Physics Seminar of the School of Physical Sciences
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Flow of particulate systems: from dry granular matter to shear thickening suspensions
Abhinendra Singh
City College of CUNY, New York
Date: September 13, 2016 (Wednesday)
Time: 16:00 hrs (4:00 pm)
Venue: Seminar Room, First Floor, School of Physical Sciences (SPS), JNU
Abstract: Particulate systems (such as tea, salt, sugar, sand, toothpaste, clay etc.) are omnipresent in our daily life. Computer simulations have turned out to be a powerful tool to investigate the flow of such systems. My talk will be divided into two parts. In the first part we will ask questions like `when does the flow start?', `what is the stress required to keep them flowing?' etc. The effect of microscopic properties (such as particle friction, cohesion or softness) on the bulk yield for both slow and fast granular flows will be discussed. We show that the yield strength can be directly related to the contact network anisotropy connecting widely different particle and bulk scales. In the second part I will talk about discontinuous shear thickening which is a phenomenon where viscosity of a suspension increases by a order of magnitude above a `critical shear rate'. This mechanism has recently been linked to a transition from `frictionless rheology', where interactions between suspended particles are lubricated, to `frictional rheology', where particles make unlubricated frictional contacts. Our simulations have been successful in quantitatively reproducing the experimentally observed non-Newtonian behaviour of thickening. A constitutive model to predict the steady state flow of dense frictional suspensions under simple shear will be presented.
