The Experts below are selected from a list of 2352 Experts worldwide ranked by ideXlab platform
Eric S G Shaqfeh - One of the best experts on this subject based on the ideXlab platform.
-
the rheology of soft bodies suspended in the simple shear flow of a viscoelastic Fluid
Journal of Non-newtonian Fluid Mechanics, 2019Co-Authors: Christopher J Guido, Eric S G ShaqfehAbstract:Abstract Many industrial applications involve soft suspended bodies in viscoelastic Fluids. Moreover, many biological Fluids contain high molecular weight macromolecules which impart viscoelasticity to the Fluid, and any cells which are suspended in such Fluids again form a suspension of elastic bodies in a viscoelastic Fluid. For control purposes, microFluidic platforms are beginning to utilizing viscoelastic solvents to perform tasks such as cell focusing [34]. However, despite numerical studies into the kinematics of such deformable bodies in viscoelastic Fluids, no studies currently consider the rheology of such systems. Due to the competing effects of the viscoelasticity of the Fluid and the elasticity of the solids it is clear that there exists a non-trivial rheological behavior exhibited by such suspensions. In this study, we present simulations of dilute systems of deformable particles with viscoelastic Suspending Fluids. We compute the effective viscosity and the first/second normal stresses for a suspension of neoHookean particles sheared in a Giesekus Suspending Fluid up to modest deformations characterized by a capillary number, Ca, up to Ca = 0.3. The results indicate that the per particle extra stress that originates from the Suspending Fluid (the particle induced Fluid stress) remains relatively constant regardless of deformation. In contrast, the component of the extra stress that arises from the stress inside the particle (the stresslet) is a strong function of both the capillary number and the Weissenberg number for the parameter space investigated. Note that we find the suspensions “thicken” and/or “thin” with increasing shear depending on the range of parameter space examined.
-
mechanism of shear thickening in suspensions of rigid spheres in boger Fluids part ii suspensions at finite concentration
Journal of Rheology, 2018Co-Authors: Mengfei Yang, Eric S G ShaqfehAbstract:The steady shear rheology of nondilute suspensions of noncolloidal, rigid spheres in highly elastic, constant viscosity Fluids is studied via numerical simulation using three-dimensional, finite-volume methods and via experiments using cone-and-plate measurements. In the numerical study, we use an immersed boundary method to simulate an ensemble of particles as a function of time until they achieve steady average bulk properties, and the simulations include fully resolved particle-scale hydrodynamics and Fluid stresses. The simulations show that for low volume fraction, nondilute suspensions, the viscosity thickens at high shear and this effect can be fully determined by considering a single particle’s interactions with the Suspending Fluid. In fact, we show that experimentally measured viscosities of suspensions up to ϕ∼0.25, where ϕ is the volume fraction of particles, can be characterized by a shift factor that determines the zero-shear viscosity and a master curve that describes the viscosity thickeni...
-
mechanism of shear thickening in suspensions of rigid spheres in boger Fluids part i dilute suspensions
Journal of Rheology, 2018Co-Authors: Mengfei Yang, Eric S G ShaqfehAbstract:The mechanism for shear thickening of the viscometric functions of rigid non-Brownian sphere suspensions in highly elastic Fluids is studied numerically. Particular focus is placed on the particle-induced Fluid stress, which is the dominant contribution to the shear thickening behavior, especially at moderate to high Weissenberg numbers. We determine the Weissenberg number scaling for both the magnitude of the particle-induced Fluid stress and the volume containing most of the particle-induced Fluid stress to understand the overall suspension behavior at moderate Weissenberg numbers. Furthermore, we analyze the flow type in the regions of significant polymer-induced Fluid stress and find that the stretch of polymers in strain-dominated flow within closed streamlines around the particles generates the large stresses that contribute to the thickening behavior. Thus, understanding the response of the Suspending Fluid to extensional deformation is important for predicting the shear rheology of the bulk suspension. Lastly, we explore the effect of polymer viscosity and polymer extensibility on the behavior of the particle-induced Fluid stress.The mechanism for shear thickening of the viscometric functions of rigid non-Brownian sphere suspensions in highly elastic Fluids is studied numerically. Particular focus is placed on the particle-induced Fluid stress, which is the dominant contribution to the shear thickening behavior, especially at moderate to high Weissenberg numbers. We determine the Weissenberg number scaling for both the magnitude of the particle-induced Fluid stress and the volume containing most of the particle-induced Fluid stress to understand the overall suspension behavior at moderate Weissenberg numbers. Furthermore, we analyze the flow type in the regions of significant polymer-induced Fluid stress and find that the stretch of polymers in strain-dominated flow within closed streamlines around the particles generates the large stresses that contribute to the thickening behavior. Thus, understanding the response of the Suspending Fluid to extensional deformation is important for predicting the shear rheology of the bulk suspen...
