A multiphase, micro-scale PIV measurement technique for liquid film velocity measurements in annular two-phase flow

Ashwood, Andrea C.; Hogen, S.J. Vanden; Rodarte, M.A.; Kopplin, C.R.; Rodriguez, Daniel J.; Hurlburt, Evan T.; Shedd, Timothy A.

doi:10.1016/j.ijmultiphaseflow.2014.09.003

Cited by 49 publications

(23 citation statements)

References 34 publications

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“…In this case, PTVderived velocity profiles revealed multiple recirculation zones inside the disturbance waves (in a reference frame moving with the wave speed), that the authors hypothesized might be linked to liquid entrainment as well as mass and momentum transfer from the near-wall zone towards the liquid-gas interface. Also using micro-PIV, Ashwood et al [63] provided mean velocity-profile data in cocurrent upward flows in a rectangular duct, and suggested that modifications to the UVP must be implemented to accurately track their results. Finally, by applying micro-PIV, Dietze et al [58] linked changes in the surface curvature and ensuing adverse pressure gradients to backflow in the capillary trough closest to the solitary wave crest, and flow deceleration in the second capillary trough.…”

Section: Experimental Methodsmentioning

confidence: 99%

Detailed hydrodynamic characterization of harmonically excited falling-film flows: A combined experimental and computational study

et al. 2017

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We present results from the simultaneous application of planar laser-induced fluorescence (PLIF), particle image velocimetry (PIV) and particle tracking velocimetry (PTV), complemented by direct numerical simulations, aimed at the detailed hydrodynamic characterization of harmonically excited liquid-film flows falling under the action of gravity. The experimental campaign comprises four different aqueous-glycerol solutions corresponding to four Kapitza numbers (Ka = 14, 85, 350, 1800), spanning the Reynolds number range Re = 2.3-320, and with forcing frequencies f w = 7 and 10 Hz. PLIF was employed to generate spatiotemporally resolved film-height measurements, and PIV and PTV to generate two-dimensional velocity-vector maps of the flow field underneath the wavy film interface. The latter allows for instantaneous, highly localized velocity-profile, bulk-velocity, and flow-rate data to be retrieved, based on which the effect of local film topology on the flow field underneath the waves is studied in detail. Temporal sequences of instantaneous and local film height and bulk velocity are generated and combined into bulk flow-rate time series. The time-mean flow rates are then decomposed into steady and unsteady components, the former represented by the product of the mean film height and mean bulk velocity and the latter by the covariance of the film-height and bulk-velocity fluctuations. The steady terms are found to vary linearly with the flow Re, with the best-fit gradients approximated closely by the kinematic viscosities of the three examined liquids. The unsteady terms, typically amounting to 5%-10% of the mean and peaking at approximately 20%, are found to scale linearly with the film-height variance. And, interestingly, the instantaneous flow rate is found to vary linearly with the instantaneous film height. Both experimental and numerical flow-rate data are closely approximated by a simple analytical relationship with only minor deviations. This relationship includes terms such as the wave speed c and mean flow rate Q, which can be obtained by relatively simple and inexpensive methods, thus allowing for spatiotemporally resolved flow-rate predictions to be made without requiring explicit knowledge of the full flow-field information underneath the wavy interface.

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Section: Experimental Methodsmentioning

confidence: 99%

Detailed hydrodynamic characterization of harmonically excited falling-film flows: A combined experimental and computational study

et al. 2017

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“…An attempt to address the deficits of standard PIV in thin-film flow investigations was recently made by Ashwood et al [48]. By borrowing strategies from micro-PIV (mainly with regards to seeding and imaging), the authors provided mean velocity profile data in a co-current upward flow, although in a rectangular duct, suggesting that certain modifications to the UVP must be implemented before a meaningful approximation of the profiles can be made.…”

Section: Review Of Experimental Methodsmentioning

confidence: 99%

A simultaneous planar laser-induced fluorescence, particle image velocimetry and particle tracking velocimetry technique for the investigation of thin liquid-film flows

