泡沫和乳状液在通道中的塑性流动
Plastic flow of foams and emulsions in a channel
摘要：
为了理解复杂流体的流动剖面，一个关键的问题是在宏观层面上表现出协同流动行为的塑性重排之间的空间相关性的出现。本文在Hele-Shaw几何条件下，对Poiffille流动中的塑性事件速率进行了实验测量。与独立测量的速度分布的相关性进行量化。为了超越实验的局限性，即壁摩擦的存在使剪切应力和剪切速率之间的关系复杂化，我们将实验与基于格子玻尔兹曼方法的乳化液滴模拟进行比较，该方法在有和没有壁摩擦的情况下进行。我们的研究结果表明，本地化长度的速度分布和本地化长度的塑性事件的数量之间的相关性。最后，前所未有的结果分布的塑性事件的方向表明，有一个非平凡的相关性与潜在的局部剪切应变。这些特征以前没有报道过局限的泡沫，进一步支持了最初用于浓缩乳液的协同机制（Goyon等人，2008年）在其他软玻璃状材料的行为中具有相似性的想法。
英文摘要：
In order to understand the flow profiles of complex fluids, a crucial issue concerns the emergence of spatial correlations among plastic rearrangements exhibiting cooperativity flow behaviour at the macroscopic level. In this paper, the rate of plastic events in a Poiseuille flow is experimentally measured on a confined foam in a Hele-Shaw geometry. The correlation with independently measured velocity profiles is quantified. To go beyond a limitation of the experiments, namely the presence of wall friction which complicates the relation between shear stress and shear rate, we compare the experiments with simulations of emulsion droplets based on the lattice-Boltzmann method, which are performed both with, and without, wall friction. Our results indicate a correlation between the localisation length of the velocity profiles and the localisation length of the number of plastic events. Finally, unprecedented results on the distribution of the orientation of plastic events show that there is a non-trivial correlation with the underlying local shear strain. These features, not previously reported for a confined foam, lend further support to the idea that cooperativity mechanisms, originally invoked for concentrated emulsions (Goyon et al. 2008), have parallels in the behaviour of other soft-glassy materials.
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