Abstract
Pressure-driven flows of viscoelastic fluids in narrow non-uniform geometries are common in physiological flows and various industrial applications. For such channel flows, one of the main interests is understanding the relationship between the flow rate š¯‘˛ and the pressure drop Ī”š¯‘¯ under steady-state conditions. However, current numerical simulations using continuum-level constitutive models are insufficient to predict experimentally observed flow rateā€“pressure drop behavior of viscoelastic fluids in contracting geometries. In fact, there is a contradiction between experiments and simulations: while experiments show the increase in the flow resistance Ī”š¯‘¯/q, simulations predict its decrease.
In my talk, I will discuss our theoretical approach to understanding and potentially resolving this contradiction. I will present a theoretical framework for calculating the flow rateā€“pressure drop relation of viscoelastic fluids in arbitrarily shaped, narrow geometries using the Oldroyd-B constitutive model1.2,3. Since the Oldroyd-B model represents the simplest combination of viscous and elastic stresses, it is important to find the response of the simplest model before investigating more complicated constitutive equations. I will present a theory for low- and high-Deborah numbers, which is in excellent agreement with numerical simulations. I will show that for the flow-rate-controlled situation, the dimensionless pressure drop of the Oldroyd-B fluid in the contraction geometry monotonically decreases with the Deborah number and identify two physical mechanisms for such pressure drop reduction. We believe that our approach is important in providing insight into the cause of the disagreement between experiments and simulations and resolving it by accounting for additional microscopic features of polymer flows4.
About the Speaker
Evgeniy Boyko is an Assistant Professor of Mechanical Engineering at Technion. He heads of the Technion Complex Fluids Lab. Evgeniy is equally interested in understanding basic physical mechanisms related to fluid mechanics of non-Newtonian fluids and in leveraging them to improve existing applications and create new technologies using complex fluids. Currently, Evgeniy is the recipient of the Yigal Alon Fellowship from the Israeli Council for Higher Education. Evgeniy earned his B.Sc. (2015) and Ph.D. (direct track) (2020) from the Faculty of Mechanical Engineering at Technion. He was a postdoctoral research fellow at Purdue University in 2021-2022 and a postdoctoral research fellow at Princeton University in 2020-2021. He received the Adams Fellowship for Ph.D. studies, the Jacobs Publication Award, and the Rothschild, Zuckerman, Blavatnik, and Gilbreth Fellowships for postdoctoral studies. Recently, Evgeniy received the ISF grant and the BSF grant as part of the NSF-BSF collaborative program with Princeton University.
Host: Professor Jie Feng