Interface-resolved simulations of particle suspensions in Newtonian, shear thinning and shear thickening carrier fluids
Interface-resolved simulations of particle suspensions in Newtonian, shear thinning and shear thickening carrier fluids
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DOI：
10.1017/jfm.2018.532
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发表时间：
2017-11
影响因子：
3.7
通讯作者：
Dhiya Alghalibi;I. Lashgari;L. Brandt;S. Hormozi
中科院分区：
文献类型：
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作者：
Dhiya Alghalibi;I. Lashgari;L. Brandt;S. Hormozi
我们提出了一个数值研究的非胶体球形和刚性颗粒悬浮在牛顿，剪切变稀和剪切增稠流体采用浸没边界方法。我们考虑了一个线性库埃特配置，以探索广泛的固体体积分数（$0.1\leqslant \unicode[STIX]{x1 D 6 F7}\leqslant 0.4$）和颗粒雷诺数（$0.1\leqslant Re_{p}\leqslant 10$）。我们报告的固体和流体相的速度和固体体积分数的分布，并表明，接近边界的惯性效应导致在固体和流体相之间的显着的滑移速度。局部固体体积分数曲线表明靠近壁的颗粒分层，其随标称$\unicode[STIX]{x1 D 6 F7}$而增加。这一特征与限制效应有关。我们计算了局部应变率的概率密度函数，并将后者的平均值与Chateau等人（J. Rheol.，第52卷，2008年，pp. 489-506），表明在斯托克斯制度合理的协议。局部应变率的平均值和标准差均随固相体积分数的增大而增大，随Re_{p}的增大而减小。局部剪切速率的宽频谱及其对$\unicode[STIX]{x1 D 6 F7}$和$Re_{p}$的依赖性指出了局部剪切速率的平均值在估计这些非胶体复杂悬浮液的流变性方面的不足。最后，我们表明，在惯性的存在下，这些非胶体悬浮液的有效粘度偏离斯托克斯悬浮液。我们讨论了惯性如何影响的微观结构，并提供了一个缩放参数给封闭的牛顿和幂律悬浮液的悬浮剪切应力。应力封闭对于中等颗粒雷诺数O（Re_{p}）\sim 10$是有效的。
We present a numerical study of non-colloidal spherical and rigid particles suspended in Newtonian, shear thinning and shear thickening fluids employing an immersed boundary method. We consider a linear Couette configuration to explore a wide range of solid volume fractions ( $0.1\leqslant \unicode[STIX]{x1D6F7}\leqslant 0.4$ ) and particle Reynolds numbers ( $0.1\leqslant Re_{p}\leqslant 10$ ). We report the distribution of solid and fluid phase velocity and solid volume fraction and show that close to the boundaries inertial effects result in a significant slip velocity between the solid and fluid phase. The local solid volume fraction profiles indicate particle layering close to the walls, which increases with the nominal $\unicode[STIX]{x1D6F7}$ . This feature is associated with the confinement effects. We calculate the probability density function of local strain rates and compare the latter’s mean value with the values estimated from the homogenisation theory of Chateau et al. (J. Rheol., vol. 52, 2008, pp. 489–506), indicating a reasonable agreement in the Stokesian regime. Both the mean value and standard deviation of the local strain rates increase primarily with the solid volume fraction and secondarily with the $Re_{p}$ . The wide spectrum of the local shear rate and its dependency on $\unicode[STIX]{x1D6F7}$ and $Re_{p}$ point to the deficiencies of the mean value of the local shear rates in estimating the rheology of these non-colloidal complex suspensions. Finally, we show that in the presence of inertia, the effective viscosity of these non-colloidal suspensions deviates from that of Stokesian suspensions. We discuss how inertia affects the microstructure and provide a scaling argument to give a closure for the suspension shear stress for both Newtonian and power-law suspending fluids. The stress closure is valid for moderate particle Reynolds numbers, $O(Re_{p})\sim 10$ .