Computation of Lagrangian coherent structures from experimental fluid trajectory measurements in a mechanically agitated vessel

Kun Li; Chiya Savari; Mostafa Barigou

doi:10.1016/j.ces.2022.117598

Computation of Lagrangian coherent structures from experimental fluid trajectory measurements in a mechanically agitated vessel

Kun Li, Chiya Savari, Mostafa Barigou^*

^*Corresponding author for this work

Chemical Engineering

Research output: Contribution to journal › Article › peer-review

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Abstract

In mechanically agitated vessels, bulk flow circulation which plays a leading role in macroscale mixing is controlled by hidden Lagrangian coherent structures (LCSs). We use a numerical finite-time Lyapunov exponent (FTLE) approach, for the first time, to resolve such LCSs. Experimental 3D Lagrangian trajectories obtained from a unique positron emission particle tracking (PEPT) technique are used to drive the FTLE model. By computing forward and backward FTLE fields and extracting repelling and attracting FTLE ridges in various azimuthal planes of the flow, a highly complex flow topology is unravelled which varies significantly with azimuthal position. We demonstrate how LCSs organise and quantify the chaotic behaviour of fluid particle paths that underpin mixing through the exchange of fluid between zones of different kinematics. This new Lagrangian approach driven by unique PEPT data is able to unfold some of the complexities of turbulent flow that are beyond the capability of traditional methods.

Original language	English
Article number	117598
Number of pages	13
Journal	Chemical Engineering Science
Volume	254
Early online date	10 Mar 2022
DOIs	https://doi.org/10.1016/j.ces.2022.117598
Publication status	Published - 8 Jun 2022

Bibliographical note

Funding Information:
This work was supported by EPSRC Programme Grant EP/R045046/1: Probing Multiscale Complex Multiphase Flows with Positrons for Engineering and Biomedical Applications (PI: Prof. M. Barigou, University of Birmingham).

Keywords

Finite-time Lyapunov Exponent
Lagrangian coherent structures
Mixing
PEPT
Turbulence

ASJC Scopus subject areas

General Chemistry
General Chemical Engineering
Industrial and Manufacturing Engineering

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10.1016/j.ces.2022.117598Licence: Creative Commons: Attribution (CC BY)

Li2022_Computation_of_LagranianFinal published version, 5.31 MBLicence: Creative Commons: Attribution (CC BY)

Probing Multiscale Complex Multiphase Flows with Positrons for Engineering and Biomedical Applications
Barigou, M. & Parker, D.
Engineering & Physical Science Research Council
1/10/18 → 30/09/24
Project: Research Councils

Cite this

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title = "Computation of Lagrangian coherent structures from experimental fluid trajectory measurements in a mechanically agitated vessel",

abstract = "In mechanically agitated vessels, bulk flow circulation which plays a leading role in macroscale mixing is controlled by hidden Lagrangian coherent structures (LCSs). We use a numerical finite-time Lyapunov exponent (FTLE) approach, for the first time, to resolve such LCSs. Experimental 3D Lagrangian trajectories obtained from a unique positron emission particle tracking (PEPT) technique are used to drive the FTLE model. By computing forward and backward FTLE fields and extracting repelling and attracting FTLE ridges in various azimuthal planes of the flow, a highly complex flow topology is unravelled which varies significantly with azimuthal position. We demonstrate how LCSs organise and quantify the chaotic behaviour of fluid particle paths that underpin mixing through the exchange of fluid between zones of different kinematics. This new Lagrangian approach driven by unique PEPT data is able to unfold some of the complexities of turbulent flow that are beyond the capability of traditional methods.",

keywords = "Finite-time Lyapunov Exponent, Lagrangian coherent structures, Mixing, PEPT, Turbulence",

author = "Kun Li and Chiya Savari and Mostafa Barigou",

note = "Funding Information: This work was supported by EPSRC Programme Grant EP/R045046/1: Probing Multiscale Complex Multiphase Flows with Positrons for Engineering and Biomedical Applications (PI: Prof. M. Barigou, University of Birmingham).",

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AU - Savari, Chiya

AU - Barigou, Mostafa

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PY - 2022/6/8

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N2 - In mechanically agitated vessels, bulk flow circulation which plays a leading role in macroscale mixing is controlled by hidden Lagrangian coherent structures (LCSs). We use a numerical finite-time Lyapunov exponent (FTLE) approach, for the first time, to resolve such LCSs. Experimental 3D Lagrangian trajectories obtained from a unique positron emission particle tracking (PEPT) technique are used to drive the FTLE model. By computing forward and backward FTLE fields and extracting repelling and attracting FTLE ridges in various azimuthal planes of the flow, a highly complex flow topology is unravelled which varies significantly with azimuthal position. We demonstrate how LCSs organise and quantify the chaotic behaviour of fluid particle paths that underpin mixing through the exchange of fluid between zones of different kinematics. This new Lagrangian approach driven by unique PEPT data is able to unfold some of the complexities of turbulent flow that are beyond the capability of traditional methods.

AB - In mechanically agitated vessels, bulk flow circulation which plays a leading role in macroscale mixing is controlled by hidden Lagrangian coherent structures (LCSs). We use a numerical finite-time Lyapunov exponent (FTLE) approach, for the first time, to resolve such LCSs. Experimental 3D Lagrangian trajectories obtained from a unique positron emission particle tracking (PEPT) technique are used to drive the FTLE model. By computing forward and backward FTLE fields and extracting repelling and attracting FTLE ridges in various azimuthal planes of the flow, a highly complex flow topology is unravelled which varies significantly with azimuthal position. We demonstrate how LCSs organise and quantify the chaotic behaviour of fluid particle paths that underpin mixing through the exchange of fluid between zones of different kinematics. This new Lagrangian approach driven by unique PEPT data is able to unfold some of the complexities of turbulent flow that are beyond the capability of traditional methods.

KW - Finite-time Lyapunov Exponent

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Computation of Lagrangian coherent structures from experimental fluid trajectory measurements in a mechanically agitated vessel

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

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Projects

Probing Multiscale Complex Multiphase Flows with Positrons for Engineering and Biomedical Applications

Cite this