椭圆颗粒在剪切流中旋转特性的数值研究

发布时间：2018-11-25 13:26

【摘要】：研究颗粒在流体剪切作用下的运动特性是理解和预测颗粒悬浮流流动行为的关键.当流体的惯性不能忽略时,颗粒的运动往往变得非常复杂.本文采用格子Boltzmann方法对中等雷诺数下椭圆颗粒在剪切流中的旋转运动进行了模拟.首先,研究了雷诺数(0Re 170)的影响,结果表明当雷诺数低于临界值时,颗粒以周期性的方式旋转,角速度最小时对应的长轴方向随着雷诺数的增大而逐渐远离水平方向,而且这一倾角与雷诺数呈分段线性关系;当雷诺数大于临界值时,椭圆形颗粒最终保持静止状态,且静止时的转角与雷诺数呈幂函数关系,雷诺数越大,转角越小,椭圆的长轴越远离水平位置.其次,研究了椭圆颗粒的长短轴之比α(1α10)的影响,结果表明颗粒旋转的周期与α呈幂函数关系,α越大,颗粒旋转周期越小.此外,当α超过临界值时,颗粒也在水平位置附近保持静止状态,此时的转角与α也呈幂函数关系,α越大,转角越小.研究还发现,当雷诺数较大时椭圆颗粒在旋转过程中会产生过冲现象.
[Abstract]:It is a key to understand and predict the flow behavior of suspensions by studying the motion characteristics of particles under the action of fluid shear. When the inertia of the fluid can not be ignored, the movement of particles often becomes very complicated. In this paper, the lattice Boltzmann method is used to simulate the rotational motion of elliptical particles in shear flow with medium Reynolds number. Firstly, the influence of Reynolds number (0Re 170) is studied. The results show that when Reynolds number is lower than the critical value, the particle rotates periodically, and the direction of the long axis moves away from the horizontal direction with the increase of Reynolds number. Moreover, there is a piecewise linear relationship between the inclination angle and Reynolds number. When the Reynolds number is larger than the critical value, the elliptical particle will remain at rest, and the angle of rotation and Reynolds number will be power function. The larger the Reynolds number is, the smaller the rotation angle is, and the longer the axis of the ellipse is far away from the horizontal position. Secondly, the effect of the ratio 伪 (1 伪 10) on the long axis of elliptical particles is studied. The results show that the period of particle rotation is a power function, and the larger a is, the smaller the rotation period of particles is. In addition, when 伪 exceeds the critical value, the particle also remains in a stationary state near the horizontal position, and the rotation angle is also a power function relationship with 伪. The larger 伪, the smaller the rotation angle. It is also found that when the Reynolds number is large, the elliptical particles will overshoot in the process of rotation.
【作者单位】：中国计量大学计量测试工程学院;
【基金】：国家自然科学基金(11272302,11132008) 浙江省自然科学基金(LY15A020004)资助项目
【分类号】：O357.1;O347.7

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