Patrick T Spicer - One of the best experts on this subject based on the ideXlab platform.
-
variations of the herschel bulkley exponent reflecting contributions of the viscous continuous phase to the shear rate dependent stress of soft glassy materials
Journal of Rheology, 2020Co-Authors: Marco Caggioni, Veronique Trappe, Patrick T SpicerAbstract:We explore the flow behavior of concentrated emulsions for which the viscosity of the continuous phase can be significantly varied by changing the temperature. The exponents obtained by fitting the shear rate-dependent stress with the popular Herschel–Bulkley (HB) model display a systematic dependence on the viscosity of the continuous phase, revealing that viscous dissipation via the Suspending Fluid cannot be neglected in the description of the flow behavior of soft glassy systems. We thus propose a simple constitutive equation that accounts for three distinct dissipation mechanisms: elastic, plastic, and viscous dissipation. This three component model describes the flow behavior of soft glassy materials as accurately as the HB model, albeit maintaining a clear physical insight into the dissipation processes at work.
Marco Caggioni - One of the best experts on this subject based on the ideXlab platform.
-
variations of the herschel bulkley exponent reflecting contributions of the viscous continuous phase to the shear rate dependent stress of soft glassy materials
Journal of Rheology, 2020Co-Authors: Marco Caggioni, Veronique Trappe, Patrick T SpicerAbstract:We explore the flow behavior of concentrated emulsions for which the viscosity of the continuous phase can be significantly varied by changing the temperature. The exponents obtained by fitting the shear rate-dependent stress with the popular Herschel–Bulkley (HB) model display a systematic dependence on the viscosity of the continuous phase, revealing that viscous dissipation via the Suspending Fluid cannot be neglected in the description of the flow behavior of soft glassy systems. We thus propose a simple constitutive equation that accounts for three distinct dissipation mechanisms: elastic, plastic, and viscous dissipation. This three component model describes the flow behavior of soft glassy materials as accurately as the HB model, albeit maintaining a clear physical insight into the dissipation processes at work.
Guillaume Ovarlez - One of the best experts on this subject based on the ideXlab platform.
-
imaging non brownian particle suspensions with x ray tomography application to the microstructure of newtonian and viscoplastic suspensions
Journal of Rheology, 2018Co-Authors: Stephanie Deboeuf, Nicolas Lenoir, David Hautemayou, Michel Bornert, Frederic Blanc, Guillaume OvarlezAbstract:A key element in the understanding of the rheological behavior of suspensions is their microstructure. Indeed, the spatial distribution of particles is known to depend on flow history in suspensions, which has an impact on their macroscopic properties. These micro-macrocouplings appeal for the development of experimental tools allowing for the rheological characterization of a suspension and the imaging of particles. In this paper, we present the technique we developed to image in three dimensions the microstructure of suspensions of non-Brownian particles, using X-ray computed tomography and subvoxel identification of particle centers. We also give examples of the information we can get in the case of Newtonian and viscoplastic suspensions, referring to Newtonian and viscoplastic Suspending Fluid. We compute three dimensional pair distribution functions and show that it is possible to get a nearly isotropic microstructure after mixing. Under shear, this microstructure becomes anisotropic in the shear pla...
-
Rheological behaviour of suspensions of bubbles in yield stress Fluids
Journal of Non-Newtonian Fluid Mechanics, 2015Co-Authors: Lucie Ducloué, Xavier Chateau, Olivier Pitois, Julie Goyon, Guillaume OvarlezAbstract:The rheological properties of suspensions of bubbles in yield stress Fluids are investigated through experiments on model systems made of monodisperse bubbles dispersed in concentrated emulsions. Thanks to this highly tunable system, the bubble size and the rheological properties of the Suspending yield stress Fluid are varied over a wide range. We show that the macroscopic response under shear of the suspensions depends on the gas volume fraction and the bubble stiffness in the Suspending Fluid. This relative stiffness can be quantified through capillary numbers comparing the capillary pressure to stress scales associated with the rheological properties of the Suspending Fluid. We demonstrate that those capillary numbers govern the decrease of the elastic and loss moduli, the absence of variation of the yield stress and the increase of the consistency with the gas volume fraction, for the investigated range of capillary numbers. Micro-mechanical estimates are consistent with the experimental data and provide insight on the experimental results.
