Elastic instabilities in planar elongational flow of monodisperse polymer solutions.
Elastic instabilities in planar elongational flow of monodisperse polymer solutions.
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DOI：
10.1038/srep33029
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发表时间：
2016-09-12
影响因子：
4.6
通讯作者：
Shen AQ
中科院分区：
文献类型：
--
作者：
Haward SJ;McKinley GH;Shen AQ
我们研究纯弹性流动不稳定性的几乎理想的平面驻点拉伸流场所产生的微流控优化形状的交叉槽拉伸流变仪（OSCER）。我们使用时间分辨流速仪和全场双折射显微镜来研究一系列的特性良好的粘弹性聚合物解决方案的低流体惯性的条件下，在很宽的范围内施加变形率的行为。在低变形率的流动是稳定的和对称的，并出现牛顿样，而在高变形率，我们观察到一个流的不对称性类似的纯弹性不稳定性报告中的标准形状的十字槽装置的发病。然而，对于中间速率，我们观察到一种新型的弹性不稳定性，其特征在于横向位移和时间相关的运动的停滞点。在这个新的不稳定性的发病，我们评估一个众所周知的无量纲标准M，预测发病的弹性不稳定性的基础上的几何和流变标度参数。该标准产生的最大值的M比较以及与临界值的M的弹性不稳定性在粘性扭转流的发病。我们的结论是，相同的机制，张力作用沿着弯曲的流线支配的弹性不稳定性在拉伸（无旋）和扭转（旋转）粘弹性流的发病。
We investigate purely elastic flow instabilities in the almost ideal planar stagnation point elongational flow field generated by a microfluidic optimized-shape cross-slot extensional rheometer (OSCER). We use time-resolved flow velocimetry and full-field birefringence microscopy to study the behavior of a series of well-characterized viscoelastic polymer solutions under conditions of low fluid inertia and over a wide range of imposed deformation rates. At low deformation rates the flow is steady and symmetric and appears Newtonian-like, while at high deformation rates we observe the onset of a flow asymmetry resembling the purely elastic instabilities reported in standard-shaped cross-slot devices. However, for intermediate rates, we observe a new type of elastic instability characterized by a lateral displacement and time-dependent motion of the stagnation point. At the onset of this new instability, we evaluate a well-known dimensionless criterion M that predicts the onset of elastic instabilities based on geometric and rheological scaling parameters. The criterion yields maximum values of M which compare well with critical values of M for the onset of elastic instabilities in viscometric torsional flows. We conclude that the same mechanism of tension acting along curved streamlines governs the onset of elastic instabilities in both extensional (irrotational) and torsional (rotational) viscoelastic flows.
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影响因子：
4.6
作者：
GRAESSLEY, WW
通讯作者：
GRAESSLEY, WW
影响因子：
3.1
作者：
DUNLAP, PN;LEAL, LG
通讯作者：
LEAL, LG
影响因子：
4.6
作者：
GARDNER, K;PIKE, ER;TANAKA, K
通讯作者：
TANAKA, K
影响因子：
3.4
作者：
Casanellas L;Alves MA;Poole RJ;Lerouge S;Lindner A
通讯作者：
Lindner A
影响因子：
2.4
作者：
Gulati, Shelly;Liepmann, Dorian;Muller, Susan J.
通讯作者：
Muller, Susan J.