E. Lemaire

• Professor
• directrice de recherche at Université Côte d'Azur

The transient shear-induced particle migration of frictional non-Brownian suspensions is studied using particle-resolved simulations. The numerical method-the fictitious domain method-is well suited to heterogeneous flows thanks to a frame-invariant formulation of the subgrid (lubrication) corrections that does not involve the ambient flow (Orsi et...

The normal and shear viscosities of non-Brownian suspensions are measured by optical suspension imaging for particle volume fractions $\phi$ between $0.3\phi _m$ and $0.98\phi _m$ , where $\phi _m$ is the jamming fraction. Two distinct refractive-index-matched suspensions, made with the same polymethyl methacrylate spherical particles dispersed in...

This paper presents a compilation of experimental and numerical results that both show that particles in a suspension under shear flow come into contact through surface roughness. Accounting for those frictional contacts captures well the measured viscosity values as well as the shear-thinning observed in many concentrated non-Brownian suspensions....

https://sor.scitation.org/action/showLargeCover?doi=10.1122%2Fjor.2022.66.issue-1

We attempt to identify the impact of particle stiffness on the shear-thinning behavior exhibited by frictional and adhesive non-Brownian suspensions. To this aim, we compare the rheological behavior of three suspensions whose particles have different Young’s moduli. The stiffest particles are soda-lime glass beads with a Young modulus of 70 GPa. Th...

We attempt to identify the impact of particle stiffness on the shear-thinning behavior exhibited by frictional and adhesive non-Brownian suspensions. To this aim, we compare the rheological behavior of three suspensions whose particles have different Young's moduli. The stiffest particles are Soda-lime glass beads with a Young modulus of 70 GPa. Th...

We propose a general, versatile and broad in scope two-steps approach for the elaboration of cross-linked polymer microparticles (µPs) with tunable functionalities and surface properties. Surface-functionalized cross-linked polymer µPs with diameter in the 80 μm range are prepared by the combination of: 1) suspension free radical copolymerization o...

This paper focuses on shear-thinning in non-Brownian suspensions. In particular, it proposes a quantitative experimental validation of the model proposed by Lobry et al. [J. Fluid Mech., 2019, 860, 682-710] that links viscosity to microscopic friction between particles and, in particular, shear-thinning to load-dependent friction coefficient. To th...

We perform local measurements of both the velocity and the particle volume fraction tostudy viscous resuspension in non-Brownian suspensions for Shields numbers ranging from 10−3 to 1.With this aim, a suspension of polymethacrylate spherical particlesdispersed in a lighter Newtonian fluid (TritonX100) is sheared in a vertical Couette cell where bot...

Non-Brownian concentrated suspensions are present in a lot of industrial applications and natural flows. Complex flows like extrusion or coating process need a comprehensive understanding of the rheological behaviour to be well described. Nevertheless, these fluids are not completely understood and a micro revolution happens in the last ten years....

Non-Brownian concentrated suspensions are present in a lot of industrial applications and natural flows. Complex flows like extrusion or coating process need a comprehensive understanding of the rheological behaviour to be well described. Nevertheless, these fluids are not completely understood and a micro revolution happens in the last ten years....

Rheology of hard sphere suspension is an active domain which had great contributions in 2012 that shown the importance of the friction in the all flow process. Since the contact is drive by the surface of contact, we managed to change the Young modulus to tunes the friction and change the rheology. By using PDMS particles, which are a thousand time...

Shear reversal is a smart rheological protocol allowing inspection of the contribution of the nonhydrodynamic contact forces between particles on the rheology of concentrated suspensions. In this paper, this protocol is applied to concentrated suspensions of rigid fibers dispersed in a Newtonian liquid at three aspect ratios ranging from 10 to 31 a...

We perform local measurements of both the shear rate and the particle fraction to study viscous resuspension in non-Brownian suspensions. A suspension of PMMA spherical particles dispersed in a lighter Newtonian fluid (Triton X100) is sheared in a vertical Couette cell. The vertical profiles of the particle volume fraction are measured for Shields...

We perform local measurements of both the shear rate and the particle fraction to study viscous resuspension in non-Brownian suspensions. A suspension of PMMA spherical particles dispersed in a lighter Newtonian fluid (Triton X100) is sheared in a vertical Couette cell. The vertical profiles of the particle volume fraction are measured for Shields...

This paper presents an experimental facility that allows simultaneous viscosimetric and Particle Image velocimetry measurements on concentrated suspensions in a wide-gap Couette rheometer. The experimental procedure is detailed: the optical characteristics of the index-matched suspension are carefully studied, the bottom end effect on both the visc...

