Graham Michael D.
Department of Chemical Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706-1691.
Chaos. 1999 Mar;9(1):154-163. doi: 10.1063/1.166386.
Flows of polymeric liquids undergo instabilities whose origins are quite different from those of Newtonian flows, due to their elastic character and the complexity of the fluid/solid boundary condition. This article reviews recent studies of one such instability, the sharkskin phenomenon observed during extrusion of many linear polymers. Key experimental observations are summarized; one important fact that has become clear is the importance of the interaction between the molten polymer and the solid walls of the flow channel, especially near the contact line at the exit of the channel. Recent developments in understanding the relationship between wall slip and disentanglement of wall-adsorbed polymers from the bulk flow are briefly described, and putative heuristic mechanisms relating the instability to slip and contact line motion are presented. Finally, we review mathematical analyses of the stability of viscoelastic shear flows with slip boundary conditions. Some recent analyses yield instability predictions that are consistent with experiments, but further work is required to discriminate between the various mechanisms that have been proposed. (c) 1999 American Institute of Physics.
由于其弹性特性以及流体/固体边界条件的复杂性，聚合物流体的流动会经历一些不稳定性，这些不稳定性的起源与牛顿流体流动的起源截然不同。本文综述了对其中一种不稳定性的最新研究，即在许多线性聚合物挤出过程中观察到的鲨鱼皮现象。总结了关键的实验观察结果；一个已明确的重要事实是熔融聚合物与流动通道固体壁之间相互作用的重要性，特别是在通道出口处的接触线附近。简要描述了在理解壁面滑移与壁面吸附聚合物从主流体中解缠结之间关系方面的最新进展，并提出了将这种不稳定性与滑移和接触线运动相关联的假定启发式机制。最后，我们综述了具有滑移边界条件的粘弹性剪切流稳定性的数学分析。一些最新分析得出的不稳定性预测与实验结果一致，但仍需要进一步开展工作以区分已提出的各种机制。（c）1999美国物理研究所。
