Fu Xueqiong, Liu Yanwei, Lu Jibao, Sun Rong
School of Civil Engineering and Architecture, Anyang Normal University, Anyang 455000, China; Shenzhen Institute of Advanced Electronic Materials, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518103, China.
College of Engineering, Peking University, Beijing 100871, China.
J Colloid Interface Sci. 2024 May 15;662:1044-1051. doi: 10.1016/j.jcis.2024.02.033. Epub 2024 Feb 5.
Shear thickening of multimodal suspensions has proven difficult to understand because the rheology depends largely on the microscopic details of stress-induced frictional contacts at different particle size distributions (PSDs). Our discrete particle simulations below a critical volume fraction ϕ over a broad range of shear rates and PSDs elucidate the basic mechanism of order-disorder transition. Around the theoretical optimal PSD (relative content of small particles ζ= 0.26), particles order into a layered structure in the Newtonian regime. At the onset of shear thickening, this layered structure transforms to a disordered one, accompanied by an abrupt viscosity jump. Minor increase in large-large particle contacts after the order-disorder transition causes apparent increase in radial force along the compressional axis. Bidisperse suspensions with less regular but stable layered structure at ζ= 0.50 show good fluidity in the shear thickening regime. This work shows that in inertial flows where particle collisions dominate, order-disorder transition could play an essential role in shear thickening for bidisperse suspensions.
多模态悬浮液的剪切增稠现象一直难以理解，因为其流变学很大程度上取决于不同粒径分布（PSD）下应力诱导摩擦接触的微观细节。我们在低于临界体积分数ϕ的情况下，针对广泛的剪切速率和粒径分布进行的离散颗粒模拟，阐明了有序-无序转变的基本机制。在理论最优粒径分布（小颗粒的相对含量ζ = 0.26）附近，颗粒在牛顿流体区域内排列成层状结构。在剪切增稠开始时，这种层状结构转变为无序结构，同时伴随着粘度的突然跃升。有序-无序转变后，大颗粒与大颗粒之间接触的轻微增加导致沿压缩轴方向的径向力明显增加。在ζ = 0.50时具有不太规则但稳定的层状结构的双分散悬浮液在剪切增稠区域表现出良好的流动性。这项工作表明，在颗粒碰撞占主导的惯性流中，有序-无序转变可能在双分散悬浮液的剪切增稠中起关键作用。
