Start
Apr 16, 2015 - 17:15
End
Apr 16, 2015 - 18:15
Venue
Main Auditorium Victor Menezes Convention Centre
Event Type
Speaker
Prof. Prabhu R. Nott Department of Chemical Enginering Indian Institute of Science Bangalore
Title
How similar to fluids are collections of grains? Similar and very different.
Abstract: Collections of grains (such as sand food grains mineral ores) often exhibit fluid-like behaviour despite the obvious differences between macroscopic grains and fluid molecules. But there are qualitative differences in the details of their kinematic and stress response. The lecture will highlight the broad features of granular flows their importance to industrial processes and very briefly outline the continuum-mechanical models that describe them. Prof. Prabhu R. Nott will describe recent experiments that reveal the kinematics and stress in sheared granular materials and compare it with that of fluids. The rheological properties of fluids are measured in devices that generate a class of simple flows called viscometric flows — the cylindrical Couette cell consisting of two coaxial cylinders is such a device. When a fluid is sheared by rotating the inner cylinder the streamlines are circular for low angular speeds; above a critical speed a centrifugal instability causes a secondary flow in the form of a vertical train of counter-rotating Taylor vortices. In contrast experiments on dense granular materials show a large single vortex that spans the entire column. The sense of the vortex is opposite to that of the Taylor vortex and is present at very small angular speeds suggesting that it is not the result of an instability but an inherent feature of the flow. These observations are not explained by the existing continuum-mechanical models for granular materials. The speaker in his lecture will be suggesting how our anomalous observations may be explained and comment on its relevance to the rheometry of granular materials.About the Speaker: Prof. Prabhu R. Nott is a faculty member of Chemical Engineering at the Indian Institute of Science where he has worked for the past 21 years. He received his PhD from Princeton University and held a post doctoral fellowship at Caltech. He has held visiting positions at Caltech the University of California at San Diego and Aix-Marseille Université. He conducts research on complex fluids and on the motility and quorum-sensing of bacteria. Note : Attendance is mandatory for CL702/CL704 participants