Critical role of flow-modified permittivity in electrorheology: Model and computer simulation

Dassanayake, Ujitha M.; Offner, Stella S. R.; Hu, Yue

doi:10.1103/physreve.69.021507

Cited by 7 publications

(13 citation statements)

References 27 publications

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“…In a shear flow of shear rate _ g, a spherical sphere spins at an angular velocity of v = _ g=2(v = vŷ) (Dassanayake et al, 2004). Because the rotational motion that leads to a displacement of its polarized charges on the surface and the relaxation of the surface charges, the rate of change in the dipole moment of the rotating dielectric sphere in an electric field is given by (Wan et al, 2000) dp…”

Section: Modelmentioning

confidence: 99%

Dielectric relaxation effect on flow behavior of electrorheological fluids

Wang

Gong

Yang

et al. 2014

Journal of Intelligent Material Systems and Structures

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The dielectric relaxation effect on the flow behavior of electrorheological fluids under dynamic shear was studied. The flow curves of electrorheological fluids in the dynamic state were simulated with shear rates from 0.1 to 1000 s 21 under different relaxation times. When the magnitude of the relaxation time is smaller than 10 22 s, the break shear rate changes little at different relaxation times. But the break shear rate changes obviously when the magnitude of the relaxation time is larger than 10 22 s. To further understand the influence of the relaxation time, Sr/Ba-doped TiO 2 electrorheological fluids were prepared and their dielectric properties and flow curves under shear flow were tested. The relaxation time of the electrorheological fluid is influenced by the Sr/Ti mole ratio but not the Ba/Ti mole ratio, and the electrorheological effects of the fluids were highly influenced by varying the Sr/Ti mole ratios. The experimental results agreed well with the above computer simulation. Finally, a possible mechanism was proposed to explain the effect of dielectric relaxation on flow behavior of electrorheological fluids.

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Section: Modelmentioning

confidence: 99%

Dielectric relaxation effect on flow behavior of electrorheological fluids

Wang

Gong

Yang

et al. 2014

Journal of Intelligent Material Systems and Structures

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“…(6) or Eq. (17)] provide guidelines for numerical simulation on the dynamic effect in ER fluids [5] and should be distinguished from those effective medium theories developed for composites of anisotropic inclusions, [21] bi-anisotropic media, [22] and chiral media, [23,24] etc. Extension to nonlinear ac responses [25,26] is possible.…”

Section: Discussionmentioning

confidence: 99%

“…At the same time, the magnitude of the steady-state polarization is reduced by a factor as compared to the resting case. [5,9] which is determined by the same competition. As the interparticle force depends crucially on the magnitude and direction of polarizations, the complications due to the rotational motion were shown to be dramatic.…”

Section: Introductionmentioning

confidence: 99%

“…In many aspects, an electrorheological (ER) fluid containing suspensions at rest is quite different from an ER fluid containing suspensions subjected to rotational motions, [1,2,3,4,5,6,7,8] which has been referred to the dynamic effect in ER fluid, [9,10,11] and is of great relevance in various applications of ER fluid. Reports regarding this dynamic effect have been extensive in the literature.…”

Section: Introductionmentioning

confidence: 99%

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Dynamic Polarizability of Rotating Particles in Electrorheological Fluids

Xiao

Huang

2008

J. Phys. Chem. B

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A rotating particle in electrorheological (ER) fluid leads to a displacement of its polarization charges on the surface which relax towards the external applied field E0, resulting in a steadystate polarization at an angle with respect to E0. This dynamic effect has shown to affect the ER fluids properties dramatically. In this paper, we develop a dynamic effective medium theory (EMT) for a system containing rotating particles of finite volume fraction. This is a generalization of established EMT to account for the interactions between many rotating particles. While the theory is valid for three dimensions, the results in a special two dimensional configuration show that the system exhibits an off-diagonal polarization response, in addition to a diagonal polarization response, which resembles the classic Hall effect. The diagonal response monotonically decreases with an increasing rotational speed, whereas the off-diagonal response exhibits a maximum at a reduced rotational angular velocity ω0 comparing to the case of isolated rotating particles. This implies a way of measurement on the interacting relaxation time. The dependencies of the diagonal and off-diagonal responses on various factors, such as ω0, the volume fraction, and the dielectric contrast, are discussed.

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“…When the electric field E 0 is applied along the z direction, each particle gets an induced dipole moment p = (1/2)πβε 0 ε f σ 3 E loc in the fluid with relative dielectric constant ε f (in the Système International unit system) where β = (ε p − ε f )/(ε p + 2ε f ) and E loc is the local field, with E loc = E 0ẑ if β 1. In a shear flow of shear rateγ , a spherical sphere spins at an angular velocity of ω =γ 2(ω = ωŷ) [24]. For the rotating dielectric sphere in an electric field, because of the rotational motion that leads to a displacement of its polarized charges on the surface and the relaxation of the surface charges, the rate of change in the dipole moment is given by [25] …”

Section: Model and Simulationmentioning

confidence: 99%

Boundary effect in electrorheological fluids

et al. 2011

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The effect of the boundary friction coefficient on the rheological properties of the electrorheological (ER) fluids in quasistatic and dynamic states is investigated by computer simulation. The relation between the shear stress and the boundary friction coefficient in quasistatic and dynamic states is discussed qualitatively and quantitatively, and the trend matches the previously reported experimental results well. The flow curves of ER fluids, under different friction coefficients, are calculated, and it is found that the friction coefficient affects the flow curves. In two dimensions, the transitions in structure corresponding to the shear stress variations are presented to understand the mechanism of ER fluids.

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Critical role of flow-modified permittivity in electrorheology: Model and computer simulation

Cited by 7 publications

References 27 publications

Dielectric relaxation effect on flow behavior of electrorheological fluids

Dielectric relaxation effect on flow behavior of electrorheological fluids

Dynamic Polarizability of Rotating Particles in Electrorheological Fluids

Boundary effect in electrorheological fluids

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