Wide-gap Couette flows of dense emulsions: Local concentration measurements, and comparison between macroscopic and local constitutive law measurements through magnetic resonance imaging

Ovarlez, Guillaume; Rodts, Stéphane; Ragouilliaux, Alexandre; Coussot, Philippe; Goyon, Julie; Colin, Annie

doi:10.1103/physreve.78.036307

Cited by 108 publications

(130 citation statements)

References 43 publications

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“…In fact, we found that the same master line, representing eqn (5) (1) Systems in which the power-law index n z 1/2. 9,16,17,[23][24][25]54,55 In these systems n varied between 0.42 and 0.5 (centred at n z 0.47), depending on the specific surfactant and glycerol concentration in the foaming solution.…”

Section: Inside-foam Viscous Frictionmentioning

confidence: 99%

The role of surfactant type and bubble surface mobility in foam rheology

et al. 2009

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This paper is an overview of our recent understanding of the effects of surfactant type and bubble surface mobility on foam rheological properties. The focus is on the viscous friction between bubbles in steadily sheared foams, as well as between bubbles and confining solid wall. Large set of experimental results is reviewed to demonstrate that two qualitatively different classes of surfactants can be clearly distinguished. The first class is represented by the typical synthetic surfactants (such as sodium dodecylsulfate) which are characterised with low surface modulus and fast relaxation of the surface tension after a rapid change of surface area. In contrast, the second class of surfactants exhibits high surface modulus and relatively slow relaxation of the surface tension. Typical examples for this class are the sodium and potassium salts of fatty acids (alkylcarboxylic acids), such as lauric and myristic acids. With respect to foam rheology, the second class of surfactants leads to significantly higher viscous stress and to different scaling laws of the shear stress vs. shear rate in flowing foams. The reasons for these differences are discussed from the viewpoint of the mechanisms of viscous dissipation of energy in sheared foams and the respective theoretical models. The process of bubble breakup in sheared foams (determining the final bubble-size distribution after foam shearing) is also discussed, because the experimental results and their analysis show that this phenomenon is controlled by foam rheological properties.

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Section: Inside-foam Viscous Frictionmentioning

confidence: 99%

The role of surfactant type and bubble surface mobility in foam rheology

et al. 2009

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“…58 We note that the Couette gap-width of 1mm is sufficiently small to eliminate gap-width effects. 12,13,59 The solid line in Fig. 8(a) is a comparison with our theory.…”

Section: Preliminary Experimentsmentioning

confidence: 99%

Constitutive equations for the flow behavior of entangled polymeric systems: Application to star polymers

Briels¹,

Vlassopoulos²,

Kang³

et al. 2011

The Journal of Chemical Physics

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A semimicroscopic derivation is presented of equations of motion for the density and the flow velocity of concentrated systems of entangled polymers. The essential ingredient is the transient force that results from perturbations of overlapping polymers due to flow. A Smoluchowski equation is derived that includes these transient forces. From this, an equation of motion for the polymer number density is obtained, in which body forces couple the evolution of the polymer density to the local velocity field. Using a semimicroscopic Ansatz for the dynamics of the number of entanglements between overlapping polymers, and for the perturbations of the pair-correlation function due to flow, body forces are calculated for nonuniform systems where the density as well as the shear rate varies with position. Explicit expressions are derived for the shear viscosity and normal forces, as well as for nonlocal contributions to the body force, such as the shear-curvature viscosity. A contribution to the equation of motion for the density is found that describes mass transport due to spatial variation of the shear rate. The two coupled equations of motion for the density and flow velocity predict flow instabilities that will be discussed in more detail in a forthcoming publication.

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“…flow to stop abruptly at R(τ < τ 0 ), the flow profile for a yield stress fluid is smooth [1][2][3][4].…”

Section: Introductionmentioning

confidence: 99%

What is fluidity? Designing an experimental system to probe stress and velocity fluctuations in flowing suspensions

2017

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Abstract. We develop a method to investigate the microscopic origin of granular fluidity. We design a Couette cell in which we can probe the flow of soft hydrogel suspensions. As we drive the suspension with a rheometer, we have access to global flow characteristics. In addition, the Couette cell has been modified to have a transparent bottom and lid, allowing for imaging of suspension characteristics in transmission, for example flow fields. We can also use transmission imaging to probe local stresses in the suspension: we use hydrogel particles composed of gelatin, which through its photoelastic properties gives access to local stress fluctuations. We thus have access to all local microscopic variables that are relevant in the understanding of granular suspensions. We show here that our setup can indeed visualize stress fields inside the suspensions and perform flow field measurements in transmission mode. We compare the profiles of the gelatin suspension to that of a polyacrylamide hydrogel suspension, to assess robustness of observed phenomenology. We find that the flow profiles for both types of hydrogels are different; gelatin suspensions feature narrower and less rate-dependent flow profiles. We speculate on the origin of the observed difference by considering the frictional properties of the suspended particles.

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Wide-gap Couette flows of dense emulsions: Local concentration measurements, and comparison between macroscopic and local constitutive law measurements through magnetic resonance imaging

Cited by 108 publications

References 43 publications

The role of surfactant type and bubble surface mobility in foam rheology

The role of surfactant type and bubble surface mobility in foam rheology

Constitutive equations for the flow behavior of entangled polymeric systems: Application to star polymers

What is fluidity? Designing an experimental system to probe stress and velocity fluctuations in flowing suspensions

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