Migration of particles undergoing pressure-driven flow in a circular conduit
Migration of particles undergoing pressure-driven flow in a circular conduit
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DOI：
10.1122/1.550863
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发表时间：
1997-05-01
影响因子：
3.3
通讯作者：
Altobelli, SA
中科院分区：
文献类型：
--
作者：
Hampton, RE;Mammoli, AA;Altobelli, SA
这项研究集中在圆形管道中缓慢的压力驱动弓中球体的中性浮力悬浮液的分离。在静态在线混合器上测量了不同长度的颗粒固相分数Phi和悬浮速度v的分布。在体积平均固体分数Phi(体积)(小于或等于Phi小于或等于0.5)的范围内和颗粒半径与圆形管道半径的两个不同比率R(a/R=0.0256和a/R=0.0625)上进行了实验。当phi(体积)大于或等于0.20时，颗粒迅速迁移到管道中心的低剪切速率区域。这种迁移导致了相对于均匀牛顿流体中观察到的抛物线剖面的v剖面的钝化。对于a/R比较小的流动几何形状，PHI分布在中心形成一个尖锐的最大值或尖点。在较高a/R的实验中观察到了粒子结构。p_i场和v场发展的入射长度分别是a/R和p_i(体相)的强函数。随着Phi和a/R的增大，L-Phi和L-v迅速减小。在我们的数据范围内，观察到v分布比Phi分布发展得更快。实验结果与完全发展的剪切诱导迁移(SIM)模型和悬浮平衡(SE)模型的流动预测进行了比较。在a/R越小时，SIM模型对实验结果的预测越准确。在较大的a/R下，SE模型能较好地预测实验结果的某些定性特征，但两个模型都不能提供很好的定量预测，特别是在低phi(体积)时。(C)1997年香港流变学学会。
This study focuses on the demixing of neutrally buoyant suspensions of spheres during slow, pressure driven Bows in circular conduits. Distributions of the solid fraction of particles, phi, and the suspension velocity, v, are measured at different lengths from a static in-line mixer. Experiments were conducted over a range of volume average solids fractions, phi(bulk) (0.10 less than or equal to phi less than or equal to 0.50), and at two different ratios of the particle radius, a, to the radius of the circular conduit, R (a/R = 0.0256 and a/R = 0.0625). At phi(bulk) greater than or equal to 0.20, the particles rapidly migrate to the low-shear-rate region in the center of the conduit. This migration results in a blunting of the v profile, relative to the parabolic profile observed in homogeneous Newtonian fluids. For the flow geometry with the smaller ratio of a/R, the phi profile builds to a sharp maximum or cusp in the center. Particle structures are observed in the experiments with the higher a/R. The entrance lengths for the development of the phi and v fields, L-phi and L-v, respectively, are strong functions of a/R and phi(bulk). L-phi and L-v rapidly decrease as phi and a/R increase. Over the range of our data, the v profiles are observed to develop more rapidly than the phi profiles. The experimental results are compared with fully developed flow predictions from the shear-induced migration (SIM) model and the suspension balance (SE) model. At the smaller a/R, the SIM model more accurately predicts the experimental results. At larger a/R, some qualitative features of the experimental results are better predicted by the SE model, however, neither model provides good quantitative predictions,especially at low phi(bulk). (C) 1997 The Society of Rheology.