复杂颗粒悬浮液流变特性及其微介观机理研究综述

Rheological properties and micro-mesoscopic mechanisms of complex particle suspensions:A review

颗粒悬浮液由离散颗粒相和连续流体相构成,具有非牛顿、凝胶化等特殊的流变行为并在近年来受到广泛关注.大量研究表明,悬浮液组成和外场作用都影响其内部微观结构的形成或破坏,表现为宏观复杂的流变行为,因此建立微介观颗粒结构与宏观流变的联系是颗粒悬浮液研究的关键.本文从由刚性球形颗粒与不可压牛顿流体组成的理想颗粒悬浮液出发,介绍了其宏观流变理论与微观物理模型.在此基础上,分别从颗粒相、流体相和外场作用的角度综述了复杂颗粒悬浮液的研究进展.复杂颗粒相往往具有更加复杂的受力、变形和运动特征.我们重点介绍了非球形、柔性颗粒和活性颗粒三种类型颗粒悬浮液宏观流变性质与单颗粒动力学以及微介观结构的关联.对复杂流体相而言,我们归纳了流体相为纯黏性流体、屈服应力流体及黏弹性流体悬浮液黏度的研究进展,并介绍了引入第二连续相流体的毛细悬浮液的流变行为及其与液桥结构的联系.此外,我们从外场作用的角度,介绍了电、磁场等对流变性质的调控及恒压场剪切测试对稠密颗粒悬浮液本构模型的启发.最后,本文从颗粒相、流体相及本构理论的角度,对颗粒悬浮液研究的问题与前景进行了展望.

Particle suspensions with interesting rheological properties such as non-Newtonian behavior,gelation,and phase transitions consist of a discrete particle phase and a continuous fluid phase.In recent years,there has been a great deal of interest in understanding,predicting,and designing the rheological properties of particle suspensions.Numerous studies have shown that both flow and external field correlate to the construction or destruction of the internal microstructure of the suspension,which manifests itself in complex rheological behaviors at the macroscopic level,and thus establishing the correlation between micro-or mesoscopic particle structure evolution and macroscopic rheology is the key to the study of particle suspensions.This review starts from the ideal particle suspension consisting of monodispersed rigid spherical particles and an incompressible Newtonian fluid,the macroscopic rheological theory and the microphysical models are introduced.For particle suspensions with a low volume fraction(ϕ<0.15),the viscosity-volume fraction relationship can be obtained from Einstein’s analytical formula and its corrections.As the particle volume fraction increases,the flow disturbance generated by the particles,the hydrodynamic interaction and contact between particles becomes more significant.The empirical fitting based on experimental data and the numerical simulations based on lubricant dynamics(LD)-discrete element methods(DEM)are both capable of predicting the viscosity and non-Newtonian behavior of semi-dilute to dense particle suspensions.For more complex particle suspensions,we review the recent research progress from three different perspectives:The effects of particle phase,fluid phase and external fields.The complex particle phases tend to have more complicated forces,deformation and kinematic behaviors.We focus on the correlation of the macroscopic rheological properties of three types of particles,namely non-spherical(fine rod-like and lamellar particles),flexible and active particles,with the dynamics of single particles as well as with the micro-mesoscopic structure.For complex fluid phases,we summarize advances in experimental and numerical simulation studies of particle suspensions in non-Newtonian fluid phases.In addition,the macroscopic rheological behavior of capillary suspensions formed by a second continuous phase fluid and its relationship to microscopic capillary bridge forces and structures are presented.Furthermore,we summarize the effects of external fields on particle suspensions.The modulation of rheological properties by electric,magnetic and optical fields is presented.A pressure-constant test method is introduced which sheds light on the constitutive model of dense particle suspensions.Finally,this review provides a research outlook on the prospects of particle suspensions from the perspectives of particle phase,fluid phase and constitute theory.