On the calibration of Astigmatism particle tracking velocimetry for suspensions of different volume fractions

Brockmann, Philipp; Hussong, Jeanette

doi:10.1007/s00348-020-03120-4

“…In Fig. 6c,d, we show a y plotted over a x which is required for the Euclidean calibration Brockmann et al 2020;Brockmann and Hussong 2021). Obviously here, for both the autocorrelation and the binarization approach, the curves for the small particles (small dots) and the large particles (large dots) intersect (Fig.…”

Section: Calibration Proceduresmentioning

confidence: 92%

“…8a). Preliminary tests showed that a polynomial degree of at least 14 (as utilized here) is required to adapt to the different sets of calibration data that arise from different magnifications, particle sizes and processing parameters such as the autocorrelation coefficient (Brockmann and Hussong 2021). By plotting the fits of a y (denoted as a y ) over the fit of a x (denoted as a x ), the conventional Euclidean calibration (CEC) curve is obtained (Fig.…”

Section: Calibration Proceduresmentioning

confidence: 99%

“…The particle velocities were reconstructed using both the CEC and the EEC procedure. It should be mentioned that in case of the CEC, all data from the measurement with I < I thr have been removed to avoid excessive outliers biasing the data (Brockmann and Hussong 2021). Figures 15a,b exemplarily show the scatter velocity data obtained with the CEC and the EEC reconstruction procedure.…”

Section: Validation Of Extended Euclidean Calibration Reconstruction ...mentioning

confidence: 99%

“…They also extended the Euclidean calibration approach developed by by additionally considering the light intensity of particles as a calibration parameter. Further, the recent work of Brockmann and Hussong (2021) successfully applied APTV to measure particle dynamics in neutrally buoyant suspensions of up to = 19.9% using a RIM technique. To compensate the effect of optical distortions induced by suspension particles, they adapted an interpolation procedure developed by Brockmann et al (2020) and validated their method in a channel flow.…”

Section: Introductionmentioning

confidence: 99%

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Utilizing APTV to investigate the dynamics of polydisperse suspension flows beyond the dilute regime

Brockmann

¹

,

Symanczyk

²

,

Ennayar

³

et al. 2022

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We present a methodology that allows to measure the dynamics of polydisperse suspension flows by means of Astigmatism Particle Tracking Velocimetry (APTV). Measurements are successfully performed with tridisperse suspensions flows in a square duct of up to $$\varPhi =9.1\%$$ Φ = 9.1 % particle volume fraction. Using a refractive index matching technique, a small amount of the particles ($$\varPhi =0.08\%$$ Φ = 0.08 % ) is labeled with fluorescent dye to be visible to the camera during the particle tracking procedure. Calibration measurements are performed for ten different particles diameters $$d_p$$ d p ranging from $$d_p= {15}\upmu \mathrm{m}$$ d p = 15 μ m to $$d_p= {260}\,\upmu \mathrm{m}$$ d p = 260 μ m . It is shown that Euclidean calibration curves of different $$d_p$$ d p overlap outside the focal planes, which induces ambiguities in a polydisperse APTV measurement. In the present approach, this ambiguity can be overcome utilizing the light intensity of a particle image which increases sharply with $$d_p$$ d p . In this way, extended Euclidean calibration curves can be generated for each particle group which are spatially separated through the light intensity which serves as an additional calibration parameter (Brockmann et al. in Exp Fluids 61(2):67, 2020). The extended Euclidean calibration allows to simultaneously differentiate particles of different sizes and determine their 3D location. This facilitates to investigate the migration behavior of mono- and tridisperse suspension flows which we demonstrate here for square duct flows with cross-sectional areas of $$0.6\times 0.6\,\mathrm{mm}^2$$ 0.6 × 0.6 mm 2 and $$0.4\times 0.4\,\mathrm{mm}^2$$ 0.4 × 0.4 mm 2 at bulk Reynolds numbers of $$\mathrm{Re}_b \approx 20$$ Re b ≈ 20 and $$\mathrm{Re}_b \approx 40$$ Re b ≈ 40 for particle volume fractions of $$\varPhi =0.08\%$$ Φ = 0.08 % and $$\varPhi =9.1\%$$ Φ = 9.1 % . At $$\varPhi =0.08\%$$ Φ = 0.08 % and $$\mathrm{Re}_b=20$$ Re b = 20 , we observe particles to arrange themselves in a ring-like formation inside the capillary, henceforth referred to as Pseudo Segré Silberberg Annulus (PSSA), with no significant differences between mono- and polydisperse suspension particle distributions. At $$\varPhi =9.1\%$$ Φ = 9.1 % , particles in monodisperse suspensions scatter around the PSSA. This scattering decreases when $$d_p$$ d p increases or $$Re_b$$ R e b increases from 20 to 40. Striking differences are observed in polydisperse suspensions. Large particles ($${60}\,\upmu \mathrm{m}$$ 60 μ m ) scatter significantly less around the PSSA in the polydisperse case compared to a monodisperse suspension of the same overall volume fraction. In contrast, small and intermediate particles ( $${30}\,\upmu \mathrm{m}$$ 30 μ m , $${40}\,\upmu \mathrm{m}$$ 40 μ m ) are repelled by larger particles resulting in regions of high concentration close to the channel walls which can be only observed in the polydisperse case. Graphical abstract

