Shear flows of nematic polymers. I. Orienting modes, bifurcations, and steady state rheological predictions

1993 ◽  
Vol 37 (2) ◽  
pp. 289-314 ◽  
Author(s):  
Yalda Farhoudi ◽  
Alejandro D. Rey
Keyword(s):  
Steady State ◽  
Shear Flows ◽  
Nematic Polymers

Transient and steady state behaviors of rapid granular shear flows

2005 ◽  
Vol 39 (3) ◽  
pp. 554-563 ◽  
Author(s):  
P. Jalali ◽  
J. Ritvanen ◽  
P. Sarkomaa
Keyword(s):  
Steady State ◽  
Shear Flows ◽  
Granular Shear ◽  
Transient And Steady State

An investigation on modelling and measurements of transient elongational rheology of polymer melts by SER testing platform

e-Polymers ◽  
2009 ◽  
Vol 9 (1) ◽  
Author(s):  
Mahmoud Rajabian ◽  
Ghassem Naderi ◽  
Hamid Piroozfar ◽  
Mohammad H. Beheshty ◽  
Mohammad Samadfam
Keyword(s):  
Steady State ◽  
Simple Shear ◽  
Shear Flows ◽  
Polymer Melts ◽  
Elongational Viscosity ◽  
Extensional Viscosity ◽  
Molten State ◽  
Diffusion Term ◽  
Hencky Strain ◽  
Elongational Rheology

AbstractTransient elongational rheology of PP is investigated experimentally. A specifically designed fixture consisting of two drums mounted on a TA Instruments ARES rotational rheometer was used to measure the transient uniaxial extensional viscosity of two commercial grades polypropylene in the molten state. The Hencky strain was varied from 0.003 to 2 s-1 and the temperature was fixed at 180 oC. The measurements show that the steady state elongational viscosity was reached at the measured Hencky strains for polypropylene. Eslami and Grmela have recently introduced a reptation diffusion term arising from the intermolecular chain forces into the rigid FENE-P dumbbells model. The same approach has been used in this study to interpret the transient rheological data in both shear-free and simple shear flows.

TRANSIENT AND STEADY-STATE DYNAMICS OF GRANULAR SHEAR FLOWS

2001 ◽  
Vol 04 (04) ◽  
pp. 369-377 ◽  
Author(s):  
W. LOSERT ◽  
G. KWON
Keyword(s):  
Steady State ◽  
Shear Band ◽  
Shear Flow ◽  
Opposite Direction ◽  
Shear Flows ◽  
Lag Time ◽  
Fast Imaging ◽  
Shear Surface ◽  
Granular Shear ◽  
Transient And Steady State

The initiation and steady-state dynamics of granular shear flow are investigated experimentally in a Couette geometry with independently moveable outer and inner cylinders. The motion of particles on the top surface is analyzed using fast imaging. During steady state rotation of both cylinders at different rates, a shear band develops close to the inner cylinder for all combinations of speeds of each cylinder we investigated. Experiments on flow initiation were carried out with one of the cylinders fixed. When the inner cylinder is stopped and restarted after a lag time of seconds to minutes in the same direction, a shear band develops immediately. When the inner cylinder is restarted in the opposite direction, shear initially spans the whole material, i.e. particles far from the shear surface are moving significantly more than in steady state.

Modeling of the blood rheology in steady-state shear flows

2014 ◽  
Vol 58 (3) ◽  
pp. 607-633 ◽  
Author(s):  
Alex J. Apostolidis ◽  
Antony N. Beris
Keyword(s):  
Steady State ◽  
Shear Flows ◽  
Blood Rheology

scholarly journals The Linear Stability of Time-Dependent Baroclinic Shear

2010 ◽  
Vol 40 (3) ◽  
pp. 568-581 ◽  
Author(s):  
F. J. Poulin
Keyword(s):  
Steady State ◽  
Linear Stability ◽  
Growth Rates ◽  
Shear Flows ◽  
Mathieu Equation ◽  
Extreme Case ◽  
Time Dependent ◽  
Time Variability ◽  
Bounded Noise ◽  
Wide Range

Abstract This article aims to advance the understanding of inherent randomness in geophysical fluids by considering the particular example of baroclinic shear flows that are spatially uniform in the horizontal directions and aperiodic in time. The time variability of the shear is chosen to be the Kubo oscillator, which is a family of time-dependent bounded noise that is oscillatory in nature with various degrees of stochasticity. The author analyzed the linear stability of a wide range of temporally periodic and aperiodic shears with a zero and nonzero mean to get a more complete understanding of the effect of oscillations in shear flows in the context of the two-layer quasigeostrophic Phillips model. It is determined that the parametric mode, which exists in the periodic limit, also exists in the range of small and moderate stochasticities but vanishes in highly erratic flows. Moreover, random variations weaken the effects of periodicity and yield growth rates more similar to that of the time-averaged steady-state analog. This signifies that the periodic shear flows possess the most extreme case of stabilization and destabilization and are thus anomalous. In the limit of an f plane, the linear stability problem is solved exactly to reveal that individual solutions to the linear dynamics with time-dependent baroclinic shear have growth rates that are equal to that of the time-averaged steady state. This implies that baroclinic shear flows with zero means are linearly stable in that they do not grow exponentially in time. This means that the stochastic mode that was found to exist in the Mathieu equation does not arise in this model. However, because the perturbations grow algebraically, the aperiodic baroclinic shear on an f plane can give rise to nonlinear instabilities.

Sign in / Sign up

Export Citation Format

Share Document