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(0<Re 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.
A thorough understanding of the behavior of particles freely suspended in a shear flow is fundamentallyimportant for understanding and predicting flow behavior of particle suspensions.The motion of particles is very complexwhen the fluid inertia is taken into account.In the present study,the lattice Boltzmann method has been used to simulatethe rotation of an elliptical particle in simple shear flow at intermediate Reynolds numbers.Firstly,the e ect of theReynolds number(0<Re6170)has been studied.Results show that the particle rotates periodically when Re is smallerthan a critical value.The orientation of the particle at which the particle has its minimum angular velocity decreases as Reincreases,which has a piecewise linear relationship with Re.Moreover,the rotation period has a power-law relationshipwith Re.The larger Re is,the larger the rotation period is.However,when Re is greater than the critical value,theelliptical particle will reach a steady state.Results show that the final orientation of the elliptical particle has a power-lawrelationship with Re for the steady state.The larger Re is,the smaller the orientation is.Secondly,the e ect of the ratioof major axis/minor axis(16610)has also been studied.It shows that there is also a power-law relationshipbetween the rotation period and.The larger the value of is,the smaller the rotation period is.Similarly,when is greater than a critical value,the elliptical particle does not rotate.The final orientation of the elliptical particle has apower-law relationship with.The larger the value of is,the smaller the orientation is.Furthermore,it also shows thatthe overshoot is observed when the elliptical particle is rotating if Re is larger enough.
作者
陈荣前
聂德明
Chen Rongqian;Nie Deming(College of Metrology and Measurement Engineering,China Jiliang University,Hangzhou 310018,China)
出处
《力学学报》
EI
CSCD
北大核心
2017年第2期257-267,共11页
Chinese Journal of Theoretical and Applied Mechanics
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
