Rigid ring-shaped particles that align in simple shear flow
Rigid ring-shaped particles that align in simple shear flow
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在简单剪切流中排列的刚性环形颗粒
DOI：
10.1017/jfm.2013.53
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发表时间：
2013
影响因子：
3.7
通讯作者：
A. Stroock
中科院分区：
文献类型：
--
作者：
Vikram Singh;D. Koch;A. Stroock
摘要 大多数刚性、无扭矩、低雷诺数、轴对称粒子在简单剪切流中经历时间周期翻滚运动，其对称轴遵循一组闭合的杰弗里轨道。我们已经确定了一类刚性的环状粒子，其对称轴在速度梯度方向附近达到永久对齐，粒子平面在流涡平面附近对齐。小颗粒纵横比（平行于对称轴的长度与垂直于轴的直径之比）的渐近分析表明，外缘较薄、内缘较厚的环截面适当的不对称性会导致其向与涡度相反的方向旋转的趋势；这种趋势可以平衡与颗粒有限厚度相关的通常旋转速率。有限粒子纵横比的边界积分计算用于确定导致对准行为和对准粒子的对称轴的最终方向的纵横比和不对称程度的条件。排列粒子遵循类似于小分子向列液晶指向矢的莱斯利-埃里克森方程的运动方程。然而，虽然指向矢的排列是由分子间相互作用产生的，但环状粒子的排列仅是由于其在低雷诺数流中的固有旋转运动。
Abstract Most rigid, torque-free, low-Reynolds-number, axisymmetric particles undergo a time-periodic tumbling motion in a simple shear flow, with their axes of symmetry following a set of closed Jeffery orbits. We have identified a class of rigid, ring-like particles whose axes of symmetry instead reach a permanent alignment near the velocity gradient direction with the plane of the particle aligning near the flow–vorticity plane. An asymptotic analysis for small particle aspect ratio (ratio of length parallel to the axis of symmetry to diameter perpendicular to the axis) shows that an appropriate asymmetry of the ring cross-section with a thinner outer edge and thicker inner edge leads to a tendency to rotate in a direction opposite to the vorticity; this tendency can balance the usual rotation rate associated with the finite thickness of the particle. Boundary integral computations for finite particle aspect ratios are used to determine the conditions of aspect ratio and degree of asymmetry that lead to the aligning behaviour and the final orientation of the axis of symmetry of the aligned particles. The aligning particle follows an equation of motion similar to the Leslie–Erickson equation for the director of a small-molecule nematic liquid crystal. However, whereas the alignment of the director arises from intermolecular interactions, the ring-like particle aligns solely due to its intrinsic rotational motion in a low-Reynolds-number flow.
影响因子：
56.9
作者：
Edwards, DA;Hanes, J;Langer, R
通讯作者：
Langer, R