"STARTUP STEADY SHEAR FLOW FROM THE OLDROYD 8-CONSTANT FRAMEWORK"

Dear All,

Mathematics, Mechanics, and Materials Unit (Fried Unit) would like to invite you to a Seminar by Prof. Jeffrey Giacomin from Chemical Engineering, and Mechanical and Materials Engineering at Queen’s University.

Date: Wednesday, November 7, 2018
Time: 14:00-14:30
Venue: C015, Level C, Lab1

Speaker:
Jeffrey Giacomin
Professor of Chemical Engineering and of Mechanical and Materials Engineering at Queen’s University

Title:
STARTUP STEADY SHEAR FLOW FROM THE OLDROYD 8-CONSTANT FRAMEWORK

Abstract:
One good way to explore fluid microstructure, experimentally, is to suddenly subject the fluid to a large steady shearing deformation, and to then observe the evolving stress response. If the steady shear rate is high enough, the shear stress and also the normal stress differences can, overshoot, and then, they can even undershoot. We call such responses nonlinear, and this experiment shear stress growth. This paper is devoted to providing exact analytical solutions for interpreting measured nonlinear shear stress growth responses. Specifically, we arrive at the exact solution for the Oldroyd 8-constant constitutive framework. This framework includes a rich diversity of special cases, including, for instance, the corotational Jeffreys and the Johnson-Segalman fluids. In this paper, we test these special cases against the measured behaviours of wormlike micellar solutions. We find that, at high shear rates, these  solutions overshoot in stress growth without subsequent undershoot. We find that the corotational Jeffreys fluid to be inadequate at high shear rates for shear stress overshoots, and that the  JohnsonSegalman predicts these more accurately.