We propose to explain shear-thinning behaviour observed in most concentrated non-Brownian suspensions by variable friction between particles. Considering the low magnitude of the forces experienced by the particles of suspensions under shear flow, it is first argued that rough particles come into solid contact through one or a few asperities. In su...

We compare the rheology of two kinds of non-Brownian suspensions. One is made of spherical monodisperse polystyrene particles (80μm in diameter), and the other is made of faceted sugar particles (average size, 100μm), both suspended in a Newtonian silicon oil. We perform shear reversal experiments on both suspensions for several particle volume fra...

This work is focused on shear thinning behavior of suspensions of rigid non-Brownian fibers dispersed in a Newtonian liquid. The work consists of developing a new theoretical model and conducting accurate experimental measurements. The shear thinning is expected to be caused by adhesive interactions between fibers. Experiments on polyamide (PA) fib...

This work is focused on the modelling of the shear and normal stresses in fibre suspensions that are subjected to a simple shear flow in the presence of short-range lubrication forces, van der Waals and electrostatic forces, as well as solid friction forces between fibres. All of these forces are weighed by the contact probability. The theory is de...

In this paper, we present an experimental study of the normal stress differences that arise in non-Brownian rigid fiber suspensions subject to a shear flow. While early measurements of the normal stress in fiber suspensions in Newtonian fluids measured only N 1 − N 2, the recent work of Snook et al. [J. Fluid Mech. 758, 486–507 (2014)] and the pres...

We perform particle scale simulations of suspensions submitted to shear reversal. The simulations are based on the Force Coupling method, adapted to account for short range lubrication interactions together with direct contact forces between particles, including surface roughness, contact elasticity, and solid friction. After shear reversal, three...

This paper presents three-dimensional numerical simulations of non-colloidal dense suspensions in a wall-bounded shear flow at zero Reynolds number. Simulations rely on a fictitious domain method with a detailed modelling of particle–particle and wall–particle lubrication forces, as well as contact forces including particle roughness and friction....

Dense suspensions display complex flow properties, intermediate between solid and liquid. When sheared, a suspension self-organizes and forms particle clusters that are likely to percolate, possibly leading to significant changes in the overall behavior. Some theoretical conjectures on percolation in suspensions were proposed by de Gennes some 35 y...

his paper presents three-dimensional numerical simulations of non-Brownian concen-trated suspensions in a Couette flow at zero Reynolds number using a fictitious domain method. Contacts between particles are modelled using a DEM-like approach (Discrete Element Method), which allows for a more physical description, including roughness and friction....

The fall velocity of a dense large ball in a suspension of neutrally buoyant non-Brownian particles subjected to horizontal oscillatory shear is studied. As the strain amplitude is increased, the velocity increases up to a maximum value before decreasing to the value that it would have in a resting suspension. The higher the frequency is, the stron...

Low Reynolds number concentrated suspensions do exhibit an intricate physics which can be partly unraveled by the use of numerical simulation. To this end, a Lagrange multiplier-free fictitious domain approach is described in this work. Unlike some methods recently proposed, the present approach is fully Eulerian and therefore does not need any tra...

Nous présentons une méthode expérimentale qui nous a permis de mesurer les contraintes normales particulaires dans des suspensions concentrées de particules non-browniennes. La méthode repose sur la mesure conjointe du profil radial de la contrainte normale dans la direction du gradient de vitesse et de la pression dans le fluide interstitiel en éc...

This paper addresses the modeling of the phenomenon of particle migration in the flow of monodispersed non-colloidal suspensions at neglected inertia using the Suspension Balance Model (SBM). The SBM describes the migration flux of particles as the divergence of the particle stress tensor. It is selected in this work because of its parameters that...

We present an experimental approach used to measure both normal stress differences and the particle phase contribution to the normal stresses in suspensions of non-Brownian hard spheres. The methodology consists of measuring the radial profile of the normal stress along the velocity gradient direction in a torsional flow between two parallel discs....

The shear-induced microstructure in non-Brownian suspensions is studied. The Pair Distribution Function in the shear plane is experimentally determined for particle volume fractions ranging from 0.05 to 0.56. Transparent suspensions made of PMMA particles (172µm in diameter) dispersed in a fluorescent index matched Newtonian liquid is sheared in a...

Poster Workshop on flocculated suspensions - Champs sur Marne, 28-29 June 2012

In this paper, we discuss the different modelisations of the rupture of aggregates in ER or MR fluids. In particular, we show that microstructural models which take into account the separation between the particles inside tha aggregates give predictions very different from those based on a continuum approach. Some experimental results help us to di...

We present here the study of field induced phase separation in E.R. and M.R. fluids. Two thermodynamic models — one for the formation of chais of particles and the other for phase separation are presented and compared with experimental results obtained with two kinds of suspensions. One was made of silica particles in silicone oil and the other was...

