New Symmetry Breaking in Nonlinear Electroconvection of Nematic Liquid Crystals

Plaut, Emmanuel; Decker, Werner; Rossberg, Axel G.; Kramer, Lorenz; Pesch, Werner; Belaidi, Ahmed; Ribotta, R.

doi:10.1103/physrevlett.79.2367

Cited by 70 publications

(39 citation statements)

References 16 publications

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“…With increasing applied ac voltage, the following sequence of transitions takes place: zigzag instability accompanied by the formation of oblique rolls transition to "abnormal" rolls "varicose" instability. This scenario of transitions was predicted using extended nonlinear analysis of the standard model of NLC electrohydrodynamics, which takes into account activation of the homogeneous twist mode [18,19]. In contrast to a number of earlier studies [18,22,31], we observed for the first time the complete sequence of secondary instabilities.…”

Section: Resultssupporting

confidence: 44%

“…A characteristic feature of elec troconvection in NLCs above the threshold for the formation of convective rolls is a large variety of sec ondary instabilities and scenarios of the evolution of nonequilibrium structures due to various nonlinear interactions of hydrodynamic and orientational modes. One of the most important mechanisms deter mining the evolution of secondary instabilities in the supercritical region is the excitation of a homogeneous (in the plane of the layer) twist mode of the director [18,19]. It has been established that an increase in the applied ac voltage to a value above the electroconvec tion threshold in a planar layer of an NLC leads to excitation of the twist mode and is accompanied by the formation of so called abnormal rolls [18,20,21].…”

Section: Introductionmentioning

confidence: 99%

“…One of the most important mechanisms deter mining the evolution of secondary instabilities in the supercritical region is the excitation of a homogeneous (in the plane of the layer) twist mode of the director [18,19]. It has been established that an increase in the applied ac voltage to a value above the electroconvec tion threshold in a planar layer of an NLC leads to excitation of the twist mode and is accompanied by the formation of so called abnormal rolls [18,20,21]. In addition, the interaction of the twist mode with con vective modes of rolls in an ac electric field may lead to the evolution of local oscillations between two degen erate states of oblique rolls (so called zigzag rolls) [19].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

On the role of flexoeffect in synchronization of electroconvective roll oscillations in nematics

Batyrshin

Krekhov

Scaldin

et al. 2012

J. Exp. Theor. Phys.

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We describe the dynamics of zigzag oscillations in a system of convective rolls in a nematic liquid crystal above the electroconvection threshold under the action of an ac voltage with a biased position of the mean value. It is found that an increase in the contribution from the constant component leads to a substantial increase in the spatiotemporal ordering of zigzag rolls and their synchronization with the homogeneous twist mode. The results confirm the flexoelectric mechanism of locking.

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Section: Resultssupporting

confidence: 44%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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On the role of flexoeffect in synchronization of electroconvective roll oscillations in nematics

Batyrshin

Krekhov

Scaldin

et al. 2012

J. Exp. Theor. Phys.

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“…Another type of fluid subject to electric field, closely related to EHD, is that of nematic liquid crystals. The amplitude equation and the pattern formation for nematic liquid crystals have been discussed by Pesch & Kramer (1986), Kramer & Pesch (1995) and more recently by Plaut et al (1997). The main dissimilar feature between the two fluids lies in the difference that the nematic liquid crystals are anisotropic with a preferred axis while the EHD flow of non-polar liquids, the working fluids that we are considering, is isotropic in all the wall-parallel directions when a constant potential difference is imposed across the infinite electrodes.…”

Section: Weakly Nonlinear Stability Analysismentioning

confidence: 96%

Weakly nonlinear stability analysis of subcritical electrohydrodynamic flow subject to strong unipolar injection

Zhang

2016

J. Fluid Mech.

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We analyse in detail the weakly nonlinear stability of electrohydrodynamic (EHD) flow of insulating fluids subject to strong unipolar injection, with and without cross-flow. We first consider the hydrostatic electroconvetion induced by a Coulomb force confined between two infinite flat electrodes, taking into account the charge diffusion effect. The effects of various non-dimensionalized parameters are examined in order to depict in detail and to understand better the subcritical bifurcation of hydrostatic electroconvetion. In addition, electrohydrodynamics with low-or high-Re cross-flow is also considered for investigating the combined effect of inertia and the electric field. It is found that the base cross-flow is modified by the electric effect and that, even when the inertia is dominating, the electric field can still strengthen effectively the subcritical characteristics of canonical channel flow. In this process, however, the electric field does not contribute directly to the subcriticality of the resultant flow and the intensified subcritical feature of such flow is thus entirely due to the modified hydrodynamic field as a result of the imposed electric field. This finding might be important for flow control strategies involving an electric field. Theoretically, the above results are obtained from a multiple-scale expansion method, which gives rise to the Ginzburg-Landau equation governing the amplitude of the first-order perturbation. The conclusions are deduced by probing the changes of value of the coefficients in this equation. In particular, the sign of the first Landau coefficient indicates the type of bifurcation, being subcritical or supercritical. Moreover, as a quintic-order Ginzburg-Landau equation is derived, the effects of higher-order nonlinear terms in EHD flow are also discussed.

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“…Recent topics of interest include, among others, aspects of spatial symmetry breaking, localized states, or effects of low dimensionality [3]. The easy manipulation of control parameters, convenient time scales, and straightforward observation techniques, among other advantages, have triggered its comprehensive investigation in the past (for a review, see e.g., Ref.…”

mentioning

confidence: 99%

Preparation of subharmonic patterns in nematic electroconvection

John¹,

Stannarius²

2004

Phys. Rev. E

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Nematic electroconvection is studied under asymmetric periodic excitation with a driving electric field E(t)=E(t+T) not equal -E(t+T/2). A new dynamic regime, distinguished by subharmonic dynamics, is discovered in the pattern state diagram between conventional conductive and dielectric regimes. The spatial and temporal pattern characteristics are investigated experimentally. The dynamics, threshold fields, and selected pattern wavelengths at onset, calculated from a Floquet analysis of the linearized electrohydrodynamic equations with a test mode ansatz, are in good agreement with experimental results.

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New Symmetry Breaking in Nonlinear Electroconvection of Nematic Liquid Crystals

Cited by 70 publications

References 16 publications

On the role of flexoeffect in synchronization of electroconvective roll oscillations in nematics

On the role of flexoeffect in synchronization of electroconvective roll oscillations in nematics

Weakly nonlinear stability analysis of subcritical electrohydrodynamic flow subject to strong unipolar injection

Preparation of subharmonic patterns in nematic electroconvection

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