-
homogenization approach to the behavior of suspensions of noncolloidal particles in yield stress Fluids
Journal of Rheology, 2008Co-Authors: Xavier Chateau, Guillaume Ovarlez, Kien Luu TrungAbstract:The behavior of suspensions of rigid particles in a non-Newtonian Fluid is studied in the framework of a nonlinear homogenization method. Estimates for the overall properties of the composite material are obtained. In the case of a Herschel–Bulkley Suspending Fluid, it is shown that the properties of a suspension with overall isotropy can be satisfactorily modeled as that of a Herschel–Bulkley Fluid with an exponent equal to that of the Suspending Fluid. Estimates for the yield stress and the consistency at large strain rate levels are proposed. These estimates compare well to both experimental data obtained by Mahaut et al. [J. Rheol. 52(1), 287–313 (2008)] and to experimental data found in the literature.The behavior of suspensions of rigid particles in a non-Newtonian Fluid is studied in the framework of a nonlinear homogenization method. Estimates for the overall properties of the composite material are obtained. In the case of a Herschel–Bulkley Suspending Fluid, it is shown that the properties of a suspension with overall isotropy can be satisfactorily modeled as that of a Herschel–Bulkley Fluid with an exponent equal to that of the Suspending Fluid. Estimates for the yield stress and the consistency at large strain rate levels are proposed. These estimates compare well to both experimental data obtained by Mahaut et al. [J. Rheol. 52(1), 287–313 (2008)] and to experimental data found in the literature.
Mengfei Yang - One of the best experts on this subject based on the ideXlab platform.
-
mechanism of shear thickening in suspensions of rigid spheres in boger Fluids part ii suspensions at finite concentration
Journal of Rheology, 2018Co-Authors: Mengfei Yang, Eric S G ShaqfehAbstract:The steady shear rheology of nondilute suspensions of noncolloidal, rigid spheres in highly elastic, constant viscosity Fluids is studied via numerical simulation using three-dimensional, finite-volume methods and via experiments using cone-and-plate measurements. In the numerical study, we use an immersed boundary method to simulate an ensemble of particles as a function of time until they achieve steady average bulk properties, and the simulations include fully resolved particle-scale hydrodynamics and Fluid stresses. The simulations show that for low volume fraction, nondilute suspensions, the viscosity thickens at high shear and this effect can be fully determined by considering a single particle’s interactions with the Suspending Fluid. In fact, we show that experimentally measured viscosities of suspensions up to ϕ∼0.25, where ϕ is the volume fraction of particles, can be characterized by a shift factor that determines the zero-shear viscosity and a master curve that describes the viscosity thickeni...
-
mechanism of shear thickening in suspensions of rigid spheres in boger Fluids part i dilute suspensions
Journal of Rheology, 2018Co-Authors: Mengfei Yang, Eric S G ShaqfehAbstract:The mechanism for shear thickening of the viscometric functions of rigid non-Brownian sphere suspensions in highly elastic Fluids is studied numerically. Particular focus is placed on the particle-induced Fluid stress, which is the dominant contribution to the shear thickening behavior, especially at moderate to high Weissenberg numbers. We determine the Weissenberg number scaling for both the magnitude of the particle-induced Fluid stress and the volume containing most of the particle-induced Fluid stress to understand the overall suspension behavior at moderate Weissenberg numbers. Furthermore, we analyze the flow type in the regions of significant polymer-induced Fluid stress and find that the stretch of polymers in strain-dominated flow within closed streamlines around the particles generates the large stresses that contribute to the thickening behavior. Thus, understanding the response of the Suspending Fluid to extensional deformation is important for predicting the shear rheology of the bulk suspension. Lastly, we explore the effect of polymer viscosity and polymer extensibility on the behavior of the particle-induced Fluid stress.The mechanism for shear thickening of the viscometric functions of rigid non-Brownian sphere suspensions in highly elastic Fluids is studied numerically. Particular focus is placed on the particle-induced Fluid stress, which is the dominant contribution to the shear thickening behavior, especially at moderate to high Weissenberg numbers. We determine the Weissenberg number scaling for both the magnitude of the particle-induced Fluid stress and the volume containing most of the particle-induced Fluid stress to understand the overall suspension behavior at moderate Weissenberg numbers. Furthermore, we analyze the flow type in the regions of significant polymer-induced Fluid stress and find that the stretch of polymers in strain-dominated flow within closed streamlines around the particles generates the large stresses that contribute to the thickening behavior. Thus, understanding the response of the Suspending Fluid to extensional deformation is important for predicting the shear rheology of the bulk suspen...