The turbidity of a suspension of silica particles in a silicone oil is studied in the presence of an electric field. We present experimental results which show a very strong attenuation of a laser beam when the electric field is switched on. We give a theoretical interpretation of these results with the help of a Rayleigh Gans Debye theory applied...

The rheological properties of E.R. and M.R. suspensions are determined by the strength of the structure built under the application of an electric (respectively magnetic) field. We present a general multipolar method which allows us to obtain the stress-strain curve for any sheared lattice. This is applied to infinite periodic chains of spheres arr...

The shear-induced microstructure in a semidilute noncolloidal suspension is studied. A high-resolution pair distribution function in the plane of shear is experimentally determined. It is shown to be anisotropic, with a depleted direction close to the velocity axis in the recession quadrant. The influence of roughness on the interaction between par...

Negative electrorheological responses induced by micro-particle electrorotation in two-dimensional Couette flow geometries are analyzed by a set of continuum modeling field equations originating from anti-symmetric/couple stress theories in the finite spin viscosity small spin velocity (FSV) limit. Analytical solutions are obtained for the first ti...

This paper reports experiments on the shear transient response of concentrated non-Brownian suspensions. The shear viscosity of the suspensions is measured using a wide-gap Couette rheometer equipped with a Particle Image Velocimetry (PIV) device that allows measuring the velocity field. The suspensions made of PMMA particles (31$\mu$m in diameter)...

A continuum mechanical model is presented to analyze the negative electrorheological responses of a particle-liquid mixture with the suspended micro-particles undergoing Quincke rotation for both Couette and Poiseuille flow geometries by combining particle electromechanics and continuum anti-symmetric/couple stress analyses in the zero spin viscosi...

Poster : Rhéologie locale des suspensions concentrées GFR 44 Strasbourg

The pressure-driven flow of a suspension of spinning particles in a rectangular channel is studied using an acoustic method. The suspension is made of insulating particles (PMMA) dispersed in a slightly conducting oil (Ugilec + Dielec) and is subjected to a DC electric field. In such a case, the particles are polarized in the direction opposite to...

The pressure-driven flow of a suspension of spinning particles in a rectangular channel is studied using an acoustic method. The suspension is made of insulating particles (PMMA) dispersed in a slightly conducting oil ( Ugilec + Dielec) and is subjected to a DC electric field. In such a case, the particles are polarized in the direction opposite to...

This paper deals with the Quincke rotation of small insulating particles. This dc electrorotation of insulating objects immersed in a slightly conducting liquid is usually explained by looking at the action of the free charges present in the liquid. Under the effect of the dc electric field, the charges accumulate at the surface of the insulating p...

We analyse the consequences of Quincke rotation on the conductivity of a suspension. Quincke rotation refers to the spontaneous rotation of insulating particles dispersed in a slightly conducting liquid and subject to a high DC electric field: above a critical field, each particle rotates continuously around itself with an axis pointing in any dire...

When an insulating particle immersed into a low conducting liquid is submitted to a sufficiently high DC field, E, it can rotate spontaneously around itself along any axis perpendicular to the electric field. This symmetry break is known as Quincke rotation and could have important consequences on the rheology of such a suspension of particles (ins...

This paper deals with the Quincke rotation of small particles. It is usual to explain this DC electorotation looking at the action of the free charges present in the liquid which under the application of an electric field accumulate at the surface of the insulating object. Then it acquires a dipole moment in the direction opposite to that of the fi...

The rheological behaviour of a suspension of insulating particles dispersed in a slightly conducting liquid under the action of a DC electric field is studied. The polarisation of the particles induced by the field is shown to be responsible for a rotation of the particles (Quincke rotation) which, in turn, leads to a drastic decrease of the appare...

We have measured the yield stress of a magnetic suspension as a function of the external field. To explain the existence of this yield stress, we report a comparison between two models, one based on isolated chains of particles and the other taking into account that the structure is formed by aggregates of particles.

Solid particles suspended in a liquid phase can build linear structures when a large enough electric field is applied to the suspension. These structures confer to the suspension a shear modulus G, which is measured with an oscillating plate device. This system allows to simultaneously visualize the change of structure of the suspension. We observe...

La rotation de Quincke décrit la mise en rotation d'objets par un champ électrique continu. Nous montrons ici comment nous avons pu abaisser la viscosité apparente d'une suspension de près d'un ordre de grandeur en la soumettant à un tel champ électrique.

Nonconducting particles suspended in a liquid usually decreases the bulk conductivity since they form obstacles to the ions' migration. However, for sufficiently high dc electric fields, these particles rotate spontaneously (Quincke rotation) and facilitate the ions migration: the effective conductivity of the suspension is thus increased. We prese...

