Advances in time-resolved three-dimensional Particle Tracking Velocimetry (4D-PTV) techniques have consistently revealed more accurate Lagrangian particle motions. A novel track initialization technique as a complementary part of 4D-PTV, based on local temporal and spatial coherency of neighbor trajectories, is proposed. The proposed Lagrangian Coherent Track Initialization (LCTI) applies physics-based Finite Time Lyapunov Exponent (FTLE) to build four frame coherent tracks. We locally determine Lagrangian coherent structures among neighbor trajectories by using the FTLE boundaries (i.e., ridges) to distinguish the 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 direct numerical simulation. Performance of the proposed method based on three characteristic parameters, temporal scale, particle concentration (i.e., density), and noise ratio, showed robust behavior in finding true tracks compared to the recent initialization algorithms. Sensitivity of LCTI to the number of untracked and wrong tracks is also discussed. We address the capability of using the proposed method as a function of a 4D-PTV scheme in the Lagrangian particle tracking challenge. We showed that LCTI prevents 4D-PTV divergence in flows with high particle concentrations. Finally, the LCTI behavior 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.
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September 2021
Research Article|
September 09 2021
Lagrangian coherent track initialization
Ali Rahimi Khojasteh
;
Ali Rahimi Khojasteh
a)
1
INRAE, OPAALE
, 17 avenue de Cucillé, 35044 Rennes, France
a)Author to whom correspondence should be addressed: ali.rahimi-khojasteh@inrae.fr
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Yin Yang
;
Yin Yang
1
INRAE, OPAALE
, 17 avenue de Cucillé, 35044 Rennes, France
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Dominique Heitz
;
Dominique Heitz
1
INRAE, OPAALE
, 17 avenue de Cucillé, 35044 Rennes, France
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Sylvain Laizet
Sylvain Laizet
2
Turbulence Simulation Group, Department of Aeronautics, Imperial College London
, Exhibition Road, London SW7 2AZ, United Kingdom
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a)Author to whom correspondence should be addressed: ali.rahimi-khojasteh@inrae.fr
Physics of Fluids 33, 095113 (2021)
Article history
Received:
June 21 2021
Accepted:
August 21 2021
Citation
Ali Rahimi Khojasteh, Yin Yang, Dominique Heitz, Sylvain Laizet; Lagrangian coherent track initialization. Physics of Fluids 1 September 2021; 33 (9): 095113. https://doi.org/10.1063/5.0060644
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