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“…Solely difficulties in handling of highly flammable or toxic liquids may restrict the choice of materials (Hassan and Dominguez-Ontiveros 2008;Wiederseiner et al 2011). Hence, this concept was already successfully applied for Particle Tracking Velocimetry (PTV) (Wang et al 2008), laser Doppler velocimetry (LDV) (Haam et al 2000), laser-induced fluorescence (LIF) (Chen et al 2005) and Astigmatism Particle Tracking Velocimetry (APTV) (Brockmann et al 2020;Brockmann and Hussong 2021) measurements in multiphase flows. An advantage of the PIV measurement technique compared to other optical, non-invasive measurement techniques like the APTV approach is that no sophisticated calibration technique is required and all suspension particles can be labelled and, therefore, contribute to the measurement result.…”

Section: Introductionmentioning

confidence: 99%

On the micro-PIV accuracy and reliability utilizing non-Gaussian particle images

Blahout

¹

,

Reinecke

²

,

Kruggel‐Emden

³

et al. 2021

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Optical investigations of the dynamics of concentrated suspensions, such as in blood flows (Fitzgibbon et al. in Biophys J 108(10):2601–2608, 2015. http://doi/org/10.1016/j.bpj.2015.04.013) or slurry flows (Li et al. in Ocean Eng 163(October 2017):691–705, 2018. http://doi/org/10.1016/j.oceaneng.2018.06.046), are challenging due to reduced optical accessibility. Furthermore, the suspension particle image size can strongly deviate from the optimal particle image size for PIV measurements. Optical accessibility can be achieved by refractive index matching of surface labelled suspension particles. This results in particle images that are transparent in the particle image centre, but fluoresce at the particle image rim, resulting in ring-shaped particle images. In the present study, the influence of the particle image size on the cross-correlation result of such ring-shaped particle images is compared with Gaussian and plateau-shaped particle images. Particles of Gaussian image shape result from fully labelled particles with small image diameters and are commonly used in PIV measurements. Such particles are also utilized for the determination of the continuous phase velocities in the experimental part of the present study. With increasing image diameter, fully labelled particles are observed to assume plateau-shaped particle images. Monte Carlo simulations of synthetically generated images show that ring-shaped particle images have a superior behaviour, i.e. they assume a reduced displacement estimation error for noisy as well as for noise-free image data, compared to Gaussian and plateau-shaped particle images. This is also true for large particle image diameters when particle images are intersected at interrogation window borders or when different values of nonzero particle image displacements are considered. The detectability is similar for all three particle image shapes as long as particles do not intersect with the interrogation window border. Interestingly, for intersected particles of large image diameter, ring-shaped particle images show a slightly improved detectability compared to particle images of Gaussian and plateau shape. Furthermore, the detectability is insensitive against a nonzero particle image displacement. The usage of refractive index matched, ring-shaped particle images results in a good optical accessibility of the suspension. This allows to perform simultaneous cross-correlation evaluations on large ring-shaped particle images and fluid tracers with Gaussian particle images that are two orders of magnitude smaller compared to suspension particle images. Velocity measurements are taken on a suspension containing 5 vol% surface labelled, refractive index matched 60 $$\upmu \hbox {m}$$ μ m polymethylmethacrylate (PMMA) particles. Simultaneously, $$\upmu$$ μ PIV measurements of the carrier liquid flow are performed utilizing 1.19 $$\upmu \text {m}$$ μ m fluorescent polystyrene (PS) particles. Measurement results reveal a parabolic shape of the velocity profiles of both phases with a mean slip velocity of 7.4% at the position of maximum streamwise velocity in a 580 $$\upmu \text {m}$$ μ m high trapezoidal channel. An error analysis confirms the presence of these slip velocities within a 68.5% confidence interval. A measurement uncertainty in the order of magnitude of $${\mathcal {O}}(10^{-1}\ \mathrm{px})$$ O ( 10 - 1 px ) is reached for both fluid tracers and suspension particles. Overall, the present study demonstrates theoretically and experimentally that the usage of suspension particles with ring-shaped images is superior compared to Gaussian and plateau-shaped particle images of the same size. Additionally, the present study demonstrates that the usage of ring-shaped particle images allows to investigate suspension bulk dynamics by measuring velocity fields of both the suspended and the continuous phase simultaneously and with an overall uncertainty that is in the same order of magnitude as for standard $$\upmu$$ μ PIV measurements. Graphic abstract

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Asymmetry During Fast Stretching of a Liquid Bridge

Asghar

¹

,

Brockmann

²

,

Dong

³

et al. 2023

Chem Eng & Technol

0

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The dynamics of an axisymmetric liquid bridge stretch are investigated by means of numerical simulations, and the results are validated experimentally. The constant acceleration of the lower substrate stretches the liquid bridge. A simplified simulation model of the experimental setup is developed for the unstructured volume‐of‐fluid two‐phase flow simulation method, which models the lower substrate as a fluid with a prescribed constant acceleration of the retracting substrate. The effect of stretching acceleration, fluid properties, and liquid volume on the liquid bridge dynamics is investigated. It is shown that at low acceleration the length of the lower portion of the bridge is greater than the upper portion, which is reversed at high acceleration. With increasing viscosity, this effect is decreased and the bridge becomes more symmetric.

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On the calibration of Astigmatism particle tracking velocimetry for suspensions of different volume fractions

Cited by 8 publications

References 30 publications

Utilizing APTV to investigate the dynamics of polydisperse suspension flows beyond the dilute regime

Utilizing APTV to investigate the dynamics of polydisperse suspension flows beyond the dilute regime

On the micro-PIV accuracy and reliability utilizing non-Gaussian particle images

Asymmetry During Fast Stretching of a Liquid Bridge

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