Dynamic simulation of shear thickening in concentrated colloidal suspensions

1997 ◽  
Vol 353 ◽  
pp. 1-30 ◽  
Author(s):  
D. I. DRATLER ◽  
W. R. SCHOWALTER ◽  
R. L. HOFFMAN
Keyword(s):  
Shear Rate ◽  
Hard Spheres ◽  
Shear Thickening ◽  
Colloidal Suspensions ◽  
System Size ◽  
Linear Instability ◽  
Computational Domain ◽  
Stokesian Dynamics ◽  
Rigid Spheres ◽  
Critical Shear Rate

Stokesian Dynamics has been used to investigate the origins of shear thickening in concentrated colloidal suspensions. For this study, we considered a monolayer suspension composed of charge-stabilized non-Brownian monosized rigid spheres dispersed at an areal fraction of ϕa=0.74 in a Newtonian liquid. The suspension was subjected to a linear shear field. In agreement with established experimental data, our results indicate that shear thickening in this system is associated with an order–disorder transition of the suspension microstructure. Below the critical shear rate at which this transition occurs, the suspension microstructure consists of two-dimensional analogues of experimentally observed sliding layer configurations. Above this critical shear rate, suspensions are disordered, contain particle clusters, and exhibit viscosities and microstructures characteristic of suspensions of non-Brownian hard spheres. In addition, suspensions possessing the sliding layer microstructure at the beginning of supercritical shearing tend to retain this microstructure for a period of time before disordering. The onset of this disorder is due to the formation of particle doublets within the suspension. Once formed, these doublets rotate, due to the bulk motion, and disrupt the long-range order of the suspension. The cross-stream component of the centre-to-centre separation vector associated with the two particles forming a doublet, which is zero when the doublet is perfectly aligned with the bulk velocity vector, grows exponentially with time. This strongly suggests that the evolution of these doublets is due to a change in the stability of the sliding layer configurations, with this type of ordered microstructure being linearly unstable above a critical shear rate. This contention is supported by results of a stability analysis. The analysis shows that a single string of particles is subject to a linear instability leading to the formation of particle doublets. Simulations were repeated with different numbers of particles in the computational domain, with the results found to be qualitatively independent of system size.

scholarly journals Shear thickening behavior in dense repulsive and attractive suspensions of hard spheres

Soft Matter ◽  
2021 ◽  
Author(s):  
Vikram Rathee ◽  
Alessandro Monti ◽  
Marco Edoardo Rosti ◽  
Amy Q Shen
Keyword(s):  
Flow Curve ◽  
Hard Spheres ◽  
Shear Thickening ◽  
Colloidal Suspensions ◽  
Thickening Behavior ◽  
The Stability

Shear thickening in stable dense colloidal suspensions is a reversible phenomenon and no hysteresis is observed in the flow curve measurements. However, a reduction in the stability of colloids promotes...

scholarly journals The non-Newtonian rheology of dilute colloidal suspensions

2002 ◽  
Vol 456 ◽  
pp. 239-275 ◽  
Author(s):  
J. BERGENHOLTZ ◽  
J. F. BRADY ◽  
M. VICIC
Keyword(s):  
Boundary Layer ◽  
Normal Stress ◽  
Volume Fraction ◽  
Hydrodynamic Lubrication ◽  
Hard Spheres ◽  
Pair Correlation ◽  
Colloidal Suspensions ◽  
Brownian Diffusion ◽  
Concentrated Suspensions ◽  
Stokesian Dynamics

The non-Newtonian rheology is calculated numerically to second order in the volume fraction in steady simple shear flows for Brownian hard spheres in the presence of hydrodynamic and excluded volume interactions. Previous analytical and numerical results for the low-shear structure and rheology are confirmed, demonstrating that the viscosity shear thins proportional to Pe2, where Pe is the dimensionless shear rate or Péclet number, owing to the decreasing contribution of Brownian forces to the viscosity. In the large Pe limit, remnants of Brownian diffusion balance convection in a boundary-layer in the compressive region of the flow. In consequence, the viscosity shear thickens when this boundary-layer coincides with the near-contact lubrication regime of the hydrodynamic interaction. Wakes are formed at large Pe in the extensional zone downstream from the reference particle, leading to broken symmetry in the pair correlation function. As a result of this asymmetry and that in the boundary-layer, finite normal stress differences are obtained as well as positive departures in the generalized osmotic pressure from its equilibrium value. The first normal stress difference changes from positive to negative values as Pe is increased when the hard-sphere limit is approached. This unusual effect is caused by the hydrodynamic lubrication forces that maintain particles in close proximity well into the extensional quadrant of the flow. The study demonstrates that many of the non-Newtonian effects observed in concentrated suspensions by experiments and by Stokesian dynamics simulations are present also in dilute suspensions.

Steady shear and dynamic strain thickening of halloysite nanotubes and fumed silica shear thickening composite

2018 ◽  
Vol 38 (10) ◽  
pp. 915-923
Author(s):  
Pavni Passey ◽  
Mansi Singh ◽  
Sanjeev K. Verma ◽  
Debarati Bhattacharya ◽  
Rajeev Mehta
Keyword(s):  
Shear Rate ◽  
Fumed Silica ◽  
Shear Thickening ◽  
Halloysite Nanotubes ◽  
Spherical Particles ◽  
Dynamic Strain ◽  
Critical Shear Rate ◽  
Shear Thickening Fluids ◽  
Protective Fabrics ◽  
Critical Viscosity

Abstract Developing the shear thickening fluids (STF) which can be used for soft body armours requires an in depth study of various parameters related to its constituents so that a high critical viscosity along with high critical shear rate can be obtained. Shape of the constituting particles is one such important parameter. Elongated and nanosize particles provide high critical viscosity to the fluid, whereas spherical particles show high critical shear rates. STF were prepared using halloysite (Hal) nanotubes of different concentrations with fumed silica (spheres) and their rheological properties were studied. A better non-flocculated structure was obtained at 1% Hal in 20% fumed silica composition, exhibiting a critical viscosity of 25 Pas at a critical shear rate 160 s−1 as compared to that of only spherical particle STF (10 Pas and 200 s−1). The oscillatory tests revealed that this composition, with a better consistent reproducible behaviour and better stability than the STF without Hal, would be suitable as a high impact resistant material. Gel formation does not take place, rather the fluid behaves like a dispersed sol, making it a better choice for using with protective fabrics. The rheology was studied at different temperatures ranging from 0°C to 55°C.

scholarly journals The Chain Distribution Tensor: Linking Nonlinear Rheology and Chain Anisotropy in Transient Polymers

Polymers ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 848 ◽  
Author(s):  
Shankar Lalitha Sridhar ◽  
Franck Vernerey
Keyword(s):  
Shear Rate ◽  
Polymer Networks ◽  
Shear Thickening ◽  
Shear Thinning ◽  
Underlying Mechanism ◽  
Weissenberg Number ◽  
Critical Shear Rate ◽  
Nonlinear Rheology ◽  
Non Gaussian ◽  
Chain Force

Transient polymer networks are ubiquitous in natural and engineered materials and contain cross-links that can reversibly break and re-form. The dynamic nature of these bonds allows for interesting mechanical behavior, some of which include nonlinear rheological phenomena such as shear thickening and shear thinning. Specifically, physically cross-linked networks with reversible bonds are typically observed to have viscosities that depend nonlinearly on shear rate and can be characterized by three flow regimes. In slow shear, they behave like Newtonian fluids with a constant viscosity. With further increase in shear rate, the viscosity increases nonlinearly to subsequently reach a maximum value at the critical shear rate. At this point, network fracture occurs followed by a reduction in viscosity (shear-thinning) with a further increase in shear rate. The underlying mechanism of shear thickening in this process is still unclear with debates between a conversion of intra-chain to inter-chain cross-linking and nonlinear chain stretch under high tension. In this paper, we provide a new framework to describe the nonlinear rheology of transient polymer networks with the so-called chain distribution tensor using recent advances from the transient network theory. This tensor contains quantitatively and statistical information of the chain alignment and possible anisotropy that affect network behavior and mechanics. We investigate shear thickening as a primary result of non-Gaussian chain behavior and derive a relationship for the nonlinear viscosity in terms of the non-dimensional Weissenberg number. We further address the criterion for network fracture at the critical shear rate by introducing a critical chain force when bond dissociation is suddenly accelerated. Finally, we discuss the role of cross-linker density on viscosity using a “sticky” reptation mechanism in the context of previous studies on metallo-supramolecular networks with reversible cross-linkers.

