Experimental analysis of lagrangian coherent structures and chaotic mixing in Rayleigh-Benard convection

Masahito Watanabe, Yusuke Kitamura, Naoki Hatta, Hiroaki Yoshimura

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

It is known that some fluid particles may be transported chaotically in Lagrangian description although the velocity field seems to be stable in Eulerian description. A typical example can be found in the system of two-dimensional Rayleigh-Benard convection with perturbed velocity fields, which has been investigated as a low dimensional mechanical model of fluid phenomena associated with natural convection in order to clarify the mechanism of fluid transport (see, for instance, [2]). In this study, we make an experimental study on the global structures of chaotic mixing appeared in the two-dimensional perturbed Rayleigh-Benard convection by analyzing Lagrangian coherent structures (LCSs), which correspond to the invariant manifolds of time-dependent mechanical systems. We develop an apparatus to measure the velocity field by Particle Image Velocimetry (PIV) and then show the LCSs which can be numerically detected from the experimental data by computing Finite-time Lyapunov exponent (FTLE) fields. Finally, we show the global structures of chaotic mixing appeared in the perturbed Rayleigh-Benard convection as well as the steady convection by experiments. In particular, we clarify how the LCSs are entangled with each other around the cell boundaries to carry out chaotic Lagrangian transports.

Original languageEnglish
Title of host publicationFluid Applications and Systems; Fluid Measurement and Instrumentation
PublisherAmerican Society of Mechanical Engineers (ASME)
ISBN (Electronic)9780791883716
DOIs
Publication statusPublished - 2020
EventASME 2020 Fluids Engineering Division Summer Meeting, FEDSM 2020, collocated with the ASME 2020 Heat Transfer Summer Conference and the ASME 2020 18th International Conference on Nanochannels, Microchannels, and Minichannels - Virtual, Online
Duration: 2020 Jul 132020 Jul 15

Publication series

NameAmerican Society of Mechanical Engineers, Fluids Engineering Division (Publication) FEDSM
Volume1
ISSN (Print)0888-8116

Conference

ConferenceASME 2020 Fluids Engineering Division Summer Meeting, FEDSM 2020, collocated with the ASME 2020 Heat Transfer Summer Conference and the ASME 2020 18th International Conference on Nanochannels, Microchannels, and Minichannels
CityVirtual, Online
Period20/7/1320/7/15

Keywords

  • Chaotic mixing
  • Lagrangian coherent structure
  • Lobe dynamics
  • Rayleigh-Benard convection

ASJC Scopus subject areas

  • Mechanical Engineering

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