Eulerian spectrum of finite-time Lyapunov exponents in compound channels

Francesco Enrile, Giovanni Besio, Alessandro Stocchino

Research output: Journal article publicationJournal articleAcademic researchpeer-review

Abstract

Fluid flows reveal a wealth of structures, such as vortices and barriers to transport. Usually, either an Eulerian or a Lagrangian frame of reference is employed in order to detect such features of the flow. However, the two frameworks detect structures that have different properties. Indeed, common Eulerian diagnostics (Hua-Klein and Okubo-Weiss criterion) employed in order to detect vortices do not always agree with Lagrangian diagnostics such as finite-time Lyapunov exponents. Besides, the former are Galilean-invariant whereas the latter is objective. However, both the Lagrangian and the Eulerian approaches to coherent structure detection must show some links under any inertial-frame. Compound channels flows have been accurately studied in the past, both from a Lagrangian and an Eulerian point of view. The features detected do not superimpose: Eulerian vortices do not coincide with barriers to transport. The missing link between the two approaches is here recovered thanks to a spectral analysis.

Original languageEnglish
Pages (from-to)1821-1828
Number of pages8
JournalMeccanica
Volume55
Issue number9
DOIs
Publication statusPublished - 1 Sep 2020
Externally publishedYes

Keywords

  • Eulerian frame of reference
  • Lagrangian Coherent Structures (LCS)
  • Lagrangian frame of reference
  • Lyapunov exponents
  • Power spectral density (PSD)
  • River dynamics

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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