Tuning the Rheology of Nano-Sized Silica Suspensions with Silicon Nitride Particles

2019 ◽  
Vol 56 ◽  
pp. 63-70 ◽  
Author(s):  
Selim Gürgen
Keyword(s):  
Silicon Nitride ◽  
Shear Rate ◽  
Shear Thickening ◽  
Critical Shear Rate ◽  
Rheological Measurements ◽  
Additive Particles ◽  
Thickening Behavior ◽  
Silica Suspensions ◽  
Nanosized Silica

In this paper, a non-Newtonian fluid was fabricated dispersing nanosized silica particles in a polyethylene glycol medium. The rheology of the suspension was investigated in a stress-controlled rheometer under increasing shear rate. Based on the rheological measurements, the suspension exhibited shear thickening behavior which gives a drastic viscosity grow with the increase in the shear rate. In order to investigate the role of the micro-sized additive particles on the rheology of silica based suspension, silicon nitride particles were included in the suspension with three different concentrations. The results were discussed in terms of important parameters for the shear thickening mechanism such as critical shear rate, peak viscosity, thickening ratio and initial viscosity. According to the results, shear thickening behavior can be controlled altering the amount of silicon nitride particles in the suspension.

scholarly journals Investigation of penetration into woven fabric specimens impregnated with shear thickening fluid

2018 ◽  
Vol 25 (1) ◽  
pp. 205-212 ◽  
Author(s):  
Naser Kordani ◽  
Ali Sadough Vanini
Keyword(s):  
Molecular Weight ◽  
Hydrogen Bond ◽  
Shear Rate ◽  
High Molecular Weight ◽  
Particle Surface ◽  
Shear Thickening ◽  
Silica Particles ◽  
Woven Fabric ◽  
Critical Shear Rate ◽  
Shear Thickening Fluid

AbstractIn this paper, the effect of weight fraction of nano silica (hydrophilic fumed silica particles) and molecular mass of polyethylene glycol (PEG) on the rheological properties such as the critical shear rate of fluids has been studied. Dynamic moduli based on strain and the effects of increasing the molecular weight are presented. Constructed samples with high-molecular-weight PEG have higher initial, final and critical viscosities. Also, higher molecular chains in the polymer and preventing the movement of most of these chains against the relative motion of liquid (viscosity) will cause higher viscosity in samples. Critical shear rate is lower in the provided samples with high-molecular-weight PEG. Polymer branches in these suspensions are absorbed by the surface of the particles. Due to OH bonds in the silica particles and also due to the presence of this bond in PEG, creating a hydrogen bond is likely. Such a hydrogen bond between the polymer yarn and the particle surface causes surface absorption of the particles. To show the effect of molecular weight on fibers, woven fabric specimens impregnated with shear thickening fluid (STF) have been examined by penetration and pressure test diagrams have been investigated. In a sample with higher molecular weight, displacement to yield point is higher and residence to penetration does not show much difference.

scholarly journals Continuous phenomenological modeling for the viscosity of shear thickening fluids

2018 ◽  
Vol 8 ◽  
pp. 184798041878655 ◽  
Author(s):  
Minghai Wei ◽  
Li Sun ◽  
Peipei Qi ◽  
Chunguang Chang ◽  
Chunyang Zhu
Keyword(s):  
Shear Rate ◽  
Shear Thickening ◽  
Data Sets ◽  
External Energy ◽  
Critical Shear Rate ◽  
Phenomenological Modeling ◽  
Shear Thickening Fluid ◽  
Shear Thickening Fluids ◽  
Viscosity Modeling ◽  
Independent Experimental Data

In general, shear thickening fluids show a marked increase in viscosity beyond a critical shear rate, which can be attributed to the hydrodynamic clustering effects, where in any external energy acting on a shear thickening fluid is dissipated quickly. However, there is a lack of theoretical modeling to predict the viscosity curve of shear thickening fluids, which changes continuously with the increasing shear rate. In this article, a phenomenological continuous viscosity modeling for a class of shear thickening fluids is proposed. The modeling predicts shear thickening and thinning behaviors that are naturally exhibited by shear thickening fluids for high and high enough values of the shear rate. The result shows that the phenomenological modeling provides a very good fit for several independent experimental data sets. Therefore, the proposed modeling can be used in numerical simulations and theoretical analysis across different engineering fields.

