Effect of DLVO interactions on the rheology and microstructure of non-Brownian suspensions
Effect of DLVO interactions on the rheology and microstructure of non-Brownian suspensions
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DOI：
10.1007/s10409-023-22469-x
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发表时间：
2023-04
影响因子：
3.5
通讯作者：
Jinhe Wang;Dingyi Pan
中科院分区：
文献类型：
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作者：
Jinhe Wang;Dingyi Pan
悬浮液的宏观流变特性往往与其微观结构的变化密不可分，大量的实验研究表明DLVO（Derjaguin-Landau-Verwey-Overbeek）相互作用，即悬浮液中颗粒表面电荷引起的微观排斥力和吸引力，对悬浮液的微观结构，特别是对团簇的形成有重要影响。在这项研究中，非布朗悬浮液的流变特性和它们的微观结构相结合的DLVO相互作用与流体力学和摩擦接触的数值模拟研究。不同的机制已被确定为不同的排斥性和粘性悬浮液的流变响应，揭示了显着的关联颗粒簇的演变和悬浮液流变学。在排斥系统中，排斥力和流体动力之间的竞争以及由此产生的最小颗粒分离分布的变化是低剪切速率下第一剪切稀化的原因。在高剪切速率下观察到剪切增稠，并且由颗粒接触主导。增强吸引力引起悬浮液的粘度，同时模糊剪切增稠，并且颗粒甚至在第一剪切稀化条件下进行接触。第二法向应力差随粘度的变化规律相似，而第一法向应力差主要受波动控制。微观结构分析表明，在排斥性悬浮液中出现了摩擦团簇，随着剪切速率的增加，摩擦团簇的数量和尺寸都在增加。另一方面，在强粘性悬浮液中的团簇破碎成较小的团簇，导致粘度降低。形状各向异性的计算表明，摩擦集团排斥悬浮液往往会扩大均匀的模拟盒，而在高吸引力的强度，集团变形更圆柱形时，强烈剪切。微观结构的研究可以从根本上弥合微观演化与宏观流变响应之间的差距，从而有助于建立非布朗悬浮液的本构模型。
The macroscopic rheological properties of suspensions are often inextricably related to changes in their microstructure, and a number of experimental studies have demonstrated the significant influence of DLVO (Derjaguin-Landau-Verwey-Overbeek) interactions, namely microscopic repulsive and attractive forces due to surface charge on particles in suspensions, on the microstructure of suspensions, especially on cluster formation. In this study, the rheological properties of non-Brownian suspensions and their microstructures are investigated by numerical simulations combining DLVO interactions with hydrodynamics and frictional contacts. Different mechanisms have been identified to account for diverse rheological responses of repulsive and adhesive suspensions, revealing a significant association between the evolution of particle clusters and suspension rheology. In repulsive systems, competitions between repulsive and hydrodynamic forces and the resulting change in the distribution of minimum particle separation are responsible for the first shear thinning at low shear rates. Shear thickening is observed at high shear rates and is dominated by particles contacts. Enhancing attractive forces give rise to the viscosity of the suspensions while obscuring shear thickening, and particles make contacts even at the first shear thinning conditions. The second normal stress difference exhibit similar evolution with viscosity while the first normal stress difference is mainly dominated by fluctuations. Microstructure analysis shows frictional clusters appear in repulsive suspensions with growth in both quantity and size as shear rate increases. Clusters in strongly adhesive suspensions, on the other hand, break into smaller ones, resulting in a viscosity reduction. The calculation of the shape anisotropy indicates that frictional clusters in repulsive suspensions tend to expand uniformly in simulation box whereas at high attractive strength, clusters deform more cylindrical when strongly sheared. Our studies in microstructure can fundamentally help in bridging the gap between microscale evolution and macroscale rheological responses, thus contributing to the foundation of the constitutive model of non-Brownian suspensions.