Non-linear magnetorheological behaviour of an inverse ferrofluid

Gans, Berend-Jan de; Hoekstra, H.G.M.; Mellema, J.

doi:10.1039/a809229j

Cited by 54 publications

(39 citation statements)

References 19 publications

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“…Simulations performed here demonstrated that the effect of polydispersity is negligible in the critical strain associated to the maximum in the stress; it remains essentially constant within the range of 0.1-0.5 for shear rates _ c Ã 2 ½10 À3 ; 10. Simulations on monodispersed suspensions by Parthasarathy and Klingenberg (1995b), and micromechanical model predictions by Martin and Anderson (1996) and de Gans et al (1999) give a critical strain of 0.1 and 0.34, respectively, in good agreement with our simulations results. Finally, the steady response is obtained by averaging the stress values in the high strain plateau for strain values between c ¼ 2 and c ¼ 10.…”

Section: Stress Growth Simulations: Yield Stresssupporting

confidence: 91%

Simulations of polydisperse magnetorheological fluids: A structural and kinetic investigation

Fernández-Toledano

Ruiz-López

Hidalgo‐Álvarez

et al. 2015

Journal of Rheology

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A simulation method is proposed to explore the effect of particle size polydispersity in magnetorheology including Brownian motion. The method aims to extend the classical particle-level simulation methodology developed by Klingenberg et al. [J. Chem. Phys. 91, 7888–7895 (1989)] for the case of polydisperse magnetorheological (MR) fluids. The simulation study concerns the aggregation kinetics at rest as well as the rheological behavior under start-up of steady shear and dynamic oscillatory shear tests at increasing strain amplitudes. Results demonstrate that the effect of polydispersity is only relevant at the transition regime between magnetostatic to hydrodynamic control of the suspension structure. The yielding behavior is correlated to the structural characteristics (radial distribution functions, pair correlation functions, and angular connectivities) of the MR fluids before the onset of flow. A more abrupt transition is observed for polydisperse MR fluids because interparticle links are weaker in this case if compared to monodisperse suspensions in spite of the fact that polydisperse MR fluids exhibit a larger connectivity.

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Section: Stress Growth Simulations: Yield Stresssupporting

confidence: 91%

Simulations of polydisperse magnetorheological fluids: A structural and kinetic investigation

Fernández-Toledano

Ruiz-López

Hidalgo‐Álvarez

et al. 2015

Journal of Rheology

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“…magnetic "holes") are obtained by dispersing inert particles in a ferrofluid matrix 124 , whereby a tunable permeability mismatch induced by the external field produces a virtual dipole associated with each "hole". The magnetorheology of inverse ferrofluids based on nonmagnetic silica nanoparticles (diameter σ ≈ 100 − 700nm) dispersed at a volume fraction φ ≈ 1 − 26% has been previously reported as a function of the shear rate and magnetic field strength in terms of the Mason number 123,[125][126][127] . The corresponding intrinsic viscosity is reproduced in Figure 18 along with the fits to our simulation data using the chain model showing overall good agreement.…”

Section: Other Dipolar Systemsmentioning

confidence: 99%

Self-assembly and rheology of dipolar colloids in simple shear studied using multi-particle collision dynamics

2017

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a Magnetic nanoparticles in a colloidal solution self-assemble in various aligned structures, which has a profound influence on the flow behavior. However, the precise role of the microstructure in the development of the rheological response has not been reliably quantified. We investigate the self-assembly of dipolar colloids in simple shear using hybrid molecular dynamics and multiparticle collision dynamics simulations with explicit coarse-grained hydrodynamics; conduct simulated rheometric studies and apply micromechanical models to produce master curves, showing evidence of the universality of the structural behavior governed by the competition of the bonding (dipolar) and erosive (thermal and/or hydrodynamic) stresses. The simulations display viscosity changes across several orders of magnitude in fair quantitative agreement with various literature sources, substantiating the universality of the approach, which seems to apply generally across vastly different length scales and a broad range of physical systems.

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“…Ramos et al [36] also used a silica-based inverse ferrofluid to study the magnetorheology behavior under small-amplitude oscillatory shear in the presence of an external magnetic field. Their results were compared with those of de Gans et al [43,44] and chain models and excellent agreement was obtained.…”

Section: Introductionmentioning

confidence: 66%

Oscillatory shear response of dilute ferrofluids: Predictions from rotational Brownian dynamics simulations and ferrohydrodynamics modeling

2011

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Ferrofluids are colloidal suspensions of magnetic nanoparticles that exhibit normal liquid behavior in the absence of magnetic fields but respond to imposed magnetic fields by changing their viscosity without loss of fluidity. The response of ferrofluids to constant shear and magnetic fields has received a lot of attention, but the response of ferrofluids to oscillatory shear remains largely unexplored. In the present work we used rotational Brownian dynamics to study the dynamic properties of ferrofluids with thermally blocked nanoparticles under oscillatory shear and constant magnetic fields. Comparisons between simulations and modeling using the ferrohydrodynamics equations were also made. Simulation results show that, for small rotational Péclet number, the in-phase and out-of-phase components of the complex viscosity depend on the magnitude of the magnetic field and frequency of the shear, following a Maxwell-like model with field-dependent viscosity and characteristic time equal to the field-dependent transverse magnetic relaxation time of the nanoparticles. Comparison between simulations and the numerical solution of the ferrohydrodynamic equations shows that the oscillatory rotational magnetoviscosity for an oscillating shear field obtained using the kinetic magnetization relaxation equation quantitatively agrees with simulations for a wide range of Péclet number and Langevin parameter but has quantitative deviations from the simulations at high values of the Langevin parameter. These predictions indicate an apparent elastic character to the rheology of these suspensions, even though we are considering the infinitely dilute limit in which there are negligible particle-particle interactions and, as such, chains do not form. Additionally, an asymptotic analytical solution of the ferrohydrodynamics equations, valid for Pe<<2, was used to demonstrate that the Cox-Merz rule applies for dilute ferrofluids under conditions of small shear rates. At higher shear rates the Cox-Merz rule ceases to apply.

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Non-linear magnetorheological behaviour of an inverse ferrofluid

Cited by 54 publications

References 19 publications

Simulations of polydisperse magnetorheological fluids: A structural and kinetic investigation

Simulations of polydisperse magnetorheological fluids: A structural and kinetic investigation

Self-assembly and rheology of dipolar colloids in simple shear studied using multi-particle collision dynamics

Oscillatory shear response of dilute ferrofluids: Predictions from rotational Brownian dynamics simulations and ferrohydrodynamics modeling

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