei和更弹性的流体。
This study examines the impact of dilute polymer solutions on the unique isolated secondary flows between concentric, rotating cylinders, namely Taylor-Couette (TC) flow. We mapped the stability of flow states using Newtonian and dilute polyethylene oxide (PEO) solutions over the Reynolds number range of − 100 < Reo < 500 and 0 < Rei < O(103), where subscripts ‘o’ and ‘i’ refer to outer and inner cylinders, respectively. Elasticity number (El) of the PEO fluids, defined as the ratio of elastic to inertial forces, ranges from O(10− 4) to O(10− 2). This work expands on previous studies by (a) significantly expanding the range of Rei, Reo, and El examined, (b) use of a consistent, conservative protocol for reaching flow states, and (c) rheological characterization of the solutions via shear and capillary breakup extensional rheometry. Using spectral analysis of flow visualization of the r-z or z-θ planes, we find the effect of El on the critical conditions for laminar and chaotic axisymmetric and nonaxisymmetric flow states is nonmonotonic and mode-dependent, with greater modification of higher order transitions involving small-scale features. While the critical conditions are modified by low El for all transitions, the flow states vary from those for Newtonian fluids at higher Rei and for the more elastic fluids.