Townsend Adam K, Wilson Helen J
Department of Mathematics, University College London, Gower Street, London, WC1E 6BT UK.
J Eng Math. 2017;107(1):179-200. doi: 10.1007/s10665-017-9935-5. Epub 2017 Sep 15.
In recent experiments, Blanc et al. (J Fluid Mech 746:R4, 2014) dropped a heavy sphere through a concentrated suspension of smaller, neutrally buoyant particles. They found that the application of a lateral oscillatory shear flow caused the heavy ball to fall faster on average, and that for highly concentrated suspensions, at certain moments of the cycle of shear oscillation, the heavy ball moved upwards. We use Stokesian Dynamics to model these experiments and other related scenarios. We show how the motion of the heavy particle and the microstructure of the suspension depend on two key dimensionless parameters: the frequency of the oscillations (relative to a typical settling time) and the strength of repulsive interparticle forces, relative to the buoyancy-adjusted weight of the heavy ball. We offer a mechanism which describes some of the observed behaviours: the formation and breakup of vertical repulsion chains.
在最近的实验中，布兰克等人（《流体力学杂志》746:R4，2014年）让一个重球体穿过由较小的中性浮力颗粒构成的浓缩悬浮液。他们发现，施加横向振荡剪切流会使重球平均下落得更快，而且对于高浓度悬浮液，在剪切振荡周期的某些时刻，重球会向上移动。我们使用斯托克斯动力学对这些实验及其他相关情形进行建模。我们展示了重颗粒的运动和悬浮液的微观结构如何取决于两个关键的无量纲参数：振荡频率（相对于典型沉降时间）以及颗粒间排斥力的强度（相对于重球经浮力调整后的重量）。我们提出了一种机制来描述一些观察到的行为：垂直排斥链的形成与断裂。
