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.

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.

Responses of human adipose-derived stem cells to interstitial level of extremely low shear flows regarding differentiation, morphology, and proliferation

Lab on a Chip ◽  
2017 ◽  
Vol 17 (12) ◽  
pp. 2115-2124 ◽  
Author(s):  
Sung-Hwan Kim ◽  
Kihoon Ahn ◽  
Joong Yull Park
Keyword(s):  
Stem Cells ◽  
Shear Stress ◽  
Shear Flow ◽  
Shear Flows ◽  
Stress Gradient ◽  
Adipose Derived Stem Cells ◽  
Shear Stress Gradient ◽  
Low Shear

We developed a shear stress-gradient chip, which mimickedin vivointerstitial level of flow. With this system, hASCs' quantitative responses to the interstitial level of shear flow are identified.

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 Advanced Constitutive Modeling of the Thixotropic Elasto-Visco-Plastic Behavior of Blood: Steady-State Blood Flow in Microtubes

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 367
Author(s):  
Konstantinos Giannokostas ◽  
Yannis Dimakopoulos ◽  
Andreas Anayiotos ◽  
John Tsamopoulos
Keyword(s):  
Blood Flow ◽  
Steady State ◽  
Constitutive Model ◽  
Blood Plasma ◽  
Constitutive Modeling ◽  
Flow Direction ◽  
Momentum Balance ◽  
Plastic Behavior ◽  
Flow Investigation ◽  
The Impact

The present work focuses on the in-silico investigation of the steady-state blood flow in straight microtubes, incorporating advanced constitutive modeling for human blood and blood plasma. The blood constitutive model accounts for the interplay between thixotropy and elasto-visco-plasticity via a scalar variable that describes the level of the local blood structure at any instance. The constitutive model is enhanced by the non-Newtonian modeling of the plasma phase, which features bulk viscoelasticity. Incorporating microcirculation phenomena such as the cell-free layer (CFL) formation or the Fåhraeus and the Fåhraeus-Lindqvist effects is an indispensable part of the blood flow investigation. The coupling between them and the momentum balance is achieved through correlations based on experimental observations. Notably, we propose a new simplified form for the dependence of the apparent viscosity on the hematocrit that predicts the CFL thickness correctly. Our investigation focuses on the impact of the microtube diameter and the pressure-gradient on velocity profiles, normal and shear viscoelastic stresses, and thixotropic properties. We demonstrate the microstructural configuration of blood in steady-state conditions, revealing that blood is highly aggregated in narrow tubes, promoting a flat velocity profile. Additionally, the proper accounting of the CFL thickness shows that for narrow microtubes, the reduction of discharged hematocrit is significant, which in some cases is up to 70%. At high pressure-gradients, the plasmatic proteins in both regions are extended in the flow direction, developing large axial normal stresses, which are more significant in the core region. We also provide normal stress predictions at both the blood/plasma interface (INS) and the tube wall (WNS), which are difficult to measure experimentally. Both decrease with the tube radius; however, they exhibit significant differences in magnitude and type of variation. INS varies linearly from 4.5 to 2 Pa, while WNS exhibits an exponential decrease taking values from 50 mPa to zero.

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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