Effects of elasticity on high Reynolds number instabilities<br/><br/> in Taylor-Couette flow

Monday, October 12, 2009 - 9:00am - 9:40am
EE/CS 3-180
Susan Muller (University of California, Berkeley)
Keywords: Elasticity, viscoelastic instability, nonlinear transitions,
drag-reducing polymers

Abstract: Taylor-Couette flow (i.e., flow between concentric, rotating
cylinders) has long served as a paradigm for studies of
hydrodynamic stability. For Newtonian fluids, the rich cascade
of transitions from laminar, Couette flow to turbulent flow
occurs through a set of well-characterized flow states that
depend on the Reynolds numbers of both the inner and outer
cylinders (Rei and Reo). While extensive work has been done on
(a) the effects of weak viscoelasticity on the first few
transitions for Reo = 0 and (b) the effects of strong
viscoelasticity in the limit of vanishing inertia
(Rei and Reo
both vanishing), the viscoelastic Taylor-Couette problem
presents an enormous parameter space, much of which remains
completely unexplored. Here we describe our recent experimental
efforts to examine the effects of drag reducing polymers on the
complete range of flow states observed in the Taylor-Couette
problem. Of particular importance in the present work is 1)
the rheological characterization of the test solutions via both
shear and extensional (CaBER) rheometry, 2) the wide range of
parameters examined, including Rei, Reo, and Elasticity number
El, and 3) the use of a consistent, conservative protocol for
accessing flow states. We hope to gain insights into the roles
of weak elasticity and of co- and counter-rotation on nonlinear
transitions in this flow.
MSC Code: