Shear and shearless Lagrangian structures in compound channels

F. Enrile, G. Besio, A. Stocchino

Research output: Journal article publicationJournal articleAcademic researchpeer-review

4 Citations (Scopus)

Abstract

Transport processes in a physical model of a natural stream with a composite cross-section (compound channel) are investigated by means of a Lagrangian analysis based on nonlinear dynamical system theory. Two-dimensional free surface Eulerian experimental velocity fields of a uniform flow in a compound channel form the basis for the identification of the so-called Lagrangian Coherent Structures. Lagrangian structures are recognized as the key features that govern particle trajectories. We seek for two particular class of Lagrangian structures: Shear and shearless structures. The former are generated whenever the shear dominates the flow whereas the latter behave as jet-cores. These two type of structures are detected as ridges and trenches of the Finite-Time Lyapunov Exponents fields, respectively. Besides, shearlines computed applying the geodesic theory of transport barriers mark Shear Lagrangian Coherent Structures. So far, the detection of these structures in real experimental flows has not been deeply investigated. Indeed, the present results obtained in a wide range of the controlling parameters clearly show a different behaviour depending on the shallowness of the flow. Shear and Shearless Lagrangian Structures detected from laboratory experiments clearly appear as the flow develops in shallow conditions. The presence of these Lagrangian Structures tends to fade in deep flow conditions.

Original languageEnglish
Pages (from-to)141-154
Number of pages14
JournalAdvances in Water Resources
Volume113
DOIs
Publication statusPublished - Mar 2018
Externally publishedYes

Keywords

  • FTLE
  • Ridges
  • River dynamics
  • Shear Lagrangian Structure
  • Shearless Lagrangian Structure
  • Shearlines
  • Trenches

ASJC Scopus subject areas

  • Water Science and Technology

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