Rheology of a lamellar liquid crystalline phase using the lattice Boltzmann simulation technique

Kumaran, V.; Jariwala, Soham; Hussain, S

doi:10.1016/s0009-2509(01)00168-3

Cited by 17 publications

(17 citation statements)

References 10 publications

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“…Many earlier studies have proposed a picture in which a layer undulation instability in three-dimensional smectic liquid crystals emerges above a critical shear rate 12,13,24,53,54 . Molecular dynamics simulations on lyotropic smectics place this in a regime of flow rates well above those we have applied in the present study 14,15 .…”

Section: Discussionmentioning

confidence: 99%

“…In principle the dependence of the state of order on flow rate could be smooth, or could entail a nonequilibrium phase transition -for instance if the perfectly ordered state ceased to be stable above a certain shear rate 12,24,53,54 . In practice, however, starting as we do from an initially amorphous lamellar texture, a perfectly ordered state is generally not reached for large systems even if it might be stable once formed.…”

Section: Two Dimensionsmentioning

confidence: 99%

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Rheology of lamellar liquid crystals in two and three dimensions: a simulation study

et al. 2012

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We present large scale computer simulations of the nonlinear bulk rheology of lamellar phases (smectic liquid crystals) at moderate to large values of the shear rate (Peclet numbers 10 − 100), in both two and three dimensions. In two dimensions we find that modest shear rates align the system and stabilise an almost regular lamellar phase, but high shear rates induce the nucleation and proliferation of defects, which in steady state is balanced by the annihilation of defects of opposite sign. The shear rateγ c at onset of this second regime is controlled by thermodynamic and kinetic parameters; we offer a scaling analysis that relatesγ c to a critical "capillary number" involving those variables. Within the defect proliferation regime, the defects may be partially annealed by slowly decreasing the applied shear rate; this causes marked memory effects, and history-dependent rheology. Simulations in three dimensions show instead shear-induced ordering even at the highest shear rates studied here. This suggests thatγ c shifts markedly upward on increasing dimensionality. This may in part reflect the reduced constraints on defect motion, allowing them to find and annihilate each other more easily. Residual edge defects in the 3D aligned state mostly point along the flow velocity, an orientation impossible in two dimensions.

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Section: Discussionmentioning

confidence: 99%

Section: Two Dimensionsmentioning

confidence: 99%

Rheology of lamellar liquid crystals in two and three dimensions: a simulation study

et al. 2012

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“…(14) are neglected in the leading approximation, and the equations reduce to the standard equations for a defect in a lamellar mesophase. 22 The equation for the displacement field due to an applied force is given by…”

Section: Deformation Around An Edge Dislocationmentioning

confidence: 99%

“…A realistic sample of thickness 1 mm would typically contain about 10 4 −10 5 layers, whereas the largest system size in simulations is about 100 layers in two dimensions. These simulations [10][11][12][13][14][15][16] typically employ a mesoscale model, in which the concentration field is defined as the difference in the local concentrations of the hydrophilic and hydrophobic constituents of the lamellar phase. The lamellar modulation of the concentration field is modeled using a suitable free energy functional, and the dynamical equations for the coupled concentration field and the fluid momentum fields (equivalent to the model-H equations for a binary fluid 17 ) are solved.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of edge dislocations in a sheared lamellar mesophase

Kumaran

2013

The Journal of Chemical Physics

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The dynamics and interactions of edge dislocations in a nearly aligned sheared lamellar mesophase is analysed to provide insights into the relationship between disorder and rheology. First, the mesoscale permeation and momentum equations for the displacement field in the presence of external forces are derived from the model H equations for the concentration and momentum field. The secondary flow generated due to the mean shear around an isolated defect is calculated, and the excess viscosity due to the presence of the defect is determined from the excess energy dissipation due to the secondary flow. The excess viscosity for an isolated defect is found to increase with system size in the cross-stream direction as L(3/2) for an isolated defect, though this divergence is cut-off due to interactions in a defect suspension. As the defects are sheared past each other due to the mean flow, the Peach-Koehler force due to elastic interaction between pairs of defects is found to cause no net displacement relative to each other as they approach from large separation to the distance of closest approach. The equivalent force due to viscous interactions is found to increase the separation for defects of opposite sign, and decrease the separation for defects of same sign. During defect interactions, we find that there is no buckling instability due to dilation of layers for systems of realistic size. However, there is another mechanism, which is the velocity difference generated across a slightly deformed bilayer due to the mean shear, which could result in the creation of new defects.

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“…that have strong influence on rheological properties (Kumaran et al, 2001;Trickett and Eastoe, 2008). Due to their amphiphilic nature of surfactant molecules which consists of a hydrophilic head and a hydrophobic tail, they can distribute their head and tail parts to the corresponding polar and non-polar solvents and form a monolayer film between them (Pan et al, 2015;Salager et al, 2012;Schrader et al, 2013;Zhang and Wei, 2013).…”

Section: Introductionmentioning

confidence: 99%

Phase behaviour and thermodynamic properties of lamellar liquid crystal developed for viscoelastic surfactant based fracturing fluid

Baruah

Pathak

Ojha

2015

Chemical Engineering Science

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Rheology of a lamellar liquid crystalline phase using the lattice Boltzmann simulation technique

Cited by 17 publications

References 10 publications

Rheology of lamellar liquid crystals in two and three dimensions: a simulation study

Rheology of lamellar liquid crystals in two and three dimensions: a simulation study

Dynamics of edge dislocations in a sheared lamellar mesophase

Phase behaviour and thermodynamic properties of lamellar liquid crystal developed for viscoelastic surfactant based fracturing fluid

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