ABSTRACT

Granular materials, a collection of discrete macroscopic particles (e.g., sand, stones, nuts), occur widely in nature and are processed in various industrial applications. The complicated rheological behavior of these materials, coupled with the segregation (i.e., unmixing) of particles due to differences in density, size, shape etc. has puzzled the industry and academia alike. The first part of the talk will focus on these issues with a fluid mechanical perspective and the ideas of buoyancy and viscous drag are extended to dense flow of granular materials. Using the discrete element method (DEM) to simulate granular flow over an inclined plane, we calculate forces due to buoyancy and “viscous” drag on a heavy spherical tracer particle settling in the “granular fluid”. These fundamental insights about forces acting at the grain level help us formulate a segregation model for different density particle mixtures. Inspired from the “granular fluid” analogy, we extend the viscoplastic rheology of mono-dispersed dense granular flows to the generic case of mixtures of particles differing in size and/or density. By combining the new mixture rheological model with the density segregation model, a complete theoretical description of the flow of binary mixture of different density particles is achieved. The second part of the talk will focus on a novel, facile method for achieving antifouling/self-cleaning surfaces for microfluidic applications. Inspired by biological organisms that utilize actively beating cilia for fouling prevention, we show that similar effects can be achieved by passive, artificial cilia by utilizing the oscillations in the ambient flow.

ABOUT THE SPEAKER

Dr. Anurag Tripathi completed his B.Tech. in 2005 from Chemical Engineering Department of Indian Institute of Technology Bombay. He obtained his PhD in 2011 with an “Excellence in PhD thesis in Chemical Engineering” award from IIT Bombay. He is currently working as a Post-Doctoral fellow in Chemical Engineering department, Swanson School of Engineering at University of Pittsburgh. His current research interests include the rheology of complex fluids, granular materials, fluid mechanics and microfluidics.