Lagrangian Coherent Structures with Guaranteed Material Separation

Germer, Tobias; Otto, Mathias; Peikert, Ronald; Theisel, Holger

doi:10.1111/j.1467-8659.2011.01925.x

Cited by 9 publications

(5 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A good agreement between the FTLE pattern and LCSs is present especially comparing the structure located north-west of the GoT that closes the Gulf of Monfalcone, i.e., an internal Gulf of the GoT. [18] show that ridges of FTLE coincide in many cases well with material structures. However, in general, they are not exact material structures, no matter which ridge definition of a scalar field is adopted.…”

Section: A Ftle Fields and Lagrangian Coherent Structuresmentioning

confidence: 65%

Lagrangian coherent structures deduced from HF radar measurements

Enrile

Besio

Magaldi

et al. 2015

OCEANS 2015 - Genova

View full text Add to dashboard Cite

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.

show abstract

Section: A Ftle Fields and Lagrangian Coherent Structuresmentioning

confidence: 65%

Lagrangian coherent structures deduced from HF radar measurements

Enrile

Besio

Magaldi

et al. 2015

OCEANS 2015 - Genova

View full text Add to dashboard Cite

show abstract

“…[SLM05]. This synthetic data set is frequently used to illustrate the performance and suitability of FTLE approaches such as strain lines [FH12] or material separation fields [GOPT11]. We consider integration times

τ = 12

and

τ = 20

.…”

Section: Resultsmentioning

confidence: 99%

“…Germer et al . [GOPT11] present an explicit and continuous reconstruction of binary level sets that guarantee certain material properties. Üffinger et al .…”

Section: Related Workmentioning

confidence: 99%

Time Line Cell Tracking for the Approximation of Lagrangian Coherent Structures with Subgrid Accuracy

Kühn

Engelke

Rössl

et al. 2013

Computer Graphics Forum

Self Cite

View full text Add to dashboard Cite

Lagrangian coherent structures (LCSs) have become a widespread and powerful method to describe dynamic motion patterns in time-dependent flow fields. The standard way to extract LCS is to compute height ridges in the finite-time Lyapunov exponent field. In this work, we present an alternative method to approximate Lagrangian features for 2D unsteady flow fields that achieve subgrid accuracy without additional particle sampling. We obtain this by a geometric reconstruction of the flow map using additional material constraints for the available samples. In comparison to the standard method, this allows for a more accurate global approximation of LCS on sparse grids and for long integration intervals. The proposed algorithm works directly on a set of given particle trajectories and without additional flow map derivatives. We demonstrate its application for a set of computational fluid dynamic examples, as well as trajectories acquired by Lagrangian methods, and discuss its benefits and limitations.

show abstract

“…These surfaces are called "ridges". FTLE fields are computed using backward time integration of particle grids [14]. The LCS represents attracting material lines and separate regions of separated flow around the airfoil and unsteady flow in the wake.…”

Section: Lagrangian Methodsmentioning

confidence: 99%

Numerical Study of Unsteady Flow Separation on Small Scale Wings Using Vortex Identification Methods

2024

JST: ETSD

View full text Add to dashboard Cite

The goal of this work is to develop vortex identification methods for better understanding the unsteady separation using particle-based direct numerical simulation for the unsteady incompressible flow past small wings. It is shown that in flows with Reynolds number 1000, the first vortex identification method, vorticity contour, is used to capture the vortical region behind the surface in which the package of unsteady vortex bubbles is observed in different angles of attack. The second vortex identification method, Q-criterion, has shown the advantages in order to capture the vortical region and track the near-wall separation by recording the vortex strengths of leading edge vortex and trailing edge vortex at high angle of attacks. The time history of the strengths has shown a good agreement to the time history of drag coefficient. The third vortex identification method, Lagrangian coherent structure, has shown its strength to record the most stretching, attracting, and shearing material surfaces that form the skeletons of Lagrangian particle dynamics in the far-field wake region. Accordingly, the tracking of particles in high shear surfaces, which is very important to determine the roadmap of unsteadiness, is well captured.

show abstract

Lagrangian Coherent Structures with Guaranteed Material Separation

Cited by 9 publications

References 27 publications

Lagrangian coherent structures deduced from HF radar measurements

Lagrangian coherent structures deduced from HF radar measurements

Time Line Cell Tracking for the Approximation of Lagrangian Coherent Structures with Subgrid Accuracy

Numerical Study of Unsteady Flow Separation on Small Scale Wings Using Vortex Identification Methods

Contact Info

Product

Resources

About