Effect of confinement on the rheology of a yield-stress fluid

Liu, Yang; Lorusso, Daniel; Holdsworth, David W.; Poepping, Tamie L.; Bruyn, John R. de

doi:10.1016/j.jnnfm.2018.08.002

Cited by 16 publications

(11 citation statements)

References 24 publications

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“…On the other hand, the factor K in the constitutive model of Seth et al (2011) is only occurring in the combination K 2 /E * and both parameters are not independently experimentally verified (Mohan et al (2013b)), so that their absolute values might differ. Also recent simulations by Liu et al (2018) support the key role that the elastic contribution and thus the interparticle pressure term has on the flow behaviour of soft particle suspensions. While these simulations indicate that near-field drag forces (as the f EHD that we use for deriving the square root relation of stress and rate in Equation 11) are subdominant to the far-field (hindered Stokes) drag, they confirm that it is predominantly the elastic force balancing the drag that determines the flow properties, as well as the general time scale of solvent viscosity times the elastic force of Equation 14 or the constitutive model in Seth et al (2011).…”

Section: Microscopic Origin Of Stress In the Flowing Samplementioning

confidence: 81%

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Effect of geometrical confinement on the flow of soft microgel particle pastes

et al. 2020

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In this paper we determine the effect of confinement on the shear flow of concentrated soft microgel particle suspensions. Utilizing a Flexure-based Microgap Rheometer (FMR), aqueous suspensions of swollen P(NIPAM-co-AA) microgel particles of 4 µm diameter at different volume fractions larger than 64 vol% are subjected to shearing deformations between plates separated by gaps of 5 −120 µm while monitoring the stress response at different rates. Describing the stress evolution from a balance of elastohydrodynamic lubrication and elastic forces following the approach of Cloitre and Bonnecaze, it could be shown that already below a critical confinement level on the order of 10 particle diameters an increase of the interparticle pressure leads to a rising shear stress at a given rate in the yielded regime. This effect is strongest for particle volume fractions close to the critical closest packing, with two orders of magnitude increase in flow resistance when approaching the single particle confinement level, whereas this confinement effect on the flow decreases when raising the concentration. Furthermore, it could be shown that, at the onset of the yielding of the suspensions, the confinement is increasing the effective modulus, but not the yield strain. 2 Giovanni Vleminckx et al. Rheologica Acta manuscript No.

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Section: Microscopic Origin Of Stress In the Flowing Samplementioning

confidence: 81%

“…However, so far no systematic study for confinement levels above single microgel particle confinement have been performed. A recent study by Liu et al (2018) looked at channel flow of soft microgel particles at different confinement levels, however, not for a uniform deformation rate profile.…”

Section: Hydrogelmentioning

confidence: 99%

Effect of geometrical confinement on the flow of soft microgel particle pastes

et al. 2020

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“…A third class of studies refers to microscopic flows where the influence of the confinement is expected to play an important role and can not be de-coupled from the wall slip and yielding behaviour, [17][18][19][20]. As compared to the second class, this third class of studies is somewhat less represented although the microscopic wall slip behaviour is relevant to a number of microscopic experimental settings such as the impact and/or atomisation of viscoplastic drops [21][22][23][24] with a number of applications in fuel industry and microscopic blood flows [25,26].…”

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confidence: 99%

“…They found a strong disagreement between the bulk prediction of the velocity profiles and the ones measured in the micro-channels and they attribute this discrepancy to the confinement of the flow. Liu et al [17] compared the measured velocity profiles in microchannels to simulations performed based on the bulk rheology. They show that the confinement effects become important when the dimensions of the channel are comparable to the characteristic size of the material's microstructure and, consequently, the measured velocity profiles differ from those computed numerically using the Herschel-Bulkley constitutive relation.…”

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confidence: 99%

“…computing the wall shear rate using the the flow rate or pre-assuming a Herschel-Bukley like velocity profile which, as shown in Ref. [17]) is not accurate in the presence of confinement. The overall conclusion is that, in spite of the reliability of the macroscopic scale experiments in capturing the wall slip behaviour, there seems to exist no universal consensus on neither the scaling behaviour nor the fundamental physical mechanisms responsible for the wall slip behaviour.…”

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confidence: 99%

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Slippery flows of a Carbopol gel in a micro-channel

Younes,

Castelain,

Bertola

et al. 2020

Preprint

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The ability to predict and/or control wall slip is a fundamental problem in the hydrodynamics of yield stress fluids, which is poorly understood to date and has important applications in bio-and micro-fluidic systems. Systematic measurements of steady flows of a simple yield stress fluid (Carbopol Ultrez 10) in a plane acrylic micro-channel are used to establish rigorous scaling laws for the wall velocity gradient and the slip velocity. By means of epi-fluorescent microscopy combined with a custom developed Digital Particle Image Velocimetry (DPIV) technique, times series of velocity fields were measured within a wide range of flow rates and three distinct flow regimes were identified: full plug, partial plug and fully yielded. Corresponding to each flow regime, wall velocity gradients and slip velocities were obtained by extrapolating the velocity profiles using a smoothing spline function. By combining the flow field measurements with the macro-rheological measurements, scaling laws for the wall velocity gradient and the slip velocity with the wall shear stress were identified, and compared with results from the literature. Detailed microscopic measurements of the velocity field enabled an assessment of the effectiveness of a chemical treatment of the channel walls meant to suppress wall slip proposed by Metivier and coworkers in Ref. [1]. Contents I. Experimental methods A. Choice, preparation and rheological characterization of the working fluid 1. Fluid preparation 2. Rheological measurements B. Micro-channel design, microscopic flow control and data acquisition protocol C. Data analysis II. Results A. Description of the flow regimes in the presence of wall slip B. Scaling behavior at the wall within various flow regimes C. Comparison with previous results from the literature III. On the possibility of inhibiting the wall slip in an acrylic made micro-channel A. Chemical treatment of the micro-channel B. Assessment of wall slip behavior via macro-rheological measurements C. Slip behavior in chemically treated micro-channels IV. Summary of conclusions, outlook V. Acknowledgements Notes and references List of Figures * Eliane

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Analysis of flow and slip behavior of microgel solution inside microchannel

Kim

Nam

2021

Chemical Engineering Science

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Effect of confinement on the rheology of a yield-stress fluid

Cited by 16 publications

References 24 publications

Effect of geometrical confinement on the flow of soft microgel particle pastes

Effect of geometrical confinement on the flow of soft microgel particle pastes

Slippery flows of a Carbopol gel in a micro-channel

Analysis of flow and slip behavior of microgel solution inside microchannel

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