Charogiannis

Markides

2015

Experimental Thermal and Fluid Science

113

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A simultaneous measurement technique based on planar laser-induced fluorescence imaging (PLIF) and particle image/tracking velocimetry (PIV/PTV) is described for the investigation of the hydrodynamic characteristics of harmonically excited liquid thin-film flows. The technique is applied as part of an extensive experimental campaign that covers four different Kapitza (Ka) number liquids, Reynolds (Re) numbers spanning the range 2.3 -320, and inlet-forced/wave frequencies in the range 1 -10 Hz. Film thicknesses (from PLIF) for flat (viscous and unforced) films are compared to micrometer stage measurements and analytical predictions (Nusselt solution), with a resulting mean deviation being lower than the nominal resolution of the imaging setup (around 20 μm). Relative deviations are calculated between PTV-derived interfacial and bulk velocities and analytical results, with mean values amounting to no more than 3.2% for both test cases. In addition, flow rates recovered using LIF/PTV (film thickness and velocity profile) data are compared to direct flowmeter readings. The mean relative deviation is found to be 1.6% for a total of six flat and nine wavy flows. The practice of wave/phase locked flow-field averaging is also implemented, allowing the generation of highly localized velocity profile, bulk velocity and flow rate data along the wave topology. Based on this data, velocity profiles are extracted from 20 locations along the wave topology and compared to analytically derived ones based on local film thickness measurements and the Nusselt solution. Increasing the waviness by modulating the forcing frequency is found to result in lower absolute deviations between experiments and theoretical predictions ahead of the wave crests, and higher deviations behind the wave crests. At the wave crests, experimentally derived interfacial velocities are overestimated by nearly 100%. Finally, locally non-parabolic velocity profiles are identified ahead of the wave crests; a phenomenon potentially linked to the cross-stream velocity field.

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“…For single phase measurements, small scale flow structures around a Rushton turbine (Sharp and Adrian, 2001;Li et al, 2011), angle-resolved specific TKE and EDR distributions (Ducci and Yianneskis, 2006;Gabriele et al, 2009;Delafosse et al, 2011), the influence of PIV spatial resolution on EDR values (Piirto et al, 2000;Saarenrinne et al, 2001;Baldi and Yianneskis, 2003) and the modification of isotropic assumptions in stirred tanks (Delafosse et al, 2011) have been successfully studied. For gas/solid-liquid phase measurements, the use of a spectroscope with two cameras (Sathe et al, 2010) and a particle-isolating algorithm (Ashwood et al, 2015) while matching refraction indices is recommended for liquid-liquid systems to prevent the appearance of opacity (Tabib and Schwarz, 2011;Tabib et al, 2012) and to describe the flow motions of both phases in identical images (Liu, 2005;Svensson and Rasmuson, 2006;Hlawitschka and Bart, 2012). It should be noted that PIV cannot resolve all flow fields due to limitations in camera capacity and the scale of the tracer particles.…”

Section: Introductionmentioning

confidence: 99%

A PIV investigation of the effect of disperse phase fraction on the turbulence characteristics of liquid–liquid mixing in a stirred tank

Liu

Wang

Han

et al. 2016

Chemical Engineering Science

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In this paper, utilizing 2D angle-resolved particle image velocimetry (PIV), the flow field of a dilute aqueous-in-oil dispersion is experimentally studied in a stirring tank. Opacity during liquid-liquid mixing is eliminated by matching the refractive indices of both phases. Anisotropy of the turbulence flow field is analysed via the turbulent kinetic energy (TKE) and energy dissipation rate (EDR) obtained at different measuring angles. The influence of spatial resolution is compared and discussed. TKE and EDR are observed to increase with increment of dispersed phase fraction while a small range of disorder and fluctuation is observed in the impeller region. The effect of dispersed droplets should be attributed to the strengthened fluctuation of velocities and spatial differences. Further work concerning higher resolution and the disperse fraction is necessary.

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A multiphase, micro-scale PIV measurement technique for liquid film velocity measurements in annular two-phase flow

Cited by 49 publications

References 34 publications

Detailed hydrodynamic characterization of harmonically excited falling-film flows: A combined experimental and computational study

Detailed hydrodynamic characterization of harmonically excited falling-film flows: A combined experimental and computational study

A simultaneous planar laser-induced fluorescence, particle image velocimetry and particle tracking velocimetry technique for the investigation of thin liquid-film flows

A PIV investigation of the effect of disperse phase fraction on the turbulence characteristics of liquid–liquid mixing in a stirred tank

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