Damped Oscillations in the Viscosity of Suspensions of Rigid Rods. I. Monomodal Suspensions

Ivanov, Yatchko; Ven, Theo G. M. van de; Mason, S. G.

doi:10.1122/1.549664

Cited by 43 publications

(16 citation statements)

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“…The normal force was shown to vanish every quarter period and become negative when the axis of the spheroid was in the quadrant from 45 ° to 135 ° to the flow direction. By relaxing the assumption of monodisperse particle size distribution or allowing interactions between the particles in denser suspensions, the above authors and also Ivanov et al [17] showed that the oscillations became damped and a steady state was achieved, in which a constant viscosity and zero normal stresses were predicted.…”

Section: Introductionmentioning

confidence: 96%

Primary normal-stress difference for two liquid crystalline copolyesters

Gotsis

Baird

1986

Rheol Acta

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Abstract:The primary normal-stress difference, N1, was determined in both steady and transient shear flow experiments for thermotropic copolyesters of 60 and 80 mole% p-hydroxybenzoic acid (PItB) and polyethylene terephthalate (PET). N 1 was observed to be negative for the 80 mole% system at low shear rates and temperatures below 332 °C (a tensile stress, e.g. all is taken here to be positive). At higher shear rates and for temperatures above 332 °C, N 1 was found to be positive. Values of N~ for the 60 mole% pHBA/PET system were always positive over the same range of shear rates. Although it is not certain as to the origin of the negative values, a probable cause is small density changes upon the inception of flow as well as the existence of a solid phase or some texture development in the melt. However, it is shown that it is thermodynamically admissible for liquid crystalline fluids to exhibit negative values of N l .

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Section: Introductionmentioning

confidence: 96%

Primary normal-stress difference for two liquid crystalline copolyesters

Gotsis

Baird

1986

Rheol Acta

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“…Mason and his coworkers have carried out extensive theoretical and experimental investigations to search out the causes of the "indeterminacy" in Jeffery's solution since such "indeterminacy" is seldom found experimentally. They considered the following effects on particle orientations that were originally neglected by Jeffery: (1) fluid inertia [6]; (2) nonuniform shear field [7]; (3) non-uniform particle size distribution [8][9][10][11]]; (4) particle interactions [12]; (5) particle Brownian motion [9,13,14]. All these investigations show that if any of the above effects is introduced, then an intrinsically preferred orientation will exist and a steady-state distribution independent of initial conditions will be reached.…”

Section: Introductionmentioning

confidence: 99%

Orientation and rheology of rodlike particles with weak Brownian diffusion in a second-order fluid under simple shear flow

Cohen

Chung

1987

Rheol Acta

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Abstract." An analysis of particle orientation in a dilute suspension of rodlike particles in a second-order fluid was performed to examine the effects of the elasticity of the fluid and of weak Brownian diffusion of the particle on its orientation. Distributions of particle orientation under a simple shear flow with rate of shear 9 have been obtained as a function of a single nondimensional parameter, fl* =fl/r2(D/g), which combines the effects of the particle aspect ratio re, the weak fluid elasticity fl, and the weak Brownian rotation diffusion coefficient D of the particle. In the limit of large re, when the fluid elasticity is strong enough to overcome the rotational diffusion effect on the particle motion, most of the particles will orient close to the vorticity axis. A new shear-thinning mechanism of the shear viscosity of such systems is predicted by the theory.

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“…This tumbling motion suggests that the stress response of a dilute suspension of rods in simple shear is oscillatory. Experimental evidence abounds however (Ivanov, van de Ven & Mason 1982), indicating that these fluctuations are transient, and that a well-defined, time-independent macroscopic viscosity can eventually be assigned to the dispersion. Many randomizing factors have been implicated, including polydispersity and other imperfections in the particle shape, Brownian motion, and hydrodynamic interactions (including wall effects).…”

Section: Perturbation Of Jefery Orbits and Migration In Shear Flowmentioning

confidence: 99%

Suspensions of prolate spheroids in Stokes flow. Part 1. Dynamics of a finite number of particles in an unbounded fluid

1993

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A new simulation method is presented for low-Reynolds-number flow problems involving elongated particles in an unbounded fluid. The technique extends the principles of Stokesian dynamics, a multipole moment expansion method, to ellipsoidal particle shapes. The methodology is applied to prolate spheroids in particular, and shown to be efficient and accurate by comparison with other numerical methods for Stokes flow. The importance of hydrodynamic interactions is illustrated by examples on sedimenting spheroids and particles in a simple shear flow.

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Damped Oscillations in the Viscosity of Suspensions of Rigid Rods. I. Monomodal Suspensions

Cited by 43 publications

References 0 publications

Primary normal-stress difference for two liquid crystalline copolyesters

Primary normal-stress difference for two liquid crystalline copolyesters

Orientation and rheology of rodlike particles with weak Brownian diffusion in a second-order fluid under simple shear flow

Suspensions of prolate spheroids in Stokes flow. Part 1. Dynamics of a finite number of particles in an unbounded fluid

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