In this study, we investigated the motion of solid particles dispersed in highly viscous complex fluids agitated in a stirred vessel. We used a refractive index matching method and a combination of planar laser-induced fluorescence (PLIF), particle image velocimetry (PIV), and particle-tracking velocimetry (PTV) techniques to measure the velocity fields of the solid and fluid phases simultaneously along with the spatiotemporal distribution of the solids in the tank. The experimental data show that in a Newtonian ambient fluid, particles disperse uniformly in the plane of measurement, while in a strongly shear-thinning viscoelastic ambient fluid they tend to accumulate in the core of the vortices formed in the flow domain. We found that the solids migrate to the core of the vortices also when the ambient fluid is a Boger fluid, i.e., viscoelastic but not shear thinning. The effect of the first normal stress difference, $N1$, on the vortex sizes and circulation intensities was also examined, with both properties decreasing for increasing $N1$. Finally, we observed that the clustering time of the solids in the vessel for viscoelasticity-induced migration was at least three orders of magnitude lower than that obtained from the literature for inertia-induced migration.

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粘弹性在搅拌槽内固液分离的实验研究

在这项研究中，我们研究了分散在搅拌容器中搅拌的高粘度复杂流体中的固体颗粒的运动。我们使用了折射率匹配方法，并结合了平面激光诱导荧光（PLIF），粒子图像测速（PIV）和粒子跟踪测速（PTV）技术，以同时测量固相和液相的速度场，以及储罐中固体的时空分布。实验数据表明，在牛顿环境流体中，颗粒均匀地分散在测量平面中，而在强剪切稀化的粘弹性环境流体中，它们倾向于积聚在流域中形成的涡流的核心中。我们发现，当环境流体是Boger流体时，固体也会迁移到涡流的核心，即 粘弹性，但不剪切稀。第一法向应力差的影响$ñ\mathrm{1个}$，还检查了涡旋的大小和循环强度，两种性质均随着增加而减小 $ñ\mathrm{1个}$。最后，我们观察到，固体在容器中用于粘弹性引起的迁移的聚集时间比从文献中获得的惯性引起的迁移的聚集时间至少低三个数量级。