We report some experimental results that show that, if the particles of a suspension rotate faster than the surrounding liquid, the apparent viscosity is lessened. The increase of the particles’ spin rate is induced by Quincke rotation, which is the spontaneous rotation of an insulating particle immersed in a slightly conducting liquid when submitt...

We present experimental results on the formation of different sheet structures obtained in a colloidal suspension of silica particles in the presence of an electric field and of an oscillating shear flow. The characteristics of the structure depend on the amplitude of the imposed strain; at low strain the sheets are perpendicular to the velocity li...

In this paper, we show that the viscosity of a suspension can be drastically reduced if its particles are rotating faster than the surrounding liquid. We propose to induce particle rotation by applying a DC electric field to a suspension of insulating particles dispersed in a slightly conducting liquid (Quincke rotation). We have studied the flow o...

This paper reports an experimental and numerical study conducted to investigate the behavior of macroscopic monomodal concentrated suspensions (40%) undergoing a creeping torsional flow between two rotating plates. An experimental technique based on the detection of tracers by measurement of light absorption is developed and used to quantify the ti...

In this paper, we report experimental evidence of Lorenz chaos for the Quincke rotor dynamics. We study the angular motion of an insulating cylinder immersed in slightly conducting oil and submitted to a direct current electric field. The simple equations which describe the dynamics of the rotor are shown to be equivalent to the Lorenz equations. I...

We present a new method of measuring the electrophoretic mobility of a particle in a concentrated suspension. The method is used to measure the electrophoretic mobility of PMMA particles (diameter 10 microm) suspended in a mixture of liquid hydrocarbons. The particle volume fraction of the suspension is varied from 0 up to 0.30 and the resulting va...

We report experiments on a magnetic cohesive granular material made of steel spheres in the millimeter range. A magnetic field magnetizes the spheres, so that an interaction force between grains appears. A rotating magnetic field is applied parallel to plane of the quasi-two-dimensional cell containing the spheres so that only the time averaged for...

We study the dynamics of an insulating cylinder in a weakly conducting liquid when submitted to a DC electric field. The cylinder is free to rotate along its long axis which is perpendicular to the applied field. Above a threshold value of the electric field, the cylinder rotates in either direction with constant angular velocity. This instability...

When particles immersed in a semi-insulating liquid are submitted to a sufficiently high DC field, they can rotate spontaneously around any axis perpendicular to the field (Quincke rotation). Recently we have shown that due to Quincke effect the effective viscosity of a colloidal suspension could be reduced. When the suspension is submitted to a sh...

When particles immersed in a semi-insulating liquid are submitted to a sufficiently high DC field, they can rotate spontaneously around any axis perpendicular to the field (Quincke rotation). Recently we have shown that due to Quincke effect the effective viscosity of a colloidal suspension could be reduced. When the suspension is submitted to a sh...

The stability of a colloidal system occupies a central position in colloid science. According to the DLVO theory, the interparticle potential admits two contributions: the Van der Waals attraction and the electrostatic repulsion. In this paper, we present a comparison of two methods to study the interaction forces between particles when their dista...

We present an experimental evidence of a "colloidal motor" behavior of a suspension. Previous attempts to observe such a phenomenon with ferrofluids under alternating magnetic fields have failed. Here, negative viscosity is obtained by making use of Quincke rotation: the spontaneous rotation of insulating particles suspended in a weakly conducting...

We present an experimental evidence of a "colloidal motor" behavior of a suspension. Previous attempts to observe such a phenomenon with ferrofluids under alternating magnetic fields have failed. Here, negative viscosity is obtained by making use of Quincke rotation: the spontaneous rotation of insulating particles suspended in a weakly conducting...

We study the dynamics of an ellipsoidal particle in a weakly conducting dielectric liquid when submitted to a dc electric field. At low field intensities, the particle long axis is aligned in the field direction. When the field strength is increased, we show that, depending on the initial orientation of the particle, there exist two stable orientat...

A review of some models of dielectric suspensions accounting for the internal rotations due to the finite Maxwell relaxation time is given. We present the consequences of particle rotation on the rheological and electrical behavior of a suspension submitted to a DC field. We show that this spontaneous rotation leads to a negative apparent viscosity...

The static yield stress of magnetic colloidal suspensions is measured as a function of the applied magnetic field in a controlled stress rheometer. The experimental results are analysed with the help of the magnetization curve for different volume fractions. The experimental yield stress scales as the square of the magnetization but its magnitude i...

To our knowledge, we present the first experimental evidence of a “colloidal motor” behavior of a suspension. Previous attempts to observe such a phenomenon with ferrofluids under alternating magnetic fields have failed. Here, the viscosity decrease is obtained by making use of Quincke rotation: the spontaneous rotation of insulating particles susp...