Theory of particle segregation in rimming flows of suspensions containing neutrally buoyant particles
Theory of particle segregation in rimming flows of suspensions containing neutrally buoyant particles
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含有中性浮力颗粒的悬浮液边缘流中的颗粒分离理论
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
A. Acrivos
中科院分区：
文献类型：
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作者：
Bo Jin;A. Acrivos
最近有报道称，在部分填充的水平旋转圆柱体中，中性浮力颗粒的初始均匀悬浮在一定条件下，可以分离成由低颗粒浓度甚至无颗粒液体区域隔开的颗粒带[M]。Tirumkudulu， A. Mileo和A. Acrivos，物理学家。流体学报，1615(2000)]。对这一现象的解释是基于一个轴向粘度变化的边缘流动模型，加上实验观察，当液体含有再循环区域（水坑）时，颗粒通过从水坑向单向圆周流动的迁移而径向分离。对稀悬液的线性稳定性分析表明，这种颗粒分布对轴向扰动是不稳定的，表面张力负责选择放大最快的扰动的波长。计算结果与实测结果吻合较好。此外，由于在没有水坑的情况下，颗粒浓度在整个膜的横截面上似乎保持均匀，因此，即使通过冷却圆柱体的预先选定部分来施加轴向粘度变化，也没有预测到轴向颗粒偏析发生，也没有在实验中看到过。
It has recently been reported that an initially uniform suspension of neutrally buoyant particles within a partially filled horizontal rotating cylinder can, under certain conditions, segregate into bands of particles separated by regions of low particle concentration or even particle-free liquid [M. Tirumkudulu, A. Mileo, and A. Acrivos, Phys. Fluids 12, 1615 (2000)]. An explanation for this phenomenon is proposed on the basis of a model of rimming flows with an axially varying viscosity plus the experimental observation that, when the liquid contains a recirculating region (puddle), the particles segregate radially by migrating out of the puddle into the unidirectional circumferential flow. A linear stability analysis for dilute suspensions shows that such a particle distribution is unstable to axial perturbations with the surface tension being responsible for the selection of the wavelength of the most rapidly amplified disturbance. The calculated and measured spacings between the bands are in good agreement. In addition, since, in the absence of a puddle, the particle concentration appears to remain uniform throughout the cross section of the film, no axial particle segregation is predicted to occur nor has it ever been seen experimentally, even when an axial viscosity variation is imposed on the flow by cooling a preselected portion of the cylinder.