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Fluids 2018, 3(4), 99; https://doi.org/10.3390/fluids3040099

Time-Dependent Diffusion Coefficients for Chaotic Advection due to Fluctuations of Convective Rolls

1
Department of Applied Quantum Physics and Nuclear Engineering, Faculty of Engineering, Kyushu University, Fukuoka 819-0395, Japan
2
Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Ube 755-8611, Japan
*
Author to whom correspondence should be addressed.
Received: 16 October 2018 / Revised: 19 November 2018 / Accepted: 22 November 2018 / Published: 27 November 2018
(This article belongs to the Special Issue Multiscale Turbulent Transport)
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Abstract

The properties of chaotic advection arising from defect turbulence, that is, weak turbulence in the electroconvection of nematic liquid crystals, were experimentally investigated. Defect turbulence is a phenomenon in which fluctuations of convective rolls arise and are globally disturbed while maintaining convective rolls locally. The time-dependent diffusion coefficient, as measured from the motion of a tagged particle driven by the turbulence, was used to clarify the dependence of the type of diffusion on coarse-graining time. The results showed that, as coarse-graining time increases, the type of diffusion changes from superdiffusion → subdiffusion → normal diffusion. The change in diffusive properties over the observed timescale reflects the coexistence of local order and global disorder in the defect turbulence. View Full-Text
Keywords: weak turbulence; chaotic advection; Lagrangian chaos; time-dependent diffusion coefficient; nematic electroconvection; defect turbulence weak turbulence; chaotic advection; Lagrangian chaos; time-dependent diffusion coefficient; nematic electroconvection; defect turbulence
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Yamanaka, K.; Narumi, T.; Hashiguchi, M.; Okabe, H.; Hara, K.; Hidaka, Y. Time-Dependent Diffusion Coefficients for Chaotic Advection due to Fluctuations of Convective Rolls. Fluids 2018, 3, 99.

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