CHE Seminars  

Speaker Dr. Arijit Sarkar
Postdoctoral research associate at University of Pennsylvania, USA
Topic A model for complex flows of soft glassy materials
Date 21,April 2015 (Tuesday)
Place IME C5
4 pm. - 5 pm.

Deformable nano-carriers are used in a range of applications like drug delivery, batteries, oil exploration etc. Under flow such microstructures tend to align withthe flow. The rheological characterization of a class of such nano-carriers indicates that their response to time-dependent simple shearing flows is similar to soft glasses, which have been described by the Soft Glassy Rheology (SGR) model. The model considers a distribution of mesoscopic fluid elements that hop from trap to trap at a rate, which is enhanced by the work done to strain the fluid element. We introduce a tensorial model based on soft glassy fluid behavior. It includes an anisotropic hopping rate that depends on the orientation of the fluid elements relative to the mean stress field. This anisotropic hopping rate changes the transport properties. The predictions are compared against experimental observations of solvent-free nanoparticle hybrid material, developed by Lynden Archer and co-workers. As an application of this model we consider the flow of a soft glassy material through a dilute fixed bed of isotropically oriented fibers. The flow of soft glassy fluids in a porous medium is strongly influenced by the presence of regions of strong elongation of the fluid and by the transient nature of the flow. The exponential dependence of the hopping rate on strain leads to an SGR strain that grows logarithmically with Deborah number at high Deborah numbers. SGR fluids having a broad range of trap energies flowing through fixed beds can exhibit a range of rheological behaviors ranging from a power law response to Newtonian behavior.

Arijit Sarkar is a postdoctoral research associate at University of Pennsylvania. He has worked in the area of drying colloidal dispersion, non-Newtonian fluid flow. Most recently, his research has focused on biological application of deformable nano-carriers. Prior to joining University of Pennsylvania in 2013, he was a postdoc at Cornell University from 2011 to 2013 and served Praxair as an engineer from 2005 to 2006. Arijit Sarkar has received a PhD from Indian Institute of Technology Bombay in 2011.

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