GPU-accelerated MART and concurrent cross-correlation for tomographic PIV

Zeng, Xin; He, Chuangxin; Liu, Yingzheng

doi:10.1007/s00348-022-03444-3

Cited by 16 publications

(9 citation statements)

References 45 publications

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“…Figure 15 shows the Eulerian flow field with iso-surfaces of Q = 0.5 U 0 2 /D e 2 colored by streamwise velocity. For comparison, the Tomo-PIV result in figure 15(a) is reconstructed using a custom GPU-based Tomo-PIV framework [51]. Notably, the flow-field noise is large, and the non-zero divergence of velocity is significant (most absolute values greater than 0.11 U 0 2 /D e 2 ) in the Tomo-PIV data.…”

Section: Resultsmentioning

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: Resultsmentioning

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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“…As shown in Fig. 1(a), a tall octagonal tank (with sides of 250 mm and a height of 900 mm) filled with tap water was designed to investigate the dynamical behavior of 3D jet flows at various Re and visualize 3D jet flows , He et al 2021, He et al 2022. Owing to this design and its deformable nozzle outlets, jet experiments at different AR values were conducted in this octagonal tank.…”

Section: Methodsmentioning

confidence: 99%

“…1, a measurement area of 50 mm (2.5D in the x-direction)  100 mm (5D in the y-direction)  50 mm (2.5D in the z-direction) was reconstructed with a discretization of 11 voxels/mm to obtain the particle field. The velocity vectors were efficiently calculated from the raw particle volumes using a graphics processing unit-based Tomo-PIV framework developed in-house (Zeng et al 2022). The interrogation volume was set in turn to 64 3 and 32 3 voxels with a 50% overlap, which realized a resolution of 14 vectors per D. The measurement of the circular nozzle was repeated three times with 6,320 image sets each time, which yielded 9,960 frames of 3D flow field snapshots.…”

Section: Methodsmentioning

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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“…The particle displacement in the mainstream for each pair of images is approximately 4 pixels according to the imaging time interval. GPU-accelerated code (Zeng, He & Liu 2022) based on the MART algorithm, combined with the iterative multigrid volumetric cross-correlation approach with a final pass interrogation volume size of 32 × 32 × 32 voxels and 50 % overlap, is used to determine the three-dimensional velocity fields. This yields a spatial resolution of the velocity vectors of 1.2 mm.…”

Section: Computational and Synthesis Tomo-piv Set-upsmentioning

confidence: 99%

Four-dimensional variational data assimilation of a turbulent jet for super-temporal-resolution reconstruction

He,

Zeng,

Wang

et al. 2024

J. Fluid Mech.

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The super-temporal-resolution (STR) reconstruction of turbulent flows is an important data augmentation application for increasing the data reach in measurement techniques and understanding turbulence dynamics. This paper proposes a data assimilation (DA) strategy based on weak-constraint four-dimensional variation to conduct an STR reconstruction in a turbulent jet beyond the Nyquist limit from given low-sampling-rate observations. Highly resolved large-eddy simulation (LES) data are used to produce synthetic measurements, which are used as observations and for validation. A segregated assimilation procedure is realised to assimilate the initial condition, inflow boundary condition and model error separately. Different types of observational data are tested. The first type is down-sampled LES data containing many small-scale turbulence structures with or without synthetic noise. The DA results show that the temporal variation of the small-scale structures is well recovered even with noise in the observations. The spectra are resolved to a frequency approximately one order of magnitude higher than what can be captured within the Nyquist limit. The second type of observation is low-sampling-rate tomographic particle image velocimetry (tomo-PIV) data with or without the injection of small-scale structures. The modulation between the large-scale structures contained in the tomo-PIV fields and the small scales injected from the observations is improved. The resultant small scales in the STR reconstruction have the characteristics of authentic turbulence to a considerable extent. Additionally, DA yields much smaller errors in the prediction of particle positions when compared with the Wiener filter, demonstrating the great potential for Lagrangian particle tracking in measurement techniques.

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GPU-accelerated MART and concurrent cross-correlation for tomographic PIV

Cited by 16 publications

References 45 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

Four-dimensional variational data assimilation of a turbulent jet for super-temporal-resolution reconstruction

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