Modified normalized Rortex/vortex identification method

Liu, Jianming; Liu, Chaoqun

doi:10.1063/1.5109437

Cited by 109 publications

(31 citation statements)

References 23 publications

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“…Also, the Liutex vector is Galilean invariant [18][19][20]. According to Liu et al [7], the Liutex method, Liutex-Omega method [16], Liutex Core Line method, and other Liutex-based methods [21][22][23] are the third generation (3G) of vortex identification methods. The Liutex method is discussed briefly in section 2.6.…”

Section: Introductionmentioning

confidence: 99%

Stretching and shearing contamination analysis for Liutex and other vortex identification methods

Shrestha

Nottage

et al. 2021

Adv. Aerodyn.

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The newly developed vortex-identification method, Liutex, has provided a new systematic description of the local fluid rotation, which includes scalar, vector, and tensor forms. However, the advantages of Liutex over the other widely used vortex-identification methods such as Q, ∆, λ2, and λci have not been realized. These traditional methods count on shearing and stretching as a part of vortex strength. But, in the real flow, shearing and stretching do not contribute to fluid rotation. In this paper, the decomposition of the velocity gradient tensor is conducted in the Principal Coordinate for uniqueness. Then the contamination effects of stretching and shearing of the traditional methods are investigated and compared with the Liutex method in terms of mathematical analysis and numerical calculations. The results show that the Liutex method is the only method that is not affected by either stretching or shear, as it represents only the local fluid rigid rotation. These results provide supporting evidence that Liutex is the superior method over others.

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Section: Introductionmentioning

confidence: 99%

Stretching and shearing contamination analysis for Liutex and other vortex identification methods

Shrestha

Nottage

et al. 2021

Adv. Aerodyn.

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“…After the Liutex concept was proposed, the new vortex identification method named as modified Omega-Liutex was developed by Liu and Liu [14] to improve the existing vortex identification methods such as 𝑄-criterion and λ -criterion. This method is a dimensionless relative quantity from 0 to 1.…”

Section: 𝑅 = 𝝎 𝒓 − (𝝎 𝒓) − 4𝜆 mentioning

confidence: 99%

Liutex core line and POD analysis on hairpin vortex formation in natural flow transition

2020

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In this study, the new concept of vortex core line based on Liutex definition is applied to demonstrate that vortex ring is not part of the Λ-vortex and the generation of ring-like vortex is formed separately from the Λ-vortex. The proper orthogonal decomposition (POD) is also applied to analyze the Kelvin-Helmholtz (K-H) instability happening in hairpin ring areas of flow transition on the flat plate to understand the ring-like vortex formation. The new identification method named modified Omega-Liutex method is efficiently used to visualize and observe the shapes of vortex structures in 3-D. The streamwise vortex structure characteristics can be found in POD Mode1 as the mean flow. The other POD modes are in spanwise structures and have the fluctuation motions, which are induced by K-H instability. Moreover, the result shows that fluctuated POD modes are in pairs and share the same characteristics such as amplitudes, mode shapes and time evolutions. The vortex core and POD results confirm that the Λ-vortex is not selfdeformed to a hairpin vortex, but it is formed by the K-H instability during the formation of Λvortex and hairpin vortex in boundary layer flow transition.

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“…The latter was modified in Ref. 21 to improve vortices identification and to cure the bulging phenomenon on the iso-surfaces caused by x R . The authors in Ref.…”

Section: Introductionmentioning

confidence: 99%

A hybrid identification and tracking of Lagrangian mesoscale eddies

Aouni

2021

Physics of Fluids

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Automatic identification and tracking of mesoscale eddies are crucial in large oceanic observational and numerical model data. This work proposes a fully automated method that identifies and tracks from a single Lagrangian advection, all mesoscale eddies, without prior knowledge of their lifespans. The eddies' detection and tracking use a hybrid method based on geometrical properties of the evolving velocity along Lagrangian trajectories and a grid density-based clustering algorithm. The high eddies' monitoring capacity of the proposed method is demonstrated by automatically identifying and tracking these structures from two different datasets: satellite-derived surface geostrophic velocity fields and a two-dimensional fluid simulation. The proposed approach gives complete dynamical features and evolution of the detected mesoscale eddies by identifying their genesis event, monitoring their coherent core, and describing their splitting and vanishing image.

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Modified normalized Rortex/vortex identification method

Cited by 109 publications

References 23 publications

Stretching and shearing contamination analysis for Liutex and other vortex identification methods

Stretching and shearing contamination analysis for Liutex and other vortex identification methods

Liutex core line and POD analysis on hairpin vortex formation in natural flow transition

A hybrid identification and tracking of Lagrangian mesoscale eddies

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