Structural change in non-fractal particle clusters under fluid stress

Harada, Shusaku; Tanaka, Ryoichi; Nogami, H.; Sawada, Manabu; Asakura, Kuniomi

doi:10.1016/j.colsurfa.2007.03.003

Cited by 16 publications

(39 citation statements)

References 19 publications

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“…It must be noted here that, as opposed to some other research works 42,58 dealing with the breakup of colloidal aggregates and taking into account colloidal particle−particle interactions, no arbitrary bounds have been imposed on the potentials.…”

Section: Model Formulationmentioning

confidence: 99%

Universal Breakup of Colloidal Clusters in Simple Shear Flow

Harshe

Lattuada

2016

J. Phys. Chem. B

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ABSTRACT:We have studied the long-term dynamics of shear-induced breakage of individual colloidal clusters, covering a wide range of fractal dimensions, using Stokesian dynamics. We found that the time evolution of the normalized average size of the fragments generated by the breakup process could be scaled using a unique dimensionless time defined by multiplying the real time with the cluster breakage rate constant (τ = t·k B ). Clusters with different masses but the same fractal dimension exhibited almost identical breakage dynamics when exposed to equal overall hydrodynamic forces (ηγR g,0 2 ). The steady-state values of the average size, mass, and standard deviation of fragment mass distribution showed a universal scaling depending only on the overall hydrodynamic force, irrespective of the initial cluster properties. We also identified two asymptotic regimes for the evolution of the fractal dimension, ⟨d f ⟩, of fragments: open clusters (d f ≤ 2

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Section: Model Formulationmentioning

confidence: 99%

Universal Breakup of Colloidal Clusters in Simple Shear Flow

Harshe

Lattuada

2016

J. Phys. Chem. B

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“…Therefore the 17 installation of tangential force model is possible to influence the simulation results on dynamic behaviors of a 18 non-fractal aggregate as shown here. However, a physically-proved model on the tangential force has not 19 been fully established in colloidal particulate system and the proposed models have undecided coefficients. 20 Therefore we did not include the tangential force models in this simulation to avoid tuning parameters of the 21 simulation results.…”

mentioning

confidence: 99%

“…In this study, the coordination number is defined by the average number of 16 particles existing within 2nm from each particle. 17 In our previous studies 8,19 , we simulated the breakup behavior of aggregate in shear flow for a wide range 18 of shear rate condition and reported the dependence of aggregate behaviors on the shear rate, i.e., the aggregate 19 breaks up immediately for high shear rate, while it is hard to break up for low shear rate conditions. As 20 mentioned in Introduction, the dispersion behavior is determined by Fragmentation number Fa, which is the 21 ratio of characteristic fluid stress γ µ  to cohesive strength of aggregate σ.…”

mentioning

confidence: 99%

“…In general, a soft matter in simple shear flow shows complicated structural change owing to both 26 rotation and elongation effects of the flow field, even though it has a simple chain-like or string-like structure 27 16,17 . There have been many numerical studies on the restructuring of aggregate in shear flow [18][19][20][21][22][23][24] . These 28 studies have reported that the magnitude relation between the bend stress by fluid force and the hold moment 1 by inter-particle force is important for the restructuring of fractal aggregate.…”

mentioning

confidence: 99%

“…The relation between mass distribution of fragments and fluid stress has been discussed [7][8][9][10] . The 18 second topic is regarding the fluid force and the resultant internal stress on a rigid (non-deformable) 19 aggregate in fluid flow [11][12][13][14][15] . There have been a considerable number of researches on the dependence of the 20 fluid force on the aggregate structure and the distribution of the inter-particle force of the aggregate with an 21 open structure.…”

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confidence: 99%

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Strength Deterioration of Nonfractal Particle Aggregates in Simple Shear Flow

2015

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The restructuring of a non-fractal particle aggregate in simple shear flow was simulated by Stokesian dynamics approach. We studied the deformation and the resultant strength change of aggregate by surrounding flow under the condition that the cohesive strength of aggregate is comparable with the fluid stress. In particular, we focused on how the aggregate deteriorates due to the fluid stress exerted on it periodically. The image analysis was applied to visualized simulation results for quantitative estimation of irreversible change in aggregate configuration.We examined the structural change of aggregate from various perspectives, i.e., the outer shape, the internal strength and the fluid stress on the surface of the aggregate. The simulation results show that the aggregate gets squashed after intricate restructuring process and it elongates along with streamline as experimentally observed in the previous study. Regarding the internal strength, the weakest point locally develops in the aggregate by periodically-varying fluid stress. Combination of rotation and elongation effects of shear flow is complexly-involved in the deterioration of internal strength of aggregate.

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Determination of maximum turbulent energy dissipation rate generated by a rushton impeller through large eddy simulation

et al. 2013

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Large eddy simulation (LES) of a stirred tank equipped with a Rushton impeller and four cylindrical baffles was used to characterize the flow pattern and to assess the maximum turbulent kinetic energy dissipation rate e max . While the shorter baffle-impeller distance significantly affects the radial velocity profile and the trailing vortices expansion, the flow field in the impeller vicinity is comparable to that of a standard setup with rectangular baffles connected to the wall. The phase-resolved profile of e max indicates its very strong variation from 10 Á N 3 D 2 to 130 6 13 Á N 3 D 2. When using peak values of the corresponding hydrodynamic stress s max 5 ffiffiffiffiffiffiffiffiffiffiffiffiffiffi lqe max p À Á , the maximum stable aggregate size measured in the same stirred tank closely correlates with breakage data obtained under laminar conditions using the same initial aggregates. This indicates that the same mechanism was involved in the aggregate breakup under both conditions, allowing us to predict aggregates breakup under various conditions.

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Structural change in non-fractal particle clusters under fluid stress

Cited by 16 publications

References 19 publications

Universal Breakup of Colloidal Clusters in Simple Shear Flow

Universal Breakup of Colloidal Clusters in Simple Shear Flow

Strength Deterioration of Nonfractal Particle Aggregates in Simple Shear Flow

Determination of maximum turbulent energy dissipation rate generated by a rushton impeller through large eddy simulation

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