Vortex profiles in grid turbulence observed by PIV

Duda, Daniel; Yanovych, Vitalii; Uruba, Václav

doi:10.1063/5.0120078

Cited by 3 publications

(1 citation statement)

References 18 publications

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“…Indeed, most vortex identifications are based on the symmetric and anti-symmetric components of the local velocity gradient. Taking the Galilean invariance into consideration, vortex identifications such as the Q criterion, ∆ criterion, λ 2 criterion, and λ ci criterion are proposed [12][13][14][15]. New Eulerian vortex identification methods continue to be proposed in modern academia, and the Liutex criterion was proposed with the aim of solving the Symmetry 2024, 16, 344 2 of 20 problem in threshold determination and vortex behavior near the wall [16], subsequently being used to analyze complex flows in turbomachinery [17,18].…”

Section: Introductionmentioning

confidence: 99%

A Lagrangian Analysis of Tip Leakage Vortex in a Low-Speed Axial Compressor Rotor

Hou,

Liu,

Tang

2024

Symmetry

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A Lagrangian method is introduced to analyze the tip leakage vortex (TLV) behavior in a low-speed axial compressor rotor. The finite-time Lyapunov exponent (FTLE) fields are calculated based on the delayed detached-eddy simulation (DDES) results and identifying the FTLE ridges as Lagrangian coherent structures (LCSs). The computational method of the FTLE field in three-dimensional unsteady flow fields is discussed and then applied to the instantaneous flow fields at both the design and near-stall conditions. Results show that the accuracy of the particle trajectory and the density of the initial grid of the particle trajectory greatly affect the results of the FTLE field and, thus, the LCSs. Compared to the Eulerian Q method, which is calculated based on the symmetric and anti-symmetric components of the local velocity gradient tensor, the Lagrangian method has great potential in unraveling the mechanism of complex vortex structures. The LCSs show a transport barrier between the TLV and the secondary TLV, indicating two separate vortices. The aLCSs show the bubble-like and bar-like structure in the isosurfaces corresponding to the bubble and spiral breakdown patterns.

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Section: Introductionmentioning

confidence: 99%

A Lagrangian Analysis of Tip Leakage Vortex in a Low-Speed Axial Compressor Rotor

Hou,

Liu,

Tang

2024

Symmetry

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Effect of sharp/oblate nose on a model subsonic rocket measured by PIV

Klátil,

Brtník,

Peprný

et al. 2023

MATEC Web Conf.

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What is the difference between the wake past a rocket with sharp nose or with oblate nose? The measurement by Particle Image Velocimetry tries to answer at velocities 5 – 20 m/s (i.e. Reynolds numbers 20 thousand to 79 thousand). A simple model rocket is 3D printed with body diameter of 60 mm, total height 4 D, i.e. 240 mm. The maps of mean stream-wise velocity, stream-wise fluctuations and span-wise fluctuations are compared.

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Interaction of stream-wise vortices generated by swirler grid

Duda,

Yanovych

2024

Physics of Fluids

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A system of stream-wise vortices has been created using a grid of swirling elements with alternating orientations (like a chessboard). The particle image velocimetry method has been used to map the velocity field in several planes perpendicular to the stream. The mesh-based Reynolds number is 1.35×104 and 2.71×104, respectively. The stream-wise development of turbulent kinetic energy (TKE) shows first an increase in a distance of x≈10M, followed by power-law decay. Individual vortices are detected in each snapshot. The radial profile of TKE transformed to a vortex coordinate system is almost constant, either with maximum as in static frame or zero as observed by previous research. The properties of detected vortices are studied statistically: the meandering amplitude expressed as the standard deviation of vortex positions grows roughly as ∼ex, i.e., faster than expected random-walk growth ∼x. Vortex circulation decays exponentially as predicted by classical Helmholtz theorem. The interaction between neighboring vortices is expressed via correlation of selected quantities. Correlation of energy develops downstream from anticorrelation to a positive correlation. The strongest correlation is observed between the first vortex circulation and the second vortex position perpendicular to their connection line. Other correlations are weak.

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Vortex profiles in grid turbulence observed by PIV

Cited by 3 publications

References 18 publications

A Lagrangian Analysis of Tip Leakage Vortex in a Low-Speed Axial Compressor Rotor

A Lagrangian Analysis of Tip Leakage Vortex in a Low-Speed Axial Compressor Rotor

Effect of sharp/oblate nose on a model subsonic rocket measured by PIV

Interaction of stream-wise vortices generated by swirler grid

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