ABSTRACT

Concentrated suspension of solid particles in viscous liquids has many practical applications in natural, industrial and biological systems. The rheology and dynamics of such suspensions are significantly different from that of equivalent homogeneous fluid. At moderate particle concentration the hydrodynamic interactions between the particles significantly alter the flow characteristics and we often observe many interesting phenomena, which are not seen in the flow of a Newtonian homogeneous fluid. In almost all practical applications the dynamics are mediated not just by the interaction of suspended particles with each other but also by the interactions of the particles with the confining boundaries. The influence of confining geometries on the dynamics of particles is even more important in micro- and bio-fluidics systems. There have been several experimental observations on the distinctive mechanisms in the wall-bounded suspensions, such as shear-induced migration of particles, apparent wall-slip, particle structuring etc. Besides the experimental investigations there has been significant number of studies based on particle level simulations as well as continuum simulations. Stokesian dynamics is a particle level mesh-free numerical technique similar to the molecular dynamics which is used for the simulation of particles in viscous liquids interacting via hydrodynamic and non-hydrodynamic forces. In this talk we shall discuss the application of Stokesian dynamics to study the rheology and dynamics of suspension of spherical as well as non-spherical particles. Characterization of shear induced particle migration and apparent wall slip in bounded flow of concentrated suspensions would be presented. Though, the Stokesian dynamics is quite accurate in capturing the many body hydrodynamic interactions, their use is limited to small number of particles due to large computational power and memory requirements. On the other hand continuum models allow simulation of realistic macroscopic problems in large systems which are of considerable interest. There are mainly two classes of continuum models to explain shear induced particle migration in concentrated suspensions: 'diffusive flux' and 'suspension balance' models. Both the models have been used extensively to study the unidirectional and steady flow in simple one and two dimensional geometries, while flow in complex geometries are not adequately addressed despite the fact that many processes involve flow of suspension through complex 3D geometries. We shall discuss the application of these models to understand particle migration in complex bifurcating channels which are common in micro-fluidic devices.

ABOUT THE SPEAKER

Dr. Anugrah Singh is presently working as Professor in the Department of Chemical Engineering at the Indian Institute of Technology Guwahati. He joined the institute in 2004. Prior to joining IIT Guwahati he worked as post-doctoral fellow at the Israel Institute of Technology, Technion, Israel. After finishing PhD in chemical engineering at the Indian Institute of Science, Bangalore in the year 2000 he joined Fluent India Pvt. Ltd. (now ANSYS) Pune as a CFD application engineer and worked there for 2 years. He holds B.Tech. and M.Tech. degrees in Petroleum Engineering from ISM Dhanbad. His current research interests are focused on studying the suspension flow using experimental techniques and CFD simulations.