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首页> 外文期刊>Journal of Non-Newtonian Fluid Mechanics >Numerical analysis of the motion of a single fiber interacting with a solid wall in a wall-bounded shear flow
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Numerical analysis of the motion of a single fiber interacting with a solid wall in a wall-bounded shear flow

机译：壁边剪切流动中单纤维相互作用的单纤维运动的数值分析

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摘要

In order to investigate the effect of a solid wall on the interaction between the motion of a fiber and a suspending fluid flow, direct numerical simulations of single-fiber dynamics in a wall-bounded shear flow are conducted. A Cartesian grid method using a consistent direct discretization approach and its extension to a moving boundary problem is used for accurate prediction of a three-dimensional fluid flow around a rotating fiber. The fiber is modeled as an ellipsoid with an aspect ratio ranging from 2 to 8, while the suspending fluid is assumed to be an incompressible Newtonian fluid with a particle Reynolds number of less than 0.1. After the validity of the simulations is ascertained in a far-field condition through comparisons with theoretical results, the wall effect on the fiber motion is investigated in detail. The wall effect appears when the minimum distance between the fiber and the wall c is less than 5 times the length of the major radius of the fiber b. The rotation period increases with decreasing fiber-wall distance and increasing aspect ratio, and the ratio of the rotation period with respect to the theoretical period is well normalized by (c/b)/(b/d), where d is the equivalent radius obtained from the cross-sectional area of the fiber. Based on visualization of the flow field, the fiber motion is found to be strongly affected by the hydrodynamic torque caused by the shear stress and the pressure distribution on the fiber surface. The pressure distribution acts as a decelerating torque on the fiber when the fiber is parallel to the wall, while it acts as an accelerating torque when the fiber is perpendicular to the wall. These pressure variations are augmented as the fiber-wall distance decreases, resulting in an increase in the rotation period as well as time-averaged fiber orientation in the streamwise direction.
机译：为了探讨固体壁对纤维运动和悬浮流体流动之间的相互作用的影响，进行了壁限剪切流中的单纤维动力学的直接数值模拟。使用一致直接离散化方法的笛卡尔栅格方法及其对移动边界问题的扩展用于精确预测旋转光纤周围的三维流体流动。纤维被建模为椭球，其纵横比范围为2至8，而悬浮液被假设是一种不可压缩的牛顿流体，粒子雷诺数小于0.1。通过与理论结果的比较在远场条件下确定模拟的有效性之后，详细研究了对纤维运动的壁效应。当光纤和壁C之间的最小距离小于纤维B的主半径的长度的5倍时，出现壁效应。旋转周期随着光纤壁距离和增加纵横比而增加，并且旋转周期相对于理论周期的比率良好地由（C / B）/（B / D）归一化，其中D是等效半径从纤维的横截面积获得。基于流场的可视化，发现光纤运动受到由剪切应力和纤维表面上的压力分布引起的流体动力扭矩的强烈影响。当纤维平行于壁时，压力分布用作纤维上的减速扭矩，而当纤维垂直于壁时，它用作加速扭矩。由于光纤壁距离减小，因此增加了这些压力变化，从而导致旋转周期的增加以及流动方向上的时间平均光纤取向。

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