Dynamic simulation of suspensions of non-Brownian hard spheres

1996 ◽  
Vol 325 ◽  
pp. 53-77 ◽  
Author(s):  
D. I. Dratler ◽  
W. R. Schowalter
Keyword(s):  
Hydrodynamic Model ◽  
Short Range ◽  
Hard Spheres ◽  
Particle Separation ◽  
Repulsive Force ◽  
Stokesian Dynamics ◽  
Rigid Spheres ◽  
Dense Suspensions ◽  
Dynamics Simulations ◽  
Repulsive Forces

In this work, we investigate the suitability of models based solely on continuum hydrodynamics for Stokesian Dynamics simulations of sheared suspensions of non-Brownian hard spheres. The suspensions of interest consist of monolayers of uniform rigid spheres subjected to a linear shear field. Areal fractions ranged from ϕa = 0.2 to 0.6. For these suspensions, two sets of Stokesian Dynamics simulations were performed. For the first set, particle interactions were assumed to be strictly hydrodynamic in nature. These simulations are analogous to those of Brady & Bossis (1985) and Chang & Powell (1993). For the second set of simulations, particles were subjected to both hydrodynamic and short-range repulsive forces. The repulsion serves as a qualitative model of non-hydrodynamic effects important when particle separation distances are small. Results from both sets of simulations were found to be within the range of established experimental data for viscosities of suspensions. However, simulations employing the pure hydrodynamic model lead to very small separation distances between particles. These small separations give rise to particle overlaps that could not be eliminated by time-step refinement. The instantaneous number of overlaps increased with density and typically exceeded the number of particles at the highest densities considered. More critically, for very dense suspensions the simulations failed to approach a long-time asymptotic state. For simulations employing a short-range repulsive force, these problems were eliminated. The repulsion had the effect of preventing extremely small separations, thereby eliminating particle overlaps. At high concentrations, viscosities computed using the two methods are significantly different. This suggests that the dynamics of particles near contact have a significant impact on bulk properties. Furthermore, the results suggest that a critical aspect of the physics important at small particle separation distances is missing from the pure hydrodynamic model, making it unusable for computing microstructures of dense suspensions. In contrast, simulations employing a short-range repulsive force appear to produce more realistic microstructures, and can be performed even at very high densities.

Characterization and Application of Shear Thickening Fluids

2013 ◽  
Vol 405-408 ◽  
pp. 2503-2506
Author(s):  
Zi Guo Wang ◽  
Zhi Wu Yu ◽  
Yu Yan Sun ◽  
Qing Yuan Li
Keyword(s):  
Shear Rate ◽  
Impact Loading ◽  
Protective Clothing ◽  
Shear Thickening ◽  
Van Der Waals Forces ◽  
Cementitious Materials ◽  
Critical Shear Rate ◽  
Interparticle Forces ◽  
Shear Thickening Fluids ◽  
Liquid To Solid Transition

The shear thickening phenomenon was explained in this paper. The characteristics of shear thickening fluids (STFs), including reversibility and liquid to solid transition at critical shear rate were presented. Also, the applications of STFs for protective clothing and equipment were discussed. Since little references can be found which concern the effect of interparticle forces like Van der Waals forces on the performance of cementitious materials subjected to impact loading, understanding the mechanism of STF and knowing how its structure affects the properties, behaviors, and resulting applications is expected to inspire potential designs for building cementitious materials.

scholarly journals Tuning Rheological Performance of Silica Concentrated Shear Thickening Fluid by Using Graphene Oxide

2015 ◽  
Vol 2015 ◽  
pp. 1-5 ◽  
Author(s):  
Wenchao Huang ◽  
Yanzhe Wu ◽  
Ling Qiu ◽  
Cunku Dong ◽  
Jie Ding ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Shear Rate ◽  
Storage Modulus ◽  
Colloidal Silica ◽  
Loss Modulus ◽  
Shear Thickening ◽  
Light Weight ◽  
Critical Shear Rate ◽  
Shear Thickening Fluid ◽  
Significant Change

The addition of a small amount of graphene oxide into a traditional colloidal silica-based shear thickening fluid (STF) can lead to a significant change in viscosity, critical shear rate, storage modulus, and loss modulus of STF. This finding provides an effective way to prepare stronger and light-weight STFs.

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