Time- and frequency-domain spectral proper orthogonal decomposition of a swirling jet by tomographic particle image velocimetry

Zeng, Xin; Zhang, Yuyao; He, Chuangxin; Liu, Yingzheng

doi:10.1007/s00348-022-03542-2

Cited by 9 publications

(3 citation statements)

References 73 publications

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“…Using mirrors, as indicated by the green dashed line for the top view of the two cameras and their relative positions in figure 12(b) [49], four different views with image resolutions of 1000 × 2000 pixels in the radial direction can be obtained using only two cameras. Further details of the experimental setup can be found in the literature [50].…”

Section: Methodsmentioning

confidence: 99%

A polynomial model with line-of-sight constraints for Lagrangian particle tracking under interface refraction

Zeng,

Qu,

et al. 2024

Meas. Sci. Technol.

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This paper introduces an improvement of the “Shake-The-Box (STB)” (Schanz, Gesemann, and Schröder, Exp. Fluids 57.5, 2016) technique using the polynomial calibration model and the line-of-sight constraints (LOSC) to overcome the refractive interface issues in Lagrangian particle tracking (LPT) measurement. The method (named LOSC-LPT) draws inspiration from the two-plane polynomial camera calibration in tomographic particle image velocimetry (Tomo-PIV) (Worth and Nickels, Thesis, 2010) and the STB-based open-source Lagrangian particle tracking (OpenLPT) framework (Tan, Salibindla, Masuk, and Ni, Exp. Fluids 61.2, 2019). The LOSC-LPT introduces polynomial mapping functions into STB calibration in conditions involving gas–solid–liquid interfaces at container walls exhibiting large refractive index variations, which facilitates the realization of particle stereo matching, three-dimensional (3D) triangulation, iterative particle reconstruction, and further refinement of 3D particle position by shaking the LOS. Performance evaluation based on synthetic noise-free images with a particle image density of 0.05 particle per pixel (ppp) in the presence of refractive interfaces demonstrates that LOSC-LPT can detect a higher number of particles and exhibits lower position uncertainty in the reconstructed particles, resulting in higher accuracy and robustness than that achieved with OpenLPT. In the application to an elliptical jet flow in an octagonal tank with refractive interfaces, the use of polynomial mapping results in smaller errors (mean calibration error < 0.1 px) and thus more long trajectories identified by LOSC-LPT (13,000) compared with OpenLPT (4,500) which uses the pinhole Tsai model (mean calibration error > 1.0 px). Moreover, 3D flow-field reconstructions demonstrate that the LOSC-LPT framework can recover a more accurate 3D Eulerian flow field and capture more complete coherent structures in the flow, and thus holds great potential for widespread application in 3D experimental fluid measurements.

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Section: Methodsmentioning

confidence: 99%

A polynomial model with line-of-sight constraints for Lagrangian particle tracking under interface refraction

Zeng,

Qu,

et al. 2024

Meas. Sci. Technol.

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“…In this study, the advanced SPOD method was applied to resolve and monitor the dynamics of axis-switching vortex structures. SPOD offers possibilities beyond POD and DMD, enabling the deterministic coherent structure to be captured, stochastic features to be separated, and the dynamic time evolution of different structures to be recorded (Zeng et al 2023).…”

Section: Spodmentioning

confidence: 99%

“…Coherent structures at specific frequencies can be resolved and extracted using mode decomposition techniques such as POD (Lumley 1967) or SPOD (Sieber, et al 2016). SPOD was selected for its performance in capturing deterministic coherent structures, separating stochastic features, and recording the time dynamic evolution of different structures (Zeng, et al 2023); it is also computationally inexpensive. The decomposition results with circular and elliptical jets using the SPOD method described above are summarized in Fig.…”

Section: Coherent Structure Extraction and Vortex Dynamicsmentioning

confidence: 99%

Dynamics and Entrainment Mechanism of the Jet Flows from an Elliptical Nozzle: Time-Resolved Tomographic PIV Measurements

Zeng

ZHANG

et al. 2023

Preprint

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In this study, the coherent structure dynamics and entrainment capability of elliptical jets emitted from an elliptical nozzle with aspect ratio (AR) values of 1 (i.e., a circular jet), 2, and 4 at a fixed Reynolds number of 3,000 were experimentally characterized by flow reconstruction using tomographic particle image velocimetry and modal decomposition using the spectral proper orthogonal decomposition method. Statistical analysis indicated that the elliptical synthetic jet had a greater entrainment rate and momentum flux than the circular jet. The temporal dynamics of the coherent structure showed that all the jets emitted from the elliptical nozzle at AR = 1 (i.e., a circular jet), 2, and 4 had a dominant frequency at Strouhal number (St) = 0.39, representing the leading Kelvin–Helmholtz (K-H) vortex ring in each jet. The frequency of the trailing vortex was also at St = 0.39 at AR = 1 and 2, whereas that at AR= 4 was at St = 0.70. It was found that vortex ring pairing and merging, as well as axis switching, are common in elliptical jets. When AR was 4, there was also a large-scale single vortex ring between the two merged vortex rings, this large-scale single vortex alone underwent axis transformation and breakage. The merger always occurred in the major plane in elliptical jets because in the major plane, the leading and trailing vortices approached each other as a result of self-induction and mutual induction. The entrainment rate was strongly correlated with the K-H vortex ring dynamics in circular jets and weakly correlated with the K–H vortex ring passing in elliptical jets. The entrainment appeared in the upstream part of the K-H vortex ring structures in circular jets, whereas it was enhanced in the axis-switching region in elliptical jets. An analysis of the contribution of each mode to mass entrainment showed that the entrainment rate of the elliptical nozzle was better than that of the circular nozzle, mainly because many streamwise vortices were generated.

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Dynamics and entrainment mechanism of the jet flows from an elliptical nozzle: time-resolved tomographic PIV measurements

Zeng

Zhang

et al. 2023

Exp Fluids

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Time- and frequency-domain spectral proper orthogonal decomposition of a swirling jet by tomographic particle image velocimetry

Cited by 9 publications

References 73 publications

A polynomial model with line-of-sight constraints for Lagrangian particle tracking under interface refraction

A polynomial model with line-of-sight constraints for Lagrangian particle tracking under interface refraction

Dynamics and Entrainment Mechanism of the Jet Flows from an Elliptical Nozzle: Time-Resolved Tomographic PIV Measurements

Dynamics and entrainment mechanism of the jet flows from an elliptical nozzle: time-resolved tomographic PIV measurements

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