LCS Tool: A computational platform for Lagrangian coherent structures

Onu, Kristjan; Huhn, Florian; Haller, George

doi:10.1016/j.jocs.2014.12.002

Cited by 111 publications

(112 citation statements)

References 33 publications

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“…The operator P uses spatial fields of these eigenvalues and eigenvectors to identify curves (in 2D [69,68,70]) or surfaces (in 3D [71,72]) of extremal attraction or repulsion in the time-slice t, with respect to the time evolution from t to τ . The variational methods also exist for elliptic and parabolic structures [9], and the excellent review article [9] is recommended for readers requiring additional information on how to compute variational LCSs.…”

Section: Lcs Diagnostic Methodsmentioning

confidence: 99%

“…5 relates to the variational definition of LCSs due to Haller [9,81], in which curves which experience extremal repulsion (in backward time) are classified. Both computations were performed using LCS Tool [70] for our parameter values, and using the default tolerances in the package. The left figure shows the interior of two elliptic LCSs, curves which are stationary with respect to averaged tangential stretching [9,153].…”

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confidence: 99%

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Generalized Lagrangian coherent structures

Balasuriya

Ouellette

Rypina

2018

Physica D: Nonlinear Phenomena

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The notion of a Lagrangian Coherent Structure (LCS) is by now well established as a way to capture transient coherent transport dynamics in unsteady and aperiodic fluid flows that are known over finite time. We show that the concept of an LCS can be generalized to capture coherence in other quantities of interest that are transported by, but not fully locked to, the fluid. Such quantities include those with dynamic, biological, chemical, or thermodynamic relevance, such as temperature, pollutant concentration, vorticity, kinetic energy, plankton density, and so on. We provide a conceptual framework for identifying the Generalized Lagrangian Coherent Structures (GLCSs) associated with such evolving quantities. We show how LCSs can be seen as a special case within this framework, and provide an overarching discussion of various methods for identifying LCSs. The utility of this more general viewpoint is highlighted through a variety of examples. We also show that although LCSs approximate GLCSs in certain limiting situations under restrictive assumptions on how the velocity field affects the additional quantities of interest, LCSs are not in general sufficient to describe their coherent transport.

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Section: Lcs Diagnostic Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

Generalized Lagrangian coherent structures

Balasuriya

Ouellette

Rypina

2018

Physica D: Nonlinear Phenomena

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“…The numerical detection of these LCSs is carried out by the publicly available software LCS Tool [13].…”

Section: Hyperbolic Lagrangian Coherent Structuresmentioning

confidence: 99%

“…Thanks to the available velocity fields of the sea surface of the Gulf of Trieste, a comparison between Finite-Time Lyapunov Exponents fields and Lagrangian Coherent Structures detected by LCS Tool [13] is carried out. A further investigation is developed since real drifter trajectories are available and a direct comparison between drifters data and LCS is possible.…”

Section: Lagrangian Coherent Structures In the Gulf Of Triestementioning

confidence: 99%

“…The present work examines the differences between FiniteTime Lyapunov Exponent scalar fields and Lagrangian Coherent Structures detected according to [5][6] [13] in the Gulf of Trieste (GoT), located in the north-eastern Adriatic Sea, see in the Western and Eastern part of the Mediterranean Sea. Gathered data are combined in a useful decision support tool for authorities in charge of marine emergency response.…”

Section: Introductionmentioning

confidence: 99%

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Lagrangian coherent structures deduced from HF radar measurements

Enrile

Besio

Magaldi

et al. 2015

OCEANS 2015 - Genova

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In the present paper Lagrangian Coherent Structures are detected in the Gulf of Trieste, i.e., a Gulf located in the north-eastern part of the Adriatic Sea. Lagrangian Coherent Structures are usually detected through Lyapunov exponent diagnostic tools. However, such diagnostics lack of a rigorous mathematical background and try to associate wellknown classical dynamical system structures of autonomous dynamical systems to the features of fluid flows. Such flows are studied under the perspective of non-autonomous dynamical systems, neglecting diffusion. In this work we try to detect Lagrangian Coherent Structures, i.e., the key material lines that shape trajectory patterns, with both the established FiniteTime Lyapunov Exponents and the recently introduced rigorous mathematical definitions implemented in the publicly available MATLAB LCS Tool. A comparison between real and simulated drifter trajectories is considered, too.

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The life cycle of a coherent Lagrangian Agulhas ring

2016

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Abstract. We document the long-term evolution of an Agulhas ring detected from satellite altimetry using a technique from nonlinear dynamical systems that enables objective (i.e., observer-independent) eddy framing. Such objectively detected eddies have Lagrangian (material) boundaries that remain coherent (unfilamented) over the detection period. The ring preserves a quite compact material entity for a period of about 2 years even after most initial coherence is lost within 5 months after detection. We attribute this to the successive development of short-term coherent material boundaries around the ring. These boundaries provide effective short-term shielding for the ring, which prevents a large fraction of the ring's interior from being mixed with the ambient turbulent flow. We show that such coherence regain events cannot be inferred from Eulerian analysis. This process is terminated by a ring-splitting event which marks the ring demise, near the South American coast. The genesis of the ring is characterized by a ring-merging event away from the Agulhas retroflection, followed by a 4-month-long partial coherence stage, scenario that is quite different than a simple current occlusion and subsequent eddy pinch off.

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LCS Tool: A computational platform for Lagrangian coherent structures

Cited by 111 publications

References 33 publications

Generalized Lagrangian coherent structures

Generalized Lagrangian coherent structures

Lagrangian coherent structures deduced from HF radar measurements

The life cycle of a coherent Lagrangian Agulhas ring

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