Velocity and concentration measurements of suspensions by nuclear magnetic resonance imaging

Altobelli, Stephen A.; Givler, Richard C.; Fukushima, Eiichi

doi:10.1122/1.550156

Cited by 143 publications

(59 citation statements)

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“…The applicability of the model in multidimensional shear flows has been supported by the investigations of Zhang and Acrivos [32] and Fang and Phan-Thien [33], who have observed a reasonable agreement between computed and experimental particle concentration in Couette flow situation. In fact, the theoretically predicted velocity and concentration profiles for flow in a circular pipe by Zhang and Acrivos [32] have been found to be in very good qualitative agreement with the experimental results reported by Altobelli et al [57] where the flow velocities and particle distributions are measured by employing the technique of nuclear magnetic resonance imaging. Also, the steady-state solution in circular Couette flow obtained by Fang and Phan-Thien [33] using a finite volume formulation with the model described by Equations (8) and (9) is indistinguishable from the exact solutions to three significant figures (Figures 2 and 3 of Fang and Phan-Thien [33]).…”

Section: Governing Equationssupporting

confidence: 57%

Numerical study of concentrated fluid–particle suspension flow in a wavy channel

Mukhopadhyay

Usha

Tulapurkara

2008

Numerical Methods in Fluids

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SUMMARYThe particle migration effects and fluid-particle interactions occurring in the flow of highly concentrated fluid-particle suspension in a spatially modulated channel have been investigated numerically using a finite volume method. The mathematical model is based on the momentum and continuity equations for the suspension flow and a constitutive equation accounting for the effects of shear-induced particle migration in concentrated suspensions. The model couples a Newtonian stress/shear rate relationship with a shear-induced migration model of the suspended particles in which the local effective viscosity is dependent on the local volume fraction of solids. The numerical procedure employs finite volume method and the formulation is based on diffuse-flux model. Semi-implicit method for pressure linked equations has been used to solve the resulting governing equations along with appropriate boundary conditions. The numerical results are validated with the analytical expressions for concentrated suspension flow in a plane channel. The results demonstrate strong particle migration towards the centre of the channel and an increasing blunting of velocity profiles with increase in initial particle concentration. In the case of a stenosed channel, the particle concentration is lowest at the site of maximum constriction, whereas a strong accumulation of particles is observed in the recirculation zone downstream of the stenosis. The numerical procedure applied to investigate the effects of concentrated suspension flow in a wavy passage shows that the solid particles migrate from regions of high shear rate to low shear rate with low velocities and this phenomenon is strongly influenced by Reynolds numbers and initial particle concentration.

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Section: Governing Equationssupporting

confidence: 57%

Numerical study of concentrated fluid–particle suspension flow in a wavy channel

Mukhopadhyay

Usha

Tulapurkara

2008

Numerical Methods in Fluids

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“…NMR also provides simultaneous velocity profiles. NMR imaging has-been utilized for measuring concentration and velocity profiles in many flow geometries, including circular pipe flow (Sinton and Chow, 1991;Altobelli et al, 1991;Arola et al, 1999;Hampton et al, 1997), wide-gap Couette flow (Abbott et al, 1991;Graham et al, 1991;Tetlow et al, 1998), narrow-gap Couette flow , parallel plates torsional flow , piston-driven contraction-expansion flow (Altobelli et al, 1997), single screw extruder flow (Corbett et al, 1995) and suspension settling (Abbott et al, 1993;Bobroff and Phillips, 1998) The best method for visualizing particle microstructure geometry and quantifying statistics of particle interactions is video image analysis applied to a refractive index-matched suspension. Leighton and Rampall (1993) applied this method to measure the pair distribution function of particles in steady homogeneous shear flow.…”

Section: Experimental Techniques Used For Concentrated Non-colloidal mentioning

confidence: 99%

Laser Doppler velocimetry measurements of particle velocity fluctuations in a concentrated suspension

