Drag force in granular shear flows: regimes, scaling laws and implications for segregation
Drag force in granular shear flows: regimes, scaling laws and implications for segregation
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DOI：
10.1017/jfm.2022.706
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发表时间：
2022-09
影响因子：
3.7
通讯作者：
L. Jing;J. Ottino;P. Umbanhowar;Richard M. Lueptow
中科院分区：
文献类型：
--
作者：
L. Jing;J. Ottino;P. Umbanhowar;Richard M. Lueptow
摘要用离散元方法模拟了稠密颗粒剪切流中球形入侵者所受的阻力。三个制度的入侵者动态观察到的阻力（或相应的入侵者速度）和流量惯性数的大小取决于：波动为主的小阻力制度;粘性制度的中间阻力;和惯性（空腔形成）制度的大阻力。从粘性状态（线性力-速度关系）到惯性状态（二次力-速度关系）的转变进一步取决于惯性数。尽管这些不同的入侵者动态，我们发现入侵者之间的定量相似性颗粒剪切流和斯托克斯阻力的入侵者雷诺数跨越五个数量级的粘性流体中的球体上的阻力。除了这个一阶描述，一个修改后的斯托克斯阻力模型的开发，占二次依赖的阻力系数的惯性数和入侵者的大小和密度比。当阻力模型与隔离力模型相结合的入侵者在稠密的颗粒流，它是可以预测的速度重力驱动的隔离的入侵者颗粒在剪切流模拟。
Abstract The drag force on a spherical intruder in dense granular shear flows is studied using discrete element method simulations. Three regimes of the intruder dynamics are observed depending on the magnitude of the drag force (or the corresponding intruder velocity) and the flow inertial number: a fluctuation-dominated regime for small drag forces; a viscous regime for intermediate drag forces; and an inertial (cavity formation) regime for large drag forces. The transition from the viscous regime (linear force-velocity relation) to the inertial regime (quadratic force-velocity relation) depends further on the inertial number. Despite these distinct intruder dynamics, we find a quantitative similarity between the intruder drag in granular shear flows and the Stokesian drag on a sphere in a viscous fluid for intruder Reynolds numbers spanning five orders of magnitude. Beyond this first-order description, a modified Stokes drag model is developed that accounts for the secondary dependence of the drag coefficient on the inertial number and the intruder size and density ratios. When the drag model is coupled with a segregation force model for intruders in dense granular flows, it is possible to predict the velocity of gravity-driven segregation of an intruder particle in shear flow simulations.