Intriguing viscosity effects in confined suspensions: A numerical study

作     者：Davit, Y. Peyla, P. 

作者机构：Univ Grenoble 1 Spectrometrie Phys Lab F-38402 St Martin Dheres France 

出 版 物：《EPL》 (欧洲物理学快报)

年 卷 期：2008年第83卷第6期

页      面：64001-64001页

核心收录：

学科分类：07[理学] 0702[理学-物理学] 

主　　题：Soft matter liquids and polymers Fluid dynamics Computational physics 

摘      要：The effective viscosity of dilute and semi-dilute suspensions in a shear flow in a microfluidic configuration is studied numerically. The suspension is composed of monodisperse and non-Brownian hard spherical buoyant particles confined between two walls in a shear flow. An abrupt change of the viscosity behaviour occurs with strong confinements: when the wall-to-wall distance is below five times the radius of the particles, we obtain a change of the sign of the contribution of the hydrodynamic interactions to the effective viscosity. This effect is the macroscopic counterpart of the peculiar micro-hydrodynamics of confined suspensions due to the influence of walls. In addition, for higher concentrations (above 25%), we find that the viscosity meets a minimum when the inter-wall distance is around five times the sphere radius. This phenomenon is reminiscent of the Fahraeus-Lindqvist effect for blood confined in small capillaries. However, we show that for sheared confined semi-dilute suspensions, the physical origin of this minimum is not due to a migration effect but to the change of hydrodynamic interactions. Copyright (c) EPLA, 2008