Shapley

Armstrong

Brown

2002

Journal of Rheology

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Recent statistical constitutive models of suspensions of neutrally buoyant, non-Brownian, noncolloidal, solid spheres in Newtonian fluids suggest that the particles nijgrate in response to gradients in "suspension temperature," defined as the average kinetic energy contained in the particle velocity fluctuations. These models have not yet been compared systematically with experimental data.In addition, the "temperature" models assume isotropic particle velocity fluctuations, since the "suspension temperature" is given as a scalar, in analogy to molecular systems. However, highly anisotropic particle velocity fluctuations have been observed in settling suspensions, which suggests that a "suspension temperature" tensor would be more realistic.We used laser Doppler velocimetry (LDV) to make a set of experimental observations of particle velocity fluctuations arising from inter-particle collisions in a concentrated non-colloidal suspension under nearly homogeneous shear flow in a narrow-gap concentric cylinder Couette device. We compared the relative sizes of the fluctuating velocity components and observed the variation of each component with particle volume fraction, shear rate, and radial position. In addition, we assessed the implications of these observations for suspension temperature models.The data indicate that the suspension temperature is anisotropic. The flow direction component is overwhelmingly the largest at every concentration and shear rate, followed by the neutral and then the gradient components. Meanwhile, each fluctuating velocity component demonstrates a distinct variation with the shear rate and with the particle volume fraction, but only slight variation with radial position, over the region of the flow accessible to measurement.Comparison between model predictions and measured shear rate and particle volume fraction profiles shows that several models capture the measured profiles qualitatively but not quantitatively, with better agreement for moderately concentrated suspensions than for highly concentrated suspensions. Also, comparison between predicted scalar suspension temperature profiles and the sum of the measured velocity fluctuation components demonstrates that most of the models underpredict the sum of the temperature components by a large factor. Finally, comparison among the models shows that the models are quite sensitive to the choice of transport coefficients that are functions of the particle volume fraction.

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“…The migration phenomenon, which leads to concentration inhomogeneities, and is at the origin of size segregation in polydisperse systems, was observed in many situations: Couette flows [Leighton and Acrivos (1987b); Graham et al (1991); Abbott et al (1991); Phillips et al (1992); Chow et al (1994); Corbett et al (1995); Tetlow et al (1998); Shapley et al (2004)], parallelplate flows [Chow et al (1994); Barentin et al (2004)], pipe flows [Sinton and Chow (1991); Altobelli et al (1991); Hampton et al (1997); Lyon and Leal (1998); Butler et al (1999); Han et al (1999)], and extrusion experiments ; Götz et al (2002)]. In the Couette flows, the consequence of migration is an excess of particles near the outer cylinder.…”

Section: Introductionmentioning

confidence: 99%

Local determination of the constitutive law of a dense suspension of noncolloidal particles through magnetic resonance imaging

Ovarlez¹,

Bertrand²,

Rodts³

2006

Journal of Rheology

234

260

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SynopsisWe investigate the flowing behavior of dense suspensions of non-colloidal particles, by coupling macroscopic rheometric experiments and local velocity and concentration measurements through MRI techniques. We find that the flow is localized at low velocities, and that the material is inhomogeneous; the local laws inferred from macroscopic rheometric observations must then be reinterpreted in the light of these local observations. We show that the short time response to a velocity step allows to characterize dense suspensions locally: they have a purely viscous behavior, without any observable influence of friction. In the jammed zone, there may be a contact network, whereas in the sheared zone there are only hydrodynamic interactions: localization consists in a change in configuration at the grain scale. From the concentration and velocity profiles, we have provided for the first time local measurements of the concentration dependence of viscosity; we find a Krieger-Dougherty law η(φ) = η 0 (1 − φ/0.605) −2 . Shear induced migration is almost instantaneous and seems inconsistent with most observations: it would imply that the diffusion coefficients strongly depend on the concentration. We finally propose a simple constitutive law for dense suspensions, based on a purely viscous behavior, that accounts for all the macroscopic and local observations.

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Velocity and concentration measurements of suspensions by nuclear magnetic resonance imaging

Cited by 143 publications

References 0 publications

Numerical study of concentrated fluid–particle suspension flow in a wavy channel

Numerical study of concentrated fluid–particle suspension flow in a wavy channel

Laser Doppler velocimetry measurements of particle velocity fluctuations in a concentrated suspension

Local determination of the constitutive law of a dense suspension of noncolloidal particles through magnetic resonance imaging

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