scholarly journals Microstructure and thickening of dense suspensions under extensional and shear flows

2017 ◽  
Vol 825 ◽  
Author(s):  
Ryohei Seto ◽  
Giulio G. Giusteri ◽  
Antonio Martiniello
Keyword(s):  
Numerical Simulation ◽  
Rheological Properties ◽  
Normal Stress ◽  
Shear Flows ◽  
Shear Thickening ◽  
Newtonian Fluids ◽  
Flow Type ◽  
Dense Suspensions ◽  
Strong Shear ◽  
Normal Stress Differences

Dense suspensions are non-Newtonian fluids that exhibit strong shear thickening and normal stress differences. Using numerical simulation of extensional and shear flows, we investigate how rheological properties are determined by the microstructure that is built under flows and by the interactions between particles. By imposing extensional and shear flows, we can assess the degree of flow-type dependence in regimes below and above thickening. Even when the flow-type dependence is hindered, non-dissipative responses, such as normal stress differences, are present and characterise the non-Newtonian behaviour of dense suspensions.

Flow-induced structure and rheological properties of multiwall carbon nanotube/polydimethylsiloxane composites

RSC Advances ◽  
2014 ◽  
Vol 4 (107) ◽  
pp. 62759-62768 ◽  
Author(s):  
Ran Niu ◽  
Jiang Gong ◽  
Donghua Xu ◽  
Tao Tang ◽  
Zhao-Yan Sun
Keyword(s):  
Molecular Weight ◽  
Carbon Nanotube ◽  
Rheological Properties ◽  
Normal Stress ◽  
Polymer Composites ◽  
Polymer Matrix ◽  
Multiwall Carbon Nanotube ◽  
Normal Stress Differences ◽  
Induced Structure ◽  
Multiwall Carbon

The structure and normal stress differences of MWNT/polymer composites are influenced by the molecular weight of the polymer matrix and the confinement effect.

scholarly journals Normal stress differences in dense suspensions

2018 ◽  
Vol 857 ◽  
pp. 200-215 ◽  
Author(s):  
Ryohei Seto ◽  
Giulio G. Giusteri
Keyword(s):  
Normal Stress ◽  
Simple Shear ◽  
Volume Fraction ◽  
Hydrodynamic Lubrication ◽  
Contact Forces ◽  
Simple Shear Flow ◽  
First Normal Stress Difference ◽  
Dense Suspensions ◽  
Normal Stress Differences ◽  
Dynamics Simulations

The presence and the microscopic origin of normal stress differences in dense suspensions under simple shear flows are investigated by means of inertialess particle dynamics simulations, taking into account hydrodynamic lubrication and frictional contact forces. The synergic action of hydrodynamic and contact forces between the suspended particles is found to be the origin of negative contributions to the first normal stress difference $N_{1}$ , whereas positive values of $N_{1}$ observed at higher volume fractions near jamming are due to effects that cannot be accounted for in the hard-sphere limit. Furthermore, we found that the stress anisotropy induced by the planarity of the simple shear flow vanishes as the volume fraction approaches the jamming point for frictionless particles, while it remains finite for the case of frictional particles.

Rheological characterization of cellular blood in shear

2013 ◽  
Vol 726 ◽  
pp. 497-516 ◽  
Author(s):  
D. A. Reasor ◽  
J. R. Clausen ◽  
C. K. Aidun
Keyword(s):  
Shear Rate ◽  
Normal Stress ◽  
Flow Direction ◽  
Coarse Grained ◽  
Particle Phase ◽  
Rheological Characterization ◽  
Shear Rates ◽  
Bending Modulus ◽  
Dense Suspensions ◽  
Normal Stress Differences

AbstractA hybrid lattice-Boltzmann spectrin-link (LB–SL) method is used to simulate dense suspensions of red blood cells (RBCs) for investigating rheological properties of blood. RBC membranes are modelled using a coarse-grained SL method and are filled with a viscous Newtonian fluid solution with viscosity five times that of the suspending fluid. Relative viscosities, normal stress differences, and particle pressures are reported for a range of capillary numbers at a physiologically realistic haematocrit value of approximately 42.5 %. Viscosity shear thinning is demonstrated for shear rates ranging from 14 to 440  s−1 and is shown to be affected by the orientation and bending modulus of RBCs. The particle-phase pressure undergoes a change in sign from positive to negative as the shear rate is increased. The particle-phase normal stress tensor values show that there is a transition from compressive to tensile states in the flow direction as the shear rate is increased. The normal stress differences are notably different from those recently reported for deformable capsule suspensions using a similar methodology, which suggests that the bending stiffness and the biconcave shape of RBCs affect the rheology of blood.

Rheological Properties of Emulsions Immersed in Electric Fields

2007 ◽  
Author(s):  
Arturo Ferna´ndez
Keyword(s):  
Viscous Fluid ◽  
Electric Field ◽  
Numerical Simulations ◽  
Rheological Properties ◽  
Normal Stress ◽  
Electric Fields ◽  
Fluid Motion ◽  
Fluid Shear ◽  
Normal Stress Differences ◽  
Viscous Fluid Motion

