Pattern Formation in Flowing Electrorheological Fluids

Pfeil, Karl von; Graham, Michael D.; Klingenberg, Daniel J.; Morris, Jeffrey F.

doi:10.1103/physrevlett.88.188301

Cited by 43 publications

(32 citation statements)

References 19 publications

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“…However, experiments indicate that structures that evolve produce concentration profiles that vary primarily in the direction perpendicular to the field direction. Our prior modeling work 13,14 produces similar results, with the most rapidly growing fluctuations being those that are independent of z for a field applied in the z direction. We will thus consider here only concentration profiles that depend only on x and y, with the macroscopic field applied in the z direction.…”

Section: Self-consistent Point-dipole Modelsupporting

confidence: 53%

“…In previous papers, 13,14 we presented a continuum model for describing the development of heterogeneous structures in quiescent and sheared ER suspensions. A conservation equation for the particle volume fraction ͑x , t͒ was derived by averaging the mass and momentum balances over the particle phase, wherein the particle flux is related to the particle contribution to the stress.…”

Section: Introductionmentioning

confidence: 99%

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Nonlocal electrostatics in heterogeneous suspensions using a point-dipole model

Pfeil

Klingenberg

2004

Journal of Applied Physics

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The electrostatic dipole moment distribution in heterogeneous suspensions is determined via a self-consistent, point-dipole model, which incorporates nonlocal electrostatics. Predictions agree qualitatively with previous asymptotic results for discontinuous concentration profiles. For small fluctuations in concentration, the dipole strength can be expressed as an expansion in gradients of the concentration. This expansion is incorporated into a linearized continuum model for structure evolution in sheared electrorheological suspensions. Prior stability analysis of a fully local continuum model predicts the formation of concentrated particle stripes oriented in the flow direction, in agreement with experimental observations. Incorporating nonlocal electrostatics suppresses the growth of high wave number fluctuations, providing a more realistic finite rate of growth of fluctuations. Incorporating nonlocal electrostatics in the full nonlinear continuum model produces a single particulate stripe at steady state.

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Section: Self-consistent Point-dipole Modelsupporting

confidence: 53%

Section: Introductionmentioning

confidence: 99%

Nonlocal electrostatics in heterogeneous suspensions using a point-dipole model

Pfeil

Klingenberg

2004

Journal of Applied Physics

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“…The behavior of ER fluids subjected to both an electric field and a shear flow was investigated in the past decade; 7,18 lamellar structures were observed in ER fluids in the presence of oscillating shear flow and also predicated by numerical simulations in steady shear flows. 19 The relations among chains, lamellar, and shear stress also been studied by Filisko. 8 In theory, Klingenberg 18,19 used a "two-fluid continuum model" to prove stripe formation in sheared suspensions.…”

Section: Introductionmentioning

confidence: 99%

“…19 The relations among chains, lamellar, and shear stress also been studied by Filisko. 8 In theory, Klingenberg 18,19 used a "two-fluid continuum model" to prove stripe formation in sheared suspensions. In this work, we shall present both a computer simulation and an experiment to understand the structure of ER fluids under an electric field and simultaneously a shear flow.…”

Section: Introductionmentioning

confidence: 99%

Structure of Electrorheological Fluids under an Electric Field and a Shear Flow: Experiment and Computer Simulation

2006

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It is known that macroscopic properties of colloidal suspensions are often determined by the microstructure of the particles in the suspensions, depending on the interparticle, Brownian, and hydrodynamic (if any) forces. We take electrorheological (ER) fluids as an example. By using a computer simulation and an experimental approach, we investigate the structure of ER fluids subjected to both an electric field and a shear flow. The microstructure evolution from random structure, to chains, and then to stable lamellar patterns, observed in the experiments, agrees very well with that obtained in the simulations. It is shown that the formation of such lamellar patterns originates from the difference between the dipole moment induced in the particles suspended in the ER fluids without shear and the one with shear. The results on the relaxation process of structural formation and the internal structure of layers are also presented. Thus, it seems possible to achieve various structures and hence desired macroscopic properties of colloidal suspensions by adjusting external fields and, simultaneously, a shear flow.

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“…In a previous article, we presented a continuum description of the evolution of the structure of ER suspensions, 15 as characterized by the time-and position-dependent particle volume fraction (x,t). This was accomplished by developing a conservation equation for the particle concentration, using an expression for the particle flux obtained from a momentum balance.…”

Section: Introductionmentioning

confidence: 99%