摘要
本文采用多松弛格子Boltzmann模型数值研究了三维方管中交错排列的扁球颗粒的动态自组装行为,着重考虑了雷诺数(Re)、平均长度分数(<L_(f>)和颗粒纵横比(AR)对整个迁移过程、分布模态和平均轴向颗粒间距(d_(i)/D)_(umi)的影响.这里颗粒AR是通过改变扁球颗粒的极轴半径来调节,相应的赤道半径保持不变.交错扁球颗粒链的整个形成过程包括向平衡位置的惯性迁移和在流向方向上的动态自组装行为.目前结果表明分布模态和交错扁球颗粒链的(d_(i)/D)_(umi)明显依赖于(L_(f))和Re.在当前研究的参数范围内,在中等(L_(f))下高Re或高(L_(f))时,颗粒链呈现连续模态.此时,所有轴向颗粒间距达到相同的值.随着<L_(f))增加,相应的(d_(i)/D)_(umi)减少.在中等(L_(f))下小Re或低(L_(f))时,颗粒链呈现间断模态。此模态下,(d_(i)/D)_(uni)主要随Re线性增加.此外,当(L_(f))=0.4时,AR从0.5变成0.75或1不会改变颗粒链的模态,即Re≤40时为间断模态,而Re≥60时为连续模态.在间断模态下,(d_(i)/D)_(umi)对AR并没有体现出明显的线性依赖关系.由于旋转直径相同,相同Re下颗粒链的面平衡位置几乎不受AR的影响.
The dynamic self-assembly of staggered oblate particle train in a three-dimensional square duct is numerically investigated via the multiple-relaxation-time lattice Boltzmann method.The present study aims to explore the effect of the Reynolds number(Re),average length fraction(〈L_(f)〉),and particle aspect ratio(AR)on the entire migration process,distribution pattern,and mean axial interparticle spacing(d_(i)/D)_(uni).Herein,it should be noted that AR is varied by changing the polar radius of the oblate particle,whereas the corresponding equatorial radius,i.e.,the rotational diameter,keeps unchanged.The whole forming process of the staggered oblate particle train consists of the inertial migration toward the face equilibrium positions and the dynamic self-assembly in the streamwise direction.Present results indicate that the distribution pattern and(di/D)uni of the staggered oblate particle train are significantly dependent on〈L_(f)〉and Re.Within the parameter range studied,continuous pattern,with all inter-particle distances being identical,preferentially appears in high〈L_(f)〉and large Re for moderate〈L_(f)〉.As〈L_(f)〉increases,the corresponding(d_(i)/D)_(uni)≈1/〈L_(f)〉decreases.Discontinuous pattern,with varying inter-particle distances,occurs in low〈L_(f)〉and small Re for moderate〈L_(f)〉,where(d_(i)/D)_(uni) is mainly determined by Re.The data show that(di/D)uni increases linearly with Re.Furthermore,at〈L_(f)〉=0.4,particles with AR=0.5,0.75,1 all self-organize into staggered train with the discontinuous pattern for Re≤40 with a non-monotonic dependence of(d_(i)/D)_(uni) on AR,while they are in the continuous pattern for Re≥60.Nevertheless,due to the same rotational diameter,particles with different AR yield almost the same face equilibrium positions.
作者
李洋
夏振华
王连平
Yang Li;Zhenhua Xia;Lian-Ping Wang(State Key Laboratory of Fluid Power and Mechatronic Systems and Department of Engineering Mechanics,Zhejiang University,Hangzhou310027,China;Department of Mechanics and Aerospace Engineering,Southern University of Science and Technology,Shenzhen 518055,China)
基金
This work was supported by the National Natural Science Foundation of China(Grant No.91852205).
