Edge-Induced Shear Banding in Entangled Polymeric Fluids.
Edge-Induced Shear Banding in Entangled Polymeric Fluids.
复制标题
缠结聚合物流体中的边缘诱导剪切带。
DOI：
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发表时间：
2018
影响因子：
8.6
通讯作者：
S. Fielding
中科院分区：
文献类型：
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作者：
E. J. Hemingway;S. Fielding
尽管经过几十年的研究，高度缠结的聚合物的溶液和熔体是否表现出剪切带作为其稳定施加的剪切流的稳态响应的问题仍然存在争议。从理论的观点来看，一个重要的未回答的问题是剪切应力σ作为剪切速率γ的函数（对于均匀剪切状态）的基本本构曲线是单调的，还是具有负斜率的区域，dσ/dγ <0，这将触发条带。试图通过流体内部流场的速度测量来解决这个问题的实验通常会被样品遇到外部空气的自由表面的不稳定性所混淆，称为“边缘断裂”。“在这里，我们通过数值模拟表明，事实上，即使只有非常温和的边缘扰动-这是全边缘断裂的前兆，但本身很可能在实验中被忽视-也会以剪切带的形式引起强烈的二次流，这些剪切带侵入流体体的深处。至关重要的是，这是真的，即使当基本的本构曲线是单调增加，排除真正的散装剪切带的边缘效应的情况下。
Despite decades of research, the question of whether solutions and melts of highly entangled polymers exhibit shear banding as their steady state response to a steadily imposed shear flow remains controversial. From a theoretical viewpoint, an important unanswered question is whether the underlying constitutive curve of shear stress σ as a function of shear rate γ[over ˙] (for states of homogeneous shear) is monotonic, or has a region of negative slope, dσ/dγ[over ˙]<0, which would trigger banding. Attempts to settle the question experimentally via velocimetry of the flow field inside the fluid are often confounded by an instability of the free surface where the sample meets the outside air, known as "edge fracture." Here we show by numerical simulation that in fact even only very modest edge disturbances-which are the precursor of full edge fracture but might well, in themselves, go unnoticed experimentally-can cause strong secondary flows in the form of shear bands that invade deep into the fluid bulk. Crucially, this is true even when the underlying constitutive curve is monotonically increasing, precluding true bulk shear banding in the absence of edge effects.
影响因子：
3.3
作者：
Adams, J. M.;Fielding, S. M.;Olmsted, P. D.
通讯作者：
Olmsted, P. D.