无剪切拉伸不稳定粘弹性微流中混合的消除
Abatement of mixing in shear-free elongationally unstable viscoelastic microflows
摘要：
向液体中添加微量的化学惰性聚丙烯酰胺聚合物导致在通过2：1收缩的稳定电渗透泵送下的大的不稳定性，表明在粘弹性材料的电渗透流中可以打破层流条件。通过排除剪切和施加对称性，我们创建了一个平台，只有拉伸粘弹性不稳定性，扩散，影响混合。与早期的研究相比，显着的剪切，发现在混合的数量级增加，我们发现，包括聚合物激发大的粘弹性不稳定性，但混合相对于无聚合物的液体减少。我们发现混合的绝对减少与以下理解一致：添加聚合物增加粘度，而粘弹性流动朝向弹性湍流（一种温和的（Batchelor）湍流）进展，并且表明电渗泵送装置是用于研究粘弹性不稳定性的理想平台，而无需补充因素。
英文摘要：
The addition of minute amounts of chemically inert polyacrylamide polymer to liquids results in large instabilities under steady electro-osmotic pumping through 2:1 constrictions, demonstrating that laminar flow conditions can be broken in electro-osmotic flow of viscoelastic material. By excluding shear and imposing symmetry we create a platform where only elongational viscoelastic instabilities, and diffusion, affect mixing. In contrast to earlier studies with significant shear that found up to orders of magnitude increase in mixing we find that inclusion of polymers excites large viscoelastic instabilities yet mixing is reduced relative to polymer-free liquids. The absolute decrease in mixing we find is consistent with the understanding that adding polymer increases viscosity while viscoelastic flows progress towards elastic turbulence, a type of mild (Batchelor) turbulence, and indicates that electro-osmotic pumped devices are an ideal platform for studying viscoelastic instabilities without supplementary factors.
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