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.

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

scholarly journals A unified constitutive model for pressure sensitive shear flow transitions in moderate dense granular materials

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Xiaohui Cheng ◽  
Shize Xiao ◽  
Alex Sixie Cao ◽  
Meiying Hou
Keyword(s):  
Shear Stress ◽  
Steady State ◽  
Shear Flow ◽  
Constitutive Model ◽  
Earthquake Engineering ◽  
Shear Flows ◽  
Low Pressure ◽  
Flow State ◽  
Granular Shear ◽  
Flow Transitions

AbstractGranular shear flows exhibit complex transitional regimes that are dramatically affected by the pressure level and shear stress state. New advances in granular shear tests at low pressure have enlightened the understanding of the two granular shear flow transitions: between quasi-static and moderate shear flows, and between steady-state and transient shear flows. However, a unified constitutive model to describe these two transitions is yet to develop. In this work, a simplified and unified model is proposed based on innovative triaxial shear flow tests, using two dimensionless physical variables. Model results validated against experimental data suggest that the shear flow transition between a quasi-static to a moderate Isotach type flow state is highly pressure-dependent. At extremely low pressure, the granular viscosity becomes the primary mechanism, suppressing the quasi-static mechanism even under “quasi-static” shear rates. In transient to steady state granular flow transitions, a mobilized shear stress ratio or mobilized friction coefficient between zero and the critical state ratio for consolidated granular packings is taken into consideration. This is coupled with the mechanism of granular viscosity. These findings have not been discussed before and are of great relevance to granular mechanics as well as space and earthquake engineering.

Effects of chain length and polydispersity on shear banding in simple shear flow of polymeric melts

Soft Matter ◽  
2020 ◽  
Vol 16 (28) ◽  
pp. 6468-6483 ◽  
Author(s):  
Mahdi Boudaghi-Khajehnobar ◽  
Brian J. Edwards ◽  
Bamin Khomami
Keyword(s):  
Steady State ◽  
Shear Rate ◽  
Shear Flow ◽  
Chain Length ◽  
Simple Shear ◽  
Polymer Melts ◽  
Shear Banding ◽  
Simple Shear Flow ◽  
Polydisperse Polymer ◽  
Transient And Steady State

Transient and steady-state shear banding are demonstrated for polydisperse polymer melts as functions of applied shear rate.

scholarly journals Combined electrokinetic and shear flows control colloidal particle distribution across microchannel cross-sections

Soft Matter ◽  
2021 ◽  
Author(s):  
Varun Lochab ◽  
Shaurya Prakash
Keyword(s):  
Shear Flow ◽  
Cross Sections ◽  
Lift Force ◽  
Shear Flows ◽  
Colloidal Particle ◽  
Particle Distribution ◽  
Particle Migration ◽  
Flow Parameters

We quantify and investigate the effects of flow parameters on the extent of colloidal particle migration and the corresponding electrophoresis-induced lift force under combined electrokinetic and shear flow.

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