Instabilities during batch sedimentation in geometries containing obstacles: A numerical and experimental study
Instabilities during batch sedimentation in geometries containing obstacles: A numerical and experimental study
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含有障碍物的几何形状中批量沉降过程中的不稳定性：数值和实验研究
DOI：
10.1002/fld.1483
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发表时间：
2007
影响因子：
1.8
通讯作者：
S. Altobelli
中科院分区：
文献类型：
--
作者：
R. Rao;L. Mondy;S. Altobelli
利用核磁共振流动可视化和颗粒迁移的连续水平数值模拟研究了非胶体颗粒悬浮液的批量沉降。实验方法给出了颗粒体积分数作为时间和位置的函数，从而为数值模型提供了验证数据。采用有限元方法对运动方程进行离散化，包括颗粒体积分数的演化方程和依赖于局部颗粒浓度的广义牛顿粘度方程。扩散通量方程基于菲利普斯模型（物理学）。流体A 1992；4:30-40)，包括Zhang和Acrivos （Int.）描述的沉积条件。J.多相流体；1994；20:579 - 591)。模型和实验以三种不同的几何形状使用，其中颗粒比悬浮流体重或轻，具体取决于实验：(1)在圆柱体中收缩沉降；(2)采用水平棒在水平圆筒内进行颗粒浮选；(3)围绕矩形包裹体浮选。在实验和模拟中，当高密度流体的区域位于低密度流体的区域之上时，都出现了二次流动。二次流动导致颗粒不均匀性、瑞利-泰勒不稳定性和再混合，尽管模拟中的影响比实验中的更明显。2007年由John Wiley & Sons出版。
Batch sedimentation of non‐colloidal particle suspensions is studied with nuclear magnetic resonance flow visualization and continuum‐level numerical modelling of particle migration. The experimental method gives particle volume fraction as a function of time and position, which then provides validation data for the numerical model. A finite element method is used to discretize the equations of motion, including an evolution equation for the particle volume fraction and a generalized Newtonian viscosity dependent on local particle concentration. The diffusive‐flux equation is based on the Phillips model (Phys. Fluids A 1992; 4:30–40) and includes sedimentation terms described by Zhang and Acrivos (Int. J. Multiphase Flow 1994; 20:579–591). The model and experiments are utilized in three distinct geometries with particles that are heavier and lighter than the suspending fluid, depending on the experiment: (1) sedimentation in a cylinder with a contraction; (2) particle flotation in a horizontal cylinder with a horizontal rod; and (3) flotation around a rectangular inclusion. Secondary flows appear in both the experiments and the simulations when a region of higher density fluid is above a lower density fluid. The secondary flows result in particle inhomogeneities, Rayleigh–Taylor‐like instabilities, and remixing, though the effect in the simulations is more pronounced than in the experiments. Published in 2007 by John Wiley & Sons, Ltd.