Shear thickening in filled Boger fluids
Shear thickening in filled Boger fluids
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填充 Boger 流体中的剪切增稠
DOI：
10.1122/1.1849185
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发表时间：
2005
影响因子：
3.3
通讯作者：
J. Mewis
中科院分区：
文献类型：
--
作者：
R. Scirocco;J. Vermant;J. Mewis
研究了微米级聚苯乙烯微球分散在Boger流体中的悬浮液的剪切增稠。与牛顿介质中悬浮液的可用数据相比，剪切增稠发生在低得多的体积分数下。在正常的非线性粘弹性介质中的悬浮液通常根本不显示剪切增稠。在Boger流体中的悬浮液中，剪切增稠的开始被示出由临界剪切应力支配。颗粒尺寸的影响与颗粒半径的三次幂成比例一致，如布朗硬球。然而，临界应力比低粘度牛顿介质中的类似悬浮液高几个数量级。第一法向应力系数也受颗粒存在的影响，但它显示剪切增稠以及剪切变稀。在流动过程中没有观察到特定的微观结构特征，似乎既没有对齐也没有水聚集。Boger流体中的剪切增稠可能是由增强的流体动力学颗粒间相互作用引起的，与悬浮介质的特定粘弹性有关，即，不存在剪切稀化和显著的拉伸硬化。最近的模拟结果似乎证实了这一点。
Shear thickening is studied in suspensions consisting of micrometer sized polystyrene spheres dispersed in Boger fluids. In comparison with available data for suspensions in Newtonian media, shear thickening occurs at much lower volume fractions. Suspensions in normal nonlinear viscoelastic media typically do not display shear thickening at all. In suspensions in Boger fluids, the onset of shear thickening is shown to be governed by a critical shear stress. The effect of particle size is consistent with a scaling with the particles radius to the third power, as for Brownian hard spheres. The critical stresses are, however, orders of magnitude higher than for similar suspensions in low viscosity, Newtonian media. The first normal stress coefficient is also affected by the presence of particles, but it displays shear thickening as well as shear thinning. No specific microstructural features have been observed during flow, neither alignment nor hydroclustering seem to occur. Shear thickening in Boger fluids is possibly caused by the enhanced hydrodynamic interparticle interactions, related to the specific viscoelastic properties of the suspending medium, i.e., the absence of shear thinning and pronounced extensional hardening. This seems to be confirmed by recent simulation results.