Shear-thinning predictions from particle motion modeling

Bilodeau, Robert R.; Bousfield, Douglas W.

doi:10.1122/1.550910

Cited by 15 publications

(5 citation statements)

References 35 publications

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“…The observation of both out-of-plane collisions in video imaging of the flow and significant vertical velocity fluctuations in LDV measurements together lead us to conclude that the neutral direction plays an important role in inter-particle interactions. This conclusion invalidates the idea employed in the original Stokesian Dynamics simulations (Nott and Brady, 1994) and more recent simulations (Dratler et al, 1997;Bilodeau and Bousfield, 1998) that a monolayer is equivalent to an interior plane in a one-dimensional or two-dimensional flow. Our data indicate that threedimensional simulations with all the real degrees of freedom are needed to recreate the experimental environment.…”

Section: Discussionmentioning

confidence: 51%

“…Although this system size is much more realistic than the original cells of 27 or 50 particles, even so, the system is only nine particle diameters wide, significantly smaller than the 16 particle diameters width at which Hampton et al (1997) experimentally observed finite size particle effects in circular tube flow. In simulations of suspensions with more complex particle interactions, such as colloidal suspensions (Dratler et al, 1997;Bilodeau and Bousfield, 1998), or suspensions of rough, non-colloidal particles (Haan and Steif, 1998), it is still standard practice to approximate the suspension as a monolayer in order to reduce computation load. Overall, the large number of particles needed to approximate a real system creates a heavy computational burden, especially for a three-dimensional simulation.…”

Section: Direct Simulations: Stokesian Dynamics and Related Methodsmentioning

confidence: 99%

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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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Section: Discussionmentioning

confidence: 51%

Section: Direct Simulations: Stokesian Dynamics and Related Methodsmentioning

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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“…The power law index ( n ) was obtained by fitting the data in the shear rate range of 10–300 1/s. As seen in Figure a, the power of shear thinning of diluted bitumen was not steep, which indicates that the interaction between asphaltenes in diluted bitumen is rather weak …”

Section: Results and Discussionmentioning

confidence: 85%

“…As seen in Figure 1a, the power of shear thinning of diluted bitumen was not steep, which indicates that the interaction between asphaltenes in diluted bitumen is rather weak. 30 3.2. Effect of Partially Oxidized Asphaltene on Viscosity.…”

Section: Resultsmentioning

confidence: 99%

Partially Oxidized Asphaltene as a Bitumen Viscosity Reducer

Choi

Kim

et al. 2017

Energy Fuels

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Heavy oil/bitumen with asphaltene requires high energy consumption for transportation, because of its high viscosity. This often causes serious pipeline problems; therefore, it is necessary to reduce the viscosity to resolve these issues. In this paper, we propose a new simple method to reduce the viscosity of diluted bitumen using partially oxidized asphaltene without removing asphaltene. This partially oxidized asphaltene, modified by exposing asphaltene to ozone, has a strong affinity to nonoxidized asphaltene via π−π stacking, hydrogen bonding, and acid−base interaction. The added oxidized asphaltene thus facilitated the agglomeration of asphaltene, so that the hydrophilic part can be hidden, and a small amount (1250 ppm) decreased the viscosity of diluted bitumen by up to 45%. We investigated the change in rheological properties of the diluted bitumen for various oxidized fractions of asphaltene and for various fractions of oxidized asphaltene to asphaltene. We showed that the decreased shear viscosity is likely to originate with the increased particle size of the asphaltene, that is, not the change in interactions between the asphaltene particles, but rather from their nonuniform distribution in size.

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“…8 In earlier computer simulations studies shear thinning has been attributed to either Brownian motion 9 or interparticle interactions. 5,10,11 Another quantity which was determined in these experiments is the high frequency elastic modulus G ϱ Ј . 12 In order to compare the experimental results for G ϱ Ј with the theoretical prediction of Elliot and Russel, 13 it was necessary to de-termine an effective interaction potential that accounts for the steric repulsion of the polymer layers.…”

Section: Introductionmentioning

confidence: 99%

Shear thinning of suspensions of sterically stabilized spheres studied by Stokesian dynamics simulations

Schaink

Nommensen

Jongschaap

et al. 2000

The Journal of Chemical Physics

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Stokesian dynamics simulations are presented of suspensions of sterically stabilized spheres in a viscous medium, subjected to simple shear. The steric repulsion between the grafted polymer layers of different particles is modeled using an interaction potential that is calculated using a self-consistent field lattice theory. The shear rate dependence and the volume fraction dependence of the suspension viscosity are calculated and compared to experimental data [Nommensen et al. Phys. Rev. E 59, 3147 (1999)]. It is found that shear thinning is mainly caused by the interaction contribution to the viscosity. The present paper, combined with a recent paper of Nommensen et al. [Langmuir 16, 1902 (2000)], shows that computer simulations, theoretical analysis, and experimental work give a consistent physical picture of the rheology of these suspensions when the proper interaction potential is used.

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Shear-thinning predictions from particle motion modeling

Cited by 15 publications

References 35 publications

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

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

Partially Oxidized Asphaltene as a Bitumen Viscosity Reducer

Shear thinning of suspensions of sterically stabilized spheres studied by Stokesian dynamics simulations

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