Lagrangian coherent track initialisation
File(s)
Accepted version
Author(s)
Khojasteh, Ali Rahimi
Yang, Yin
Heitz, Dominique
Laizet, Sylvain
Type
Journal Article
Abstract
Advances in time-resolved three-dimensional Particle Tracking Velocimetry (4D-PTV)
techniques have been consistently revealed more accurate Lagrangian particle motions.
A novel track initialisation technique as a complementary part of 4D-PTV, based on local
temporal and spatial coherency of neighbour trajectories, is proposed. The proposed Lagrangian Coherent Track Initialisation (LCTI) applies physics-based Finite Time Lyapunov
Exponent (FTLE) to build four frame coherent tracks. We locally determine Lagrangian
Coherent Structures (LCS) among neighbour trajectories by using the FTLE boundaries
(i.e., ridges) to distinguish clusters of coherent motions. To evaluate the proposed technique, we created an open-access synthetic Lagrangian and Eulerian dataset of the wake
downstream of a smooth cylinder at a Reynolds number equal to 3900 obtained from
three-dimensional (3D) Direct Numerical Simulation (DNS). Performance of the proposed
method based on three characteristic parameters, temporal scale, particle concentration
(i.e., density), and noise ratio, showed robust behaviour in finding true tracks compared to
the recent initialisation algorithms. Sensitivity of LCTI to the number of untracked and
wrong tracks are also discussed. We address the capability of using the proposed method
as a function of a 4D-PTV scheme in the Lagrangian Particle Tracking (LPT) challenge.
We showed that LCTI prevents 4D-PTV divergence in flows with high particle concentrations. Finally, the LCTI behaviour was demonstrated in a jet impingement experiment.
LCTI was found to be a reliable tracking tool in complex flow motions, with a strength
revealed for flows with high velocity and acceleration gradients.
techniques have been consistently revealed more accurate Lagrangian particle motions.
A novel track initialisation technique as a complementary part of 4D-PTV, based on local
temporal and spatial coherency of neighbour trajectories, is proposed. The proposed Lagrangian Coherent Track Initialisation (LCTI) applies physics-based Finite Time Lyapunov
Exponent (FTLE) to build four frame coherent tracks. We locally determine Lagrangian
Coherent Structures (LCS) among neighbour trajectories by using the FTLE boundaries
(i.e., ridges) to distinguish clusters of coherent motions. To evaluate the proposed technique, we created an open-access synthetic Lagrangian and Eulerian dataset of the wake
downstream of a smooth cylinder at a Reynolds number equal to 3900 obtained from
three-dimensional (3D) Direct Numerical Simulation (DNS). Performance of the proposed
method based on three characteristic parameters, temporal scale, particle concentration
(i.e., density), and noise ratio, showed robust behaviour in finding true tracks compared to
the recent initialisation algorithms. Sensitivity of LCTI to the number of untracked and
wrong tracks are also discussed. We address the capability of using the proposed method
as a function of a 4D-PTV scheme in the Lagrangian Particle Tracking (LPT) challenge.
We showed that LCTI prevents 4D-PTV divergence in flows with high particle concentrations. Finally, the LCTI behaviour was demonstrated in a jet impingement experiment.
LCTI was found to be a reliable tracking tool in complex flow motions, with a strength
revealed for flows with high velocity and acceleration gradients.
Date Issued
2021-09-09
Date Acceptance
2021-08-22
Citation
Physics of Fluids, 2021, 33, pp.1-13
ISSN
1070-6631
Publisher
American Institute of Physics
Start Page
1
End Page
13
Journal / Book Title
Physics of Fluids
Volume
33
Copyright Statement
© 2021 Author(s). This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Phys. Fluids 33, 095113 (2021); https://doi.org/10.1063/5.0060644
Identifier
https://aip.scitation.org/doi/10.1063/5.0060644
Subjects
Fluids & Plasmas
01 Mathematical Sciences
02 Physical Sciences
09 Engineering
Publication Status
Published
Date Publish Online
2021-09-09