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Anomalous Scaling, Intermittency and Turbulence in Nematic Liquid Crystals

Abstract:

Turbulent electro-convective fluctuations induced in nematic liquid crystal (NLC) by an external oscillating electric field application are studied. Electrohydrodinamic instabilities, including chaotic dynamics and irregular pattern formation, are induced by electrical forces coupled to the flow, the conductivity and the bulk forces acting on the volume charges. In particular we investigate the scaling behavior of the probability density function (PDFs) of intensity fluctuations in a NLC driven through different regimes far from the cell plates, by using the confocal fluorescence microscopy technique. Both spectral properties and scaling behavior of light intensity fluctuations PDFs are analysed at different voltages. In weak turbulent regime, for intermediate voltages, PDFs are Gaussian at large scales, while show enhanced wings at smaller scales, showing the typical intermittency of the isotropic fluid flows. At higher voltages complex dynamical scattering regimes take place. A quantitative estimation of intermittency is obtained by PDFs modeling through the Castaing distribution, and structure functions are calculated in the framework of Extended Self-Similarity. Generation of small-scale fluctuations through a fragmentation process of large-scale structures are supported by the results. Moreover, the lingering anisotropic properties of the fluctuations are highlighted by the outcomes.