The results of fully three-dimensional direct numerical simulations of the effects of electric fields on emulsions of drops will be displayed. The examination of the rheological properties of these systems is performed by imposing a simple-shear flow between two plates where the drops are immersed. An electric potential difference is applied perpendicular to the plates. The resulting electric field leads to two effects: a polarization of the drops and a viscous fluid motion on the interface between the drops and the suspending fluid. The direction and intensity of the viscous fluid motion depends on the electrical properties of the fluids. Drops more conductive than the suspending fluid exhibit a viscous fluid motion from the equator to the poles, whereas drops less conductive than the suspending fluid exhibit a viscous fluid motion from the poles to the equator. The numerical simulations show that the response of the emulsions is governed by the competition between the electric attraction and the fluid shear. The former leads to the aggregation of the drops in chains parallel to the electric field, while the latter tries to break-up the aggregated chains. The results are presented as a function of the Mason number and the electric capillary number, Mn and Ce. These non-dimensional numbers quantify the strength of the electric forces versus the fluid shear and the capillary forces, respectively. The significance of the electrical field on the viscosity and the normal stress differences will be discussed: At low Mason numbers, Mn<0.1, the application of the electric field results in the aggregation of the drops. This aggregation leads to an increase in the effective viscosity of the system and to an increase in the stresses, which result in higher normal stress differences than in hydrodynamic emulsions. At high Mason numbers, Mn>1.0, the fluid shear breaks up the aggregated structures and the properties are similar to hydrodynamic emulsions. At 0.1<Mn<1.0 the properties of the emulsions exhibit an intermediate behavior.

Dense suspensions in rotating-rod flows: normal stresses and particle migration

2011 ◽  
Vol 686 ◽  
pp. 5-25 ◽  
Author(s):  
François Boyer ◽  
Olivier Pouliquen ◽  
Élisabeth Guazzelli
Keyword(s):  
Shear Rate ◽  
Normal Stress ◽  
Volume Fraction ◽  
Particle Migration ◽  
Balance Model ◽  
Normal Stresses ◽  
Dense Suspensions ◽  
Normal Stress Differences ◽  
Neutrally Buoyant ◽  
Dependent Behaviour

AbstractNormal stress differences are measured in dense suspensions of neutrally buoyant non-Brownian spheres dispersed in a Newtonian fluid. Rotating-rod rheometry is used to characterize the suspension normal stresses which are responsible for a rod-dipping phenomenon. These normal stress differences are seen to strongly increase above a volume fraction of approximately 22 %. During the course of the experiments, a new time-dependent behaviour is also observed: the dip is filled with increasing times. This time evolution is found to be related to particle migration from regions of high shear rate to regions of low shear rate. The behaviour is compared with the predictions of a suspension balance model in which the particle migration flux is related to the normal stresses of the suspension.

scholarly journals ‘Shear thickening’ in non-shear flows: the effect of microstructure

2017 ◽  
Vol 836 ◽  
pp. 1-4 ◽  
Author(s):  
Helen J. Wilson
Keyword(s):  
Numerical Simulations ◽  
Public Engagement ◽  
Shear Flows ◽  
Shear Thickening ◽  
Underlying Mechanism ◽  
Dense Suspensions ◽  
The Difference ◽  
The Right ◽  
First Time ◽  
Effect Of Microstructure

The bizarre behaviour of a cornstarch suspension (sometimes called oobleck) is well known to all of us who have led public engagement events. At the right solids fraction, it flows smoothly at slow speeds, but can be shattered with a quick spoon movement; if you prepare a large enough sample, you can run across the surface (but if you stand still, you will sink). In rheology circles this phenomenon is known as shear thickening, though the flows described above are not necessarily shear-dominated. In recent years there has been a proliferation of research on the mechanism behind true shear thickening, using both experiments and numerical simulations of shear flows. The understanding of the underlying mechanism is improving markedly. But the paper ‘Microstructure and thickening of dense suspensions under extensional and shear flows’ (Seto, Giusteri & Martinello, J. Fluid Mech., vol. 825, 2017, R3) is the first to consider more general flows. We have, for the first time, simulations of thickening in extensional flows, which are a far better description of oobleck with a runner on top – and can begin to quantify the difference between the idealised shear thickening and the extension thickening that happens in practice.

Rheology of dense suspensions of non-colloidal spheres in yield-stress fluids

2015 ◽  
Vol 776 ◽  
Author(s):  
Simon Dagois-Bohy ◽  
Sarah Hormozi ◽  
Élisabeth Guazzelli ◽  
Olivier Pouliquen
Keyword(s):  
Shear Stress ◽  
Rheological Properties ◽  
Normal Stress ◽  
Yield Stress ◽  
Rheological Measurements ◽  
Model Based ◽  
Colloidal Spheres ◽  
Yield Stress Fluids ◽  
Dense Suspensions ◽  
Scaling Arguments

Pressure-imposed rheometry is used to study the rheological properties of suspensions of non-colloidal spheres in yield-stress fluids. Accurate measurements for both the shear stress and the particle normal stress are obtained in the dense regime. The rheological measurements are favourably compared with a model based on scaling arguments and homogenisation methods.

scholarly journals Viscous-like forces control the impact response of shear-thickening dense suspensions

2021 ◽  
Vol 923 ◽  
Author(s):  
Marc-Andre Brassard ◽  
Neil Causley ◽  
Nasser Krizou ◽  
Joshua A. Dijksman ◽  
Abram. H. Clark
Keyword(s):  
Shear Thickening ◽  
Impact Response ◽  
Dense Suspensions ◽  
The Impact

Abstract

Investigation of stresses and normal stress differences behavior on symmetric and asymmetric polymeric fluid flow through planar gradual expansions

Meccanica ◽  
2016 ◽  
Vol 52 (8) ◽  
pp. 1889-1909 ◽  
Author(s):  
M. Norouzi ◽  
A. Shahbani Zahiri ◽  
M. M. Shahmardan ◽  
H. Hassanzadeh ◽  
M. Davoodi
Keyword(s):  
Fluid Flow ◽  
Normal Stress ◽  
Polymeric Fluid ◽  
Flow Through ◽  
Normal Stress Differences
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