Magnetic resonance imaging of concentration and velocity profiles of pure fluids and solid suspensions in rotating geometries

Corbett, Alana M.; Phillips, Ronald J.; Kauten, Robert J.; McCarthy, Kathryn

doi:10.1122/1.550724

Cited by 51 publications

(34 citation statements)

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“…The gradients in shear rate that exist in a Couette geometry then generate a particle flux towards the outer cylinder, which is counterbalanced by a particle flux due to viscosity gradients. As qualitatively confirmed experimentally [20,41], one would then expect the migration phenomenon to last for a number of revolutions…”

Section: A Concentration Profilesmentioning

confidence: 91%

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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

et al. 2008

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Flows of dense emulsions show many complex features among which long range nonlocal effects pose problem for macroscopic characterization. In order to get round this problem, we study the flows of several dense emulsions, with droplet size ranging from 0.3 to 40µm, in a wide gap Couette geometry. We couple macroscopic rheometric experiments and local velocity measurements through MRI techniques. As concentration heterogeneities are expected in the wide gap Couette flows of multiphase materials, we also designed a new method to measure the local droplet concentration in emulsions with a MRI device. In contrast with dense suspensions of rigid particles where very fast migration occurs under shear in wide gap Couette flows, we show for the first time that no migration takes place in dense emulsions even for strain as large as 100000 in our systems. As a result of the absence of migration and of finite size effect, we are able to determine very precisely the local rheological behavior of several dense emulsions. As the materials are homogeneous, this behavior can also be inferred from purely macroscopic measurements. We thus suggest that properly analyzed purely macroscopic measurements in a wide gap Couette geometry can be used as a tool to study the local constitutive laws of dense emulsions. All behaviors are basically consistent with Herschel-Bulkley laws of index 0.5. The existence of a constitutive law accounting for all flows contrasts with previous results obtained within a microchannel by Goyon et al. [Nature 454, 84 (2008)]: the use of a wide gap Couette geometry is likely to prevent here from nonlocal finite size effects; it also contrasts with the observations of Bécu et al. [Phys. Rev. Lett. 96, 138302 (2006)].We also evidence the existence of discrepancies between a perfect Herschel-Bulkley behavior and the observed local behavior at the approach of the yield stress due to slow shear flows below the apparent yield stress in the case of a strongly adhesive emulsion.

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Section: A Concentration Profilesmentioning

confidence: 91%

“…In suspensions of noncolloidal rigid particles, migration has been observed in many situations: wide-gap Couette flows [12,20,21,22,23], parallel-plate flows [24], pipe flows [25,26]. In wide-gap Couette flows, the consequence of migration is an excess of particles near the outer cylinder.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2008

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“…This results in the local variation of the viscosity. Such shear-induced particle migration has been studied mainly in conduits and Couette rheometers (Abbott et al 1991, Chow et al 1994, Corbett et al 1995, Götz et al 2001, Sinton & Chow 1991) but may be not enough systematically for a full understanding of the basic processes of migration. Independent of the mechanism of migration, the measurement of the density profile for the granular paste showed that the particle volume fraction increases linearly with increasing distance from the moving inner cylinder, which qualitatively confirms that the viscosity varies within the gap owing to a flow-induced density Variation of the viscosity in a Couette cell, as deduced from the magnetic resonance imaging velocity profile.…”

Section: Mri Rheology Of Wet Granular Materialsmentioning

confidence: 99%

Some Applications of Magnetic Resonance Imaging in Fluid Mechanics: Complex Flows and Complex Fluids

Bonn

Rodts

Groenink

et al. 2008

Annu. Rev. Fluid Mech.

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“…In addition to its well-documented ability as a reliable imaging modality, MR imaging provides quantitative information about flow velocity in medical and non-medical applications [3][4][5][6][7][8][9]. The major advantage of MR velocity imaging in medicine is its unique clinical ability to measure all three spatial directions of the velocity in an imaging slice.…”

Section: Introductionmentioning

confidence: 99%

Reliable in-plane velocity measurements with magnetic resonance velocity imaging

Zhang

Halliburton

Venkatachari

et al. 2006

Flow Measurement and Instrumentation

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Magnetic resonance imaging of concentration and velocity profiles of pure fluids and solid suspensions in rotating geometries

Cited by 51 publications

References 0 publications

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

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

Some Applications of Magnetic Resonance Imaging in Fluid Mechanics: Complex Flows and Complex Fluids

Reliable in-plane velocity measurements with magnetic resonance velocity imaging

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