Virtual Seminar"Elastic instabilities and bifurcations in flows of wormlike micellar solutions: a numerical perspective with two-species constitutive model for wormlike micelles"Chandi Sasmal
Micro/Bio/Nanofluidics (Shen) Unit would like to invite you to the virtual seminar by Prof. Chandi Sasmal on August 30 (Monday)
Date: Monday, August 30, 2021
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Meeting ID: 826 6767 9268
Department of Chemical Engineering
Indian Institute of Technology, Ropar, India
Elastic instabilities and bifurcations in flows of wormlike micellar solutions: a numerical perspective with two-species constitutive model for wormlike micelles
The addition of a small amount of highly flexible surfactant molecules into a solvent like water dramatically influences the flow characteristics of the resulting solution in a broad spectrum of measurable scales. Beyond a critical concentration, these amphiphilic surfactant molecules spontaneously self-assemble and form a large aggregate called wormlike micelles. These wormlike micellar solutions (WLM) are widely used in scores of industrial settings, such as in the petroleum industry in the enhanced oil recovery process, as drag reducing agents, in cosmetics and pharmaceutical industries, in coating and paints industries, etc. The rheological behavior of these micellar solutions is found to be more complex and interesting than that seen for polymer solutions or melts under otherwise identical conditions. This is due to the presence of continuous scission and reformation of these micelles in a flow field, which is unlikely to happen for polymers due to the presence of a strong covalent backbone. Therefore, from the past several decades, a significant number of experimental studies have been carried out to study the flow characteristics of these wormlike micellar solutions in different benchmark geometries. In comparison to this, the corresponding investigations based on either theoretical analysis or numerical simulations are very limited for these WLM solutions. This is mainly due to the unavailability of a suitable constitutive equation that can consider both the scission and reformation dynamics of these micelles. Among a very few, Vasquez-Cook-McKinley (VCM) is one of the two-species models which considers both the breakage and reformation dynamics of micelles, and also shows the ability to capture some typical rheological behavior of WLM solutions, like shear-thinning, extensional hardening and subsequent thinning, etc. seen in standard rheological flows. Additionally, this model also shows its potential to reproduce some of the experimental observations seen in complex geometries with non-homogeneous flow fields. In this talk, I shall discuss the flow behavior of these wormlike micellar solutions based on this two-species VCM model in the vanishingly small Reynolds number regime in some benchmark geometries, which are very often used to study the flow behavior of complex fluids, for instance, cross slot cell or microcylinders confined in a channel. In particular, my talk will focus on the phenomena of elastic instabilities and bifurcations, which have been seen in many experimental investigations dealing with wormlike micellar solutions.
Dr. Sasmal did his undergraduate from the University of Calcutta, India, in 2009 and then did his masters from the Indian Institute of Technology Kanpur (IITK), India, in 2011. After that, he completed his PhD from the Monash University, Australia, in 2016 all from the Chemical Engineering discipline. In 2018, he has joined as an Assistant Professor in the Department of Chemical Engineering, Indian Institute of Technology Ropar (IIT Ropar), India, after having post-doctoral research experience from the University of California, Santa Barbara USA. His research interests lie in complex fluids, polymer physics, computational fluid dynamics, Brownian dynamics, microfluidics, etc. He was awarded with the Australian Postgraduate Award (APA) and International Postgraduate Research Scholarship (IPRS) during his doctoral study. Recently, he has been awarded the Early Career Research (ECR) award from the Govt. of India at IIT Ropar.
Prof. Amy Shen