Iterated stretching, extensional rheology and formation of beads-on-a-string structures in polymer solutions
Iterated stretching, extensional rheology and formation of beads-on-a-string structures in polymer solutions
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DOI：
10.1016/j.jnnfm.2006.01.014
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发表时间：
2006-08-30
影响因子：
3.1
通讯作者：
McKinley, Gareth H.
中科院分区：
文献类型：
--
作者：
Oliveira, Monica S. N.;Yeh, Roger;McKinley, Gareth H.
采用高速数字视频显微镜研究了聚氧乙烯（PEO）水溶液中的瞬态拉伸流变性和弹性毛细管减薄动力学。在很长一段时间内，螺纹半径的演化偏离自相似指数衰减，弹性、毛细力和惯性力之间的竞争导致由轴向均匀韧带连接的周期性珠子阵列的形成。这种结构是不稳定的，连续的不稳定从连接珠和韧带的颈部传播。这一反复的过程导致了多代珠珠沿着这条河流发育。弦与Chang等人的预测基本一致。流体，11(1999)1717]，尽管实验在连续几代珠子之间产生了不同的递归关系。在较长时间内，有限的可扩展性截断了迭代失稳，并且在流体柱最终破裂之前，沿相互连接的螺纹缓慢的头阵列轴向平移导致逐渐合并。尽管存在这些动力学上的复杂性，但仍然可以通过监测珠子之间的圆柱形韧带中由毛细血管驱动的缓慢变薄来测量瞬态拉伸粘度的稳定增长。(c) 2006 Elsevier B.V.版权所有
The transient extensional rheology and the dynamics of elastocapillary thinning in aqueous solutions of polyethylene oxide (PEO) are studied with high-speed digital video microscopy. At long times, the evolution of the thread radius deviates from self-similar exponential decay and competition between elastic, capillary and inertial forces leads to the formation of a periodic array of beads connected by axially uniform ligaments. This configuration is unstable and successive instabilities propagate from the necks connecting the beads and ligaments. This iterated process results in multiple generations of beads developing along the. string in general agreement with predictions of Chang et al. [Phys. Fluids, 11 (1999) 1717] although the experiments yield a different recursion relation between the successive generations of beads. At long times, finite extensibility truncates the iterated instability, and slow axial translation of the bead arrays along the interconnecting threads leads to progressive coalescence before the ultimate rupture of the fluid column. Despite these dynamical complexities it is still possible to measure the steady growth in the transient extensional viscosity by monitoring the slow capillary-driven thinning in the cylindrical ligaments between beads. (c) 2006 Elsevier B.V. All rights reserved.